MyBatis入门

一、简介

官方文档

二、起步

1、准备数据库

新建数据库 mybatis

新建数据表 user

   DROP TABLE IF EXISTS `user`;
   CREATE TABLE `user` (
     `id` int(11) NOT NULL AUTO_INCREMENT,
     `user_name` varchar(255) DEFAULT NULL,
     `gender` char(1) DEFAULT NULL,
     `email` varchar(255) DEFAULT NULL,
     PRIMARY KEY (`id`)
   ) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8;

   -- ----------------------------
   -- Records of user
   -- ----------------------------
   INSERT INTO `user` VALUES ('1', '小明', '1', 'xiaoming@163.com');

2、新建工程并导包（新建一个javase工程）

手动（非maven项目）
- mybatis-3.4.6.jar
- mysql-connector-java-5.1.14.jar

自动（maven项目）（将以下内容加到pom.xml中）

 <dependency>
       <groupId>junit</groupId>
       <artifactId>junit</artifactId>
       <version>4.12</version>
       <scope>test</scope>
     </dependency>
     <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
     <dependency>
       <groupId>org.mybatis</groupId>
       <artifactId>mybatis</artifactId>
       <version>3.4.1</version>
     </dependency>
     <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
     <dependency>
       <groupId>mysql</groupId>
       <artifactId>mysql-connector-java</artifactId>
       <version>5.1.14</version>
     </dependency>
     <!-- https://mvnrepository.com/artifact/org.slf4j/slf4j-log4j12 -->
     <dependency>
       <groupId>org.slf4j</groupId>
       <artifactId>slf4j-log4j12</artifactId>
       <version>1.7.25</version>
       <scope>test</scope>
     </dependency>

     <!-- https://mvnrepository.com/artifact/org.projectlombok/lombok -->
   <!-- <dependency>
       <groupId>org.projectlombok</groupId>
       <artifactId>lombok</artifactId>
       <version>1.18.0</version>
       <scope>provided</scope>
   </dependency> -->

将 Log4j.xml或log4j.properties 置与 classpath 中

log4j.xml

   <?xml version="1.0" encoding="UTF-8" ?>
   <!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">

   <log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">

    <appender name="STDOUT" class="org.apache.log4j.ConsoleAppender">
      <param name="Encoding" value="UTF-8" />
      <layout class="org.apache.log4j.PatternLayout">
       <param name="ConversionPattern" value="%-5p %d{MM-dd HH:mm:ss,SSS} %m  (%F:%L) \n" />
      </layout>
    </appender>

    <logger name="org.apache.ibatis">
      <level value="info" />
    </logger>
    <root>
      <level value="debug" />
      <appender-ref ref="STDOUT" />
    </root>
   </log4j:configuration>

log4j.properties

   log4j.rootLogger=debug,stdout
   log4j.appender.stdout=org.apache.log4j.ConsoleAppender 
   log4j.appender.stdout.layout=org.apache.log4j.PatternLayout    
   log4j.appender.stdout.layout.ConversionPattern="%-5p %m (%c:%L) \n


   log4j.logger.org.apache.ibatis=INFO

   #log4j.logger.java.sql=DEBUG

3、创建Mybatis总配置文件mybatis-config.xml(文件名可变)

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <!--<typeAliases>
        <package name="com.weixin.vo"/>
    </typeAliases> -->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="jdbc:mysql://localhost:3306/mybatis??useUnicode=true&amp;characterEncoding=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>
    <!-- <mappers>
        <mapper resource="UserMapper.xml"/>
      </mappers> -->
</configuration>

4、新建User实体类及dao文件

User.java(实体类中userName对应数据表中的user_name字段)

 package com.edu.bean;

 public class User {
     private Integer id;
     private String userName;
     private String gender;
     private String email;

     public User() {
     }

     public Integer getId() {
         return this.id;
     }

     public String getUserName() {
         return this.userName;
     }

     public String getGender() {
         return this.gender;
     }

     public String getEmail() {
         return this.email;
     }

     public void setId(Integer id) {
         this.id = id;
     }

     public void setUserName(String userName) {
         this.userName = userName;
     }

     public void setGender(String gender) {
         this.gender = gender;
     }

     public void setEmail(String email) {
         this.email = email;
     }

     @Override
     public String toString() {
         return "User{" +
                 "id=" + id +
                 ", userName='" + userName + '\'' +
                 ", gender='" + gender + '\'' +
                 ", email='" + email + '\'' +
                 '}';
     }
 }

UserMapper.java(dao文件)

 package com.edu.mapper;

 import com.edu.bean.User;

 import java.util.List;

 public interface UserMapper {
     //查询所有数据
     List<User> selectAll();
     //根据id查询一条语句
     User selectById(int id);
     //增加用户
     int inser(User user);
     //删除用户
     boolean deleteById(int id);
     //修改用户
     boolean update(User user);
 }

5、mybatis新版本支持面向接口编程，程序员不需要再写接口的实现类，转而用配置文件代替：

创建UserMapper的映射文件 UserMapper.xml：(此文件需要和dao文件同名)

 <?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">
 <mapper namespace="com.edu.mapper.UserMapper">
     <insert id="inser">
         insert into user(user_name,gender,email) values (#{userName},#{gender},#{email});
     </insert>
     <update id="update">
         update user set user_name = #{userName},gender = #{gender},email = #{email} where id = #{id}
     </update>
     <delete id="deleteById">
         delete from user where id = #{id}
     </delete>
     <select id="selectAll" resultType="com.edu.bean.User">
          select * from user
     </select>
     <select id="selectById" resultType="com.edu.bean.User">
         select * from user where id = #{id}
     </select>
 </mapper>

6、将UserMapper.xml 加载到总配置文件mybatis-config.xml中

<settings>
  <setting name="mapUnderscoreToCamelCase" value="true"/>
</settings>

<environments>
      ........
</environments>

<mappers>
     <mapper resource="UserMapper.xml"/>
</mappers>

7、测试

package com.edu;

import com.edu.bean.User;
import com.edu.mapper.UserMapper;
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 java.io.IOException;
import java.io.InputStream;
import java.util.List;

public class UserTest {

    //加载mybatis-config.xml到输入流
    InputStream inputStream = Resources.getResourceAsStream("mybatis-config.xml");
    //通过输入流构建SqlSessionFactory对象
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

    public UserTest() throws IOException {
    }

    @Test
    public void testSelectAll() throws IOException {

        //通过SqlSessionFactory对象得到一个SqlSession对象，每个数据库操作都依靠SqlSession
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //通过SqlSession对象得到一个mapper的实现对象
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> usersList = mapper.selectAll();
        System.out.println(usersList);
    }

    @Test
    public void testSelectById(){
        //通过SqlSessionFactory对象得到一个SqlSession对象，每个数据库操作都依靠SqlSession
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //通过SqlSession对象得到一个mapper的实现对象
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        User user = mapper.selectById(1);
        System.out.println(user);
    }

    @Test
    public void testInsert(){
        //通过SqlSessionFactory对象得到一个SqlSession对象，每个数据库操作都依靠SqlSession
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //通过SqlSession对象得到一个mapper的实现对象
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        User user = new User();
        user.setUserName("小美");
        user.setGender("2");
        user.setEmail("7777@163.com");

        int inser = mapper.inser(user);

        System.out.println(inser);

        //提交事务
        sqlSession.commit();
    }

    @Test
    public void testDeleteById(){
        //通过SqlSessionFactory对象得到一个SqlSession对象，每个数据库操作都依靠SqlSession
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //通过SqlSession对象得到一个mapper的实现对象
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        boolean b = mapper.deleteById(5);

        System.out.println(b);

        sqlSession.commit();
    }

    @Test
    public void testUpdate(){
        //通过SqlSessionFactory对象得到一个SqlSession对象，每个数据库操作都依靠SqlSession
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //通过SqlSession对象得到一个mapper的实现对象
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        //先把数据查出来
        User user = mapper.selectById(1);
        user.setGender("2");

        //修改
        mapper.update(user);
        sqlSession.commit();
    }
}

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MyBatis入门

一、简介

二、起步

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MyBatis入门

一、简介

二、起步