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();
        }