MyBatis开发Dao层的两种方式（原始Dao层开发）

　　本文将介绍使用框架mybatis开发原始Dao层来对一个对数据库进行增删改查的案例。

　　Mapper动态代理开发Dao层请阅读我的下一篇博客：MyBatis开发Dao层的两种方式（Mapper动态代理方式）

　　本次使用的mybatis版本为mybatis-3.2.7，开发工具为eclipse，数据库为mysql，jdk版本jdk1.8.0_151。

　　1、首先，使用eclipse新建一个java工程，在lib目录下加入mybatis核心包、依赖包、数据驱动包，然后BuildPath一下。。

　　

　　2、添加日志文件，在classpath下创建log4j.properties如下：

# Global logging configuration
log4j.rootLogger=DEBUG, stdout
# Console output...
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%5p [%t] - %m%n

　　3、在classpath下创建config资源文件夹，并在config文件夹下创建SqlMapConfig.xml，如下：

<?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">
        <!-- 使用jdbc事务管理-->
            <transactionManager type="JDBC" />
        <!-- 数据库连接池-->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver" />
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?characterEncoding=utf-8" />
                <property name="username" value="root" />
                <property name="password" value="root" />
            </dataSource>
        </environment>
    </environments>
</configuration>

　　SqlMapConfig.xml是mybatis核心配置文件，上边文件的配置内容为数据源、事务管理。

　　4、创建数据封装使用的User类

package com.xyfer.po;

import java.util.Date;
/**
 * 
 * @author xyfer
 * 数据封装使用的User类
 *
 */
public class User {
    
    private int       id;          //id
    private String    username;    //姓名
    private String    sex;         //性别
    private Date      birthday;    // 生日
    private String    address;     // 地址
    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 getSex() {
        return sex;
    }
    public void setSex(String sex) {
        this.sex = sex;
    }
    public Date getBirthday() {
        return birthday;
    }
    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }
    public String getAddress() {
        return address;
    }
    public void setAddress(String address) {
        this.address = address;
    }

}

　　5、在classpath下的资源文件夹sqlmapper目录下创建sql映射文件User.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="test">
    <!-- 根据id查询用户 -->
    <select id="findUserById" parameterType="int" resultType="com.xyfer.po.User">
        select * from user where id = #{id}
    </select>
    <!-- 添加用户 -->
    <insert id="insertUser" parameterType="com.xyfer.po.User">
    <selectKey keyProperty="id" order="AFTER" resultType="java.lang.Integer">
        select LAST_INSERT_ID() 
    </selectKey>
      insert into user(username,birthday,sex,address) 
      values(#{username},#{birthday},#{sex},#{address})
    </insert>
    <!-- 修改用户 -->
    <update id="updateUser" parameterType="com.xyfer.po.User">
        update user set username=#{username},birthday=#{birthday},sex=#{sex},address=#{address}
        where id=#{id}
    </update>
    <!-- 删除用户 -->
    <delete id="deleteUserById" parameterType="int">
        delete from user where id=#{id}
    </delete>
    
</mapper>

　　6、mybatis框架需要加载映射文件，将Users.xml添加在SqlMapConfig.xml，如下：

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

　　7、dao层接口

package com.xyfer.dao;

import com.xyfer.po.User;

public interface UserDao {

    public User getUserById(int id);   //根据id值查询一个用户
    public void insertUser(User user); //新增一个用户
    public void updateUser(User user); //修改一个用户
    public void deleteUser(int id);    //删除一个用户
    
}

　　dao层接口实现类

package com.xyfer.dao.impl;

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

import com.xyfer.dao.UserDao;
import com.xyfer.po.User;

public class UserDaoImpl implements UserDao {
    //注入SqlSessionFactory
    public UserDaoImpl(SqlSessionFactory sqlSessionFactory){
            this.setSqlSessionFactory(sqlSessionFactory);
        }
            
    private SqlSessionFactory sqlSessionFactory;
        
    public SqlSessionFactory getSqlSessionFactory() {
        return sqlSessionFactory;
    }

    public void setSqlSessionFactory(SqlSessionFactory sqlSessionFactory) {
        this.sqlSessionFactory = sqlSessionFactory;
    }

    @Override
    public User getUserById(int id) {
        SqlSession session = sqlSessionFactory.openSession();
        User user = null;
        try {
            //通过sqlsession调用selectOne方法获取一条结果集
            //参数1：指定定义的statement的id,参数2：指定向statement中传递的参数
            user = session.selectOne("test.findUserById", 1);
            System.out.println(user);
                        
        } finally{
            session.close();
        }
        return user;
    }

    @Override
    public void insertUser(User user) {
        SqlSession sqlSession = sqlSessionFactory.openSession();
        try {
            sqlSession.insert("test.insertUser", user);
            sqlSession.commit();
        } finally{
            sqlSession.close();
        }
    }

    @Override
    public void updateUser(User user) {
        SqlSession sqlSession = sqlSessionFactory.openSession();
        try {
            sqlSession.update("test.updateUser", user);
            sqlSession.commit();
        } finally{
            sqlSession.close();
        }
    }

    @Override
    public void deleteUser(int id) {
        SqlSession sqlSession = sqlSessionFactory.openSession();
        try {
            sqlSession.delete("test.deleteUserById", id);
            sqlSession.commit();
        } finally{
            sqlSession.close();
        }
    }

}

　　8、创建一个JUnit的测试类，对UserDao进行测试。

package com.xyfer.dao.impl;

import static org.junit.Assert.*;

import java.io.InputStream;
import java.util.Date;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Before;
import org.junit.Test;

import com.xyfer.dao.UserDao;
import com.xyfer.po.User;

public class UserDaoImplTest {

    private SqlSessionFactory sqlSessionFactory;
    
    @Before
    public void init() throws Exception {
        SqlSessionFactoryBuilder sessionFactoryBuilder = new SqlSessionFactoryBuilder();
        InputStream inputStream = Resources.getResourceAsStream("SqlMapConfig.xml");
        sqlSessionFactory = sessionFactoryBuilder.build(inputStream);
    }

    @Test
    public void testGetUserById() {
        UserDao userDao = new UserDaoImpl(sqlSessionFactory);
        User user = userDao.getUserById(22);
        System.out.println(user);
    }

    @Test
    public void testInsertUser() {
        User user = new User();
        user.setUsername("小李");
        user.setSex("男");
        user.setBirthday(new Date());
        user.setAddress("杭州市");
        UserDao userDao = new UserDaoImpl(sqlSessionFactory);
        userDao.insertUser(user);
    }

    @Test
    public void testUpdateUser() {
        User user = new User();
        user.setId(10);
        user.setUsername("小威");
        user.setSex("男");
        user.setBirthday(new Date());
        user.setAddress("杭州市");
        UserDao userDao = new UserDaoImpl(sqlSessionFactory);
        userDao.updateUser(user);
    }

    @Test
    public void testDeleteUser() {
        UserDao userDao = new UserDaoImpl(sqlSessionFactory);
        userDao.deleteUser(10);
    }

}

　　以上步骤，完成使用mybatis框架开发原始dao层，并对数据库进行增删改查操作。

　　需要注意的是，上文提到的config文件夹和sqlmapper文件夹均为资源文件夹（source folder），默认会加载该路径下的文件。