使用mybatis开发原始Dao层
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。
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.update("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。
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