Mybatis之XML、注解

前言

　　上篇简单介绍了Mybatis的简单实用，本篇先对上次实验环境的一些内容进行优化，然后验证Mybatis的XML配置以及注解方式。

实验环境优化

　　数据库配置

　　在mybatis的配置文件中，引入数据库配置文件db.properties，然后修改配置文件

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/mybatis
name=root
password=admin

mybatis配置文件 mybatis-config.xml

<?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>
    <!-- 数据库配置文件 -->
    <properties resource="db.properties"/>
<!--
    development : 开发模式
    work : 工作模式
 -->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC" />
            <dataSource type="POOLED">
                <property name="driver" value="${driver}" />
                <property name="url" value="${url}" />
                <property name="username" value="${name}" />
                <property name="password" value="${password}" />
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com/lion/mapper/UserMapper.xml" />
    </mappers>
</configuration>

实体类定义别名

　　没有为实体定义别名时，在sql映射xml中应用实体时，比如parameterType resultType 中就需要配置实体的全路径名（全限定名）。

　　当为实体定义了别名后，映射文件中可以直接配置实体的别名即可。因此为实体类定义别名，可以简化Sql映射xml文件中对实体的引用配置。

　　mybatis配置文件中<typeAlises>定义实体别名有两种方式：

• typeAlias 单个为每个实体定义别名 当实体类比较多是 配置增多 不方便
• package 指定实体的包  会自动为改包下的所有实体自动设定各自的类名为别名

　　

　　优化后的Mybatis配置文件mybatis-config.xml

<?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>
    <!-- 数据库配置文件 -->
    <properties resource="db.properties"/>

    <!-- 配置实体的别名 -->
    <typeAliases>
        <!-- 此种方式是分别为每一个实体设置别名 mapper xml 中resultType即为alias的值-->
        <!-- <typeAlias type="com.lion.pojo.User" alias="_User"/> -->
        <!-- package 设置别名的方式会自动为该包下的所有JavaBean设置别名为其类名称 -->
        <package name="com.lion.pojo"/>
    </typeAliases>
<!--
    development : 开发模式
    work : 工作模式
 -->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC" />
            <dataSource type="POOLED">
                <property name="driver" value="${driver}" />
                <property name="url" value="${url}" />
                <property name="username" value="${name}" />
                <property name="password" value="${password}" />
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com/lion/mapper/UserMapper.xml" />
    </mappers>
</configuration>

Mybatis实现方式

　　分别使用XML和注解的方式实现对User的CURD。
　　XML方式

　　sql中参数定义为 #{} 在Mybatis配置文件中已经配置对实体类的自动设置别名，因此此处可以直接使用实体类的别名进行引用。

<?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.lion.mapper.UserMapper">
  <select id="selectUser" parameterType="int" resultType="User">
    select * from users where id = #{id}
  </select>

  <delete id="deleteUser" parameterType="int">
      delete from users where id = #{id}
  </delete>

  <update id="updateUser" parameterType="User">
      update users set name = #{name},age = #{age} where id = #{id}
  </update>

  <insert id="addUser" parameterType="User">
      insert into users(name,age) values(#{name},#{age})
  </insert>

  <select id="selectAll" resultType="User" >
      select * from users
  </select>
</mapper>

　　

 package com.lion.test;

 import java.io.IOException;
 import java.util.List;

 import org.apache.ibatis.session.SqlSession;
 import org.apache.ibatis.session.SqlSessionFactory;
 import org.junit.Test;

 import com.lion.pojo.User;
 import com.lion.util.MybatisUtils;

 public class TestUserCURDByXML {

     @Test
     public void testAdd() {
         try {
             SqlSessionFactory factory = MybatisUtils.getFactory();
             SqlSession session = factory.openSession();

             String statement = "com.lion.mapper.UserMapper.addUser";
             // id mysql设置的自增长 此处设为 -1
             User user = new User(-1, "Spring", 25);
             session.insert(statement, user);

             // 不提交的话 数据无法提交到数据库
             session.commit();
             session.close();
         } catch (IOException e) {
             e.printStackTrace();
         }
     }

     @Test
     public void testDelete() {
         try {
             SqlSessionFactory factory = MybatisUtils.getFactory();
             // 自动提交事务
             SqlSession session = factory.openSession(true);

             String statement = "com.lion.mapper.UserMapper.deleteUser";
             session.delete(statement, 4);

             session.close();
         } catch (IOException e) {
             e.printStackTrace();
         }
     }

     @Test
     public void testUpdate() {
         try {
             SqlSessionFactory factory = MybatisUtils.getFactory();
             // 自动提交事务
             SqlSession session = factory.openSession(true);

             String statement = "com.lion.mapper.UserMapper.updateUser";
             User user = new User(1, "mali", 18);
             session.update(statement, user);

             session.close();
         } catch (IOException e) {
             e.printStackTrace();
         }
     }

     @Test
     public void testSelect() {
         try {
             SqlSessionFactory factory = MybatisUtils.getFactory();
             // 自动提交事务
             SqlSession session = factory.openSession(true);

             String statement = "com.lion.mapper.UserMapper.selectAll";
             List<User> users = session.selectList(statement);
             for (User user : users) {
                 System.out.println(user);
             }

             session.close();
         } catch (IOException e) {
             e.printStackTrace();
         }
     }

 }

　　

　　注解方式

package com.lion.testAnnotation;

import java.util.List;

import org.apache.ibatis.annotations.Delete;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.Update;

import com.lion.pojo.User;

public interface UserMapper {
    @Insert("insert into users(name,age) values(#{name},#{age})")
    int insertUser(User user);

    @Delete("delete from users where id = #{id}")
    int deleteUser(int id);

    @Update("update users set name = #{name},age = #{age} where id = #{id}")
    int updateUser(User user);

    @Select("select * from users where id = #{id}")
    User selectUser(int id);

    @Select("select * from users")
    List<User> selectAll();
}

　　Mybatis配置文件中注册映射接口  class

    <mappers>
        <mapper resource="com/lion/mapper/UserMapper.xml" />
        <mapper class="com.lion.testAnnotation.UserMapper"/>
    </mappers>

　　针对同一实体的映射文件不能放到同一个包中。

 package com.lion.testAnnotation;

 import java.io.IOException;
 import java.util.List;

 import org.apache.ibatis.session.SqlSession;
 import org.apache.ibatis.session.SqlSessionFactory;
 import org.junit.Before;
 import org.junit.Test;

 import com.lion.pojo.User;
 import com.lion.util.MybatisUtils;

 public class TestUserCURDByAnnotaion2 {

     private SqlSessionFactory factory;

     @Before
     public void loadFactory() {
         try {
             factory = MybatisUtils.getFactory();
         } catch (IOException e) {
             e.printStackTrace();
         }
     }

     @Test
     public void testAdd() {
         SqlSession session = factory.openSession(true);
         // 映射器
         UserMapper mapper = session.getMapper(UserMapper.class);

         int i = mapper.insertUser(new User(-1, "xiazis", 24));

         System.out.println(i);

         session.close();

     }

     @Test
     public void testDelete() {
         SqlSession session = factory.openSession(true);
         // 映射器
         UserMapper mapper = session.getMapper(UserMapper.class);

         int i = mapper.deleteUser(1);

         System.out.println(i);

         session.close();

     }

     @Test
     public void testUpdate() {
         SqlSession session = factory.openSession(true);
         // 映射器
         UserMapper mapper = session.getMapper(UserMapper.class);

         int i = mapper.updateUser(new User());

         System.out.println(i);

         session.close();

     }

     @Test
     public void testSelect() {
         SqlSession session = factory.openSession(true);
         // 映射器
         UserMapper mapper = session.getMapper(UserMapper.class);

         User user = mapper.selectUser(2);

         System.out.println(user);

         session.close();

     }

     @Test
     public void testSelectAll() {
         SqlSession session = factory.openSession(true);
         // 映射器
         UserMapper mapper = session.getMapper(UserMapper.class);

         List<User> users = mapper.selectAll();

         for (User user : users) {
             System.out.println(user);
         }

         session.close();

     }

 }