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。