mybatis 运用mapper开发

作者: 林太浪先生 | 来源:发表于2019-02-26 20:35 被阅读0次

转自https://blog.csdn.net/xiangshuai198807/article/details/78640647

mapper接口（相当于dao接口），但不用再写mapper接口的实现类了，直接用mapper接口的代理对象来操作/ 创建mapper对象 -- DBUserMapper对象

SqlSessionsqlsession =sqlSessionFactory.openSession();

DBUserMappermapper = sqlsession.getMapper(DBUserMapper.class);

用mapper对象来操作sql即可

Mapper代理使用的是jdk的代理策略

Mapper代理的开发规范

1、 mapper接口的全限定名要和mapper映射文件的namespace值一致。

2、 mapper接口的方法名称要和mapper映射文件的statement的id一致。

3、 mapper接口的方法参数类型要和mapper映射文件的statement的parameterType的值一致，而且它的参数是一个。

4、 mapper接口的方法返回值类型要和mapper映射文件的statement的resultType的值一致。

说简单点，其实mapper开发和我们dao开发是一样的,但不用再创建mapper接口的实现类，就是将dao接口换成mapper接口，

其实和dao接口一样也是个接口，只是这个接口要满足如上 mapper代理开发的开发规范，然后直接DBUserMapper mapper= sqlsession.getMapper(DBUserMapper.class)，再用mapper操作sql完成持久化即可。

步骤：

Jar包导入，生成数据库表，创建与src同级资源目录config,test目录(注意，config,test均为资源目录)

Mybatis开发方式之mapper代理开发—mybatis推荐的开发方式，和我写过的最简单的2dao接口开发方式，和hibernate写demo差不多一模一样,改成遵守一系列规范的mapper接口和其实现类而已，也是先创建实体类DBUser，再建实体类对应的映射文件DBUserMapper.xml（局部xml文件）,再将DBUserMapper.xml mapper到SqlMapConfig.xml（全局配置文件），再严格按照DBUserMapper.xml的sql弄个mapper接口DBUserMapper（此接口的全类名对应DBUserMapper.xml 的namespane标签，方法名对应DBUserMapper.xml的sql id,方法参数和返回类型也需与DBUserMapper.xml对应），无须弄mapper接口的实现类直接再弄个测试类Demo1来测下即可

1.创建实体类：

DBUser.java

package com.xiangshuai.mybatis.pojo;

import java.util.Date;

public classDBUser {

private int id;

private Integer sex;

private Date birthday;

private String address;

private String username;

public DBUser(Integer sex, Date birthday, String address, String username) {

super();

this.sex = sex;

this.birthday = birthday;

this.address = address;

this.username = username;

}

public DBUser() {

super();

// TODO Auto-generated constructor stub

}

public String getUsername() {

return username;

}

public void setUsername(String username) {

this.username = username;

}

public int getId() {

return id;

}

public void setId(int id) {

this.id = id;

}

public Integer getSex() {

return sex;

}

public void setSex(Integer sex) {

this.sex = sex;

}

public Date getBirthday() {

return birthday;

}

public void setBirthday(Date birthday) {

this.birthday = birthday;

}

public String getAddress() {

return address;

}

public void setAddress(String address) {

this.address = address;

}

@Override

public String toString() {

return "DBUser [id="+ id + ", sex="+ sex+ ", birthday=" + birthday+ ", address=" + address+ ", username="

+username + "]";

}

2.建实体类对应的映射文件DBUserMapper.xml（局部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">

<!-- 注意：在mapper代理时，它具有特殊及重要的作用，在这里 namespace="com.xiangshuai.mybatis.mapper.DBUserMapper"

对应mapper接口DBUserMapper的全类名-->

<!-- resultType：输出结果的所映射的java类型（单条结果所对应的java类型 ===

对应mapper接口DBUserMapper的方法返回类型-） -->

<select id="findDBUserById" parameterType="int"

resultType="com.xiangshuai.mybatis.pojo.DBUser">

SELECT* FROM DBUSER WHERE id =#{id}

</select>

UPDATE DBUSER SET username=#{username},sex=#{sex},birthday=#{birthday},address=#{address}where id=#{id}

</update>

DELETE FROM DBUSER WHERE id=#{id}

</delete>

<!-- 增加后入参的dbuser对象仍然没有带id,如果要数据库持久化后入参带id，则需要在insert标签中加seleteKey标签从数据库中将id

查出来再赋予给入参下个id="insertDBUser1"就是mysql主键是int类型自增就是这样的 -->

INSERT INTO DBUSER

(username,birthday,sex,address)

VALUES(#{username},#{birthday},#{sex},#{address});

</insert>

<!-- ${}：表示一个sql的连接符，会原样输出，而#{}会转成varchar也就是String类型

比如一个id为int类型id=3 #{id}后会变成'3' 但${value}就是3-->

<select id="findDBUsersByName" parameterType="java.lang.String"

resultType="com.xiangshuai.mybatis.pojo.DBUser">

SELECT* FROM DBUSER WHERE username LIKE '%${value}%'

</select>

<select id="findDBUsersByNameConcat" parameterType="java.lang.String"

resultType="com.xiangshuai.mybatis.pojo.DBUser">

SELECT* FROM DBUSER WHERE username LIKE concat('%',#{name},'%')

</select>

<!-- order：指定查询主键的sql和insert语句的执行顺序，相当于insert语句来说

AFTER之后也就是在执行完insert完成持久化记录之后将这条记录的id查出来再赋值给入参参数DBUse对象 -->

SELECTLAST_INSERT_ID()

</selectKey>

INSERTINTO DBUSER

(username,birthday,sex,address)

VALUES(#{username},#{birthday},#{sex},#{address})

</insert>

SELECTUUID()

</selectKey>

INSERTINTO DBUSER

(id,username,birthday,sex,address)

VALUES(#{id},#{username},#{birthday},#{sex},#{address})

</insert>

SELECTseq.nextval FROM dual

</selectKey>

INSERTINTO DBUSER

(id,username,birthday,sex,address)

VALUES(#{id},#{username},#{birthday},#{sex},#{address})

</insert>

</mapper>

4.严格参照DBUserMapper.xml 按照mapper规范创建mapper接口DBUserMapper.java

packagecom.xiangshuai.mybatis.mapper;

import java.util.List;

importcom.xiangshuai.mybatis.pojo.DBUser;

public interface DBUserMapper {

public DBUser findDBUserById(Integer id);

public void udateDBUser(DBUser user);

public void deleteDBUser(Integer id);

public void insertDBUser(DBUser user);

public void insertDBUser1(DBUseruser);

public List<DBUser> findDBUsersByName(String username);

public List<DBUser> findDBUsersByNameConcat(String username);

}

5.测试类Demo1.java

package com.xiangshuai.test;

import java.io.IOException;

import java.io.InputStream;

import java.text.ParseException;

import java.text.SimpleDateFormat;

import java.util.Date;

import java.util.List;

importorg.apache.ibatis.io.Resources;

importorg.apache.ibatis.session.SqlSession;

importorg.apache.ibatis.session.SqlSessionFactory;

importorg.apache.ibatis.session.SqlSessionFactoryBuilder;

import org.junit.Before;

import org.junit.Test;

import com.xiangshuai.mybatis.mapper.DBUserMapper;

importcom.xiangshuai.mybatis.pojo.DBUser;

public class Demo1 {

/*mybatis开发方式mapper开发非mapper开始：查询，操作和hibernate很像，也是先造实体类，然后配实体类的XML映射文件，然后将实体类的XML映射文件mapper到全局映射 XML文件

SqlMapConfig.xml中去，

* */

privateSqlSessionFactory sqlSessionFactory;

@Before

publicvoid before(){

//读取配置文件

//全局配置文件的路径

Stringresource = "SqlMapConfig.xml";

InputStreaminputStream = null;

try{

inputStream= Resources.getResourceAsStream(resource);

}catch (IOException e) {

//TODO Auto-generated catch block

e.printStackTrace();

}

//创建SqlSessionFactory

sqlSessionFactory = newSqlSessionFactoryBuilder().build(inputStream);

}

@Test

public void findDBUserById(){

//创建mapper对象 -- DBUserMapper对象

SqlSessionsqlsession = sqlSessionFactory.openSession();

DBUserMappermapper = sqlsession.getMapper(DBUserMapper.class);

//调用mapper完成增删改查方法

DBUseruser = mapper.findDBUserById(31);

sqlsession.close();

System.out.println(user);

}

//模糊查询之 like'%${value}%'，之所以不用 %#{username}%是因为 mybatis 将#{username}转成 %'诗'%而不是像${}原样输出

@Test

public void findDBUserByUsername(){

//创建mapper对象 -- DBUserMapper对象

SqlSessionsqlsession = sqlSessionFactory.openSession();

DBUserMappermapper = sqlsession.getMapper(DBUserMapper.class);

//调用mapper完成增删改查方法

//第一个参数：表示statement的唯一标示,namespace.id(DBUserMapper.xml中sql标签 id)

List<DBUser> users=mapper.findDBUsersByName("诗");

sqlsession.close();

System.out.println(users);

}

// 测试用 mysql concat()完成模糊查询用户列表

@Test

public void findDBUsersByNameConcat(){

//创建mapper对象 -- DBUserMapper对象

SqlSessionsqlsession = sqlSessionFactory.openSession();

DBUserMappermapper = sqlsession.getMapper(DBUserMapper.class);

//调用mapper完成增删改查方法

//第一个参数：表示statement的唯一标示,namespace.id(DBUserMapper.xml中sql标签 id)

List<DBUser> users=mapper.findDBUsersByNameConcat("诗");

sqlsession.close();

System.out.println(users);

}

@Test

publicvoid updateDBUser(){

//创建mapper对象 -- DBUserMapper对象

SqlSessionsqlsession = sqlSessionFactory.openSession();

DBUserMappermapper = sqlsession.getMapper(DBUserMapper.class);

//调用mapper完成增删改查方法

DBUser user = mapper.findDBUserById(31);

user.setSex(2);user.setUsername("刘小敏");

mapper.udateDBUser(user);

sqlsession.commit();

sqlsession.close();

}

@Test

publicvoid deleteDBUserById(){

//创建mapper对象 -- DBUserMapper对象

SqlSessionsqlsession = sqlSessionFactory.openSession();

DBUserMappermapper = sqlsession.getMapper(DBUserMapper.class);

//调用mapper完成增删改查方法;

mapper.deleteDBUser(38);

sqlsession.commit();

sqlsession.close();

}

//在insert标签中不加selectKey标签,不返回id给dbuser对象的增加测试

@Test

publicvoid insertUser() throws ParseException{

//创建mapper对象 -- DBUserMapper对象

SqlSessionsqlsession = sqlSessionFactory.openSession();

DBUserMappermapper = sqlsession.getMapper(DBUserMapper.class);

//调用mapper完成增删改查方法

SimpleDateFormatsdf = new SimpleDateFormat("yyyy-MM-dd");

Dateda = sdf.parse("1997-11-12");

DBUseruser = new DBUser(1,da,"广西梧州","刘小诗");

mapper.insertDBUser(user);

sqlsession.commit();

sqlsession.close();

System.out.println(user);//打印结果无id,但数据库中已经有这条id记录 DBUser [id=0, sex=1, birthday=Wed Nov 1200:00:00 CST 1997, address=广西梧州, username=刘小诗]

}

//在insert标签中加selectKey标签,并且设order="AFTER"表示在insert持久化后将这条记录的id查出粜,赋给入参 dbuser对象的增加测试

@Test

publicvoid insertUserHaveId() throws ParseException{

//创建mapper对象 -- DBUserMapper对象

SqlSessionsqlsession = sqlSessionFactory.openSession();

DBUserMappermapper = sqlsession.getMapper(DBUserMapper.class);

//调用mapper完成增删改查方法

SimpleDateFormatsdf = new SimpleDateFormat("yyyy-MM-dd");

Dateda = sdf.parse("1997-11-13");

DBUseruser = new DBUser(1,da,"北京西城","刘诗诗");

mapper.insertDBUser1(user);

sqlsession.commit();

sqlsession.close();

System.out.println(user);//打印结果带id的DBUser[id=36, sex=1, birthday=Thu Nov 13 00:00:00 CST 1997, address=北京西城,username=刘诗诗]

}

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