MyBatis学习练习

转自：http://ccchhhlll1988-163-com.iteye.com/blog/1415621

基本目的：利用Mybatis完成对一个表简单的select、insert、update、delete操作。达到熟悉MyBatis基本用法的目的。 
用到的jar：MyBatis.jar,数据库驱动.jar（如mysql-connector.jar）

MyBatis的配置文件MyBatisConfig.xml。可以进行数据源和事务管理器的配置，以及其他影响MyBatis执行的变量。

MyBatisConfig.xml代码：

<?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>
 <!-- 引入外部文件 -->
 <properties resource="config.properties"></properties>
 <!-- end properties -->
 <!-- 定义vo --> 
    <typeAliases>
        <typeAlias alias="User" type="com.mybatis.test.vo.User" />
    </typeAliases>
 <!-- end define -->
 <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="${username}" />
    <property name="password" value="${password}" />
   </dataSource>
  </environment>
 </environments>
 <mappers>
  <mapper resource="com/mybatis/test/maps/UserMapper.xml" />
 </mappers>
</configuration>

MyBatis的映射文件UserMapper.xml。文档中评价这个文件时奇迹发生的地方：

UserMapper.xml代码：

<?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.mybatis.test.dao.UserDAO">
 <select id="selectUser" parameterType="int" resultType="User">
  select *
  from user where id = #{id}
 </select>
 <select id="selectAllUser" resultType="User">
  select id, username from
  user
 </select>
 <insert id="insertUser" parameterType="User">
  insert into user(username)
  values ( #{username})
 </insert>
 <update id="updateUser" parameterType="User">
  update user set
  username=#{username}, password=#{password} where id = #{id}
 </update>
 <delete id="deleteUser" parameterType="User">
  delete from user where
  username=#{username} and password=#{password}
 </delete>
</mapper>

UserMapper接口文件，该文件与UserMapper.xml有着某些地方一一对应的关系，注意哦。

代码：

package com.mybatis.test.dao;
import java.util.List;
import com.mybatis.test.vo.User;
public interface UserDAO {
    public User selectUser(int id);
    public List<User> selectAllUser();
    public int insertUser(User user);
    public void updateUser(User user);
    public void deleteUser(User user);
}

MyBatis文件，其中定义了产生SqlSessionFactory的工厂单例类。

代码：

package com.mybatis.test.util;
import java.io.IOException;
import java.io.Reader;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
/**
 * @author chl 工厂单例模式，生成SqlSessionFactory实例。
 *
 */
public class MyBatis {
    private MyBatis() {
    };
    private static SqlSessionFactory ssf = null;
    public static SqlSessionFactory getSessionFactory() throws IOException {
        if (null == ssf) {
            String resource = "mybatisConfig.xml";
            Reader reader = Resources.getResourceAsReader(resource);
            ssf = new SqlSessionFactoryBuilder().build(reader);
        }// if
        return ssf;
    }
}

User文件，定义了User javabean实体类。

package com.mybatis.test.vo;

public class User {
    private int id;
    private String username;
    private String password;

public int getId() {
        return id;
    }

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

public String getUsername() {
        return username;
    }

public void setUsername(String username) {
        this.username = username;
    }

public String getPassword() {
        return password;
    }

public void setPassword(String password) {
        this.password = password;
    }

@Override
    public String toString() {
        return "id is:" + id + " name is: " + username;
    }
}

userAction类，方法体中获取SqlSessionFactory实例，获得SqlSession，获取SqlMapper，然后调用映射的方法。

package com.mybatis.test.util;

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

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

import com.mybatis.test.dao.UserDAO;
import com.mybatis.test.vo.User;

/**
 * @author chl 对user的操作。 其中将SqlSession放于方法级范围。
 */
public class UserAction {

public void insert(User user) {
        SqlSessionFactory ssf = null;
        SqlSession session = null;
        try {
            ssf = MyBatis.getSessionFactory();
            session = ssf.openSession(true);// 设定事务自动提交(方式一)
            UserDAO userDAO = session.getMapper(UserDAO.class);

userDAO.insertUser(user);
            selectAll();
            System.out.println("==================================");
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (null != session) {
                session.close();
                session = null;
            }
        }

}

public void update(User user) {
        SqlSessionFactory ssf = null;
        SqlSession session = null;
        try {
            ssf = MyBatis.getSessionFactory();
            session = ssf.openSession();
            UserDAO userDAO = session.getMapper(UserDAO.class);

userDAO.updateUser(user);

session.commit();// 设定事务自动提交(二)
            selectAll();
            System.out.println("==================================");
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (null != session) {
                session.close();
                session = null;
            }
        }
    }

public void selectAll() {
        SqlSessionFactory ssf = null;
        SqlSession session = null;
        try {
            ssf = MyBatis.getSessionFactory();
            session = ssf.openSession();
            UserDAO userDAO = session.getMapper(UserDAO.class);

List<User> users = userDAO.selectAllUser();
            for (User u : users) {
                System.out.println(u.getUsername() + "    " + u.getId());
            }

System.out.println("session is null? " + (session == null));
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (null != session) {
                session.close();
                session = null;
            }
        }
    }

public void delete(User user) {
        SqlSessionFactory ssf = null;
        SqlSession session = null;

try {
            ssf = MyBatis.getSessionFactory();
            session = ssf.openSession(true);
            UserDAO userDAO = session.getMapper(UserDAO.class);
            userDAO.deleteUser(user);

selectAll();
            System.out.println("==================================");
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (null != session) {
                session.close();
                session = null;
            }
        }
    }

public static void main(String[] args) {
        UserAction userAction = new UserAction();

User user = new User();
        user.setUsername("horizon");
        user.setPassword("123456");
        userAction.delete(user);
    }
}

config.properties代码：

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/tt
username=root
password=root

这是参照转载的网站代码修正的，转载的事务处理有点问题，在此进行了修改.....