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
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<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!!!
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:123456@qq.com
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","123456@qq.com");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","123456@qq.com");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","123456@qq.com");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");}
}