MybatisPlus入门（下）-阿里云开发者社区

MybatisPlus入门（中）+https://developer.aliyun.com/article/1492262

如何使用！

1、配置拦截器组件即可

/**
 * 注册分页
 * @return
 */
@Bean
public PaginationInterceptor paginationInterceptor() {
    return new PaginationInterceptor();
}

2、测试

/**
 * 分页
 */
@Test
void testPage(){
    //  参数1：当前页；参数2：页面大小; 以5条记录作为一页查询数据
    Page<User> page = new Page<>(1, 5);
    userMapper.selectPage(page, null);
    page.getRecords().forEach(System.out::println);
    System.out.println(page.getTotal());
}

3、测试结果

底层还是使用的limit

Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@7da31a40] was not registered for synchronization because synchronization is not active
JDBC Connection [HikariProxyConnection@805536380 wrapping com.mysql.cj.jdbc.ConnectionImpl@29b40b3] will not be managed by Spring
 JsqlParserCountOptimize sql=SELECT  id,name,age,email,version,create_time,update_time  FROM user
==>  Preparing: SELECT COUNT(1) FROM user 
==> Parameters: 
<==    Columns: COUNT(1)
<==        Row: 9
==>  Preparing: SELECT id,name,age,email,version,create_time,update_time FROM user LIMIT 0,5 
==> Parameters: 
<==    Columns: id, name, age, email, version, create_time, update_time
<==        Row: 1, lpp, 220, test1@baomidou.com, 3, 2021-09-24 13:49:18, 2021-09-24 15:04:20
<==        Row: 2, Jack, 20, test2@baomidou.com, 1, 2021-09-24 13:49:18, null
<==        Row: 3, Tom, 28, test3@baomidou.com, 1, 2021-09-24 13:49:18, null
<==        Row: 4, Sandy, 21, test4@baomidou.com, 1, 2021-09-24 13:49:18, null
<==        Row: 5, Billie, 24, test5@baomidou.com, 1, 2021-09-24 13:49:18, null
<==      Total: 5
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@7da31a40]
User(id=1, name=lpp, age=220, email=test1@baomidou.com, version=3, createTime=Fri Sep 24 13:49:18 CST 2021, updateTime=Fri Sep 24 15:04:20 CST 2021)
User(id=2, name=Jack, age=20, email=test2@baomidou.com, version=1, createTime=Fri Sep 24 13:49:18 CST 2021, updateTime=null)
User(id=3, name=Tom, age=28, email=test3@baomidou.com, version=1, createTime=Fri Sep 24 13:49:18 CST 2021, updateTime=null)
User(id=4, name=Sandy, age=21, email=test4@baomidou.com, version=1, createTime=Fri Sep 24 13:49:18 CST 2021, updateTime=null)
User(id=5, name=Billie, age=24, email=test5@baomidou.com, version=1, createTime=Fri Sep 24 13:49:18 CST 2021, updateTime=null)
9

删除操作

基本删除操作

/**
     * 根据ID删除
     */
    @Test
    void deleteById(){
        userMapper.deleteById(1L);
    }
    /**
     * 批量删除
     */
    @Test
    void deleteBatch(){
        userMapper.deleteBatchIds(Arrays.asList(2, 3));
    }
    /**
     * 根据多条件删除
     */
    @Test
    void deleteByMap(){
        Map<String, Object> objectMap = new HashMap<>();
        objectMap.put("name", "Billie");
        objectMap.put("age", 24);
        userMapper.deleteByMap(objectMap);
    }

逻辑删除

物理删除：从数据库中直接移除

逻辑删除：在数据库中没有被移除，而是通过一个变量让他失效，deleted = 0 / deleted = 1

测试：

1、增加字段 deleted

2、实体类中增加属性

/**
 * 逻辑删除
 */
@TableLogic
private Integer deleted;

3、注册逻辑删除组件

/**
 * 逻辑删除组件
 * @return
 */
@Bean
public ISqlInjector sqlInjector(){
  return new LogicSqlInjector();
}

4、增加配置

mybatis-plus:
    global-config:
      db-config:
        logic-delete-value: 1 # 逻辑已删除值(默认为 1)
        logic-not-delete-value: 0 # 逻辑未删除值(默认为 0)

5、测试

/**
 * 根据ID删除
 */
@Test
void deleteById(){
    userMapper.deleteById(6L);
}

删除时，只是更新了deleted的状态

Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@5762658b] was not registered for synchronization because synchronization is not active
JDBC Connection [HikariProxyConnection@1328705686 wrapping com.mysql.cj.jdbc.ConnectionImpl@1d61a348] will not be managed by Spring
==>  Preparing: UPDATE user SET deleted=1 WHERE id=? AND deleted=0 
==> Parameters: 6(Long)
<==    Updates: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@5762658b]

搜索时，自动忽略deleted=1的数据

性能分析插件

作用

性能分析拦截器，用于输出每条SQL语句及其执行时间。

MP提供性能分析插件，如果超过指定的时间就停止运行、抛出异常。

如何使用

1、导入插件

@Bean
@Profile({"dev"}) // 设置dev环境开启
public PerformanceInterceptor performanceInterceptor() {
    PerformanceInterceptor performanceInterceptor = new PerformanceInterceptor();
    performanceInterceptor.setMaxTime(1);
    performanceInterceptor.setFormat(true);
    return performanceInterceptor;
}

注意匹配对应的环境信息，如下为dev

2、测试使用

@Test
void contextLoads() {
    // wrapper是条件构造器
    List<User> users = userMapper.selectList(null);
    users.forEach(System.out::println);
}

Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@6dc9da2d] was not registered for synchronization because synchronization is not active
JDBC Connection [HikariProxyConnection@1637821180 wrapping com.mysql.cj.jdbc.ConnectionImpl@df921b1] will not be managed by Spring
==>  Preparing: SELECT id,name,age,email,version,deleted,create_time,update_time FROM user WHERE deleted=0 
==> Parameters: 
<==    Columns: id, name, age, email, version, deleted, create_time, update_time
<==        Row: 4, Sandy, 21, test4@baomidou.com, 1, 0, 2021-09-24 13:49:18, null
<==        Row: 1441249447918751745, 断言, 24, Jay@, 1, 0, 2021-09-24 13:49:18, null
<==        Row: 1441249447918751746, 断言, 24, Jay@, 1, 0, 2021-09-24 13:49:18, null
<==        Row: 1441249447918751747, 断言1, 24, Jay@, 1, 0, 2021-09-24 14:22:13, 2021-09-24 14:22:13
<==      Total: 4
 Time：27 ms - ID：com.jay.mybatisplus.mapper.UserMapper.selectList
Execute SQL：
    SELECT
        id,
        name,
        age,
        email,
        version,
        deleted,
        create_time,
        update_time 
    FROM
        user 
    WHERE
        deleted=0
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@6dc9da2d]
org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.exceptions.PersistenceException: 
### Error querying database.  Cause: com.baomidou.mybatisplus.core.exceptions.MybatisPlusException:  The SQL execution time is too large, please optimize ! 
### The error may exist in com/jay/mybatisplus/mapper/UserMapper.java (best guess)
### The error may involve com.jay.mybatisplus.mapper.UserMapper.selectList
### The error occurred while handling results
### SQL: SELECT  id,name,age,email,version,deleted,create_time,update_time  FROM user  WHERE  deleted=0
### Cause: com.baomidou.mybatisplus.core.exceptions.MybatisPlusException:  The SQL execution time is too large, please optimize !

条件构造器

测试1:

@Test
void contextLoads() {
    QueryWrapper<User> queryWrapper = new QueryWrapper();
    queryWrapper.isNotNull("name").isNotNull("email").ge("age",24);
    List<User> users = userMapper.selectList(queryWrapper);
    users.forEach(System.out::println);
}

测试2:

@Test
void test1() {
    QueryWrapper queryWrapper = new QueryWrapper();
    queryWrapper.eq("name", "Sandy");
    User user = userMapper.selectOne(queryWrapper);
    System.out.println(user);
}

测试3:

@Test
void test2() {
    QueryWrapper<User> queryWrapper = new QueryWrapper<>();
    queryWrapper.between("age",20,24);
    Integer count = userMapper.selectCount(queryWrapper);
    System.out.println(count);
}

测试4:

@Test
void test3() {
    QueryWrapper<User> queryWrapper = new QueryWrapper<>();
    // name不包含J，email以t开头
    queryWrapper.notLike("name", "J").likeRight("email","t");
    // 查询结果
    userMapper.selectMaps(queryWrapper).forEach(System.out::println);
}

测试5:

@Test
void test4() {
    QueryWrapper<User> queryWrapper = new QueryWrapper<>();
    // id 子查询
    queryWrapper.inSql("id", "select id from user where age < 22");
    // 查询结果
    userMapper.selectMaps(queryWrapper).forEach(System.out::println);
}

MybatisPlus入门（下）

如何使用！

删除操作

逻辑删除

性能分析插件

作用

如何使用

条件构造器

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