1 首先添加插件配置

@Configuration
public class MybatisPlusConfig {
    @Bean
    public PaginationInterceptor paginationInterceptor(){
        return new PaginationInterceptor();
    }
}

2 简单的查询示例

在查询的时候 ，结果会自动填充到page中，类似于插入的之后，id会自动填充到实体当中

@Test
public void testPage() {
    String name = "梅";
    LambdaQueryWrapper<User> userQueryWrapper = Wrappers.<User>lambdaQuery();
    userQueryWrapper.like(User::getName,name);
    Page<User> page= new Page<>(1,1);
    Page<User> page1 = userMapper.selectPage(page, userQueryWrapper);
    //page和page1输出的结果是相同的，所以在userMapper.selectPage(page, userQueryWrapper);的时候，结果已经填充到page中了，完全可以不需要page1
    System.out.println(page.getRecords()+":"+page.getTotal());
    //输出：[User(id=1, name=梅长苏, age=40, email=boss@qq.com, parentId=null, createTime=Fri Jan 11 14:20:20 CST 2019)]:5
    System.out.println(page1.getRecords()+":"+page.getTotal());
    //输出：[User(id=1, name=梅长苏, age=40, email=boss@qq.com, parentId=null, createTime=Fri Jan 11 14:20:20 CST 2019)]:5
}

2.1 打印sql

会有两个sql，一个查询总数，一个查询分页list

JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@30ec211a] will not be managed by Spring
JsqlParserCountOptimize sql=SELECT  id,name,age,email,parent_id,create_time  FROM user 
 
 WHERE (name LIKE ?)
==>  Preparing: SELECT COUNT(1) FROM user WHERE (name LIKE ?)
==> Parameters: %梅%(String)
<==    Columns: COUNT(1)
<==        Row: 1
==>  Preparing: SELECT id,name,age,email,parent_id,create_time FROM user WHERE (name LIKE ?) LIMIT ?
==> Parameters: %梅%(String), 1(Long)
<==    Columns: id, name, age, email, parent_id, create_time
<==        Row: 1, 梅长苏, 40, boss@qq.com, null, 2019-01-11 14:20:20
<==      Total: 1

3 注意点

3.1 new Page<>(1,1,false)传false就会只查询记录数，不会查询总数;默认是true

    @Test
    public void testPage2() {
        String name = "梅";
        LambdaQueryWrapper<User> userQueryWrapper = Wrappers.<User>lambdaQuery();
        userQueryWrapper.like(User::getName,name);
        Page<User> page= new Page<>(1,1,false);
        Page<User> page1 = userMapper.selectPage(page, userQueryWrapper);
        //输出[User(id=1, name=梅长苏, age=40, email=boss@qq.com, parentId=null, createTime=Fri Jan 11 14:20:20 CST 2019)]:0
        //这个时候total是空的
        System.out.println(page.getRecords()+":"+page.getTotal());
    }

3.2 mp自定义的分页的使用

自定义分页方法

@Mapper
@Component
public interface UserMapper extends BaseMapper<User> {
    Page MyPage(Page<User> page, @Param("ew") Wrapper<User> queryWrapper);
}

对于的xml

<select id="myPage" resultType="com.fj.entity.User">
    select * from user ${ew.customSqlSegment}
</select>