MyBatis中实现动态的SQL语句,分页以及mybatis的常用的配置

1.动态SQL:在SQL语句中加入流程控制。比如加入ifforeach等。
 重点掌握if语句:

 案例1

<update id="updateItem" parameterType="com.gxa.bj.modle.UserInfo">
       update UserInfo set 
       <if test="userName!=null">
           userName=#{userName},
       </if>
       <if test="userPwd!=null">
           userPwd=#{userPwd},
       </if>
       <if test="userEmail!=null">
           userEmail=#{userEmail},
       </if>
       userId=#{userId} where userId=#{userId}       
 </update>

实现列:

UserInfo u=new UserInfo();
   u.setUserId(7);
   u.setUserName("李大名");
   u.setUserPwd("123");
   u.setUserEmail("[email protected]");
   userMapper.updateItem(u);
   sqlSessin.commit();   
   System.out.println("修改成功");

案列2:

<select id="getList" resultType="com.gxa.bj.modle.UserInfo" parameterType="com.gxa.bj.modle.UserInfo">
        select * from UserInfo where 1=1
        <if test="userName!=null">
            and userName like #{userName}
        </if>
        <if test="userId>0">
            and userId=#{userId}
        </if>
        <if test="userPwd!=null and userPwd!=''">
            and userPwd like #{userName}
        </if>
 </select>

实现列:


u.setUserName("小白");
   List<UserInfo> list= userMapper.getList(u);
   for(UserInfo u1:list){
    System.out.println("用户信息:"+u1.getUserPwd());
   }

2.分页的实现?

分页的时候考虑的问题:

分页的大小,分页的索引。

比如:分页的大小为10,分页的起始索引为1(索引从1开始)

第一页:110.    起始行号: (页的索引-1*分页大小+1

                   结束行号: 页的索引*分页大小

 

实现方案:

1)比如针对UserInfo的实体对象做分页处理,那么先创建一个分页的实体类,该类继承自UserInfo package com.gxa.bj.modle

package com.gxa.bj.modle;
public class UserInfoPage extends UserInfo{ 
private int pageIndex;//分页的索引

     private int pageSize;//分页的大小

private int startNum;//分页起始行
     private int endNum;//分页结束行

public int getPageIndex() {
return pageIndex;
}
public void setPageIndex(int pageIndex) {
this.pageIndex = pageIndex;
}
public int getPageSize() {
return pageSize;
}
public void setPageSize(int pageSize) {
this.pageSize = pageSize;
}
public int getStartNum() {
return startNum;
}
public void setStartNum(int startNum) {
this.startNum = startNum;
}
public int getEndNum() {
return endNum;
}
public void setEndNum(int endNum) {
this.endNum = endNum;
} 
}

2)在接口只陪你过定义一个方法:

public List<UserInfo> getListByPage(UserInfoPage upage);

3)在Mapper文件中编写SQL语句:

<select id="getListByPage" resultType="com.gxa.bj.modle.UserInfoPage" parameterType="com.gxa.bj.modle.UserInfoPage">
        select u.*
        From(select rownum as num, userinfo.*
              from userinfo
              <where>
                      <if test="userName!=null">
                          and userName like #{userName}
                      </if>
                      <if test="userId>0">
                          and userId=#{userId}
                      </if>
                      <if test="userPwd!=null and userPwd!=''">
                          and userPwd like #{userName}
                      </if>
              </where>
              ) u where u.num between #{startNum}and#{endNum}
 </select>


4)测试代码:

 
UserInfoPage u1= new UserInfoPage();
   u1.setUserName("userName");
   u1.setPageIndex(2);//查询第几页
      u1.setPageSize(2);//分布每页的条数
      int startNum=(u1.getPageIndex()-1)*u1.getPageSize()+1;
      int endNum=u1.getPageIndex()*u1.getPageSize();
      u1.setStartNum(startNum);
      u1.setEndNum(endNum);
      List<UserInfo> list=userMapper.getListByPage(u1);
      for(UserInfo t :list){
    System.out.println("id:"+t.getUserId());
    }






































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