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
    2、增加
    3、修改
    4、删除
    三、总结

    ---

    前言

    在MyBatis项目中编写代码实现对MySql数据库的增删查改

    ---

    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

    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 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 getAllUser();
    
    }

    SelectMapper的xml文件下写sql语句

    
    
    
    
    
        
            select *from user
        
    
    

    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 {
    
        @Test
        public 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 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！！！ 

    ---

    2、增加功能 

    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：[email protected]

     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 getAllUser();
    
        //插入用户信息
        void insertUser(User user);
    }
    

    SelectMapper的xml文件下写sql语句

    
    
    
    
    
        
            select *from user
        
    
    
        
            insert into user values (null,#{username},#{password},#{age},#{sex},#{email})
        
    
    

    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 {
    
        @Test
        public 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 allUser = mapper.getAllUser();
            allUser.forEach(s-> System.out.println(s));
        }
    
        @Test
        public 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","[email protected]");
            mapper.insertUser(user);
        }
    
    }
    

    

    成功添加用户信息！！！  

    ---

    3、修改功能 

    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 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

    
    
    
    
    
        
            select *from user
        
    
    
        
            insert into user values (null,#{username},#{password},#{age},#{sex},#{email})
        
    
    
        
            update user set sex = '女' where username=#{username}
        
    
    

    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 {
    
        @Test
        public 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 allUser = mapper.getAllUser();
            allUser.forEach(s-> System.out.println(s));
        }
    
        @Test
        public 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","[email protected]");
            mapper.insertUser(user);
        }
    
       @Test
        public 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 

    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 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

    
    
    
    
    
        
            select *from user
        
    
    
        
            insert into user values (null,#{username},#{password},#{age},#{sex},#{email})
        
    
    
        
            update user set sex = '女' where username=#{username}
        
    
    
        
            delete  from user where username = #{username}
        
    

    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 {
    
        @Test
        public 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 allUser = mapper.getAllUser();
            allUser.forEach(s-> System.out.println(s));
        }
    
        @Test
        public 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","[email protected]");
            mapper.insertUser(user);
        }
    
       @Test
        public 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");
        }
    
        @Test
        public 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！！！

    ---

    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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