1 MyBatis的Dao編寫 【一般不用,有更多好方式】
package com.tzb.dao;
import com.tzb.model.User;
public interface IUserDao {
public void save(User user);
public User findUserById(int id);
}
package com.tzb.dao;
import com.tzb.model.User;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
public class UserDaoImpl implements IUserDao {
private SqlSessionFactory ssf;
public UserDaoImpl() {
}
public UserDaoImpl(SqlSessionFactory ssf) {
this.ssf = ssf;
}
@Override
public void save(User user) {
SqlSession session = ssf.openSession();
session.insert("insertUser", user);
session.commit();
session.close();
}
@Override
public User findUserById(int id) {
SqlSession session = ssf.openSession();
User user = session.selectOne("selectUser",id);
session.close();
return user;
}
}
2 MyBatis的Dao編寫【mapper代理方式實現】
- Mapper代理的開發方式,程序員只需要編寫mapper接口(相當於dao接口)即可。Mybatis會自動的爲mapper接口生成動態代理實現類。
- 要實現mapper代理的開發方式,需要遵循一些開發規範。
開發規範
- mapper接口的全限定名要和mapper映射文件的namespace的值相同。
- mapper接口的方法名稱要和mapper映射文件中的statement的id相同;
- mapper接口的方法參數只能有一個,且類型要和mapper映射文件中statement的parameterType的值保持一致。
- mapper接口的返回值類型要和mapper映射文件中statement的resultType值或resultMap中的type值保持一致;
通過規範式的開發mapper接口,可以解決原始dao開發當中存在的問題:
- 模板代碼已經去掉;
- 剩下去不掉的操作數據庫的代碼,其實就是一行代碼。這行代碼中硬編碼的部分,通過第一和第二個規範就可以解決。
- 第一步
重新寫個UserMapper配置文件和定義mapper映射文件UserMapper.xml(內容同Users.xml,除了namespace的值),放到新創建的目錄mapper下。
package com.tzb.mapper;
import com.tzb.model.User;
public interface UserMapper {
/**
*
* @param user
* @return 返回受影響的行數
*/
public int save(User user);
public User findUserById(int id);
}
<?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.tzb.mapper.UserMapper">
<insert id="save" parameterType="com.tzb.model.User">
<!-- 這裏的佔位寫模型的屬性-->
INSERT INTO user (username,sex,birthday,address)
VALUE (#{username},#{sex},#{birthday},#{address});
</insert>
<select id="findUserById" parameterType="int" resultType="com.tzb.model.User">
SELECT * FROM user WHERE id = #{id};
</select>
</mapper>
- 添加映射配置文件
SqlMapConfig.xml
<?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>
<!-- 配置mybatis的環境信息 -->
<environments default="development">
<environment id="development">
<!-- 配置JDBC事務控制,由mybatis進行管理 -->
<transactionManager type="JDBC"></transactionManager>
<!-- 配置數據源,採用dbcp連接池 -->
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/mybatis_test?useUnicode=true&characterEncoding=utf8"/>
<property name="username" value="root"/>
<property name="password" value="root"/>
</dataSource>
</environment>
</environments>
<!--加載映射文件-->
<mappers>
<!--<mapper resource="com/tzb/sqlmap/User.xml"></mapper>-->
<mapper resource="com/tzb/mapper/UserMapper.xml"></mapper>
</mappers>
</configuration>
- 測試類
import com.tzb.mapper.UserMapper;
import com.tzb.model.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import java.io.IOException;
import java.io.InputStream;
import java.util.Date;
public class Demo4 {
private SqlSession session;
@Before
public void before() throws IOException {
System.out.println("before.......獲取 session");
InputStream is = Resources.getResourceAsStream("SqlMapConfig.xml");
SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(is);
session = factory.openSession();
}
@After
public void after() {
System.out.println("after.......關閉 session");
session.close();
}
@Test
public void test1() throws IOException {
// 代理
UserMapper userMapper = session.getMapper(UserMapper.class);
System.out.println(userMapper.findUserById(1));
System.out.println("----------------------------------------");
User user = new User("Mary", "女", new Date(), "廣州");
userMapper.save(user);
session.commit();
}
}