分页(Limit+RowBounds+插件)

• • 1.使用Limit分页
  • 2.RowBounds
  • 3.Mybatis分页插件PageHelper

为什么分页？

  减少数据的处理量

  语法：select *from user limit startIndex，pageSize;
  startIndex：起始位置(0开始), pageSize:记录条数

StuMapper.java

public interface StuMapper {
  List selectByLimit(Map map);
}

StuMapper.xml
这里因为表里字段和数据库字段不匹配，用了结果集映射。

   
        
    
    
    
        select  * from test.stu limit #{startIndex},#{pageSize}
    
 
StuService.java
 这是service层
 
  @Override
    public List selectByLimit(Map map) {
        return stuMapper.selectByLimit(map);
 
  工具类
 
import java.io.IOException;
import java.io.InputStream;

public class MybatisUtils {
    private static SqlSessionFactory sqlSessionFactory;
    static {
        try {
            String resources="mybatis-config.xml";
            InputStream inputStream= Resources.getResourceAsStream(resources);
            sqlSessionFactory =new SqlSessionFactoryBuilder().build(inputStream);

        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    public static SqlSession getSession(){
        return sqlSessionFactory.openSession();
    }
}

 
  测试类
 
@Test
    public void LimitTest(){
        SqlSession session=MybatisUtils.getSession();
    StuMapper mapper = session.getMapper(StuMapper.class);
    HashMapmap=new HashMap();
    map.put("startIndex",0);
    map.put("pageSize",2);
    List list = mapper.selectByLimit(map);
    for (Student student : list) {
        System.out.println(student);

    }


    session.close();
}
 
2.RowBounds 
StuMapper.java
 
public interface StuMapper {
    List selectByRowBounds();
}
 
StuMapper.xml
 resultMap是因为字段不匹配，可在上文中查找
 
   
        select  * from test.stu
    

测试类：

    @Test
    public void getUserByRowBounds(){

        SqlSession sqlSession = MybatisUtils.getSession();

 RowBounds rowBounds=new RowBounds(0,2);
        //通过java代码层面实现分页
        List list = sqlSession.selectList("com.my.mapper.StuMapper.selectByRowBounds",null,rowBounds);
        for (Student student : list) {
            System.out.println(student);
        }



        sqlSession.close();

    }

结果

      学习地址