mybatis实现数据的增删改查
概念：
- mybatis是一个持久层的框架，是apache下的顶级项目
- 让程序将主要精力放在sql上，通过mybatis提供的映射方式，自由灵活生成需要的sql语句。
- 可以将向
prepareStatement中的参数自动进行输入映射，将查询结果集灵活映射成java对象。（输出映射）
遇见的问题:
①Loading class com.mysql.jdbc.Driver'. This is deprecated. The new driver class iscom.mysql.cj.jdbc.Driver'. The driver is automatically registered via the SPI and manual loading of the driver class is generally unnecessary.
原因：使用了当前最新的mysql-connector-java-8.0.11-.jar的MySQL驱动包，新的驱动包中`com.mysql.jdbc.Driver'类已经过时，它通过SPI自动注册，不再需要手动加载驱动类
②java.sql.SQLException: The server time zone value 'Öйú±ê׼ʱ¼ä' is unrecognized or represents more than one time zone.
修改方法：value="jdbc:mysql://localhost:3306/test?serverTimezone=GMT%2B8"/
③当数据表中的内容为Date类型时，查询语句会报错。不知原因，有大佬知道的话请告诉一下
体系结构
2.png
导入所需jar包：
1.png
根据Id查询数据
- log4j.properties
log4j.rootLogger = DEBUG,Console
log4j.appender.Console = org.apache.log4j.ConsoleAppender
log4j.appender.Console.layout = org.apache.log4j.PatternLayout
log4j.appender.Console.layout.ConversionPattern = %d[%t]%-5p [%c] - %m%n
- 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">
<select id="findUserById" parameterType="int" resultType="cn.itcast.mybatis.po.Employee">//parameterType输入类型，resultType输出结果类型
select id,username,sex,address from users where id=#{id};//#{}是一个占位符
</select>
</mapper>
- 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">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.cj.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/test?serverTimezone=GMT%2B8"/>
<property name="username" value="root"/>
<property name="password" value=""/>
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="sqlmap/User.xml"/>
</mappers>
</configuration>
- Employee.java
package cn.itcast.mybatis.po;
import java.sql.Date;
public class Employee {
private int id;
private String username;
private String sex;
private String address;
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 String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
@Override
public String toString() {
return "Employee [id=" + id + ", username=" + username + ", sex=" + sex + ", address=" + address + "]";
}
}
- MybatisFirst.java
package sqlmap;
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 cn.itcast.mybatis.po.Employee;
public class MybatisFirst {
@Test
public void findUserByIdTest() throws IOException{
String resource="SqlMapConfig.xml";//配置文件
InputStream inputStream= Resources.getResourceAsStream(resource);//得到配置文件流
SqlSessionFactory sqlSessionFactory =new SqlSessionFactoryBuilder().build(inputStream);//创建会话工厂，传入配置文件信息
SqlSession sqlSession =sqlSessionFactory.openSession();//通过工厂得到sqlsession
Employee employee =sqlSession.selectOne("test.findUserById",1);//是selectOne查询一条数据
System.out.println(employee);
sqlSession.close(); //关闭会话
}
}
根据名称模糊查询数据
- SqlMapConfig.xml
<select id="findUserByName" parameterType="java.lang.String" resultType="cn.itcast.mybatis.po.Employee">
select id,username,sex,address from users where username like '%${value}%';//${}可能会引起sql注入，只是一个拼接符，不做任何改变
</select>
- 测试文件
@Test
public void findUserByNameTest() throws IOException{
String resource="SqlMapConfig.xml";
InputStream inputStream= Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory =new SqlSessionFactoryBuilder().build(inputStream);
SqlSession sqlSession =sqlSessionFactory.openSession();
java.util.List<Employee> list= sqlSession.selectList("test.findUserByName", "zhao");//selectList查询多条数据
System.out.println(list);
sqlSession.close();
}
向数据库中添加数据
- SqlMapConfig.xml
<insert id="insertUser" parameterType="cn.itcast.mybatis.po.Employee">
<selectKey keyProperty="id" order="AFTER" resultType="java.lang.Integer">
select LAST_INSERT_ID(); //查询自增的主键值
</selectKey>
insert into users(id,username,sex,address)value(#{id},#{username},#{sex},#{address});
</insert>
- 测试文件
@Test
public void insertUserTest() throws IOException{
String resource="SqlMapConfig.xml";
InputStream inputStream= Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory =new SqlSessionFactoryBuilder().build(inputStream);
SqlSession sqlSession =sqlSessionFactory.openSession();
Employee employee= new Employee();
employee.setId(10);
employee.setUsername("wu");
employee.setSex("nv");
employee.setAddress("henan");
sqlSession.insert("test.insertUser",employee);
sqlSession.commit();
System.out.println(employee.getId());//输出自增的主键值
sqlSession.close();
}
从数据库中删除文件
- SqlMapConfig.xml
<delete id="deleteUser" parameterType="java.lang.Integer">
delete from users where id=#{id};
</delete>
- 测试文件
@Test
public void deleteUserTest() throws IOException{
String resource="SqlMapConfig.xml";
InputStream inputStream= Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory =new SqlSessionFactoryBuilder().build(inputStream);
SqlSession sqlSession =sqlSessionFactory.openSession();
sqlSession.delete("test.deleteUser",12);
sqlSession.commit();
sqlSession.close();
}
更新数据库中的数据
- SqlMapConfig.xml
<update id="updateUser" parameterType="cn.itcast.mybatis.po.Employee">
update users set username=#{username},sex=#{sex},address=#{address} where id=#{id};
</update>
- 测试文件
@Test
public void updateUserTest() throws IOException{
String resource="SqlMapConfig.xml";
InputStream inputStream= Resources.getResourceAsStream(resource)；
SqlSessionFactory sqlSessionFactory =new SqlSessionFactoryBuilder().build(inputStream);
SqlSession sqlSession =sqlSessionFactory.openSession();
Employee employee= new Employee();
employee.setId(13);
employee.setUsername("sheng");
employee.setSex("nv");
employee.setAddress("diqiu");
sqlSession.update("test.updateUser",employee);
sqlSession.commit();
sqlSession.close();
}
