mybatis RowBounds 分页

mybatis 中，使用 RowBounds 分页，非常方便

不需要在 sql 语句中写 limit，mybatis 会自动拼接 sql ，添加 limit

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>

测试用例

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