Mybatis

做了个mybatis的Demo，发现mybatis和我之前实习时用的EOS开发工具中的对数据库操作的组件很类似，现在想来那个EOS就是对mybatis进行了封装。

eclipse下的Demo

数据库表

与数据表映射的实体类

//与数据表映射的实体类
package dao;

public class User {
    private int id;
    private String name;
    private int age;
    
    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 getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
     
    @Override
    public String toString() {
       return "User [id=" + id + ", name=" + name + ", age=" + age + "]";
    }
}

userMapper.xml

<!--userMapper.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">
 <mapper namespace="mapping.userMapper">
     <!-- parameterType为传入参数类型，resultType为结果返回接收的类型 -->
     <select id="getUser" parameterType="int" 
         resultType="dao.User">
         select * from users
     </select>
     
 </mapper>

mybatis配置文件

<!--  mybatis配置文件 -->

<?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" />
            <!-- 配置数据库连接信息 -->
             <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver" />
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis" />
                <property name="username" value="root" />
                <property name="password" value="000000" />
            </dataSource>
        </environment>
    </environments>
   
    <mappers>
        <!-- 注册userMapper.xml文件 -->
        <mapper resource="mapping/userMapper.xml"/>
    </mappers>
    
</configuration>

测试类

public class Test {

     public static void main(String[] args) {
        // TODO Auto-generated method stub
      //mybatis的配置文件
        String resource = "conf.xml";
        //使用类加载器加载mybatis的配置文件（它也加载关联的映射文件）
        InputStream is = Test.class.getClassLoader().getResourceAsStream(resource);
        //构建sqlSession的工厂
        SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(is);
        //使用MyBatis提供的Resources类加载mybatis的配置文件（它也加载关联的映射文件）
        //Reader reader = Resources.getResourceAsReader(resource); 
        //构建sqlSession的工厂
        //SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader);
        //创建能执行映射文件中sql的sqlSession
        
        SqlSession session = sessionFactory.openSession();

        String statement = "mapping.userMapper.getUser";//映射sql的标识字符串

        List<User> userList = session.selectList(statement);
        
        for(int i = 0;i<userList.size();i++){
            System.out.println(userList.get(i).toString());

        }
    }
}

以上输出结果是user表的所有内容。

mapper.xml的sql语句中可以随意的设置parameterType传入参数，是基本类型也可以是自定义的类，查询结果接收类型resultType也可以随便设置只要sql查询出的结果的属性能够满足是resultType属性的子集就可以（sql结果的属性name在resultType中都能有与之相对应的name）。

//mapper中设置
 <mapper namespace="mapping.userMapper">

     <select id="getUser" parameterType="dao.User" 
         resultType="dao.User">
         select * from users where id=#{id} and name = #{name}
     </select>
     
 </mapper>





//java中调用
        User user = new User();
        user.setAge(1);
        user.setId(1);
        user.setName("johnny");
//        HashMap<String, Object> map = new HashMap<String, Object>();
//        map.put("id", 2);
//        map.put("name", "asd");
        List<User> userList = session.selectList(statement, user);
        
        for(int i = 0;i<userList.size();i++){
            System.out.println(userList.get(i).toString());

        }