通过ID查询一个用户的两种开发方法

数据库建表sql语句如下：https://github.com/beyondyanyu/Sayingyy/blob/master/JDBC2-数据库sql建表语句

①，原始Dao开发：

UserDao.java（接口）:

package com.pdsu.mybatis.dao;import com.pdsu.mybatis.pojo.User;public interface UserDao {//通过用户ID查询一个用户public User selectUserById(Integer id);}

UserDaoImpl.java（实现接口）:

package com.pdsu.mybatis.dao;import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;import com.pdsu.mybatis.pojo.User;/*** * */
public class UserDaoImpl implements UserDao {//注入SQLSession工厂private SqlSessionFactory sqlsessionFactory;//构造器public UserDaoImpl(SqlSessionFactory sqlsessionFactory) {this.sqlsessionFactory = sqlsessionFactory;}//通过用户ID查询一个用户public User selectUserById(Integer id){SqlSession sqlSession = sqlsessionFactory.openSession(); return sqlSession.selectOne("user.findUserById", id);}
}

MybatisDaoTest.java测试

package com.pdsu.mybatis.junit;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.Before;
import org.junit.Test;import com.pdsu.mybatis.dao.UserDao;
import com.pdsu.mybatis.dao.UserDaoImpl;
import com.pdsu.mybatis.pojo.User;public class MybatisDaoTest {public SqlSessionFactory sqlSessionFactory;@Beforepublic void before() throws Exception{ //加载核心配置文件，加载要使用IO流进行读取String resource = "sqlMapConfig.xml";InputStream in = Resources.getResourceAsStream(resource);//创建SqlSessionFactorysqlSessionFactory = new SqlSessionFactoryBuilder().build(in);}@Testpublic void testDao() throws Exception{UserDao userDao = new UserDaoImpl(sqlSessionFactory);User user = userDao.selectUserById(10);System.out.println(user);//输出结果就是数据库中ID为10的用户信息}
}

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">
<!-- namespace：命名空间，用于隔离sql，还有一个很重要的作用，后面会讲 -->
<!-- 
命名空间：user.findUserById
命名空间：order.findUserById 
--><mapper namespace="com.pdsu.mybatis.mapper.UserMapper"><!-- resultType:返回值parameterType:输入参数 --><!-- 通过ID查询一个用户 --><select id="findUserById" parameterType="Integer" resultType="com.pdsu.mybatis.pojo.User">select * from user where id= #{sq}</select><!-- #{} === select * from user where username=     表示占位符？   sq可以随意替代=== select * from user where username= '思琪'${} === select * from user where username like '%${value}%'  表示字符串拼接  value不可以随意替代=== select * from user where username like '%琪%' 			sql 模糊语句查询=== select * from user where username like "%"'琪%'"%" 		sql 模糊语句查询=== select * from user where username like "%"#{sq}"%" --><!-- 根据用户名称模糊查询用户列表 --><select id="findUserByUsername" parameterType="String" resultType="com.pdsu.mybatis.pojo.User">select * from user where username like '%${value}%'</select><!-- 添加用户 --><insert id="insertUser" parameterType="com.pdsu.mybatis.pojo.User"><selectKey keyProperty="id" resultType="Integer" order="AFTER" >select LAST_INSERT_ID()</selectKey>insert into user(username,birthday,address,sex) values (#{username},#{birthday},#{address},#{sex})</insert><!-- 更新用户 --><update id="updateUserById" parameterType="com.pdsu.mybatis.pojo.User">update user set username = #{username},sex = #{sex},birthday = #{birthday},address = #{address}where id = #{id}</update>	<!-- 删除用户 --><delete id="deleteUserById" parameterType="Integer" >delete from user where id = #{sq}</delete></mapper>

②，Mapper动态代理开发：

UserMapper.java:

package com.pdsu.mybatis.mapper;import java.util.List;import com.pdsu.mybatis.pojo.User;public interface UserMapper {/*遵循四个原则对于：public User findUserById(Integer id);接口   方法名 == User.xml中id名 === findUserById返回值类型 与 Mapper.xml文件中返回值类型（resultType）要一致 === User === com.pdsu.mybatis.pojo.User方法的入参类型 与 Mapper.xml中入参类型（parameterType）要一致 === Integer id命名空间绑定此接口<mapper namespace="com.pdsu.mybatis.mapper.UserMapper">,User.xml中的路径为该接口全路径*/public User findUserById(Integer id);}

MybatisMapperTest.java:

package com.pdsu.mybatis.mapper;import static org.junit.Assert.*;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.pdsu.mybatis.pojo.User;public class MybatisMapperTest {@Testpublic void testMapper() throws Exception {//加载核心配置文件，加载要使用IO流进行读取String resource = "sqlMapConfig.xml";InputStream in = Resources.getResourceAsStream(resource);//创建SqlSessionFactorySqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);//SqlSessionFactoryBuilder这是一个实现类需要new一下//创建SQLSessionSqlSession sqlSession = sqlSessionFactory.openSession();	//SqlSession自动生成实现类（接口需要遵循四大原则）=== UserMapper.class为遵循四大原则的接口UserMapper userMapper = sqlSession.getMapper(UserMapper.class);User user = userMapper.findUserById(30);System.out.println(user);//输出结果就是数据库中id为30的用户信息}
}

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">
<!-- namespace：命名空间，用于隔离sql，还有一个很重要的作用，后面会讲 -->
<!-- 
命名空间：user.findUserById
命名空间：order.findUserById 
--><mapper namespace="com.pdsu.mybatis.mapper.UserMapper"><!-- resultType:返回值parameterType:输入参数 --><!-- 通过ID查询一个用户 --><select id="findUserById" parameterType="Integer" resultType="com.pdsu.mybatis.pojo.User">select * from user where id= #{sq}</select><!-- #{} === select * from user where username=     表示占位符？   sq可以随意替代=== select * from user where username= '思琪'${} === select * from user where username like '%${value}%'  表示字符串拼接  value不可以随意替代=== select * from user where username like '%琪%' 			sql 模糊语句查询=== select * from user where username like "%"'琪%'"%" 		sql 模糊语句查询=== select * from user where username like "%"#{sq}"%" --><!-- 根据用户名称模糊查询用户列表 --><select id="findUserByUsername" parameterType="String" resultType="com.pdsu.mybatis.pojo.User">select * from user where username like '%${value}%'</select><!-- 添加用户 --><insert id="insertUser" parameterType="com.pdsu.mybatis.pojo.User"><selectKey keyProperty="id" resultType="Integer" order="AFTER" >select LAST_INSERT_ID()</selectKey>insert into user(username,birthday,address,sex) values (#{username},#{birthday},#{address},#{sex})</insert><!-- 更新用户 --><update id="updateUserById" parameterType="com.pdsu.mybatis.pojo.User">update user set username = #{username},sex = #{sex},birthday = #{birthday},address = #{address}where id = #{id}</update>	<!-- 删除用户 --><delete id="deleteUserById" parameterType="Integer" >delete from user where id = #{sq}</delete></mapper>