Mybatis学习笔记-使用Mybatis开发CRUD

新增

insert into person

(id,user_name,age,remark)

values

(#{id},#{name},#{age},#{remark})

</insert>

@Test //新增

public void testInsert(){

SqlSession session = factory.openSession();

Person p = new Person();

p.setId(4);

p.setName("hellen");

p.setAge(16);

p.setRemark("xijiang");

session.insert("cn.itcast.mapper.PersonMapper.insert", p);

session.commit(); //提交事务

System.out.println("insert finished.");

}

修改

update person

set user_name=#{name},age=#{age},remark=#{remark}

where id = #{id}

</update>

public void testUpdate(){

SqlSession session = factory.openSession();

Person p = new Person();

p.setId(4);

//p.setName("hellen2");

p.setAge(18);

//p.setRemark("beijing");

session.update("cn.itcast.mapper.PersonMapper.update", p);

session.commit();

}

删除一条

delete from person

where id = #{pid}

</delete>

public void testDeleteById(){

SqlSession session = factory.openSession();

session.delete("cn.itcast.mapper.PersonMapper.deleteById", 4);

session.commit();

}

删除多条，整形数组

delete from person

where id in

#{id}

</foreach>

</delete>

@Test //删除多条-数组

public void testDeleteByArray(){

SqlSession session = factory.openSession();

int[] ids = {4,6};

session.delete("cn.itcast.mapper.PersonMapper.deleteArray", ids);

session.commit();

}

delete from person

where id in

#{id}

</foreach>

</delete>

删除多条-LIST

public void testDeleteByList(){

SqlSession session = factory.openSession();

List<Integer> _list = new ArrayList<Integer>();

_list.add(4);

_list.add(6);

session.delete("cn.itcast.mapper.PersonMapper.deleteList", _list);

session.commit();

}

删除多条,Map

delete from person

where id in

#{id}

</foreach>

</delete>

删除多条,Map , ids 代表map中key

delete from person

where id in

#{id}

</foreach>

</delete>

@Test //删除多条 MAP

public void testDeleteByMap(){

SqlSession session = factory.openSession();

Map<String,Object> paraMap = new HashMap<String,Object>();

int[] ids = {4,6};

paraMap.put("ids", ids);

session.delete("cn.itcast.mapper.PersonMapper.deleteMap", paraMap);

session.commit();

}

获取记录总数

SELECT COUNT(*) FROM person

</select>

@Test //获取记录总数

public void testCount(){

SqlSession session = factory.openSession();

int i = session.selectOne("cn.itcast.mapper.PersonMapper.count");

System.out.println(i);

}

简化
1. 别名

</typeAliases>

select * from person

where id = #{pid}

</select>

1. SQL片段

<sql id="cols">id,user_name,age,remark</sql>

select <include refid="cols"/> from person

</select>

传参：map和po对象实体，查询条件封装

例如：年龄（整数），出生日期，入职日期（日期）

日期，有开始时间，结束时间

Map随意构造

动态SQL语句
1. <where> 能自动去掉where最前面and或者or

select <include refid="cols"/> from person

<where>

</where>

</select>

1. <set>自动删除最后一个逗号

<set>

<if test="remark!=null">remark=#{remark},</if>

</set>

1. <foreach>

#{id}

</foreach>

where id in

(

#{id}

</foreach>

)

对象关联

对一，需求：人员可以有扩展信息

人员person

扩展person_info 拓展用户信息，例如

人员和扩展信息表一对一

在mybatis中关联关系只有两种

对一 <association property=""></association>，

对多<collection property=""></collection>

结果集中有重名字段。

如果发生这种情况，重名情况，Mybatis，拿一个id字段的值，放到setId内。

如何处理？

赋别名

1. 配置文件PersonInfoMapper.xml

<?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">

</resultMap>

</association>

</resultMap>

SELECT

p.id,p.user_name,p.age,p.remark,

i.id AS infoid,i.station,i.join_date

FROM

(SELECT id,user_name,age,remark FROM person) p

LEFT JOIN

(SELECT id,station,join_date FROM person_info) i

ON p.id=i.id

<where>

</where>

</select>

</mapper>

1. 客户端调用

package test;

import java.io.IOException;

import java.io.InputStream;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

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.Before;

import org.junit.Test;

import cn.itcast.domain.Person;

/**

* @Description:

* @Author: 传智播客 java学院陈子枢

* @Company: http://java.itcast.cn

* @CreateDate: 2014年11月15日

public class TestPersonInfo {

private SqlSessionFactory factory;

@Before //最先执行，初始化SessionFactory

public void init() throws IOException{

String resource = "sqlMapConfig.xml";

InputStream is = Resources.getResourceAsStream(resource);

factory = new SqlSessionFactoryBuilder().build(is);

}

@Test //查询管理的一对一

public void testPersonInfo(){

SqlSession session = factory.openSession();

Map map = new HashMap();

List<Person> personList = session.selectList("cn.itcast.mapper.PersonInfoMapper.findPersonInfo", map);

for(Person p : personList){

System.out.println(p);

}

对多，人员可以拥有多本书籍

需求，某个人有几本书

package cn.itcast.domain;

1. Book实体

/**

* @Description:

* @Author: 传智播客 java学院陈子枢

* @Company: http://java.itcast.cn

* @CreateDate: 2014年11月15日

public class Book {

private Integer id;

private String name;

private Double money;

public Integer getId() {

return id;

}

public void setId(Integer id) {

this.id = id;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public Double getMoney() {

return money;

}

public void setMoney(Double money) {

this.money = money;

}

1. 改造person对象

package cn.itcast.domain;

import java.util.List;

/**

* @Description:

* @Author: 传智播客 java学院陈子枢

* @Company: http://java.itcast.cn

* @CreateDate: 2014年11月15日

public class Person {

private PersonInfo personInfo; //对一关联

private List<Book> books; //对多关联

private Integer id;

private String name;

private Integer age;

private String remark;

public Integer getId() {

return id;

}

public void setId(Integer id) {

this.id = id;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public Integer getAge() {

return age;

}

public void setAge(Integer age) {

this.age = age;

}

public String getRemark() {

return remark;

}

public void setRemark(String remark) {

this.remark = remark;

}

public PersonInfo getPersonInfo() {

return personInfo;

}

public void setPersonInfo(PersonInfo personInfo) {

this.personInfo = personInfo;

}

public List<Book> getBooks() {

return books;

}

public void setBooks(List<Book> books) {

this.books = books;

}

1. 对多，配置

<?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">

</resultMap>

</association>

</resultMap>

</collection>

</resultMap>

SELECT

p.id,p.user_name,p.age,p.remark,

i.id AS infoid,i.station,i.join_date

FROM

(SELECT id,user_name,age,remark FROM person) p

LEFT JOIN

(SELECT id,station,join_date FROM person_info) i

ON p.id=i.id

<where>

</where>

</select>

SELECT

p.id,p.name,p.age,p.remark,

p.infoid,p.station,p.join_date,

b.book_id,b.book_name,b.money

FROM

(

SELECT

p.id,p.name,p.age,p.remark,

i.infoid,i.station,i.join_date

FROM

(SELECT id,user_name AS NAME,age,remark FROM person) p

LEFT JOIN

(SELECT id AS infoid,station,join_date FROM person_info) i

ON p.id=i.infoid

) p

LEFT JOIN

(SELECT id AS book_id,NAME AS book_name,money,person_id FROM book) b

ON p.id=b.person_id

</select>

</mapper>

1. 客户端调用

@Test //查询某个人员（人员和人员信息的一对一，人员和书籍的一对多

public void testPersonBook(){

SqlSession session = factory.openSession();

Map map = new HashMap();

List<Person> personList = session.selectList("cn.itcast.mapper.PersonInfoMapper.findPersonInfoBook", map);

System.out.println(personList.size());

}

某个用户的书籍

SQL优化

缩小中间结果集

Select p.*,info.*,book.* from person left join person_info left join book on…..

1. 视图

在做大型项目，视图可能废除。项目组不允许在项目中使用视图

1. Hibernate

它在中小型项目中使用，无法SQL优化。

Mybatis学习笔记-使用Mybatis开发CRUD

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