http://blog.csdn.net/future_it_daniel/article/details/51810489
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if,foreach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:1到10. 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());
- }
1.动态SQL:在SQL语句中加入流程控制。比如加入if,foreach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:1到10. 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());
- }