mybatis-plus学习（三）

   @Autowired(required = false)
    private UserMapper userMapper;
    @Autowired
    private IUserService iUserService;
    /**
     * 以前默认是叫EntityWrapper，现在叫QueryWrapper
     */

    /**
     * 根据条件查询
     */
    @Test
    public void select(){
        QueryWrapper<User> wrapper=new QueryWrapper<>();
        wrapper.isNotNull("name") //name不为空的用户
        .isNotNull("email") //邮箱不为空
        .ge("age",12); //年龄大于等于12

        List<User> list=userMapper.selectList(wrapper);
        System.out.println(list);
    }

    /**
     * 根据名字查询
     */
    @Test
    public void selectName(){
        QueryWrapper<User> wrapper=new QueryWrapper<>();
        wrapper.eq("name","ting");
        List<User> list=userMapper.selectList(wrapper);
        System.out.println(list);
    }
    /**
     *  查询 10 到 20 岁的用户数
     */
    @Test
    public void selectByAge(){
        QueryWrapper<User> wrapper=new QueryWrapper<>();
        wrapper.between("age",10,21);

        List<User> list=userMapper.selectList(wrapper);
        System.out.println(list);


    }
    

 /**
     * 模糊查询
     */
    @Test
    public void selectLike(){
        QueryWrapper<User> wrapper=new QueryWrapper<>();
        wrapper
                .notLike("name","2")
                .like("name","t")
                //右查询
                .likeRight("email","234");
        List<Map<String,Object>> users=userMapper.selectMaps(wrapper);
        System.out.println(users);

    }

 /**
     * 子查询
     */
    @Test
    public void selectLike2(){
        QueryWrapper<User> wrapper=new QueryWrapper<>();
        wrapper.inSql("id","select id from user where age<21");
        List<Object> users=userMapper.selectObjs(wrapper);
        System.out.println(users);
    }

 /**
     * 排序
     */
    @Test
    public void selectByOrder(){
        QueryWrapper<User> wrapper=new QueryWrapper<>();
        //降序排序
        wrapper.orderByDesc("id");

        List<User> users=userMapper.selectList(wrapper);
        System.out.println(users);
    }

  /**
     * 部分字段更新
     */
    @Test
    public void update(){
        UpdateWrapper<User> wrapper=new UpdateWrapper<>();
        User user=new User();
        //更新字段
        wrapper.set("name","xyz");
        wrapper.eq("id",1321972874844389378L);
        System.out.println("更新结果："+iUserService.update(user,wrapper));
    }

@Configuration
@MapperScan("com.king.mapper")
public class MybatisPlusConfig {
    @Bean
    public PaginationInterceptor paginationInterceptor() {
        PaginationInterceptor paginationInterceptor = new PaginationInterceptor();
        // 设置请求的页面大于最大页后操作， true调回到首页，false 继续请求  默认false
        // paginationInterceptor.setOverflow(false);
        // 设置最大单页限制数量，默认 500 条，-1 不受限制
        // paginationInterceptor.setLimit(500);
        // 开启 count 的 join 优化,只针对部分 left join
        //paginationInterceptor.setCountSqlParser(new JsqlParserCountOptimize(true));
        return paginationInterceptor;
    }
}

    /**
     * 分页
     */
    @Test
    public void page(){
        //当前页1，每页大小2
        IPage<User> userIPage=new Page<>(1,1);
        userIPage=userMapper.selectPage(userIPage,null);
        List<User> list=userIPage.getRecords();
        System.out.println(list);
    }