MyBatis之增删查改功能

文章目录

• 一、创建各种类
• 二、MyBatis的各种功能
  • 1、查询<select>
  • 2、增加<insert>
  • 3、修改<update>
  • 4、删除<delete>
• 三、总结

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前言

在MyBatis项目中编写代码实现对MySql数据库的增删查改

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一、创建各种类

1、在Java包的mapper文件下创建一个接口

我创建的接口名为：SelectMapper，

注意：接口名之后要和写sql的xml文件名保持一致

这个接口专门用来写增删查改的方法，和sql分离开

 2、在resources包的mapper文件下创建一个xml文件

我的xml文件名为SelectMapper,和接口名保持一致

这个xml文件专门用来写sql语句

 3、在text包的java文件下创建一个测试类

我的测试类名为SelectMapperText，这个名称没有固定的要求

这个测试类专门用来测试对数据库的操作是否成功

二、MyBatis的各种功能

在stu库下有一张名为User的表，下面对这张表进行各种功能实现

1、查询功能<select>

查询User表所有用户的信息

因为查询的内容返回的数据不止一条，因此我们用List集合作为返回值

SelectMapeer接口下定义方法名：List<User> getAllUser()

public interface SelectMapper {/*若查询多条，不能用实体类对象为返回值，否则报错*///查询所有信息List<User> getAllUser();}

SelectMapper的xml文件下写sql语句

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.mybatis.mapper.SelectMapper"><!--    List<User> getAllUser();--><select id="getAllUser" resultType="User">select *from user</select></mapper>

注意：mapper的namespace必须对应接口名，select的id必须是我们写的方法名，两个必须要一样。查询结果需要返回，因此有resultType为实体类名 

SelectMapperText类开始测试

import com.mybatis.Util.SqlSessionUtil;
import com.mybatis.mapper.SelectMapper;
import com.mybatis.pojo.User;
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 javax.crypto.spec.PSource;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
import java.util.Map;public class SelectMapperText {@Testpublic void getAllUser() throws IOException {InputStream is = Resources.getResourceAsStream("mybatis-config.xml");SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(is);SqlSession sqlSession = sessionFactory.openSession(true);SelectMapper mapper = sqlSession.getMapper(SelectMapper.class);List<User> allUser = mapper.getAllUser();allUser.forEach(s-> System.out.println(s));}}

 运行getAllUser后为：

成功查到所有用户信息！！！ 

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2、增加功能<insert> 

向User表增加一个用户，用户信息为：

用户名：sb,密码：123456，年龄：20，性别：男，邮件：[e-mail]

 SelectMapeer接口下定义方法名：void insertUser(User user);

package com.mybatis.mapper;import com.mybatis.pojo.User;
import org.apache.ibatis.annotations.Param;import java.util.List;
import java.util.Map;public interface SelectMapper {//查询所有信息List<User> getAllUser();//插入用户信息void insertUser(User user);
}

SelectMapper的xml文件下写sql语句

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.mybatis.mapper.SelectMapper"><!--    List<User> getAllUser();--><select id="getAllUser" resultType="User">select *from user</select><!--    void insertUser(User user);--><insert id="insertUser">insert into user values (null,#{username},#{password},#{age},#{sex},#{email})</insert></mapper>

SelectMapperText类开始测试

import com.mybatis.Util.SqlSessionUtil;
import com.mybatis.mapper.SelectMapper;
import com.mybatis.pojo.User;
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 javax.crypto.spec.PSource;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
import java.util.Map;public class SelectMapperText {@Testpublic void getAllUser() throws IOException {InputStream is = Resources.getResourceAsStream("mybatis-config.xml");SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(is);SqlSession sqlSession = sessionFactory.openSession(true);SelectMapper mapper = sqlSession.getMapper(SelectMapper.class);List<User> allUser = mapper.getAllUser();allUser.forEach(s-> System.out.println(s));}@Testpublic void insertUser() throws IOException {InputStream is = Resources.getResourceAsStream("mybatis-config.xml");SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(is);SqlSession sqlSession = sessionFactory.openSession(true);SelectMapper mapper = sqlSession.getMapper(SelectMapper.class);User user = new User(null,"sb","123456",20,"男","[e-mail]");mapper.insertUser(user);}}

成功添加用户信息！！！  

---

3、修改功能<update> 

修改用户名为admin的信息，将性别改为女

SelectMapeer接口下定义方法名： void updateUser(String username)

package com.mybatis.mapper;import com.mybatis.pojo.User;
import org.apache.ibatis.annotations.Param;import java.util.List;
import java.util.Map;public interface SelectMapper {//查询所有信息List<User> getAllUser();//插入用户信息void insertUser(User user);//修改用户信息void updateUser(@Param("username") String username);//用注释当sql名
}

SelectMapper的xml文件下写sql语句

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.mybatis.mapper.SelectMapper"><!--    List<User> getAllUser();--><select id="getAllUser" resultType="User">select *from user</select><!--    void insertUser(User user);--><insert id="insertUser">insert into user values (null,#{username},#{password},#{age},#{sex},#{email})</insert><!--    void updateUser(@Param("username") String username);--><update id="updateUser">update user set sex = '女' where username=#{username}</update></mapper>

SelectMapperText类开始测试

import com.mybatis.Util.SqlSessionUtil;
import com.mybatis.mapper.SelectMapper;
import com.mybatis.pojo.User;
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 javax.crypto.spec.PSource;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
import java.util.Map;public class SelectMapperText {@Testpublic void getAllUser() throws IOException {InputStream is = Resources.getResourceAsStream("mybatis-config.xml");SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(is);SqlSession sqlSession = sessionFactory.openSession(true);SelectMapper mapper = sqlSession.getMapper(SelectMapper.class);List<User> allUser = mapper.getAllUser();allUser.forEach(s-> System.out.println(s));}@Testpublic void insertUser() throws IOException {InputStream is = Resources.getResourceAsStream("mybatis-config.xml");SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(is);SqlSession sqlSession = sessionFactory.openSession(true);SelectMapper mapper = sqlSession.getMapper(SelectMapper.class);User user = new User(null,"sb","123456",20,"男","[e-mail]");mapper.insertUser(user);}@Testpublic void updateUser() throws IOException {InputStream is = Resources.getResourceAsStream("mybatis-config.xml");SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(is);SqlSession sqlSession = sessionFactory.openSession(true);SelectMapper mapper = sqlSession.getMapper(SelectMapper.class);mapper.updateUser("admin");}}

成功修改用户信息！！！ 

---

4、删除功能<update> 

删除用户为“root”的所有信息

SelectMapeer接口下定义方法名：void deleteUser(String username)

package com.mybatis.mapper;import com.mybatis.pojo.User;
import org.apache.ibatis.annotations.Param;import java.util.List;
import java.util.Map;public interface SelectMapper {//查询所有信息List<User> getAllUser();//插入用户信息void insertUser(User user);//修改用户信息void updateUser(@Param("username") String username);//用注释当sql名//删除用户信息void deleteUser(@Param("username") String username);
}

SelectMapper的xml文件下写sql语句

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.mybatis.mapper.SelectMapper"><!--    List<User> getAllUser();--><select id="getAllUser" resultType="User">select *from user</select><!--    void insertUser(User user);--><insert id="insertUser">insert into user values (null,#{username},#{password},#{age},#{sex},#{email})</insert><!--    void updateUser(@Param("username") String username);--><update id="updateUser">update user set sex = '女' where username=#{username}</update><!--    void deleteUser(@Param("username") String username)--><delete id="deleteUser">delete  from user where username = #{username}</delete>
</mapper>

SelectMapperText类开始测试 

import com.mybatis.Util.SqlSessionUtil;
import com.mybatis.mapper.SelectMapper;
import com.mybatis.pojo.User;
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 javax.crypto.spec.PSource;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
import java.util.Map;public class SelectMapperText {@Testpublic void getAllUser() throws IOException {InputStream is = Resources.getResourceAsStream("mybatis-config.xml");SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(is);SqlSession sqlSession = sessionFactory.openSession(true);SelectMapper mapper = sqlSession.getMapper(SelectMapper.class);List<User> allUser = mapper.getAllUser();allUser.forEach(s-> System.out.println(s));}@Testpublic void insertUser() throws IOException {InputStream is = Resources.getResourceAsStream("mybatis-config.xml");SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(is);SqlSession sqlSession = sessionFactory.openSession(true);SelectMapper mapper = sqlSession.getMapper(SelectMapper.class);User user = new User(null,"sb","123456",20,"男","[e-mail]");mapper.insertUser(user);}@Testpublic void updateUser() throws IOException {InputStream is = Resources.getResourceAsStream("mybatis-config.xml");SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(is);SqlSession sqlSession = sessionFactory.openSession(true);SelectMapper mapper = sqlSession.getMapper(SelectMapper.class);mapper.updateUser("admin");}@Testpublic void deleteUser() throws IOException {InputStream is = Resources.getResourceAsStream("mybatis-config.xml");SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(is);SqlSession sqlSession = sessionFactory.openSession(true);SelectMapper mapper = sqlSession.getMapper(SelectMapper.class);mapper.deleteUser("root");}
}

 成功删除用户信息！！！

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三、总结

        首先创造好接口写入要进行的方法名，然后创建xml文件专门写sql语句，值得注意的是：namespace要和接口名相同，id名要和接口里面的方法名相同，在测试类中：先获取映射文件，然后创建数据会议工厂生成数据会议，最后创建mapper使用接口的函数。

总之流程为：

        1、创建接口写方法名。

        2、创建xml文件写sql语句。

        3、测试类进行测试

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