MyBatis 入门(五)--分页查询（1）

 
    不使用mybatis的RowBounds方式，网络上说这个功能不怎么好了。

一、根本原理 

不管是自己实现还是利用插件方式，其根本就是利用：

•  mysql的   limit   beginrow , size(条数) 
•  ORACEL的   rownum >= 1   and rownum <= 10（1-10的记录）

二、原生方式 

•   定义需要继承Page类                

package com.elements.user;

public class Page {

    //定义分页的默认大小
    protected static int OnePageSize=5;

    //当前页数
    private int nowPage=1;

    //开始的行
    private int startRow=0;
    {
        startRow=(nowPage-1)*OnePageSize;
    }

    //结束的行
    private int endRow=0;
    {
        endRow=nowPage*OnePageSize;
    }

    //总的页数
    private int AllPages=0;

    public int getNowPage() {
        return nowPage;
    }

    public void setNowPage(int nowPage) {
        this.nowPage = nowPage;
        startRow=(nowPage-1)*OnePageSize;
        endRow=nowPage*OnePageSize;
    }
}

• 定义使用的用户类

      这里继承了我们的Page类                   

package com.elements.user.model;

import java.util.Date;

import com.elements.user.Page;

public class User extends Page{
    /**
     * This field was generated by MyBatis Generator.
     * This field corresponds to the database column user.userId
     *
     * @mbggenerated Wed Apr 27 15:05:09 CST 2016
     */
    private Integer userid;

    /**
     * This field was generated by MyBatis Generator.
     * This field corresponds to the database column user.UserName
     *
     * @mbggenerated Wed Apr 27 15:05:09 CST 2016
     */
    private String username;

    /**
     * This field was generated by MyBatis Generator.
     * This field corresponds to the database column user.UserEmail
     *
     * @mbggenerated Wed Apr 27 15:05:09 CST 2016
     */
    private String useremail;

    /**
     * This field was generated by MyBatis Generator.
     * This field corresponds to the database column user.createTime
     *
     * @mbggenerated Wed Apr 27 15:05:09 CST 2016
     */
    private String createtime;

    /**
     * This field was generated by MyBatis Generator.
     * This field corresponds to the database column user.updateTime
     *
     * @mbggenerated Wed Apr 27 15:05:09 CST 2016
     */
    private String updatetime;

    /**
     * This method was generated by MyBatis Generator.
     * This method returns the value of the database column user.userId
     *
     * @return the value of user.userId
     *
     * @mbggenerated Wed Apr 27 15:05:09 CST 2016
     */
    public Integer getUserid() {
        return userid;
    }

    /**
     * This method was generated by MyBatis Generator.
     * This method sets the value of the database column user.userId
     *
     * @param userid the value for user.userId
     *
     * @mbggenerated Wed Apr 27 15:05:09 CST 2016
     */
    public void setUserid(Integer userid) {
        this.userid = userid;
    }

    /**
     * This method was generated by MyBatis Generator.
     * This method returns the value of the database column user.UserName
     *
     * @return the value of user.UserName
     *
     * @mbggenerated Wed Apr 27 15:05:09 CST 2016
     */
    public String getUsername() {
        return username;
    }

    /**
     * This method was generated by MyBatis Generator.
     * This method sets the value of the database column user.UserName
     *
     * @param username the value for user.UserName
     *
     * @mbggenerated Wed Apr 27 15:05:09 CST 2016
     */
    public void setUsername(String username) {
        this.username = username == null ? null : username.trim();
    }

    /**
     * This method was generated by MyBatis Generator.
     * This method returns the value of the database column user.UserEmail
     *
     * @return the value of user.UserEmail
     *
     * @mbggenerated Wed Apr 27 15:05:09 CST 2016
     */
    public String getUseremail() {
        return useremail;
    }

    /**
     * This method was generated by MyBatis Generator.
     * This method sets the value of the database column user.UserEmail
     *
     * @param useremail the value for user.UserEmail
     *
     * @mbggenerated Wed Apr 27 15:05:09 CST 2016
     */
    public void setUseremail(String useremail) {
        this.useremail = useremail == null ? null : useremail.trim();
    }

    /**
     * This method was generated by MyBatis Generator.
     * This method returns the value of the database column user.createTime
     *
     * @return the value of user.createTime
     *
     * @mbggenerated Wed Apr 27 15:05:09 CST 2016
     */
    public String getCreatetime() {
        return createtime;
    }

    /**
     * This method was generated by MyBatis Generator.
     * This method sets the value of the database column user.createTime
     *
     * @param createtime the value for user.createTime
     *
     * @mbggenerated Wed Apr 27 15:05:09 CST 2016
     */
    public void setCreatetime(String createtime) {
        this.createtime = createtime ;
    }

    /**
     * This method was generated by MyBatis Generator.
     * This method returns the value of the database column user.updateTime
     *
     * @return the value of user.updateTime
     *
     * @mbggenerated Wed Apr 27 15:05:09 CST 2016
     */
    public String getUpdatetime() {
        return updatetime;
    }

    /**
     * This method was generated by MyBatis Generator.
     * This method sets the value of the database column user.updateTime
     *
     * @param updatetime the value for user.updateTime
     *
     * @mbggenerated Wed Apr 27 15:05:09 CST 2016
     */
    public void setUpdatetime(String updatetime) {
        this.updatetime = updatetime;
    }

    @Override
    public String toString() {
        return "User [userid=" + userid + ", username=" + username
                + ", useremail=" + useremail + ", createtime=" + createtime
                + ", updatetime=" + updatetime + "]\n";
    }


}

• mapper配置的XML类     

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "" >
<mapper namespace="com.elements.user.dao.UserMapper" >


  <resultMap id="BaseResultMap" type="com.elements.user.model.User" >
    <id column="userId" property="userid" jdbcType="INTEGER" />
    <result column="UserName" property="username" jdbcType="VARCHAR" />
    <result column="UserEmail" property="useremail" jdbcType="VARCHAR" />
    <result column="createTime" property="createtime" jdbcType="VARCHAR" />
    <result column="updateTime" property="updatetime" jdbcType="VARCHAR" />
  </resultMap>


  <sql id="Base_Column_List" >
    userId, UserName, UserEmail, createTime, updateTime
  </sql>

  <select id="selectUserPage" parameterType="com.elements.user.model.User" resultMap="BaseResultMap">
    select
    <include refid="Base_Column_List" />
    from user
     limit #{startRow},#{OnePageSize}
  </select>

</mapper>

package com.elements.user;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;
import com.elements.user.dao.UserMapper;
import com.elements.user.model.User;

public class TestUserPage {

    @Test
    public void TestUserPageSelect() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder()
                .build(inputStream);

        SqlSession session = sqlSessionFactory.openSession();
        try {


            UserMapper user = (UserMapper) session
                    .getMapper(UserMapper.class);

            User u=new User();
            List<User> list =user.selectUserPage(u);

            System.out.println("-----page1-------");
            System.out.println(list);

            u.setNowPage(2);
            list =user.selectUserPage(u);

            System.out.println("-----page2-------");
            System.out.println(list);

        } finally {
            session.close();
        }

    }

}

• 输出结果  

-----page1-------
[User [userid=1, username=火柴盒, useremail=likewindy, createtime=null, updatetime=null]
, User [userid=7, username=aaaaa, useremail=aaaaa, createtime=null, updatetime=null]
, User [userid=8, username=5, useremail=6, createtime=null, updatetime=null]
, User [userid=9, username=5, useremail=6, createtime=null, updatetime=null]
, User [userid=10, username=5, useremail=6, createtime=null, updatetime=null]
]
-----page2-------
[User [userid=11, username=5, useremail=6, createtime=null, updatetime=null]
, User [userid=12, username=5, useremail=6, createtime=null, updatetime=null]
, User [userid=13, username=5, useremail=6, createtime=null, updatetime=null]
, User [userid=14, username=5, useremail=6, createtime=null, updatetime=null]
, User [userid=15, username=5, useremail=6, createtime=null, updatetime=null]
]

  项目代码地址： 
   缺点：当使用复合查询（链接表查询的时候就需要你手工对结果集进行限制 ），而这就是插件可以做到的事情。