golang复制代码func toValueInt(val int){
	val = 2
}

func main(){
	a := 1
	toValueInt(a)
	fmt.Println(a)
}

js复制代码1

golang复制代码func toValueInt(val *int){
	*val = 2
}
func main(){
	a := 1
	toValueInt(&a)
	fmt.Println(a)
}

js复制代码2

gloang复制代码func toValueString(val string){
	val = "2"
}

func main(){
	b := "1"
	toValueString(b)
	fmt.Println(b)
}

js复制代码1

js复制代码func toValueString(val *string){
	*val = "2"
}

func main(){
	b := "1"
	toValueString(&b)
	fmt.Println(b)
}

js复制代码func toValueList(val [3]int){
	val[0]=4
	val[1]=5
	val[2]=5
}

func main(){
	c := [3]int{1,2,3}
	toValueList(c)
	fmt.Println(c)
}

js复制代码[1 2 3]

golang复制代码func toValueList(val *[3]int){
	val[0]=4
	val[1]=5
	val[2]=5
}

func main(){
	c := [3]int{1,2,3}
	toValueList(&c)
	fmt.Println(c)
}

js复制代码[4 5 5]

golang复制代码func toValueSplice(val []int){
	val[0]= 2
}

func main(){
	d:= []int{1}
	toValueSplice(d)
	fmt.Println(d)
}

js复制代码[2]

golang复制代码func toValueSplice(val []int){
	val[1]= 2
}

func main(){
	d:= []int{1}
	toValueSplice(d)
	fmt.Println(d)
}

js复制代码panic: runtime error: index out of range [1] with length 1

golang复制代码func toValueSplice(val []int){
     val = append(val,2)
     fmt.Println("函数中打印",val)
}

func main(){
	d:= []int{1}
	fmt.Println("main 函数打印",d)
	fmt.Println(d)
}

js复制代码[1 2]

js复制代码[1]

golang复制代码func toValueSplice(val *[]int){
	*val = append(*val,2)
	fmt.Println("函数中打印",*val)
}

func main(){
	d:= []int{1}
	toValueSplice(&d)
	fmt.Println("main 函数打印",d)
}

js复制代码[1 2]

js复制代码[1 2]

golang复制代码func toValueMap(val map[string]int){
     val["1"]=2
}

func main(){
    e:= map[string]int{"1":1}
    toValueMap(e)
    fmt.Println(e)
}

js复制代码map[1:2]

golang复制代码func toValueMap(val map[string]int){
	val1 := map[string]int{}
	for k,v := range val{
		val1[k] = v
	}
	val = val1
	val["1"]=2
}

fun main(){
   e:= map[string]int{"1":1}
    toValueMap(e)
    fmt.Println(e)
}

js复制代码map[1:1]

golang复制代码func toValueMap(val map[string]int){
	val1 := val
	val1["1"]=2
}

func main(){
    e:= map[string]int{"1":1}
    toValueMap(e)
    fmt.Println(e)
}

js复制代码map[1:2]

golang复制代码func toValueMap(val map[string]int){
	var val1 map[string]int
	str,_ := json.Marshal(val)
	json.Unmarshal(str,&val1)
	val1["1"]=2
}

golang复制代码type ss struct {
	id int
}

func toValueStruct(s ss){
	s.id = 2
}

func main(){
    s := ss{1}
    toValueStruct(s)
    fmt.Println(s)
}

js复制代码{1}

golang复制代码type ss struct {
	id int
}

func toValueStruct(s *ss){
	s.id = 2
}

func main(){
    s := ss{1}
    toValueStruct(&s)
    fmt.Println(s)
}

js复制代码{2}

js复制代码var ch chan int
func toValueChan(ch chan int){
	ch <-2
}

func main(){
    ch := make(chan int,2)
    ch <- 1
    toValueChan(ch)
    fmt.Println( <-ch,<-ch)
}

js复制代码1 2

swift复制代码public static void main(String[] args) {
        StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
        EnvironmentSettings envSettings = EnvironmentSettings.newInstance()
                .useBlinkPlanner()
                .inStreamingMode()
                .build();
        env.setParallelism(3);
        // note: 增量同步需要开启CK
        env.enableCheckpointing(10000);
        StreamTableEnvironment tableEnvironment = StreamTableEnvironment.create(env, envSettings);
            
    	tableEnvironment.executeSql(" CREATE TABLE demoOrders (\n" +
                "         `order_id` INTEGER ,\n" +
                "          `order_date` DATE ,\n" +
                "          `order_time` TIMESTAMP(3),\n" +
                "          `quantity` INT ,\n" +
                "          `product_id` INT ,\n" +
                "          `purchaser` STRING,\n" +
                "           primary key(order_id)  NOT ENFORCED" +
                "         ) WITH (\n" +
                "          'connector' = 'mysql-cdc',\n" +
                "          'hostname' = 'localhost',\n" +
                "          'port' = '3306',\n" +
                "          'username' = 'cdc',\n" +
                "          'password' = '123456',\n" +
                "          'database-name' = 'test',\n" +
                "          'table-name' = 'demo_orders'," +
                            //  全量 + 增量同步   
                "          'scan.startup.mode' = 'initial'      " +
                " )");

      		tableEnvironment.executeSql("CREATE TABLE sink (\n" +
                "         `order_id` INTEGER ,\n" +
                "          `order_date` DATE ,\n" +
                "          `order_time` TIMESTAMP(3),\n" +
                "          `quantity` INT ,\n" +
                "          `product_id` INT ,\n" +
                "          `purchaser` STRING,\n" +
                "          primary key (order_id)  NOT ENFORCED " +
                ") WITH (\n" +
                "    'connector' = 'kafka',\n" +
                "    'properties.bootstrap.servers' = 'localhost:9092',\n" +
                "    'topic' = 'mqTest02',\n" +
                "    'format' = 'changelog-json' "+
                ")");

 			tableEnvironment.executeSql("insert into sink select * from demoOrders");}

bash复制代码{"data":{"order_id":1010,"order_date":"2021-09-17","order_time":"2021-09-22 10:52:12.189","quantity":53,"product_id":502,"purchaser":"flink"},"op":"+I"}
{"data":{"order_id":1009,"order_date":"2021-09-17","order_time":"2021-09-22 10:52:09.709","quantity":31,"product_id":500,"purchaser":"flink"},"op":"+I"}
{"data":{"order_id":1008,"order_date":"2021-09-17","order_time":"2021-09-22 10:52:06.637","quantity":69,"product_id":503,"purchaser":"flink"},"op":"+I"}
{"data":{"order_id":1007,"order_date":"2021-09-17","order_time":"2021-09-22 10:52:03.535","quantity":52,"product_id":502,"purchaser":"flink"},"op":"+I"}
{"data":{"order_id":1002,"order_date":"2021-09-17","order_time":"2021-09-22 10:51:51.347","quantity":69,"product_id":503,"purchaser":"flink"},"op":"+I"}
{"data":{"order_id":1001,"order_date":"2021-09-17","order_time":"2021-09-22 10:51:48.783","quantity":50,"product_id":502,"purchaser":"flink"},"op":"+I"}
{"data":{"order_id":1000,"order_date":"2021-09-17","order_time":"2021-09-17 17:40:32.354","quantity":30,"product_id":500,"purchaser":"flink"},"op":"+I"}
{"data":{"order_id":1006,"order_date":"2021-09-17","order_time":"2021-09-22 10:52:01.249","quantity":31,"product_id":500,"purchaser":"flink"},"op":"+I"}
{"data":{"order_id":1005,"order_date":"2021-09-17","order_time":"2021-09-22 10:51:58.813","quantity":69,"product_id":503,"purchaser":"flink"},"op":"+I"}
{"data":{"order_id":1004,"order_date":"2021-09-17","order_time":"2021-09-22 10:51:56.153","quantity":50,"product_id":502,"purchaser":"flink"},"op":"+I"}
{"data":{"order_id":1003,"order_date":"2021-09-17","order_time":"2021-09-22 10:51:53.727","quantity":30,"product_id":500,"purchaser":"flink"},"op":"+I"}

## 更新 1005 的值 
{"data":{"order_id":1005,"order_date":"2021-09-17","order_time":"2021-09-22 02:51:58.813","quantity":69,"product_id":503,"purchaser":"flink"},"op":"-U"}
{"data":{"order_id":1005,"order_date":"2021-09-17","order_time":"2021-09-22 02:55:43.627","quantity":80,"product_id":503,"purchaser":"flink"},"op":"+U"}

## 删除 1000 
{"data":{"order_id":1000,"order_date":"2021-09-17","order_time":"2021-09-17 09:40:32.354","quantity":30,"product_id":500,"purchaser":"flink"},"op":"-D"}

sql复制代码//  计算主键列数据区间
select min(`order_id`), max(`order_id`) from demo_orders;

//  将数据划分为 chunkSize 大小的切片
chunk-0： [min，start + chunkSize)
chunk-1： [start + chunkSize, start + 2chunkSize)
.......
chunk-last： [max，null)

sql复制代码// 未拆分的数据排序后，取 chunkSize 条数据取最大值，作为切片的终止位置。
chunkend = SELECT MAX(`order_id`) FROM (
        SELECT `order_id`  FROM `demo_orders` 
        WHERE `order_id` >= [前一个切片的起始位置] 
        ORDER BY `order_id` ASC 
        LIMIT   [chunkSize]  
    ) AS T

ini复制代码## 快照记录数据读取SQL 
SELECT * FROM `test`.`demo_orders` 
WHERE order_id >= [chunkStart] 
AND NOT (order_id = [chunkEnd]) 
AND order_id <= [chunkEnd]

csharp复制代码private void syncWithReaders(int[] subtaskIds, Throwable t) {
    if (t != null) {
        throw new FlinkRuntimeException("Failed to list obtain registered readers due to:", t);
    }
    // when the SourceEnumerator restores or the communication failed between
    // SourceEnumerator and SourceReader, it may missed some notification event.
    // tell all SourceReader(s) to report there finished but unacked splits.
    if (splitAssigner.waitingForFinishedSplits()) {
        for (int subtaskId : subtaskIds) {
            // note: 发送 FinishedSnapshotSplitsRequestEvent 
            context.sendEventToSourceReader(
                    subtaskId, new FinishedSnapshotSplitsRequestEvent());
        }
    }
}

perl复制代码MySqlParallelSource#createReader

public SourceReader<T, MySqlSplit> createReader(SourceReaderContext readerContext) throws Exception {
	// note:  数据存储队列
FutureCompletingBlockingQueue<RecordsWithSplitIds<SourceRecord>> elementsQueue =
        new FutureCompletingBlockingQueue<>();
final Configuration readerConfiguration = getReaderConfig(readerContext);

	// note: Split Reader 工厂类
Supplier<MySqlSplitReader> splitReaderSupplier =
        () -> new MySqlSplitReader(readerConfiguration, readerContext.getIndexOfSubtask());

return new MySqlSourceReader<>(
        elementsQueue,
        splitReaderSupplier,
        new MySqlRecordEmitter<>(deserializationSchema),
        readerConfiguration,
        readerContext);
}

scss复制代码MySqlSourceEnumerator#handleSplitRequest
public void handleSplitRequest(int subtaskId, @Nullable String requesterHostname) {
    if (!context.registeredReaders().containsKey(subtaskId)) {
        // reader failed between sending the request and now. skip this request.
        return;
    }
    // note:  将reader所属的subtaskId存储到TreeSet, 在处理binlog split时优先分配个task-0
    readersAwaitingSplit.add(subtaskId);

    assignSplits();
}

// note: 分配切片
private void assignSplits() {
    final Iterator<Integer> awaitingReader = readersAwaitingSplit.iterator();
    while (awaitingReader.hasNext()) {
        int nextAwaiting = awaitingReader.next();
        // if the reader that requested another split has failed in the meantime, remove
        // it from the list of waiting readers
        if (!context.registeredReaders().containsKey(nextAwaiting)) {
            awaitingReader.remove();
            continue;
        }

        //note: 由 MySqlSplitAssigner 分配切片
        Optional<MySqlSplit> split = splitAssigner.getNext();
        if (split.isPresent()) {
            final MySqlSplit mySqlSplit = split.get();
            //  note: 发送AddSplitEvent, 为 Reader 返回切片信息
            context.assignSplit(mySqlSplit, nextAwaiting);
            awaitingReader.remove();

            LOG.info("Assign split {} to subtask {}", mySqlSplit, nextAwaiting);
        } else {
            // there is no available splits by now, skip assigning
            break;
        }
    }
}

scss复制代码@Override
public Optional<MySqlSplit> getNext() {
    if (!remainingSplits.isEmpty()) {
        // return remaining splits firstly
        Iterator<MySqlSnapshotSplit> iterator = remainingSplits.iterator();
        MySqlSnapshotSplit split = iterator.next();
        iterator.remove();
        
        //note: 已分配的切片存储到 assignedSplits 集合
        assignedSplits.put(split.splitId(), split);

        return Optional.of(split);
    } else {
        // note: 初始化阶段 remainingTables 存储了要读取的表名
        TableId nextTable = remainingTables.pollFirst();
        if (nextTable != null) {
            // split the given table into chunks (snapshot splits)
            //  note: 初始化阶段创建了 ChunkSplitter，调用generateSplits 进行切片划分
            Collection<MySqlSnapshotSplit> splits = chunkSplitter.generateSplits(nextTable);
            //  note: 保留所有切片信息
            remainingSplits.addAll(splits);
            //  note: 已经完成分片的 Table
            alreadyProcessedTables.add(nextTable);
            //  note: 递归调用该该方法
            return getNext();
        } else {
            return Optional.empty();
        }
    }
}

scss复制代码public Collection<MySqlSnapshotSplit> generateSplits(TableId tableId) {

    Table schema = mySqlSchema.getTableSchema(tableId).getTable();
    List<Column> primaryKeys = schema.primaryKeyColumns();
    // note: 必须有主键
    if (primaryKeys.isEmpty()) {
        throw new ValidationException(
                String.format(
                        "Incremental snapshot for tables requires primary key,"
                                + " but table %s doesn't have primary key.",
                        tableId));
    }
    // use first field in primary key as the split key
    Column splitColumn = primaryKeys.get(0);

    final List<ChunkRange> chunks;
    try {
         // note: 按主键列将数据划分成多个切片
        chunks = splitTableIntoChunks(tableId, splitColumn);
    } catch (SQLException e) {
        throw new FlinkRuntimeException("Failed to split chunks for table " + tableId, e);
    }
    //note: 主键数据类型转换、ChunkRange 包装成MySqlSnapshotSplit。
    // convert chunks into splits
    List<MySqlSnapshotSplit> splits = new ArrayList<>();
    RowType splitType = splitType(splitColumn);
 
    for (int i = 0; i < chunks.size(); i++) {
        ChunkRange chunk = chunks.get(i);
        MySqlSnapshotSplit split =
                createSnapshotSplit(
                        tableId, i, splitType, chunk.getChunkStart(), chunk.getChunkEnd());
        splits.add(split);
    }
    return splits;
}

scss复制代码private List<ChunkRange> splitTableIntoChunks(TableId tableId, Column splitColumn)
        throws SQLException {
    final String splitColumnName = splitColumn.name();
    //  select min, max
    final Object[] minMaxOfSplitColumn = queryMinMax(jdbc, tableId, splitColumnName);
    final Object min = minMaxOfSplitColumn[0];
    final Object max = minMaxOfSplitColumn[1];
    if (min == null || max == null || min.equals(max)) {
        // empty table, or only one row, return full table scan as a chunk
        return Collections.singletonList(ChunkRange.all());
    }

    final List<ChunkRange> chunks;
    if (splitColumnEvenlyDistributed(splitColumn)) {
        // use evenly-sized chunks which is much efficient
        // note: 按主键均匀划分
        chunks = splitEvenlySizedChunks(min, max);
    } else {
        // note: 按主键非均匀划分
        // use unevenly-sized chunks which will request many queries and is not efficient.
        chunks = splitUnevenlySizedChunks(tableId, splitColumnName, min, max);
    }

    return chunks;
}

/** Checks whether split column is evenly distributed across its range. */
private static boolean splitColumnEvenlyDistributed(Column splitColumn) {
    // only column is auto-incremental are recognized as evenly distributed.
    // TODO: we may use MAX,MIN,COUNT to calculate the distribution in the future.
    if (splitColumn.isAutoIncremented()) {
        DataType flinkType = MySqlTypeUtils.fromDbzColumn(splitColumn);
        LogicalTypeRoot typeRoot = flinkType.getLogicalType().getTypeRoot();
        // currently, we only support split column with type BIGINT, INT, DECIMAL
        return typeRoot == LogicalTypeRoot.BIGINT
                || typeRoot == LogicalTypeRoot.INTEGER
                || typeRoot == LogicalTypeRoot.DECIMAL;
    } else {
        return false;
    }
}


/**
 *  根据拆分列的最小值和最大值将表拆分为大小均匀的块，并以 {@link #chunkSize} 步长滚动块。
 * Split table into evenly sized chunks based on the numeric min and max value of split column,
 * and tumble chunks in {@link #chunkSize} step size.
 */
private List<ChunkRange> splitEvenlySizedChunks(Object min, Object max) {
    if (ObjectUtils.compare(ObjectUtils.plus(min, chunkSize), max) > 0) {
        // there is no more than one chunk, return full table as a chunk
        return Collections.singletonList(ChunkRange.all());
    }

    final List<ChunkRange> splits = new ArrayList<>();
    Object chunkStart = null;
    Object chunkEnd = ObjectUtils.plus(min, chunkSize);
    //  chunkEnd <= max
    while (ObjectUtils.compare(chunkEnd, max) <= 0) {
        splits.add(ChunkRange.of(chunkStart, chunkEnd));
        chunkStart = chunkEnd;
        chunkEnd = ObjectUtils.plus(chunkEnd, chunkSize);
    }
    // add the ending split
    splits.add(ChunkRange.of(chunkStart, null));
    return splits;
}

/**   通过连续计算下一个块最大值，将表拆分为大小不均匀的块。
 * Split table into unevenly sized chunks by continuously calculating next chunk max value. */
private List<ChunkRange> splitUnevenlySizedChunks(
        TableId tableId, String splitColumnName, Object min, Object max) throws SQLException {
    final List<ChunkRange> splits = new ArrayList<>();
    Object chunkStart = null;

    Object chunkEnd = nextChunkEnd(min, tableId, splitColumnName, max);
    int count = 0;
    while (chunkEnd != null && ObjectUtils.compare(chunkEnd, max) <= 0) {
        // we start from [null, min + chunk_size) and avoid [null, min)
        splits.add(ChunkRange.of(chunkStart, chunkEnd));
        // may sleep a while to avoid DDOS on MySQL server
        maySleep(count++);
        chunkStart = chunkEnd;
        chunkEnd = nextChunkEnd(chunkEnd, tableId, splitColumnName, max);
    }
    // add the ending split
    splits.add(ChunkRange.of(chunkStart, null));
    return splits;
}

private Object nextChunkEnd(
        Object previousChunkEnd, TableId tableId, String splitColumnName, Object max)
        throws SQLException {
    // chunk end might be null when max values are removed
    Object chunkEnd =
            queryNextChunkMax(jdbc, tableId, splitColumnName, chunkSize, previousChunkEnd);
    if (Objects.equals(previousChunkEnd, chunkEnd)) {
        // we don't allow equal chunk start and end,
        // should query the next one larger than chunkEnd
        chunkEnd = queryMin(jdbc, tableId, splitColumnName, chunkEnd);
    }
    if (ObjectUtils.compare(chunkEnd, max) >= 0) {
        return null;
    } else {
        return chunkEnd;
    }
}

scss复制代码SingleThreadFetcherManager#addSplits
public void addSplits(List<SplitT> splitsToAdd) {
    SplitFetcher<E, SplitT> fetcher = getRunningFetcher();
    if (fetcher == null) {
        fetcher = createSplitFetcher();
        // Add the splits to the fetchers.
        fetcher.addSplits(splitsToAdd);
        startFetcher(fetcher);
    } else {
        fetcher.addSplits(splitsToAdd);
    }
}

// 创建 SplitFetcher
protected synchronized SplitFetcher<E, SplitT> createSplitFetcher() {
    if (closed) {
        throw new IllegalStateException("The split fetcher manager has closed.");
    }
    // Create SplitReader.
    SplitReader<E, SplitT> splitReader = splitReaderFactory.get();

    int fetcherId = fetcherIdGenerator.getAndIncrement();
    SplitFetcher<E, SplitT> splitFetcher =
            new SplitFetcher<>(
                    fetcherId,
                    elementsQueue,
                    splitReader,
                    errorHandler,
                    () -> {
                        fetchers.remove(fetcherId);
                        elementsQueue.notifyAvailable();
                    });
    fetchers.put(fetcherId, splitFetcher);
    return splitFetcher;
}

public void addSplits(List<SplitT> splitsToAdd) {
    enqueueTask(new AddSplitsTask<>(splitReader, splitsToAdd, assignedSplits));
    wakeUp(true);
}

scss复制代码SplitFetcher#runOnce
void runOnce() {
    try {
        if (shouldRunFetchTask()) {
            runningTask = fetchTask;
        } else {
            runningTask = taskQueue.take();
        }
        
        if (!wakeUp.get() && runningTask.run()) {
            LOG.debug("Finished running task {}", runningTask);
            runningTask = null;
            checkAndSetIdle();
        }
    } catch (Exception e) {
        throw new RuntimeException(
                String.format(
                        "SplitFetcher thread %d received unexpected exception while polling the records",
                        id),
                e);
    }

    maybeEnqueueTask(runningTask);
    synchronized (wakeUp) {
        // Set the running task to null. It is necessary for the shutdown method to avoid
        // unnecessarily interrupt the running task.
        runningTask = null;
        // Set the wakeUp flag to false.
        wakeUp.set(false);
        LOG.debug("Cleaned wakeup flag.");
    }
}

typescript复制代码AddSplitsTask#run
public boolean run() {
    for (SplitT s : splitsToAdd) {
        assignedSplits.put(s.splitId(), s);
    }
    splitReader.handleSplitsChanges(new SplitsAddition<>(splitsToAdd));
    return true;
}
MySqlSplitReader#handleSplitsChanges
public void handleSplitsChanges(SplitsChange<MySqlSplit> splitsChanges) {
    if (!(splitsChanges instanceof SplitsAddition)) {
        throw new UnsupportedOperationException(
                String.format(
                        "The SplitChange type of %s is not supported.",
                        splitsChanges.getClass()));
    }

    //note: 添加切片 到队列。
    splits.addAll(splitsChanges.splits());
}

scss复制代码MySqlSplitReader#fetch
@Override
public RecordsWithSplitIds<SourceRecord> fetch() throws IOException {
    // note: 创建Reader 并读取数据
    checkSplitOrStartNext();

    Iterator<SourceRecord> dataIt = null;
    try {
        // note:  对读取的数据进行修正
        dataIt = currentReader.pollSplitRecords();
    } catch (InterruptedException e) {
        LOG.warn("fetch data failed.", e);
        throw new IOException(e);
    }

    //  note: 返回的数据被封装为 MySqlRecords 进行传输
    return dataIt == null
            ? finishedSnapshotSplit()   
            : MySqlRecords.forRecords(currentSplitId, dataIt);
}

private void checkSplitOrStartNext() throws IOException {
    // the binlog reader should keep alive
    if (currentReader instanceof BinlogSplitReader) {
        return;
    }

    if (canAssignNextSplit()) {
        // note:  从切片队列读取MySqlSplit
        final MySqlSplit nextSplit = splits.poll();
        if (nextSplit == null) {
            throw new IOException("Cannot fetch from another split - no split remaining");
        }

        currentSplitId = nextSplit.splitId();
        // note:  区分全量切片读取还是增量切片读取
        if (nextSplit.isSnapshotSplit()) {
            if (currentReader == null) {
                final MySqlConnection jdbcConnection = getConnection(config);
                final BinaryLogClient binaryLogClient = getBinaryClient(config);

                final StatefulTaskContext statefulTaskContext =
                        new StatefulTaskContext(config, binaryLogClient, jdbcConnection);
                // note: 创建SnapshotSplitReader，使用Debezium Api读取分配数据及区间Binlog值
                currentReader = new SnapshotSplitReader(statefulTaskContext, subtaskId);
            }

        } else {
            // point from snapshot split to binlog split
            if (currentReader != null) {
                LOG.info("It's turn to read binlog split, close current snapshot reader");
                currentReader.close();
            }

            final MySqlConnection jdbcConnection = getConnection(config);
            final BinaryLogClient binaryLogClient = getBinaryClient(config);
            final StatefulTaskContext statefulTaskContext =
                    new StatefulTaskContext(config, binaryLogClient, jdbcConnection);
            LOG.info("Create binlog reader");
            // note: 创建BinlogSplitReader，使用Debezium API进行增量读取
            currentReader = new BinlogSplitReader(statefulTaskContext, subtaskId);
        }
        // note: 执行Reader进行数据读取
        currentReader.submitSplit(nextSplit);
    }
}

scss复制代码public void submitSplit(MySqlSplit mySqlSplit) {
    ......
    executor.submit(
            () -> {
                try {
                    currentTaskRunning = true;
                    // note: 数据读取，在数据前后插入Binlog当前偏移量
                    // 1. execute snapshot read task。 
                    final SnapshotSplitChangeEventSourceContextImpl sourceContext =
                            new SnapshotSplitChangeEventSourceContextImpl();
                    SnapshotResult snapshotResult =
                            splitSnapshotReadTask.execute(sourceContext);

                    //  note: 为增量读取做准备，包含了起始偏移量
                    final MySqlBinlogSplit appendBinlogSplit = createBinlogSplit(sourceContext);
                    final MySqlOffsetContext mySqlOffsetContext =
                            statefulTaskContext.getOffsetContext();
                    mySqlOffsetContext.setBinlogStartPoint(
                            appendBinlogSplit.getStartingOffset().getFilename(),
                            appendBinlogSplit.getStartingOffset().getPosition());

                    //  note: 从起始偏移量开始读取           
                    // 2. execute binlog read task
                    if (snapshotResult.isCompletedOrSkipped()) {
                        // we should only capture events for the current table,
                        Configuration dezConf =
                                statefulTaskContext
                                        .getDezConf()
                                        .edit()
                                        .with(
                                                "table.whitelist",
                                                currentSnapshotSplit.getTableId())
                                        .build();

                        // task to read binlog for current split
                        MySqlBinlogSplitReadTask splitBinlogReadTask =
                                new MySqlBinlogSplitReadTask(
                                        new MySqlConnectorConfig(dezConf),
                                        mySqlOffsetContext,
                                        statefulTaskContext.getConnection(),
                                        statefulTaskContext.getDispatcher(),
                                        statefulTaskContext.getErrorHandler(),
                                        StatefulTaskContext.getClock(),
                                        statefulTaskContext.getTaskContext(),
                                        (MySqlStreamingChangeEventSourceMetrics)
                                                statefulTaskContext
                                                        .getStreamingChangeEventSourceMetrics(),
                                        statefulTaskContext
                                                .getTopicSelector()
                                                .getPrimaryTopic(),
                                        appendBinlogSplit);

                        splitBinlogReadTask.execute(
                                new SnapshotBinlogSplitChangeEventSourceContextImpl());
                    } else {
                        readException =
                                new IllegalStateException(
                                        String.format(
                                                "Read snapshot for mysql split %s fail",
                                                currentSnapshotSplit));
                    }
                } catch (Exception e) {
                    currentTaskRunning = false;
                    LOG.error(
                            String.format(
                                    "Execute snapshot read task for mysql split %s fail",
                                    currentSnapshotSplit),
                            e);
                    readException = e;
                }
            });
}

scss复制代码MySqlBinlogSplitReadTask#handleEvent
protected void handleEvent(Event event) {
	// note: 事件下发 队列
    super.handleEvent(event);
    // note: 全量读取阶段需要终止Binlog读取
    // check do we need to stop for read binlog for snapshot split.
    if (isBoundedRead()) {
        final BinlogOffset currentBinlogOffset =
                new BinlogOffset(
                        offsetContext.getOffset().get(BINLOG_FILENAME_OFFSET_KEY).toString(),
                        Long.parseLong(
                                offsetContext
                                        .getOffset()
                                        .get(BINLOG_POSITION_OFFSET_KEY)
                                        .toString()));
        // note: currentBinlogOffset > HW 停止读取
        // reach the high watermark, the binlog reader should finished
        if (currentBinlogOffset.isAtOrBefore(binlogSplit.getEndingOffset())) {
            // send binlog end event
            try {
                signalEventDispatcher.dispatchWatermarkEvent(
                        binlogSplit,
                        currentBinlogOffset,
                        SignalEventDispatcher.WatermarkKind.BINLOG_END);
            } catch (InterruptedException e) {
                logger.error("Send signal event error.", e);
                errorHandler.setProducerThrowable(
                        new DebeziumException("Error processing binlog signal event", e));
            }
            //  终止binlog读取
            // tell reader the binlog task finished
            ((SnapshotBinlogSplitChangeEventSourceContextImpl) context).finished();
        }
    }
}

csharp复制代码public Iterator<SourceRecord> pollSplitRecords() throws InterruptedException {
    if (hasNextElement.get()) {
        // data input: [low watermark event][snapshot events][high watermark event][binlogevents][binlog-end event]
        // data output: [low watermark event][normalized events][high watermark event]
        boolean reachBinlogEnd = false;
        final List<SourceRecord> sourceRecords = new ArrayList<>();
        while (!reachBinlogEnd) {
            // note: 处理队列中写入的 DataChangeEvent 事件
            List<DataChangeEvent> batch = queue.poll();
            for (DataChangeEvent event : batch) {
                sourceRecords.add(event.getRecord());
                if (RecordUtils.isEndWatermarkEvent(event.getRecord())) {
                    reachBinlogEnd = true;
                    break;
                }
            }
        }
        // snapshot split return its data once
        hasNextElement.set(false);
        //  ************   修正数据  ***********
        return normalizedSplitRecords(currentSnapshotSplit, sourceRecords, nameAdjuster)
                .iterator();
    }
    // the data has been polled, no more data
    reachEnd.compareAndSet(false, true);
    return null;
}

scss复制代码BinlogSplitReader#pollSplitRecords
public Iterator<SourceRecord> pollSplitRecords() throws InterruptedException {
    checkReadException();
    final List<SourceRecord> sourceRecords = new ArrayList<>();
    if (currentTaskRunning) {
        List<DataChangeEvent> batch = queue.poll();
        for (DataChangeEvent event : batch) {
            if (shouldEmit(event.getRecord())) {
                sourceRecords.add(event.getRecord());
            }
        }
    }
    return sourceRecords.iterator();
}

scss复制代码/**
 *
 * Returns the record should emit or not.
 *
 * 
The watermark signal algorithm is the binlog split reader only sends the binlog event that
 * belongs to its finished snapshot splits. For each snapshot split, the binlog event is valid
 * since the offset is after its high watermark.
 *
 * 

 E.g: the data input is :
 *    snapshot-split-0 info : [0,    1024) highWatermark0
 *    snapshot-split-1 info : [1024, 2048) highWatermark1
 *  the data output is:
 *  only the binlog event belong to [0,    1024) and offset is after highWatermark0 should send,
 *  only the binlog event belong to [1024, 2048) and offset is after highWatermark1 should send.
 * 

 */
private boolean shouldEmit(SourceRecord sourceRecord) {
    if (isDataChangeRecord(sourceRecord)) {
        TableId tableId = getTableId(sourceRecord);
        BinlogOffset position = getBinlogPosition(sourceRecord);
        // aligned, all snapshot splits of the table has reached max highWatermark
       
        // note:  新收到的event post 大于 maxwm ,直接下发
        if (position.isAtOrBefore(maxSplitHighWatermarkMap.get(tableId))) {
            return true;
        }
        Object[] key =
                getSplitKey(
                        currentBinlogSplit.getSplitKeyType(),
                        sourceRecord,
                        statefulTaskContext.getSchemaNameAdjuster());

        for (FinishedSnapshotSplitInfo splitInfo : finishedSplitsInfo.get(tableId)) {
            /**
             *  note: 当前 data值所属某个snapshot spilt &  偏移量大于 HWM,下发数据
             */
            if (RecordUtils.splitKeyRangeContains(
                            key, splitInfo.getSplitStart(), splitInfo.getSplitEnd())
                    && position.isAtOrBefore(splitInfo.getHighWatermark())) {
                return true;
            }
        }
        // not in the monitored splits scope, do not emit
        return false;
    }

    // always send the schema change event and signal event
    // we need record them to state of Flink
    return true;
}

kotlin复制代码org.apache.flink.connector.base.source.reader.SourceReaderBase#pollNext
public InputStatus pollNext(ReaderOutput<T> output) throws Exception {
    // make sure we have a fetch we are working on, or move to the next
    RecordsWithSplitIds<E> recordsWithSplitId = this.currentFetch;
    if (recordsWithSplitId == null) {
        recordsWithSplitId = getNextFetch(output);
        if (recordsWithSplitId == null) {
            return trace(finishedOrAvailableLater());
        }
    }

    // we need to loop here, because we may have to go across splits
    while (true) {
        // Process one record.
        // note:  通过MySqlRecords从迭代器中读取单条数据
        final E record = recordsWithSplitId.nextRecordFromSplit();
        if (record != null) {
            // emit the record.
            recordEmitter.emitRecord(record, currentSplitOutput, currentSplitContext.state);
            LOG.trace("Emitted record: {}", record);

            // We always emit MORE_AVAILABLE here, even though we do not strictly know whether
            // more is available. If nothing more is available, the next invocation will find
            // this out and return the correct status.
            // That means we emit the occasional 'false positive' for availability, but this
            // saves us doing checks for every record. Ultimately, this is cheaper.
            return trace(InputStatus.MORE_AVAILABLE);
        } else if (!moveToNextSplit(recordsWithSplitId, output)) {
            // The fetch is done and we just discovered that and have not emitted anything, yet.
            // We need to move to the next fetch. As a shortcut, we call pollNext() here again,
            // rather than emitting nothing and waiting for the caller to call us again.
            return pollNext(output);
        }
        // else fall through the loop
    }
}

private RecordsWithSplitIds<E> getNextFetch(final ReaderOutput<T> output) {
    splitFetcherManager.checkErrors();

    LOG.trace("Getting next source data batch from queue");
    // note: 从elementsQueue 获取数据
    final RecordsWithSplitIds<E> recordsWithSplitId = elementsQueue.poll();
    if (recordsWithSplitId == null || !moveToNextSplit(recordsWithSplitId, output)) {
        return null;
    }

    currentFetch = recordsWithSplitId;
    return recordsWithSplitId;
}

csharp复制代码com.ververica.cdc.connectors.mysql.source.split.MySqlRecords#nextRecordFromSplit

public SourceRecord nextRecordFromSplit() {
    final Iterator<SourceRecord> recordsForSplit = this.recordsForCurrentSplit;
    if (recordsForSplit != null) {
        if (recordsForSplit.hasNext()) {
            return recordsForSplit.next();
        } else {
            return null;
        }
    } else {
        throw new IllegalStateException();
    }
}

scss复制代码com.ververica.cdc.connectors.mysql.source.reader.MySqlRecordEmitter#emitRecord
public void emitRecord(SourceRecord element, SourceOutput<T> output, MySqlSplitState splitState)
    throws Exception {
if (isWatermarkEvent(element)) {
    BinlogOffset watermark = getWatermark(element);
    if (isHighWatermarkEvent(element) && splitState.isSnapshotSplitState()) {
        splitState.asSnapshotSplitState().setHighWatermark(watermark);
    }
} else if (isSchemaChangeEvent(element) && splitState.isBinlogSplitState()) {
    HistoryRecord historyRecord = getHistoryRecord(element);
    Array tableChanges =
            historyRecord.document().getArray(HistoryRecord.Fields.TABLE_CHANGES);
    TableChanges changes = TABLE_CHANGE_SERIALIZER.deserialize(tableChanges, true);
    for (TableChanges.TableChange tableChange : changes) {
        splitState.asBinlogSplitState().recordSchema(tableChange.getId(), tableChange);
    }
} else if (isDataChangeRecord(element)) {
    //  note: 数据的处理
    if (splitState.isBinlogSplitState()) {
        BinlogOffset position = getBinlogPosition(element);
        splitState.asBinlogSplitState().setStartingOffset(position);
    }
    debeziumDeserializationSchema.deserialize(
            element,
            new Collector<T>() {
                @Override
                public void collect(final T t) {
                    output.collect(t);
                }

                @Override
                public void close() {
                    // do nothing
                }
            });
} else {
    // unknown element
    LOG.info("Meet unknown element {}, just skip.", element);
}
}

ini复制代码com.ververica.cdc.debezium.table.RowDataDebeziumDeserializeSchema#deserialize
public void deserialize(SourceRecord record, Collector<RowData> out) throws Exception {
    Envelope.Operation op = Envelope.operationFor(record);
    Struct value = (Struct) record.value();
    Schema valueSchema = record.valueSchema();
    if (op == Envelope.Operation.CREATE || op == Envelope.Operation.READ) {
        GenericRowData insert = extractAfterRow(value, valueSchema);
        validator.validate(insert, RowKind.INSERT);
        insert.setRowKind(RowKind.INSERT);
        out.collect(insert);
    } else if (op == Envelope.Operation.DELETE) {
        GenericRowData delete = extractBeforeRow(value, valueSchema);
        validator.validate(delete, RowKind.DELETE);
        delete.setRowKind(RowKind.DELETE);
        out.collect(delete);
    } else {
        GenericRowData before = extractBeforeRow(value, valueSchema);
        validator.validate(before, RowKind.UPDATE_BEFORE);
        before.setRowKind(RowKind.UPDATE_BEFORE);
        out.collect(before);

        GenericRowData after = extractAfterRow(value, valueSchema);
        validator.validate(after, RowKind.UPDATE_AFTER);
        after.setRowKind(RowKind.UPDATE_AFTER);
        out.collect(after);
    }
}

scss复制代码com.ververica.cdc.connectors.mysql.source.reader.MySqlSourceReader#onSplitFinished
protected void onSplitFinished(Map<String, MySqlSplitState> finishedSplitIds) {
for (MySqlSplitState mySqlSplitState : finishedSplitIds.values()) {
    MySqlSplit mySqlSplit = mySqlSplitState.toMySqlSplit();

    finishedUnackedSplits.put(mySqlSplit.splitId(), mySqlSplit.asSnapshotSplit());
}
/**
 *   note: 发送切片完成事件
 */
reportFinishedSnapshotSplitsIfNeed();

//  上一个spilt处理完成后继续发送切片请求
context.sendSplitRequest();
}

private void reportFinishedSnapshotSplitsIfNeed() {
    if (!finishedUnackedSplits.isEmpty()) {
        final Map<String, BinlogOffset> finishedOffsets = new HashMap<>();
        for (MySqlSnapshotSplit split : finishedUnackedSplits.values()) {
            // note: 发送切片ID，及最大偏移量
            finishedOffsets.put(split.splitId(), split.getHighWatermark());
        }
        FinishedSnapshotSplitsReportEvent reportEvent =
                new FinishedSnapshotSplitsReportEvent(finishedOffsets);

        context.sendSourceEventToCoordinator(reportEvent);
        LOG.debug(
                "The subtask {} reports offsets of finished snapshot splits {}.",
                subtaskId,
                finishedOffsets);
    }
}

ini复制代码private MySqlBinlogSplit createBinlogSplit() {
    final List<MySqlSnapshotSplit> assignedSnapshotSplit =
            snapshotSplitAssigner.getAssignedSplits().values().stream()
                    .sorted(Comparator.comparing(MySqlSplit::splitId))
                    .collect(Collectors.toList());

    Map<String, BinlogOffset> splitFinishedOffsets =
            snapshotSplitAssigner.getSplitFinishedOffsets();
    final List<FinishedSnapshotSplitInfo> finishedSnapshotSplitInfos = new ArrayList<>();
    final Map<TableId, TableChanges.TableChange> tableSchemas = new HashMap<>();

    BinlogOffset minBinlogOffset = null;
    // note: 从所有assignedSnapshotSplit中筛选最小偏移量
    for (MySqlSnapshotSplit split : assignedSnapshotSplit) {
        // find the min binlog offset
        BinlogOffset binlogOffset = splitFinishedOffsets.get(split.splitId());
        if (minBinlogOffset == null || binlogOffset.compareTo(minBinlogOffset) < 0) {
            minBinlogOffset = binlogOffset;
        }
        finishedSnapshotSplitInfos.add(
                new FinishedSnapshotSplitInfo(
                        split.getTableId(),
                        split.splitId(),
                        split.getSplitStart(),
                        split.getSplitEnd(),
                        binlogOffset));
        tableSchemas.putAll(split.getTableSchemas());
    }

    final MySqlSnapshotSplit lastSnapshotSplit =
            assignedSnapshotSplit.get(assignedSnapshotSplit.size() - 1).asSnapshotSplit();
   	
    return new MySqlBinlogSplit(
            BINLOG_SPLIT_ID,
            lastSnapshotSplit.getSplitKeyType(),
            minBinlogOffset == null ? BinlogOffset.INITIAL_OFFSET : minBinlogOffset,
            BinlogOffset.NO_STOPPING_OFFSET,
            finishedSnapshotSplitInfos,
            tableSchemas);
}

properties复制代码spring.rabbitmq.host=localhost
spring.rabbitmq.username=guest
spring.rabbitmq.password=guest
spring.rabbitmq.port=5672

java复制代码@Configuration
public class QueueConfig {
    public static final String JAVABOY_QUEUE_NAME = "javaboy_queue_name";
    public static final String JAVABOY_EXCHANGE_NAME = "javaboy_exchange_name";
    public static final String JAVABOY_ROUTING_KEY = "javaboy_routing_key";
    public static final String DLX_QUEUE_NAME = "dlx_queue_name";
    public static final String DLX_EXCHANGE_NAME = "dlx_exchange_name";
    public static final String DLX_ROUTING_KEY = "dlx_routing_key";

    /**
     * 死信队列
     * @return
     */
    @Bean
    Queue dlxQueue() {
        return new Queue(DLX_QUEUE_NAME, true, false, false);
    }

    /**
     * 死信交换机
     * @return
     */
    @Bean
    DirectExchange dlxExchange() {
        return new DirectExchange(DLX_EXCHANGE_NAME, true, false);
    }

    /**
     * 绑定死信队列和死信交换机
     * @return
     */
    @Bean
    Binding dlxBinding() {
        return BindingBuilder.bind(dlxQueue()).to(dlxExchange())
                .with(DLX_ROUTING_KEY);
    }

    /**
     * 普通消息队列
     * @return
     */
    @Bean
    Queue javaboyQueue() {
        Map<String, Object> args = new HashMap<>();
        //设置消息过期时间
        args.put("x-message-ttl", 1000*10);
        //设置死信交换机
        args.put("x-dead-letter-exchange", DLX_EXCHANGE_NAME);
        //设置死信 routing_key
        args.put("x-dead-letter-routing-key", DLX_ROUTING_KEY);
        return new Queue(JAVABOY_QUEUE_NAME, true, false, false, args);
    }

    /**
     * 普通交换机
     * @return
     */
    @Bean
    DirectExchange javaboyExchange() {
        return new DirectExchange(JAVABOY_EXCHANGE_NAME, true, false);
    }

    /**
     * 绑定普通队列和与之对应的交换机
     * @return
     */
    @Bean
    Binding javaboyBinding() {
        return BindingBuilder.bind(javaboyQueue())
                .to(javaboyExchange())
                .with(JAVABOY_ROUTING_KEY);
    }
}

java复制代码@Component
public class DlxConsumer {
    private static final Logger logger = LoggerFactory.getLogger(DlxConsumer.class);

    @RabbitListener(queues = QueueConfig.DLX_QUEUE_NAME)
    public void handle(String msg) {
        logger.info(msg);
    }
}

java复制代码@SpringBootTest
class DelayQueueApplicationTests {

    @Autowired
    RabbitTemplate rabbitTemplate;

    @Test
    void contextLoads() {
        System.out.println(new Date());
        rabbitTemplate.convertAndSend(QueueConfig.JAVABOY_EXCHANGE_NAME, QueueConfig.JAVABOY_ROUTING_KEY, "hello javaboy!");
    }

}

js复制代码         // 父类(我就不写成父构造函数了,这样比较简洁)
        function Father(name, age) {
            (this.name = name), (this.age = age), (this.arr = [1, 2, 3]), (this.value = 33)
        }
        Father.prototype = {
            say() {
                alert('hellow')
            },
        }
        // 子类
        function Child(name, age) {
            ;
            (this.name = name), (this.age = age)
        }

        Child.prototype = new Father() // 核心实现代码--->父类的实例作为子类的原型对象
        
        // 创建实例并让constructor重新指回Child
        let newChild = new Child('zkp')
        newChild.constructor =Child  
        let newChild2 = new Child('zhy')
        newChild.constructor =Child

        // 两个不同的子类实例上都有父类里的属性和方法
        console.log(newChild.arr) //  [1, 2, 3]
        console.log(newChild2.arr) //  [1, 2, 3]
        console.log(newChild.value) // 33
        console.log(newChild2.value) // 33

        // 在一个子类实例身上修改继承的父类的基础属性值,不会影响到其他子类实例
        newChild.value = 55
        console.log(newChild.value) // 55
        console.log(newChild2.value) // 33

        // 致命缺陷: 在一个子类实例身上修改继承父类的引用属性值,其他子类实例其他子类实例的值也会跟着改变
        newChild.arr.push(100)
        console.log(newChild.arr) // [1, 2, 3 , 100]
        console.log(newChild2.arr) // [1, 2, 3 , 100]

js复制代码         // 父类
        function Father(name, age) {
            this.name = name,
            this.age =age,
            this.arr= [2, 3, 4, 5, 6]
        }
        Father.prototype = {
            say() {
                alert('hellow');
            },
        }
        // 子类
        function Child(name, age) {
            Father.call(this, name, age)  // 核心代码--->在子类中利用call()调用父类并向父类传参
        }

        let newChild = new Child('zkp', 11)  
        let newChild2 = new Child('zhy', 6)
        // 子类实例修改父类引用属性 其他子类实例上该属性不会改变
        newChild.arr.push(100)  
        console.log(newChild.arr); // [2, 3, 4, 5, 6, 100]
        console.log(newChild2.arr); // [2, 3, 4, 5, 6]

        // newChild.say() //  newChild.say is not a function  报错 只是继承了父类的构造函数 无法使用父类的原型方法

js复制代码        // 父类
        function Father(name, age) {
            this.name = 'hahaha',
            this.age = 11,
            this.arr = [2, 3, 4, 5, 6]
        }
        Father.prototype = {
            say() {
                alert('hellow');
            },
        }
        // 子类继承步骤:
        function Child(name, age) {
            Father.call(this, name, age) // 1.call方法调用父类的构造函数 并改变this的指向为子类函数(实现传参) 
        }
        // 2.子构造函数的原型对象指向父构造函数的实例 
        Child.prototype = new Father()
        
        // 3.创建实例并让constructor重新指回Child
        let newChild = new Child('zkp',12)
        newChild.constructor =Child  
        let newChild2 = new Child('zhy',6)
        newChild2.constructor =Child  
        
        newChild.say() // alert ('hellow') 页面弹出hellow  子函数的实例继承了父函数的原型中的方法
        console.log(newChild.name); // hahaha  子类的实例可以向父类传参
        
        // 一个子类实例修改引用类型属性 其他实例该引用类型不会改变
        newChild.arr.push(100)
        console.log(newChild.arr,newChild2.arr); // [2, 3, 4, 5, 6, 100] ,[2, 3, 4, 5, 6]
        // 缺点:父类的构造函数会被调用两次 call方法调用一次 new Father 一次

js复制代码        // 创建对象obj
        let obj = {a:1 , b:2 , c:[1,2,3]}
        
        // 在函数中把一个对象作为一个空构造函数的原型对象 并返回该构造函数的调用
        function CreateObj(o) {
            function F() {}
            F.prototype = o;
            return new F();
        }
        let newObj = CreateObj(obj);
        let newObj2=CreateObj(obj)

        //新创建的对象拥有obj的属性和方法
        console.log(newObj.a , newObj.b , newObj.c); // 1 , 2 , [1, 2, 3]
        console.log(newObj2.a , newObj2.b , newObj2.c); // 1 , 2 , [1, 2, 3]

        // 通过一个实例修改引用类型值 其他实例也会被改变
        newObj.c.push(100)
        console.log(newObj2.a , newObj2.b , newObj2.c); // 1 , 2 ,  [1, 2, 3, 100]
        console.log(newObj.a , newObj.b , newObj.c); // 1 , 2 ,  [1, 2, 3, 100]

js复制代码 let obj = {
                a: 1,
                b: [1, 2, 3],
                c() {
                    alert('hellow')
                },
            }

            function CreateObj(o) {
                function F() {}
                F.prototype = o
                return new F()
            }
            // 寄生继承就是在原型继承的基础上再封装 给队象增加方法和属性(对象增强) 实际上跟原型式继承是一样的
            function CreateChild(o) {
                let newObj = CreateObj(o) // 创建对象 或者用 var newObj = Object.create(o)
                // 增强对象
                newObj.x = function () {
                    alert('这是给新对象增强的方法')
                }),
                newObj.y = 'biubiu~'
                ......
                return newObj
            }

            let p = CreateChild(obj)
            p.x()  //弹出信息
            console.log(p.y)     // biubiu~
            console.log(p.a, p.b)    // 1 , [1 , 2 , 3]

js复制代码            //1. 父类 实例属性放在构造函数中
            function Father(name, age) {
                this.name = name
                this.age = age
                this.hobby = ['敲代码', '解Bug', '睡觉']
            }
            // 父类方法放在原型上实现复用
            Father.prototype.sayName = function () {
                console.log(this.name, this.age, 666)
            }

            //2. 子类
            function Child(name, age) {
                Father.call(this, name, age) // 调用父类的构造函数 (继承父类的属性)
                this.a = 1
            }

            // 3. 利用跳板创建对象
            function CreateObj(o) {
                function F() {}
                F.prototype = o
                return new F()
            }

            // 4.子类的原型对象用CreateObj(Father)创建
            Child.prototype = CreateObj(Father.prototype)
            console.log(Child.prototype.__proto__ === Father.prototype) // true 实现对Child.prototype = new Father的改造

            /* 或者直接把3,4写成es5中的Object.create() 一行代码实现
            Child.prototype = Object.create(Father.prototype) */

            // 5.创建子类实例 constructor属性指回子类
            let zkp = new Child('zkp', 12)
            zkp.constructor = Child
            let zhy = new Child('zhy', 6)
            zhy.constructor = Child
            
            // 验证:
            console.log(zkp.a , zhy.a) // 1 , 1  子类自己的属性
            // 一个子类实例修改继承的引用类型属性 其他实例不会被改变
            zkp.hobby.push('吃饭')
            console.log(zkp.name, zkp.age, zkp.hobby) // zkp , 12 , ['敲代码', '解Bug', '睡觉', '吃饭']
            console.log(zhy.name, zhy.age, zhy.hobby) // zhy , 6 , ['敲代码', '解Bug', '睡觉']
            // 子类调用父类的原型方法
            zkp.sayName() // zkp 666
            zhy.sayName() // zhy 666

js复制代码           //1. 父类 实例属性放在构造函数中
            function Father(name, age) {
                this.name = name
                this.age = age
                this.hobby = ['敲代码', '解Bug', '睡觉']
            }
            // 父类方法放在原型上实现复用
            Father.prototype.sayName = function () {
                console.log(this.name, 666)
            }
            Father.prototype.x = 1
               //2. 子类
            function Child(name, age) {
                Father.call(this, name, age) // 调用父类的构造函数 (继承父类的属性)
                this.a = 1
            }
            Child.prototype = Object.create(Father.prototype)

scss复制代码public char charAt(int index) {
    if ((index < 0) || (index >= value.length)) {
        throw new StringIndexOutOfBoundsException(index);
    }
    return value[index];
}

arduino复制代码public void getChars(int srcBegin, int srcEnd, char dst[], int dstBegin) {
    if (srcBegin < 0) {
        throw new StringIndexOutOfBoundsException(srcBegin);
    }
    if (srcEnd > value.length) {
        throw new StringIndexOutOfBoundsException(srcEnd);
    }
    if (srcBegin > srcEnd) {
        throw new StringIndexOutOfBoundsException(srcEnd - srcBegin);
    }
    System.arraycopy(value, srcBegin, dst, dstBegin, srcEnd - srcBegin);
}

ini复制代码public int compareTo(String anotherString) {
    int len1 = value.length;
    int len2 = anotherString.value.length;
    int lim = Math.min(len1, len2);
    char v1[] = value;
    char v2[] = anotherString.value;

    int k = 0;
    while (k < lim) {
        char c1 = v1[k];
        char c2 = v2[k];
        if (c1 != c2) {
            return c1 - c2;
        }
        k++;
    }
    return len1 - len2;
}

ini复制代码public int hashCode() {
    int h = hash;
    if (h == 0 && value.length > 0) {
        char val[] = value;

        for (int i = 0; i < value.length; i++) {
            h = 31 * h + val[i];
        }
        hash = h;
    }
    return h;
}

arduino复制代码public int indexOf(int ch, int fromIndex) {
    final int max = value.length;
    if (fromIndex < 0) {
        fromIndex = 0;
    } else if (fromIndex >= max) {
        // Note: fromIndex might be near -1>>>1.
        return -1;
    }

    if (ch < Character.MIN_SUPPLEMENTARY_CODE_POINT) {
        // handle most cases here (ch is a BMP code point or a
        // negative value (invalid code point))
        final char[] value = this.value;
        for (int i = fromIndex; i < max; i++) {
            if (value[i] == ch) {
                return i;
            }
        }
        return -1;
    } else {
        return indexOfSupplementary(ch, fromIndex);
    }
}

arduino复制代码public int lastIndexOf(int ch, int fromIndex) {
    if (ch < Character.MIN_SUPPLEMENTARY_CODE_POINT) {
        // handle most cases here (ch is a BMP code point or a
        // negative value (invalid code point))
        final char[] value = this.value;
        int i = Math.min(fromIndex, value.length - 1);
        for (; i >= 0; i--) {
            if (value[i] == ch) {
                return i;
            }
        }
        return -1;
    } else {
        return lastIndexOfSupplementary(ch, fromIndex);
    }
}

arduino复制代码public String substring(int beginIndex) {
    if (beginIndex < 0) {
        throw new StringIndexOutOfBoundsException(beginIndex);
    }
    int subLen = value.length - beginIndex;
    if (subLen < 0) {
        throw new StringIndexOutOfBoundsException(subLen);
    }
    return (beginIndex == 0) ? this : new String(value, beginIndex, subLen);
}


public String substring(int beginIndex, int endIndex) {
    if (beginIndex < 0) {
        throw new StringIndexOutOfBoundsException(beginIndex);
    }
    if (endIndex > value.length) {
        throw new StringIndexOutOfBoundsException(endIndex);
    }
    int subLen = endIndex - beginIndex;
    if (subLen < 0) {
        throw new StringIndexOutOfBoundsException(subLen);
    }
    return ((beginIndex == 0) && (endIndex == value.length)) ? this
            : new String(value, beginIndex, subLen);
}

ini复制代码public String concat(String str) {
    int otherLen = str.length();
    if (otherLen == 0) {
        return this;
    }
    int len = value.length;
    char buf[] = Arrays.copyOf(value, len + otherLen);
    str.getChars(buf, len);
    return new String(buf, true);
}

ini复制代码public String replace(char oldChar, char newChar) {
    if (oldChar != newChar) {
        int len = value.length;
        int i = -1;
        char[] val = value; /* avoid getfield opcode */

        while (++i < len) {
            if (val[i] == oldChar) {
                break;
            }
        }
        if (i < len) {
            char buf[] = new char[len];
            for (int j = 0; j < i; j++) {
                buf[j] = val[j];
            }
            while (i < len) {
                char c = val[i];
                buf[i] = (c == oldChar) ? newChar : c;
                i++;
            }
            return new String(buf, true);
        }
    }
    return this;
}

typescript复制代码public boolean contains(CharSequence s) {
    return indexOf(s.toString()) > -1;
}

ini复制代码public String trim() {
    int len = value.length;
    int st = 0;
    char[] val = value;    /* avoid getfield opcode */

    while ((st < len) && (val[st] <= ' ')) {
        st++;
    }
    while ((st < len) && (val[len - 1] <= ' ')) {
        len--;
    }
    return ((st > 0) || (len < value.length)) ? substring(st, len) : this;
}

python复制代码pip install opencv-python

python复制代码import cv2
import matplotlib.pyplot as plt # 用于绘制图像

python复制代码# 加载级联
face_cascade = cv2.CascadeClassifier('haarcascade_frontalface_default.xml')

python复制代码# 读取输入图像
img = cv2.imread('test.png')

# 检测人脸
faces = face_cascade.detectMultiScale(image = img, scaleFactor = 1.1, minNeighbors = 5)

# 在人脸周围绘制边界框
for (x, y, w, h) in faces:
      cv2.rectangle(img, (x, y), (x+w, y+h), (255, 0, 0), 2)

# 显示图像中检测到的人脸数量
print(len(faces),"faces detected!")

# 绘制检测到人脸的图像
finalimg = cv2.cvtColor(img, cv2.COLOR_RGB2BGR)
plt.figure(figsize=(12,12))
plt.imshow(finalimg) 
plt.axis("off")
plt.show()