mybatis的rowbounds是物理分页吗_rowbounds分页

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在 mybatis 中，使用 RowBounds 进行分页，非常方便，不需要在 sql 语句中写 limit，即可完成分页功能。但是由于它是在 sql 查询出所有结果的基础上截取数据的，所以在数据量大的sql中并不适用，它更适合在返回数据结果较少的查询中使用

最核心的是在 mapper 接口层，传参时传入 RowBounds(int offset, int limit) 对象，即可完成分页

注意：由于 java 允许的最大整数为 2147483647，所以 limit 能使用的最大整数也是 2147483647，一次性取出大量数据可能引起内存溢出，所以在大数据查询场合慎重使用
 

mapper 接口层代码如下

List<Book> selectBookByName(Map<String, Object> map, RowBounds rowBounds);

调用如下

List<Book> list = bookMapper.selectBookByName(map, new RowBounds(0, 5));

说明: new RowBounds(0, 5)，即第一页，每页取5条数据

测试示例

数据库数据

mapper 接口层

package com.demo.mapper;

import java.util.List;
import java.util.Map;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.session.RowBounds;
import com.demo.bean.Book;

@Mapper
public interface BookMapper {
	
	//添加数据
	int insert(Book book); 
	
	//模糊查询
	List<Book> selectBookByName(Map<String, Object> map, RowBounds rowBounds);

}

mapper.xml 文件

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="com.demo.mapper.BookMapper">
	
	<resultMap id="BaseResultMap" type="com.demo.bean.Book">
		<id column="id" property="id" jdbcType="VARCHAR" />
		<result column="book_name" property="bookName" jdbcType="VARCHAR" />
		<result column="book_author" property="bookAuthor" jdbcType="VARCHAR" />
		<result column="create_date" property="createDate" jdbcType="VARCHAR" />
		<result column="update_date" property="updateDate" jdbcType="VARCHAR" />
	</resultMap>
	
	<sql id="Base_Column_List">
          book_name as bookName, book_author as bookAuthor,
          create_date as createDate, update_date as updateDate
        </sql>
	
	<insert id="insert" useGeneratedKeys="true" keyProperty="id" parameterType="com.demo.bean.Book">
	  insert into book(book_name, book_author, create_date, update_date)  values(#{bookName}, #{bookAuthor}, #{createDate}, #{updateDate}) 
	</insert>
	
	<select id="selectBookByName" resultMap="BaseResultMap">
	  <bind name="pattern_bookName" value="'%' + bookName + '%'" />
	  <bind name="pattern_bookAuthor" value="'%' + bookAuthor + '%'" />
	  select * from book 
	  where 1 = 1
	  <if test="bookName != null and bookName !=''">
	    and book_name LIKE #{pattern_bookName}
	  </if>
	  <if test="bookAuthor != null and bookAuthor !=''">
	    and book_author LIKE #{pattern_bookAuthor}
	  </if>
	</select>
	
</mapper>

测试代码

package com.demo;

import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.apache.ibatis.session.RowBounds;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;
import com.demo.bean.Book;
import com.demo.mapper.BookMapper;

@RunWith(SpringRunner.class)
@SpringBootTest
public class SpringbootJspApplicationTests {
	
	@Autowired
	private BookMapper bookMapper; 

	@Test
	public void contextLoads() {
		Book book = new Book();
		book.setBookName("隋唐演义");
		book.setBookAuthor("褚人获");
		
		SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
		
		book.setCreateDate(sdf.format(new Date()));
		book.setUpdateDate(sdf.format(new Date()));
		bookMapper.insert(book);
		System.out.println("返回的主键:   "+book.getId());
	}
	
	@Test
	public void query() {
		Map<String, Object> map = new HashMap<String, Object>();
		map.put("bookName", "");
		map.put("bookAuthor", "");
		List<Book> list = bookMapper.selectBookByName(map, new RowBounds(0, 5));
		
		for(Book b : list) {
			System.out.println(b.getBookName());
		}
	}

}

运行 query 查询第一页，5 条数据，效果如下