python复制代码import requests
r = requests.get("http://www.baidu.com")

print(type(r))  # <class 'requests.models.Response'>
print(r.status_code) # 200
print(r.url)     # http://www.baidu.com/
print(r.headers)   #{'Cache-Control': 'private, no-cache, no-store, proxy-revalidate, no-transform', 'Connection': 'keep-alive', 'Content-Encoding': 'gzip', 'Content-Type': 'text/html', 'Date': 'Thu, 25 Nov 2021 08:56:15 GMT', 'Last-Modified': 'Mon, 23 Jan 2017 13:27:52 GMT', 'Pragma': 'no-cache', 'Server': 'bfe/1.0.8.18', 'Set-Cookie': 'BDORZ=27315; max-age=86400; domain=.baidu.com; path=/', 'Transfer-Encoding': 'chunked'}
print(r.cookies)   # <RequestsCookieJar[<Cookie BDORZ=27315 for .baidu.com/>]>
print(r.content) # 网页内容  
print(type(r.content))  # <class 'bytes'>
print(r.text)   # 网页内容
print(type(r.text))    # <class 'str'>
print(r.history)      # []
print(r.encoding)     # ISO-8859-1
print(r.is_redirect)  # 是否重定向 False
print(r.links)    # 子链接 {}

python复制代码import requests

data = {"name":"waws","age":18}
headers = {"User-Agent": "Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0);"}
url = "http://httpbin.org/get"
req = requests.get(url,params=data,headers=headers)
# 标准解析格式
print(req.content.decode("utf8","ignore"))

# json解析获得字典
print(req.json())  # {'args': {'age': '18', 'name': 'waws'}, 'headers': {'Accept': '*/*', 'Accept-Encoding': 'gzip, deflate', 'Host': 'httpbin.org', 'User-Agent': 'Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0);', 'X-Amzn-Trace-Id': 'Root=1-619f5084-5a1b4b6a2c4332e12ee045ab'}, 'origin': 'xxx.xxx.xxx.xx', 'url': 'http://httpbin.org/get?name=waws&age=18'
print(type(req.json()))  # <class 'dict'>

json复制代码{
  "args": {
    "age": "18", 
    "name": "waws"
  }, 
  "headers": {
    "Accept": "*/*", 
    "Accept-Encoding": "gzip, deflate", 
    "Host": "httpbin.org", 
    "User-Agent": "Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0);", 
    "X-Amzn-Trace-Id": "Root=1-619f5084-5a1b4b6a2c4332e12ee045ab"
  }, 
  "origin": "xxx.x.xxx.xxx", 
  "url": "http://httpbin.org/get?name=waws&age=18"
}

python复制代码import requests
data = {"user":"admin","pwd":"admin"}
headers = {"User-Agent": "Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0);"}
url = "https://httpbin.org/post"
req = requests.post(url,data=data,headers=headers)
print(req.content.decode("utf8","ignore"))

json复制代码{
  "args": {}, 
  "data": "", 
  "files": {}, 
  "form": {
    "pwd": "admin", 
    "user": "admin"
  }, 
  "headers": {
    "Accept": "*/*", 
    "Accept-Encoding": "gzip, deflate", 
    "Content-Length": "20", 
    "Content-Type": "application/x-www-form-urlencoded", 
    "Host": "httpbin.org", 
    "User-Agent": "Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0);", 
    "X-Amzn-Trace-Id": "Root=1-619f5125-26e1e1e526026c547bb269ed"
  }, 
  "json": null, 
  "origin": "xxx.xxx.xxx.xx", 
  "url": "https://httpbin.org/post"
}

arduino复制代码final类型的类如何拓展？
设计模式中最重要的两种关系，一种是继承/实现；另外一种是组合关系。所以当遇到不能继承的（final修饰的类），考虑用组合。

arduino复制代码public class Test {
    //编译期常量
    final int i = 1;
    final static int J = 1;
    final int[] a = {1,2,3,4};
    //非编译期常量
    Random r = new Random();
    final int k = r.nextInt();

    public static void main(String[] args) {

    }
}

java复制代码import java.util.Random;
public class Test {
    static Random r = new Random();
    final int k = r.nextInt(10);
    static final int k2 = r.nextInt(10); 
    public static void main(String[] args) {
        Test t1 = new Test();
        System.out.println("k="+t1.k+" k2="+t1.k2);
        Test t2 = new Test();
        System.out.println("k="+t2.k+" k2="+t2.k2);
    }
}

ini复制代码k=2 k2=7
k=8 k2=7

csharp复制代码public class FinalDemo {
    private int a;  //普通域
    private final int b; //final域
    private static FinalDemo finalDemo;

    public FinalDemo() {
        a = 1; // 1. 写普通域
        b = 2; // 2. 写final域
    }

    public static void writer() {
        finalDemo = new FinalDemo();
    }

    public static void reader() {
        FinalDemo demo = finalDemo; // 3.读对象引用
        int a = demo.a;    //4.读普通域
        int b = demo.b;    //5.读final域
    }
}

csharp复制代码public class FinalReferenceDemo {
    final int[] arrays;
    private FinalReferenceDemo finalReferenceDemo;

    public FinalReferenceDemo() {
        arrays = new int[1];  //1
        arrays[0] = 1;        //2
    }

    public void writerOne() {
        finalReferenceDemo = new FinalReferenceDemo(); //3
    }

    public void writerTwo() {
        arrays[0] = 2;  //4
    }

    public void reader() {
        if (finalReferenceDemo != null) {  //5
            int temp = finalReferenceDemo.arrays[0];  //6
        }
    }
}

java复制代码    public static void sort(int[] array) {
        //循环计数
        int count = 0;
        //数据交换临时变量
        int tmp = 0;
        for (int i = 0; i < array.length / 2; i++) {
            System.out.println("第" + (++count) + "次循环");
            //每轮的初始值都是true，有序标记：true代表有序
            boolean isSorted = true;
            //奇数轮，从左向右比较和交换
            for (int j = i; j < array.length - i - 1; j++) {
​
                if (array[j] > array[j + 1]) {
                    tmp = array[j];
                    array[j] = array[j + 1];
                    array[j + 1] = tmp;
                    //发生交换，不是有序，标记改成false
                    isSorted = false;
                }
            }
            //是否有序
            if (isSorted) {
                break;
            }
            //在偶数轮之前，将isSorted重新标记为true
            isSorted = true;
            System.out.println("第" + (++count) + "次循环");
            //偶数轮，方向从右向左比较和交换
            for (int j = array.length - i - 1; j > i; j--) {
                if (array[j] < array[j - 1]) {
                    tmp = array[j];
                    array[j] = array[j - 1];
                    array[j - 1] = tmp;
                    isSorted = false;
                }
            }
            //是否有序
            if (isSorted) {
                break;
            }
        }
    }

java复制代码第1次循环
第2次循环
第3次循环
[1, 2, 3, 4, 5, 6, 7, 8]

ini复制代码
Arrays.sort(nums1);
Arrays.sort(nums2);
int length1 = nums1.length, length2 = nums2.length;
int[] intersection = new int[Math.min(length1, length2)];
int index1 = 0, index2 = 0, index = 0;
while (index1 < length1 && index2 < length2) {
    if (nums1[index1] < nums2[index2]) {
        index1++;
    } else if (nums1[index1] > nums2[index2]) {
        index2++;
    } else {
        intersection[index] = nums1[index1];
        index1++;
        index2++;
        index++;
    }
}
return Arrays.copyOfRange(intersection, 0, index);

kotlin复制代码// Use Quicksort on small arrays
if (right - left < QUICKSORT_THRESHOLD)
{
       //QUICKSORT_THRESHOLD = 286
        sort(a, left, right, true);
        return;
 }

scss复制代码// Use insertion sort on tiny arrays
if (length < INSERTION_SORT_THRESHOLD)
{
    if (leftmost)
    {
        ......

css复制代码/*
 * Traditional (without sentinel) insertion sort,
 * optimized for server VM, is used in case of
 * the leftmost part.
 */
for (int i = left, j = i; i < right; j = ++i)
{
     int ai = a[i + 1];
     while (ai < a[j])
     {
          a[j + 1] = a[j];
          if (j-- == left)
          {
               break;
           }
      }
      a[j + 1] = ai;

css复制代码
// Check if the array is nearly sorted
    for (int k = left; k < right; run[count] = k) {        if (a[k] < a[k + 1]) { // ascending
            while (++k <= right && a[k - 1] <= a[k]);
        } else if (a[k] > a[k + 1]) { // descending
            while (++k <= right && a[k - 1] >= a[k]);            for (int lo = run[count] - 1, hi = k; ++lo < --hi; ) {                int t = a[lo]; a[lo] = a[hi]; a[hi] = t;
            }
        } else { // equal
            for (int m = MAX_RUN_LENGTH; ++k <= right && a[k - 1] == a[k]; ) {                if (--m == 0) {
                    sort(a, left, right, true);                    return;
                }
            }
        }        /*
         * The array is not highly structured,
         * use Quicksort instead of merge sort.
         */
        if (++count == MAX_RUN_COUNT) {
            sort(a, left, right, true);            return;
        }
    }

c复制代码#include "stdio.h"
#include "string.h"

int main(void) {
    char *a = "red\0is";
    char *b = "redis\0";
    printf("%lu\n", strlen(a));
    printf("%lu\n", strlen(b));
}

shell复制代码redis> SET msg "hello world"
OK

bash复制代码redis> RPUSH fruits "apple" "banana" "cherry"
(integer) 3

c复制代码typedef char *sds;

c复制代码/* Note: sdshdr5 is never used, we just access the flags byte directly.
 * However is here to document the layout of type 5 SDS strings. */
struct __attribute__ ((__packed__)) sdshdr5 {
    unsigned char flags; /* 3 lsb of type, and 5 msb of string length */
    char buf[];
};
struct __attribute__ ((__packed__)) sdshdr8 {
    uint8_t len; /* used */
    uint8_t alloc; /* excluding the header and null terminator */
    unsigned char flags; /* 3 lsb of type, 5 unused bits */
    char buf[];
};
struct __attribute__ ((__packed__)) sdshdr16 {
    uint16_t len; /* used */
    uint16_t alloc; /* excluding the header and null terminator */
    unsigned char flags; /* 3 lsb of type, 5 unused bits */
    char buf[];
};
struct __attribute__ ((__packed__)) sdshdr32 {
    uint32_t len; /* used */
    uint32_t alloc; /* excluding the header and null terminator */
    unsigned char flags; /* 3 lsb of type, 5 unused bits */
    char buf[];
};
struct __attribute__ ((__packed__)) sdshdr64 {
    uint64_t len; /* used */
    uint64_t alloc; /* excluding the header and null terminator */
    unsigned char flags; /* 3 lsb of type, 5 unused bits */
    char buf[];
};

c复制代码static inline size_t sdslen(const sds s) {
    unsigned char flags = s[-1];
    switch(flags&SDS_TYPE_MASK) {
        case SDS_TYPE_5:
            return SDS_TYPE_5_LEN(flags);
        case SDS_TYPE_8:
            return SDS_HDR(8,s)->len;
        case SDS_TYPE_16:
            return SDS_HDR(16,s)->len;
        case SDS_TYPE_32:
            return SDS_HDR(32,s)->len;
        case SDS_TYPE_64:
            return SDS_HDR(64,s)->len;
    }
    return 0;
}

c复制代码static inline size_t sdsavail(const sds s) {
    unsigned char flags = s[-1];
    switch(flags&SDS_TYPE_MASK) {
        case SDS_TYPE_5: {
            return 0;
        }
        case SDS_TYPE_8: {
            SDS_HDR_VAR(8,s);
            return sh->alloc - sh->len;
        }
        case SDS_TYPE_16: {
            SDS_HDR_VAR(16,s);
            return sh->alloc - sh->len;
        }
        case SDS_TYPE_32: {
            SDS_HDR_VAR(32,s);
            return sh->alloc - sh->len;
        }
        case SDS_TYPE_64: {
            SDS_HDR_VAR(64,s);
            return sh->alloc - sh->len;
        }
    }
    return 0;
}

c复制代码sds sdsnewlen(const void *init, size_t initlen);
sds sdstrynewlen(const void *init, size_t initlen);
sds sdsnew(const char *init);
sds sdsempty(void);
sds sdsdup(const sds s);
void sdsfree(sds s);
sds sdsgrowzero(sds s, size_t len);
sds sdscatlen(sds s, const void *t, size_t len);
sds sdscat(sds s, const char *t);
sds sdscatsds(sds s, const sds t);
sds sdscpylen(sds s, const char *t, size_t len);
sds sdscpy(sds s, const char *t);

sds sdscatvprintf(sds s, const char *fmt, va_list ap);
#ifdef __GNUC__
sds sdscatprintf(sds s, const char *fmt, ...)
    __attribute__((format(printf, 2, 3)));
#else
sds sdscatprintf(sds s, const char *fmt, ...);
#endif

sds sdscatfmt(sds s, char const *fmt, ...);
sds sdstrim(sds s, const char *cset);
void sdssubstr(sds s, size_t start, size_t len);
void sdsrange(sds s, ssize_t start, ssize_t end);
void sdsupdatelen(sds s);
void sdsclear(sds s);
int sdscmp(const sds s1, const sds s2);
sds *sdssplitlen(const char *s, ssize_t len, const char *sep, int seplen, int *count);
void sdsfreesplitres(sds *tokens, int count);
void sdstolower(sds s);
void sdstoupper(sds s);
sds sdsfromlonglong(long long value);
sds sdscatrepr(sds s, const char *p, size_t len);
sds *sdssplitargs(const char *line, int *argc);
sds sdsmapchars(sds s, const char *from, const char *to, size_t setlen);
sds sdsjoin(char **argv, int argc, char *sep);
sds sdsjoinsds(sds *argv, int argc, const char *sep, size_t seplen);

/* Callback for sdstemplate. The function gets called by sdstemplate
 * every time a variable needs to be expanded. The variable name is
 * provided as variable, and the callback is expected to return a
 * substitution value. Returning a NULL indicates an error.
 */
typedef sds (*sdstemplate_callback_t)(const sds variable, void *arg);
sds sdstemplate(const char *template, sdstemplate_callback_t cb_func, void *cb_arg);

/* Low level functions exposed to the user API */
sds sdsMakeRoomFor(sds s, size_t addlen);
void sdsIncrLen(sds s, ssize_t incr);
sds sdsRemoveFreeSpace(sds s);
size_t sdsAllocSize(sds s);
void *sdsAllocPtr(sds s);

/* Export the allocator used by SDS to the program using SDS.
 * Sometimes the program SDS is linked to, may use a different set of
 * allocators, but may want to allocate or free things that SDS will
 * respectively free or allocate. */
void *sds_malloc(size_t size);
void *sds_realloc(void *ptr, size_t size);
void sds_free(void *ptr);

c复制代码/* Create a new sds string starting from a null terminated C string. */
sds sdsnew(const char *init) {
    size_t initlen = (init == NULL) ? 0 : strlen(init);
    return sdsnewlen(init, initlen);
}

c复制代码sds sdsnewlen(const void *init, size_t initlen) {
    return _sdsnewlen(init, initlen, 0);
}

c复制代码/* Create a new sds string with the content specified by the 'init' pointer
 * and 'initlen'.
 * If NULL is used for 'init' the string is initialized with zero bytes.
 * If SDS_NOINIT is used, the buffer is left uninitialized;
 *
 * The string is always null-termined (all the sds strings are, always) so
 * even if you create an sds string with:
 *
 * mystring = sdsnewlen("abc",3);
 *
 * You can print the string with printf() as there is an implicit \0 at the
 * end of the string. However the string is binary safe and can contain
 * \0 characters in the middle, as the length is stored in the sds header. */
sds _sdsnewlen(const void *init, size_t initlen, int trymalloc) {
    void *sh;
    sds s;
    char type = sdsReqType(initlen);
    /* Empty strings are usually created in order to append. Use type 8
     * since type 5 is not good at this. */
    if (type == SDS_TYPE_5 && initlen == 0) type = SDS_TYPE_8;
    int hdrlen = sdsHdrSize(type);
    unsigned char *fp; /* flags pointer. */
    size_t usable;

    assert(initlen + hdrlen + 1 > initlen); /* Catch size_t overflow */
    sh = trymalloc?
        s_trymalloc_usable(hdrlen+initlen+1, &usable) :
        s_malloc_usable(hdrlen+initlen+1, &usable);
    if (sh == NULL) return NULL;
    if (init==SDS_NOINIT)
        init = NULL;
    else if (!init)
        memset(sh, 0, hdrlen+initlen+1);
    s = (char*)sh+hdrlen;
    fp = ((unsigned char*)s)-1;
    usable = usable-hdrlen-1;
    if (usable > sdsTypeMaxSize(type))
        usable = sdsTypeMaxSize(type);
    switch(type) {
        case SDS_TYPE_5: {
            *fp = type | (initlen << SDS_TYPE_BITS);
            break;
        }
        case SDS_TYPE_8: {
            SDS_HDR_VAR(8,s);
            sh->len = initlen;
            sh->alloc = usable;
            *fp = type;
            break;
        }
        case SDS_TYPE_16: {
            SDS_HDR_VAR(16,s);
            sh->len = initlen;
            sh->alloc = usable;
            *fp = type;
            break;
        }
        case SDS_TYPE_32: {
            SDS_HDR_VAR(32,s);
            sh->len = initlen;
            sh->alloc = usable;
            *fp = type;
            break;
        }
        case SDS_TYPE_64: {
            SDS_HDR_VAR(64,s);
            sh->len = initlen;
            sh->alloc = usable;
            *fp = type;
            break;
        }
    }
    if (initlen && init)
        memcpy(s, init, initlen);
    s[initlen] = '\0';
    return s;
}

markdown复制代码* noeviction：旧缓存永不过期，新缓存设置不了，返回错误
* allkeys-lru：清除最少用的旧缓存，然后保存新的缓存（推荐使用）
* allkeys-random：在所有的缓存中随机删除（不推荐）
* volatile-lru：在那些设置了expire过期时间的缓存中，清除最少用的旧缓存，然后保存新的缓存
* volatile-random：在那些设置了expire过期时间的缓存中，随机删除缓存
* volatile-ttl：在那些设置了expire过期时间的缓存中，删除即将过期的`

xml复制代码<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
       
    <bean id="config01" class="com.example.helloworlddemo.config.User">
        <property name="name" value="zhangsan"/>
        <property name="age" value="18"/>
    </bean>
    
</beans>

java复制代码@Configuration // 告诉SpringBoot 这是一个配置类 = bean.xml
public class MyConfig {

    /**
     * @Bean 等同于 <bean></bean> 标签。
     * 方法名 作为组件id
     * 返回值类型 组件类型
     * 返回值 组件在容器中的实例对象，单例的
     */
    @Bean
    public User config01() {
        return new User("张三", "18");
    }
}

java复制代码public static void main(String[] args) {
    // 返回IOC容器对象
    ConfigurableApplicationContext run = SpringApplication.run(HelloworldDemoApplication.class, args);
    // 查看容器内的所有组件
    String[] beanDefinitionNames = run.getBeanDefinitionNames();
    for (String name : beanDefinitionNames) {
        System.out.println(name);
    }
}

java复制代码    // 获取组件
    User config01 = run.getBean("config01", User.class);
    User config02 = run.getBean("config01", User.class);
    System.out.println(config01);
    System.out.println(config02);

sql复制代码update t set age=10 where id=1;

xml复制代码 <dependencies>
        <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
        <!--添加mybatis依赖-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.6</version>
        </dependency>
        <!--jdbc驱动-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.47</version>
        </dependency>
        <!--junit测试类-->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

xml复制代码<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<!--        configuration核心配置文件-->
<configuration>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/firend_mq?useSSL=false&amp;useUnicode=&amp;characterEncodeing=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>
<!--    注册mapper-->
    <mappers>
        <mapper resource="dao/UserMapper.xml"/>
    </mappers>
</configuration>

java复制代码//SqlSessionFactory
public class Mybatisutil {

    private static SqlSessionFactory sqlSessionFactory;

    static {
        try {//使用mybaatis第一步获取SqlSessionFactory对象
            String resource="mybatis-config.xml";
            InputStream inputStream= Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    //有了 SqlSessionFactory，顾名思义，我们可以从中获得 SqlSession 的实例。SqlSession
    // 提供了在数据库执行 SQL 命令所需的所有方法。你可以通过 SqlSession 实例来直接执行已映射的 SQL 语句

    public static SqlSession getSqlSession(){
        SqlSession sqlSession = sqlSessionFactory.openSession();
        return sqlSession;
    }
}

java复制代码package pojo;

public class User {
    private int id;
    private String username;
    private String password;

    public User(int id, String username, String password) {
        this.id = id;
        this.username = username;
        this.password = password;
    }

    public User() {
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                '}';
    }
}

java复制代码public interface UserDao {
    //查询所有用户
    List<User> getUserList();

    //查询指定id用户
    User getUserById(int id);

    //添加一个用户
    int addUser(User user);

    //修改用户
    int updateUser(User user);

    //删除一个用户
    int deleteUser(int id);
}

xml复制代码<!--namespace=绑定一个对应的Dao/Mapper接口-->
<mapper namespace="dao.UserDao">
<!-- select查询语句   -->
    <select id="getUserList" resultType="pojo.User">
        select * from firend_mq.users
    </select>
<!--    根据id查询-->
    <select id="getUserById" parameterType="int" resultType="pojo.User">
        select * from firend_mq.users where id = #{id}
    </select>

<!-- 添加一个用户   对象中的属性，可以直接取出去-->
    <insert id="addUser" parameterType="pojo.User">
        insert into firend_mq.users (id,username,password) value (#{id},#{username},#{password})
    </insert>

    <update id="updateUser" parameterType="pojo.User">
        update firend_mq.users set username=#{username},password=#{password}  where id=#{id};
    </update>

<!--    删除一个用户-->
    <delete id="deleteUser" parameterType="int">
        delete from firend_mq.users where id=#{id}
    </delete>
</mapper>

java复制代码public class UserDaoText {
    //查询所有用户
    @Test
    public void getUserList(){
        //第一步：获得sqlSession对象
        SqlSession sqlSession = Mybatisutil.getSqlSession();
        //方式一：getMapper
        UserDao mapper = sqlSession.getMapper(UserDao.class);
        List<User> userList = mapper.getUserList();
        for (User user : userList) {
            System.out.println(user);
        }
        sqlSession.close();
    }
//    查询指定id用户
    @Test
    public void getUserById(){
        SqlSession sqlSession = Mybatisutil.getSqlSession();
        UserDao mapper = sqlSession.getMapper(UserDao.class);
       User user = mapper.getUserById(2);
        System.out.println(user);
        sqlSession.close();
    }
    //所有的增删改都要提交事务
    //添加一个用户
    @Test
    public void addUser(){
        SqlSession sqlSession = Mybatisutil.getSqlSession();
        UserDao mapper = sqlSession.getMapper(UserDao.class);
        mapper.addUser(new User(4,"张三","10086"));
        //提交事务
        sqlSession.commit();
        sqlSession.close();
    }
    @Test
    public void updateUser(){
        SqlSession sqlSession = Mybatisutil.getSqlSession();
        UserDao mapper = sqlSession.getMapper(UserDao.class);
        mapper.updateUser(new User(4,"哈哈","123"));
        sqlSession.commit();
        sqlSession.close();
    }
    @Test
    public void deleteUser(){
        SqlSession sqlSession = Mybatisutil.getSqlSession();
        UserDao mapper = sqlSession.getMapper(UserDao.class);
        mapper.deleteUser(4);
        sqlSession.commit();
        sqlSession.close();
    }

}