mybatisplus-分页和查询删除

1.分页查询

①配置类中追加分页插件

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

②测试分页查询

//测试分页查询
    @Test
    public void selectByPageTest() {
        Page<User> page = new Page<>(1, 3);//定义page，当前页，一页现实件数
        userMapper.selectPage(page,null);//SELECT id,name,age,email,create_time,update_time,version FROM user LIMIT 0,3
        page.getRecords().forEach(System.out::println);//利用page.getRecords()获取记录，并循环输出
    }

2.根据id查询

//测试根据id获取数据集合
    @Test
    public void selectIdTest() {
        User user = userMapper.selectById(1);
        System.out.println(user);//SELECT id,name,age,email,create_time,update_time,version FROM user WHERE id=?
    }

3.根据id批量查询

//根据id批量查询数据
    @Test
    public void selectByBatchIDTest() {
        List<User> users = userMapper.selectBatchIds(Arrays.asList(1, 2));//SELECT id,name,age,email,create_time,update_time,version FROM user WHERE id IN ( ? , ? )
        users.forEach(System.out::println);
    }

4.根据map内容进行查询

//按照map的内容查询
    @Test
    public void selectByMapTest() {
        Map<String, Object> map = new HashMap<>();
        map.put("name", "Tom");
        userMapper.selectByMap(map).forEach(System.out::println);//SELECT id,name,age,email,create_time,update_time,version FROM user WHERE name = ?
    }

5.根据id删除数据

//根据id删除数据
    @Test
    public void deleteByIdTest(){
        userMapper.deleteById(1L);//DELETE FROM user WHERE id=?
    }

6.根据id批量删除数据

    @Test
    public void deleteBatchByIdTest(){
        userMapper.deleteBatchIds(Arrays.asList(2L,3L));//DELETE FROM user WHERE id IN ( ? , ? )
    }

7.根据条件删除数据

@Test
    public void deleteByMapTest() {
        Map<String, Object> map = new HashMap<>();
        map.put("name","sandy");//DELETE FROM user WHERE name = ? 
        userMapper.deleteByMap(map);
    }

8.逻辑删除

物理删除：从数据库直接删除。

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

①表中加上deleted字段

②实体类中追加deleted字段

@TableLogic
    private int deleted;

③配置类中追加逻辑删除组件

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

④配置文件中配置逻辑删除

#配置逻辑删除
mybatis-plus.global-config.db-config.logic-delete-value=1
mybatis-plus.global-config.db-config.logic-not-delete-value=0

⑤测试删除

    @Test
    public void deleteLogicTest(){
        userMapper.deleteById(5L);// UPDATE user SET deleted=1 WHERE id=? AND deleted=0
    }

@Test
    public void selectLogicTest(){
        userMapper.selectById(5L);//SELECT id,name,age,email,create_time,update_time,version,deleted FROM user WHERE id=? AND deleted=0
    }