关于mybatis的基础（简单的实现CURD功能）

Posted 2020-12-01 bleachcurtain

编写mybatis-config.xml文件

创建好了工程文件后，先将需要用到的jar包导入，创建一个mybatis-config.xml文件，源码如下：

 1 　　<environments default="development">
 2         <environment id="development">
 3             <transactionManager type="JDBC"></transactionManager>
 4             <dataSource type="POOLED">
 5                 <!--数据库驱动-->
 6                 <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
 7                 <!--数据库URL-->
 9                 <property name="url" value="jdbc:mysql://127.0.0.1:3306/**?serverTimezone=UTC"/>
10                 <!--以下是数据库用户名以及密码-->
11                 <property name="username" value="***"/>
12                 <property name="password" value="***"/>
13             </dataSource>
14         </environment>
15     </environments>
16 
17     <mappers>
18         <!--映射文件的地址-->
19         <mapper resource="com/pn/mapper/UserMapper.xml"/>
20     </mappers>

映射文件UserMapper.xml：

 1 <!--对应的接口-->
 2 <mapper namespace="com.pn.mapper.UserMapper">
 3     <!-- 语句查询结果 和 java对象的映射 -->
 4     <!--用来处理查询结果和java对象的字段对应问题-->
 5 
 6 <!--    SQL语句-->
 7     <select id="selectUser" resultType="com.pn.entity.User">
 8         select * from user where userID = #{ID}
 9     </select>
10 
11     <select id="selectAll" resultType="com.pn.entity.User">
12         select * from user
13     </select>
14 
15     <insert id="addUser" parameterType="com.pn.entity.User">
16         insert into user(userID,userName,userPassword) values (#{userID},#{userName},#{userPassword})
17     </insert>
18 
19     <update id="updataUser" parameterType="com.pn.entity.User">
20         update user set userName = #{userName},userPassword = #{userPassword} where userID = #{userID}
21     </update>
22 
23     <delete id="deleteUser" >
24         delete from user where userID = #{userID}
25     </delete>
26 </mapper>

因为要SqlSessionFactoryBuilder类去解析配置文件 并实例化sqlSessionFactory，通过sqlSessionFactory来获得sqlSession 对象，将其写成一个util。

mybatisUtil.java：

 1 public class mybatisUtil {
 2     public static SqlSessionFactory getSqlSessionFactory(){
 3         String resource = "com/pn/resource/mybatis-config.xml";
 4         InputStream inputStream = null;
 5         try {
 6             //获取配置文件的流信息
 7             inputStream = Resources.getResourceAsStream(resource);
 8         } catch (IOException e) {
 9             e.printStackTrace();
10         }
11         //通过SqlSessionFactoryBuilder类去解析配置文件 并实例化sqlSessionFactory
12         SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
13         return sqlSessionFactory;
14     }
15 
16     public static SqlSession getSession(){
17         SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
18         return sqlSessionFactory.openSession();
19     }
20 }

UserDao.java:

 1 public class UserDao {
 2     //获取全部数据
 3     public List<User> getAll(){
 4         SqlSession session = mybatisUtil.getSession();
 5         List<User> userList = session.selectList("com.pn.mapper.UserMapper.selectAll");
 6         return userList;
 7     }
 8     //通过ID查询用户数据
 9     public User getUserByID(int id){
10         SqlSession session = mybatisUtil.getSession();
11         User user = session.selectOne("com.pn.mapper.UserMapper.selectUser",id);
12         session.close();
13         return user;
14     }
15     //添加用户
16     public int addUser(User user){
17         SqlSession sqlSession = mybatisUtil.getSession();
18         int result = sqlSession.insert("com.pn.mapper.UserMapper.addUser",user);//insert的返回的是一个int类型
19         sqlSession.commit();//更改了数据库要记得将事务提交
20         sqlSession.close();
21         return result;
22     }
23     //更新用户信息
24     public int updataUser(User user){
25         SqlSession sqlSession = mybatisUtil.getSession();
26         int result = sqlSession.update("com.pn.mapper.UserMapper.updataUser",user);
27         sqlSession.commit();
28         sqlSession.close();
29         return result;
30     }
31     //通过ID删除对应的用户信息
32     public int deleteUser(int id){
33         SqlSession sqlSession = mybatisUtil.getSession();
34         int result = sqlSession.delete("com.pn.mapper.UserMapper.deleteUser",id);
35         sqlSession.commit();
36         sqlSession.close();
37         return result;
38     }
39 }

测试的方法test.java:

 1 public static void main(String[] args){
 2         UserDao userDao = new UserDao();
 3         //selectAll
 4         List<User> userList = userDao.getAll();
 5         for(User user:userList){
 6             System.out.println(user.getID()+" "+user.getUsername()+" "+user.getPwd());
 7         }
 8         //通过ID查询用户信息
 9         int id = 1500006;
10         User user  = userDao.getUserByID(id);
11         System.out.println("查询结果："+user.getID()+" "+user.getUsername()+" "+user.getPwd());
12         //insertUser
13         User user1 =new User();
14         user1.setID(123);
15         user1.setUsername("小明");
16         user1.setPwd("123456");
17         int resultInsert = userDao.addUser(user1);
18         if (resultInsert==1){
19             System.out.println("添加成功。");
20         }else {
21             System.out.println("添加失败。");
22         }
23         //updateUser
24         user1.setPwd("111111");
25         int resultUpdate = userDao.updataUser(user1);
26         if (resultUpdate==1){
27             System.out.println("更新成功。");
28         }else {
29             System.out.println("更新失败。");
30         }
31     }

附上工程文件的目录如下：

 

 在编写过程中仍有一些细节需要注意。