Mybatis简单入门

超、凢脫俗 2022-08-22 06:23 260阅读 0赞

*  **一、创建项目导入相应的jar包（数据库驱动包和mybatis jar包）**
 *  **二、在src目录下，建立conf.xml配置文件**

<?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>
        
        <typeAliases>
            <typeAlias type="com.pojo.User" alias="User" />
            <typeAlias type="com.dao.UserDao" alias="UserDao" />
        </typeAliases>
    
        
        <environments default="development">
            <environment id="development">
                <transactionManager type="JDBC" />
                <dataSource type="POOLED">
                    <property name="driver" value="com.mysql.jdbc.Driver" />
                    <property name="url" value="jdbc:mysql://127.0.0.1:3306/student?characterEncoding=utf-8" />
                    <property name="username" value="root" />
                    <property name="password" value="" />
                </dataSource>
            </environment>
        </environments>
    
        
        <mappers>
            <mapper resource="com/dao/UserDao.xml" />
        </mappers>
    
    </configuration>

*  **三、根据数据表字段建立实体类，需要一一对应关系**

package com.pojo;
    
    public class User { 
        private int userId;
        private String userName;
        private String passWord;
    
        public int getUserId() {
            return userId;
        }
    
        public void setUserId(int userId) {
            this.userId = userId;
        }
    
        public String getUserName() {
            return userName;
        }
    
        public void setUserName(String userName) {
            this.userName = userName;
        }
    
        public String getPassWord() {
            return passWord;
        }
    
        public void setPassWord(String passWord) {
            this.passWord = passWord;
        }
    
        @Override
        public String toString() {
            return "User [userId=" + userId + ", userName=" + userName + ", passWord=" + passWord + "]";
        }
    
    }

*  **四、建立操作映射文件**

<?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">
    
    
     <mapper namespace="com.dao.IUserDao">
         
         
        
         <select id="getUserById" parameterType="int" resultType="User">
             select * from user where userId=#{userId}
        </select>
    </mapper>

*  **五、建立操作接口**

package com.dao;
    import com.pojo.User;
    
    public interface IUserDao { 
    public User getUserById(int userId);
    }

*  **六、dao类**

package com.dao;
    
    import java.io.FileNotFoundException;
    import java.io.IOException;
    import java.io.InputStream;
    import java.io.Reader;
    
    import org.apache.ibatis.io.Resources;
    import org.apache.ibatis.session.SqlSession;
    import org.apache.ibatis.session.SqlSessionFactory;
    import org.apache.ibatis.session.SqlSessionFactoryBuilder;
    
    public class MyBatisBaseDao { 
        public static SqlSessionFactory sqlSessionFactory;
        public static SqlSessionFactoryBuilder sqlSessionFactoryBuilder;
        public static SqlSession session;
        // mybatis的配置文件
        public static String resource = "conf.xml";
    
        static {
    
            // 使用类加载器加载mybatis的配置文件（它也加载关联的映射文件）
            InputStream is = UserDao.class.getClassLoader().getResourceAsStream(resource);
            try {
                // 构建sqlSession的工厂
                // SqlSessionFactory sessionFactory = new
                // SqlSessionFactoryBuilder().build(is);
                // 使用MyBatis提供的Resources类加载mybatis的配置文件（它也加载关联的映射文件）
                Reader reader = Resources.getResourceAsReader(resource);
                // 构建sqlSession的工厂
                SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader);
                // 创建能执行映射文件中sql的sqlSession
                session = sessionFactory.openSession();
    
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
    测试：
    public class UserDao extends MyBatisBaseDao { 
    
        public User findUserById(int userId) {
            String statement = "com.dao.IUserDao.getUserById";// 映射sql的标识字符串
            // 执行查询返回一个唯一user对象的sql
            // UserDao.init();
            System.out.println(session);
            /**使用mybatis的代理 方法一*/
            IUserDao DAO=session.getMapper(IUserDao.class);
            User user=DAO.getUserById(8);
            /**方法二**/
    // User user = session.selectOne(statement, userId);
            System.out.println(user);
            return user;
        }
    
        public static void main(String[] args) {
            UserDao dao = new UserDao();
            dao.findUserById(8);
        }
    }

注：也可以不使用接口