前置内容 => Mybatis查询数据库
项目结构:
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">
<!-- namespace的值设置成包名+sql映射文件名,保证namespace取值唯一 -->
<mapper namespace="com.cheese.mapping.userMapper">
<!-- id属性值必须唯一,不能重复
parameterType设置查询语句接受的参数类型(userID 的数据类型)
resultType设置查询返回的结果类型
resultType="com.cheese.pojo.User"表示 t_user每行记录被封装成一个User对象
-->
<!-- 根据userid查询User对象 -->
<select id="getUser" parameterType="int" resultType="com.cheese.pojo.User">
select * from t_user where userid=#{userID}
</select>
<!-- 查询多个User对象 -->
<select id="getUserList" resultType="com.cheese.pojo.User">
select * from t_user where userid <=3
</select>
<insert id="addUser" parameterType="map">
insert into t_user(userid,username,password,name)
values(#{userID},#{userName},#{password},#{name})
</insert>
<update id="updateUser" parameterType="map">
update t_user set name=#{name},password=#{password} where userid=#{userID}
</update>
<delete id="deleteUser" parameterType="map">
delete from t_user where userid=#{userID}
</delete>
</mapper>
package com.cheese.pojo;
public class User
{
private int userID;
private String userName;//用户名
private String password;
private String name;//全名
public User()
{
}
public int getUserID() {
return userID;
}
public void setUserID(int userID) {
this.userID = userID;
}
public String getUserName()
{
return userName;
}
public void setUserName(String userName)
{
this.userName = userName;
}
public String getPassword()
{
return password;
}
public void setPassword(String password)
{
this.password = password;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
自定义Mybatis 工具类:
package com.cheese.test;
import java.io.InputStream;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
public class SessionUtil {
private static final String resource = "config.xml";//mybatis配置文件
private static InputStream is;
private static SqlSessionFactory sessionFactory;
static {
is = SessionUtil.class.getClassLoader().getResourceAsStream(resource);//加载mybatis配置文件
//创建sqlSession工厂
sessionFactory = new SqlSessionFactoryBuilder().build(is);
}
public static SqlSession getSession() {
//创建sqlSession
SqlSession session = sessionFactory.openSession();
return session;
}
}
测试程序:
package com.cheese.test;
import java.util.List;
import org.apache.ibatis.session.SqlSession;
import com.cheese.pojo.User;
import org.junit.Test;
public class TestCRUD{
@Test
public void addUser(){
SqlSession sqlSession = SessionUtil.getSession();
/**
* 映射sql的字符串,
* com.cheese.mapping.userMapper是userMapper.xml文件中mapper标签的namespace属性的值,
* addUser是insert标签的id属性值
*/
String insertStr = "com.cheese.mapping.userMapper.addUser";//namespace + id 定位到要执行的sql语句
User user = new User();
user.setUserName("Jane");
user.setPassword("a111");
user.setName("Jane Austen");
//插入
int rowCount = sqlSession.insert(insertStr,user);
sqlSession.commit();//提交事务
sqlSession.close();//关闭session
System.out.println("新增记录数:" + rowCount);
}
@Test
public void getUserList(){
SqlSession sqlSession = SessionUtil.getSession();
String getListStr = "com.cheese.mapping.userMapper.getUserList";
//执行查询操作,将查询结果自动封装成List<User>返回
List<User> userList = sqlSession.selectList(getListStr);
sqlSession.close();
System.out.println(userList.get(1).getName());//打印第个User对象的name属性值
}
@Test
public void updateUser(){
SqlSession sqlSession = SessionUtil.getSession();
String updateStr = "com.cheese.mapping.userMapper.updateUser";
User user = new User();
user.setUserID(3);
user.setName("匹特");
user.setPassword("p111");
//修改
int rowCount = sqlSession.update(updateStr,user);
sqlSession.commit();
sqlSession.close();
System.out.println("被修改记录数:" + rowCount);
}
@Test
public void deleteUser(){
SqlSession sqlSession = SessionUtil.getSession();
String deleteStr = "com.cheese.mapping.userMapper.deleteUser";
//删除
int rowCount = sqlSession.delete(deleteStr,2);
sqlSession.commit();
sqlSession.close();
System.out.println("被删除记录数:" + rowCount);
}
}
Mybatis配置文件: config.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">
<transactionManager type="JDBC" />
<!-- 配置数据库连接信息 -->
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver" />
<property name="url" value="jdbc:mysql://localhost:3306/base6"/>
<property name="username" value="btsuser" />
<property name="password" value="b111" />
</dataSource>
</environment>
</environments>
<mappers>
<!-- 注册userMapper.xml文件 -->
<mapper resource="com/cheese/mapping/userMapper.xml"/>
</mappers>
</configuration>
运行测试: