【目录】
1 普通Dao层开发
2 Mapper动态代理开发
1 普通Dao层开发
准备数据库：
创建User表
插入一些数据
在Eclipse里新建项目目录如下：
项目目录结构
给出项目代码。
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>
<environments default="development">
<environment id="development">
<!-- 使用jdbc的事务 -->
<transactionManager type="JDBC"/>
<!-- 使用连接池 连接数据库 -->
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/database?useSSL=false"/>
<property name="username" value="root"/>
<property name="password" value="admin"/>
</dataSource>
</environment>
</environments>
<!-- 配置映射器的位置 -->
<mappers>
<mapper resource="mapper/UserMapper.xml"/>
</mappers>
</configuration>
User.java：
package com.test.bean;
import java.util.Date;
public class User {
/**
* CREATE TABLE `user` (
`u_id` INT(11) NOT NULL AUTO_INCREMENT COMMENT '用户id',
`u_username` VARCHAR(64) NOT NULL COMMENT '用户名',
`u_password` VARCHAR(64) NOT NULL COMMENT '用户密码',
`u_sex` VARCHAR(16) DEFAULT NULL COMMENT '用户性别',
`u_createTime` DATETIME DEFAULT NULL COMMENT '用户创建时间',
`u_cid` INT(11) NOT NULL COMMENT '用户国家id',
*/
private Integer u_id;
private String u_username;
private String u_password;
private String u_sex;
private Date u_createTime;
private Integer u_cid;
public Integer getU_id() {
return u_id;
}
public void setU_id(Integer u_id) {
this.u_id = u_id;
}
public String getU_username() {
return u_username;
}
public void setU_username(String u_username) {
this.u_username = u_username;
}
public String getU_password() {
return u_password;
}
public void setU_password(String u_password) {
this.u_password = u_password;
}
public String getU_sex() {
return u_sex;
}
public void setU_sex(String u_sex) {
this.u_sex = u_sex;
}
public Date getU_createTime() {
return u_createTime;
}
public void setU_createTime(Date u_createTime) {
this.u_createTime = u_createTime;
}
public Integer getU_cid() {
return u_cid;
}
public void setU_cid(Integer u_cid) {
this.u_cid = u_cid;
}
@Override
public String toString() {
return "User [u_id=" + u_id + ", u_username=" + u_username + ", u_password=" + u_password + ", u_sex=" + u_sex
+ ", u_createTime=" + u_createTime + ", u_cid=" + u_cid + "]";
}
}
UserDAO.java：
package com.test.dao;
import com.test.bean.User;
public interface UserDao {
//根据id查询用户
public User getUserById(Integer id);
}
UserMapper.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="UserMapper">
<!-- 根据id查询用户 -->
<select id="selectUserById" parameterType="Integer" resultType="com.test.bean.User">
select * from user where u_id = #{id}
</select>
</mapper>
UserDaoImpl.java：
package com.test.dao;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import com.test.bean.User;
public class UserDaoImpl implements UserDao {
//sqlSession工厂
private SqlSessionFactory ssf;
//通过构造器给ssf 赋值
public UserDaoImpl(SqlSessionFactory ssf) {
this.ssf = ssf;
}
public User getUserById(Integer id) {
//生产一个sqlSession
SqlSession session = ssf.openSession();
//操作数据库
return session.selectOne("UserMapper.selectUserById", id);
}
}
UserDaoTest.java：
package com.test.test;
import java.io.IOException;
import java.io.InputStream;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;
import com.test.bean.User;
import com.test.dao.UserDao;
import com.test.dao.UserDaoImpl;
public class UserDaoTest {
//sqlSession工厂
private static SqlSessionFactory ssf;
static {
String resource = "sqlMapConfig.xml";
InputStream in;
try {
in = Resources.getResourceAsStream(resource );
SqlSessionFactoryBuilder ssfb = new SqlSessionFactoryBuilder();
ssf = ssfb.build(in);
in.close();
} catch (IOException e) {
e.printStackTrace();
}
}
@Test
public void DaoTest() {
UserDao dao = new UserDaoImpl(ssf);
User user = dao.getUserById(1);
System.out.println(user);
}
}
进行测试。
测试结果
2 Mapper动态代理开发
复制上面的项目，命名为HelloMyBatisMapper。删除dao包及包内所有文件、com.test/test/UserDaoTest.java，新建动态代理接口类mapper/UserMapper.java、测试类com.test/test/MapperTest.java，整理项目目录如下所示：
项目目录
mapper动态代理开发四大原则 + 一个注意
1、接口方法名需要与mapper.xml的要调用的sql语句的id一致
2、接口的形参类型需要与mapper.xml parameterType 一致
3、接口的返回值需要与mapper.xml resultType一致
4、mapper.xml 中namespace要与接口的全包名一致
5、注意mapper动态代理开发中，动态代理对象调用，根据返回值类型来自动选择，如果返回的是list则调用的是selectList方法,如果返回的是单个值或者是对象那么调用的是selectOne方法。（selectOne： 查询一条记录、selectList： 查询一条或多条记录。）
一个小tips：在UserMapper.xml中选中全包名+ctrl，可以检查链接是否正确。
给出相关代码。
UserMapper.java：
package com.test.mapper;
import com.test.bean.User;
public interface UserMapper {
//mapper动态代理开发四大原则 + 一个注意
//1、接口方法名需要与mapper.xml的要调用的sql语句的id一致
//2、接口的形参类型需要与mapper.xml parameterType 一致
//3、接口的返回值需要与mapper.xml resultType一致
//4、mapper.xml 中namespace要与接口的全包名一致
//5、注意mapper动态代理开发中，根据返回值类型来自动选择
//通过id查询一个用户
public User selectUserById(Integer id);
}
UserMapper.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">
<!-- 注意 namespace的修改 -->
<mapper namespace="com.test.mapper.UserMapper">
<!-- 根据id查询用户 -->
<select id="selectUserById" parameterType="Integer" resultType="com.test.bean.User">
select * from user where u_id = #{id}
</select>
</mapper>
MapperTest.java：
package com.test.test;
import java.io.IOException;
import java.io.InputStream;
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.Test;
import com.test.bean.User;
import com.test.mapper.UserMapper;
public class MapperTest {
@Test
public void Test1() throws IOException {
String resource = "sqlMapConfig.xml";
//读取配置文件
InputStream in = Resources.getResourceAsStream(resource );
//创建sqlSessionfactory
SqlSessionFactory ssf = new SqlSessionFactoryBuilder().build(in);
//生产一个sqlSession
SqlSession session = ssf.openSession();
UserMapper mapper = session.getMapper(UserMapper.class);
User user = mapper.selectUserById(1);
System.out.println(user);
}
}
进行测试。
测试结果
可以看出，使用Mapper动态代理提高了开发效率，推荐使用。
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