Mybatis步骤分解实现一个增删改查程序

1.idea新建Maven项目Mybatis-study 将项目里的src文件夹删掉 依次将此项目作为父项目

2.在Mybatis-study中新建模块mybatis-01

在mybatis的pom文件中可以看到其父项目为ybatis-study

<parent>
    <artifactId>MyBatis-study</artifactId>
    <groupId>org.example</groupId>
    <version>1.0-SNAPSHOT</version>
</parent>

3. 在Mybatis-study的pom.xml中引入如下jar包

<dependencies>
   <dependency>
     <groupId>junit</groupId>
     <artifactId>junit</artifactId>
     <version>4.11</version>
     <scope>test</scope>
   </dependency>
   <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
   <dependency>
     <groupId>org.mybatis</groupId>
     <artifactId>mybatis</artifactId>
     <version>3.5.9</version>
   </dependency>
   <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
   <dependency>
     <groupId>mysql</groupId>
     <artifactId>mysql-connector-java</artifactId>
     <version>8.0.29</version>
   </dependency>
 </dependencies>

4.将IDEA和MySQL数据库建立连接：

根据实际情况填写user和password 填写之后点击Test Connection

测试成功之后点击Schemas选择你要链接的数据库

5.新建mybatis-config.xml配置文件 引入数据库资源

<?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/smbms?useSSL=true&amp;characterEncoding=UTF-8"/>
               <property name="username" value="root"/>
               <property name="password" value="root"/>
           </dataSource>
       </environment>
   </environments>
   <mappers>
       <mapper resource="com/kero/dao/UserMapper.xml" />
   </mappers>
</configuration>

6.创建实体类User 注意:实体类中成员变量名要和数据库表中字段名完全一致

package com.kero.pojo;
public class User {
   private int id;
   private String name;
   private String password;
   public User() {
   }
   public User(int id, String name, String password) {
       this.id = id;
       this.name = name;
       this.password = password;
   }
   public int getId() {
       return id;
   }
   public void setId(int id) {
       this.id = id;
   }
   public String getName() {
       return name;
   }
   public void setName(String name) {
       this.name = name;
   }
   public String getpassword() {
       return password;
   }
   public void setpassword(String pwd) {
       this.password = pwd;
   }
   @Override
   public String toString() {
       return "User{" +
               "id=" + id +
               ", name='" + name + '\'' +
               ", pwd='" + password + '\'' +
               '}';
   }
}

7.编写工具类Utils

package com.kero.utils;
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 java.io.IOException;
import java.io.InputStream;
//sqlSessionFactory
public class MyBatisUtils {
   private static SqlSessionFactory sqlSessionFactory;
   static {
       try {
           //使用Mybatis第一步 获取sqlSessionFactory对象
           String resource = "mybatis-config.xml";
           InputStream inputStream = Resources.getResourceAsStream(resource);
           sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
       } catch (IOException e) {
           throw new RuntimeException(e);
       }
   }
/*
既然有了 SqlSessionFactory，顾名思义，我们可以从中获得 SqlSession 的实例。SqlSession
提供了在数据库执行 SQL 命令所需的所有方法。你可以通过 SqlSession 实例来直接执行已映射的 SQL 语句。例如：
*/
       public static SqlSession getSqlSession(){
           return sqlSessionFactory.openSession();
       }
}

8.定义接口

package com.kero.dao;
import com.kero.pojo.User;
import java.util.List;
public interface UserMapper {
 //查询全部用户
   List<User> getUserList();
   //根据ID查询用户
   User getUserByID(int id);
   //insert一个用户
   int addUser(User user);
 //修改一个用户
 int updateUser(User user);
 //删除一个用户
 int deleteUser(int id);
}

9.定义Mapper文件 这里的Mapper文件相当于原来传统方式中接口的实现类

<?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会绑定一个对应的Mapper接口-->
<mapper namespace="com.kero.dao.UserMapper">
   <select id="getUserList" resultType="com.kero.pojo.User">
       select * from smbms.user
   </select>
       <select id="getUserByID" parameterType="int" resultType="com.kero.pojo.User">
           select * from smbms.user where id = #{id}
       </select>
   <insert id="addUser" parameterType="com.kero.pojo.User">
       insert into smbms.user (id, name, password) VALUES (#{id},#{name},#{password})
   </insert>
   <update id="updateUser" parameterType="com.kero.pojo.User">
      update smbms.user set name=#{name},password=#{password} where id = #{id}
   </update>
   <delete id="deleteUser" parameterType="int">
       delete from smbms.user where id = #{id}
   </delete>
</mapper>

10.编写测试类

import com.kero.dao.UserMapper;
import com.kero.pojo.User;
import com.kero.utils.MyBatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
import java.util.List;
public class test {
   @Test
   public void test(){
       SqlSession session = MyBatisUtils.getSqlSession();
       UserMapper mapper = session.getMapper(UserMapper.class);
       List<User> userList = mapper.getUserList();
       for (User l:userList) {
           System.out.println(l.toString());
       }
       session.close();
   }
   @Test
   public void testgetUserByID(){
       SqlSession session = MyBatisUtils.getSqlSession();
       UserMapper mapper = session.getMapper(UserMapper.class);
       User userByID = mapper.getUserByID(1);
       System.out.println(userByID);
       session.close();
   }
   //增删改需要提交事务
   @Test
   public void testaddUser(){
       SqlSession session = MyBatisUtils.getSqlSession();
       UserMapper mapper = session.getMapper(UserMapper.class);
       int zhhgf = mapper.addUser(new User(10, "zhhgf", "1k23jbjk"));
       System.out.println(zhhgf);
       session.commit();
       //提交事务
       session.close();
   }
   @Test
   public void testupdateUser(){
       SqlSession session = MyBatisUtils.getSqlSession();
       UserMapper mapper = session.getMapper(UserMapper.class);
       int i = mapper.updateUser(new User(8,"asdfsdf","234sdfs"));
       session.commit();
       //提交事务
       session.close();
   }
   @Test
   public void testdeleteUser(){
       SqlSession session = MyBatisUtils.getSqlSession();
       UserMapper mapper = session.getMapper(UserMapper.class);
       int i = mapper.deleteUser(8);
       session.commit();
       //提交事务
       session.close();
   }
}

11.测试查询功能 : 输出结果与数据库表中数据

User{id=1, name='Sugawara Ryota', pwd='8X8Jq7HVNs'}

User{id=2, name='Shawn Mills', pwd='R78IHGDSXr'}

User{id=3, name='Matsuda Hina', pwd='mUi3CVA7mc'}

User{id=4, name='Cynthia Hawkins', pwd='NO1EwWbOs9'}

User{id=5, name='Rachel Bennett', pwd='YefuPVxzb9'}

tips:

如果一切配置正常但出现java.lang.ExceptionInInitializerError

Caused by org.apache.ibatis.execeptions.PersistenceExecepyion错误

是因为:maven由于它的约定大于配置 我们写的配置文件可能会出现无法被导出或者生效的问题解决方案 在pom.xml文件中添加如下代码

<build>
 <resources>
   <resource>
     <directory>src/main/resources</directory>
     <includes>
       <include>**/*.properties</include>
       <include>**/*.xml</include>
     </includes>
     <filtering>true</filtering>
   </resource>
   <resource>
     <directory>src/main/java</directory>
     <includes>
       <include>**/*.properties</include>
       <include>**/*.xml</include>
     </includes>
     <filtering>true</filtering>
   </resource>
 </resources>
</build>

来源：https://blog.csdn.net/TIANJIAWEN/article/details/124821285