MyBatis开发Dao层的两种方式（原始Dao层开发）

妖狐艹你老母 2023-10-18 13:32 234阅读 0赞

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）][MyBatis_Dao_Mapper]

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。

![1553771-20181212215900813-801367374.png][]

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">
            
                <transactionManager type="JDBC" />
            
                <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">
        
        <select id="findUserById" parameterType="int" resultType="com.xyfer.po.User">
            select * from user where id = #{id}
        </select>
        
        <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>
        
        <update id="updateUser" parameterType="com.xyfer.po.User">
            update user set username=#{username},birthday=#{birthday},sex=#{sex},address=#{address}
            where id=#{id}
        </update>
        
        <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：

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。

[MyBatis_Dao_Mapper]: https://blog.csdn.net/xyfer1018/article/details/86180439
[1553771-20181212215900813-801367374.png]: https://img2018.cnblogs.com/blog/1553771/201812/1553771-20181212215900813-801367374.png