Nayuki

mybatis介绍

2021-02-15 分类 mybatis 作者 Nayuki ~4.49K 字

使用原因

  • 半自动

    • sql语句交由开发人员
    • 其他环境由框架自动实现

  • 比Hiberante学习成本低

    • Hiberante是全自动全映射
    • 想要实现sql语句优化需要掌握hql

  • 低耦合

    • 框架是自动实现，不用大动干戈改代码

初次查询

  • 引入的文件

    • mybatis-3.5.6.jar
    • log4j-1.2.17.jar
    • mysql-connector-java-8.0.13.jar
    • log4j.xml

  • 创建mybatis-config.xml

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<?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>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/user?serverTimezone=UTC"/>
                <property name="username" value="root"/>
                <property name="password" value="mysql"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="UserMapper.xml"/>
    </mappers>
</configuration>
  • 创建User类
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public class User {
    int id;
    String name;
    int money;
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
    public int getMoney() {
        return money;
    }

    public void setMoney(int money) {
        this.money = money;
    }
    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", money=" + money +
                '}';
    }
}
  • 创建UserMapper.xml
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<?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="UserMapper">
    <select id="selectUser" resultType="bean.User">
        select * from user where id = #{id}
    </select>
</mapper>
  • 测试
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public void test(){
    String resource = "mybatis-config.xml";
    InputStream inputStream = null;
    try {
        inputStream = Resources.getResourceAsStream(resource);
    } catch (IOException e) {
        e.printStackTrace();
    }
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    SqlSession openSession = sqlSessionFactory.openSession();
    try {
        User user = openSession.selectOne("selectUser",1);
        System.out.println(user);
    }finally {
        openSession.close();
    }
}

接口式编程

  • 创建UserMapper接口
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public interface UserMapper {
    User getUser(Integer integer);
}
  • 创建对应UserMapper.xml
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<?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="bean.UserMapper">
    <select id="getUser" resultType="bean.User">
        select * from user where id = #{id}
    </select>
</mapper>
  • 测试
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public void test1(){
    String resource = "mybatis-config.xml";
    InputStream inputStream = null;
    try {
        inputStream = Resources.getResourceAsStream(resource);
    } catch (IOException e) {
        e.printStackTrace();
    }
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    SqlSession openSession = sqlSessionFactory.openSession();
    try {
        UserMapper userMapper = openSession.getMapper(bean.UserMapper.class);
        User user = userMapper.getUser(1);
        System.out.println(user);
    }finally {
        openSession.close();
    }
}
最后编辑：2021-02-28