mybatis的快速入门

2022-01-28 12:44:24

说明：

　　在这个部分，会写个简单的入门案例。

　　然后，会重新写一个，更加严格的程序案例。

一：案例一

1.最终的目录结构

　　mybatis的快速入门

2.新建一个普通的Java项目，并新建lib

　　在项目名上右键，不是src。

　　mybatis的快速入门

3.导入需要的jar包，并加入到classpath中

　　mybatis-3.4.5.jar
　　mysql-connector-java-5.1.18-bin.jar

　　mybatis的快速入门

4.新建数据库与表

 CREATE DATABASE mybatis;

 USE mybatis;

 CREATE TABLE users(

     ID INT PRIMARY KEY AUTO_INCREMENT,

     NAME VARCHAR(20),

     AGE INT

 );

 INSERT INTO users(NAME,age) VALUES("TOM",12);

 INSERT INTO users(NAME,AGE) VALUES("JACK",11);

mybatis的快速入门

5.新建bean--User.java

 package com.test;

 public class User {

     private int id;

     private String name;

     private int age;

     public User() {}

     public int getId() {

         return id;

     }

     public void setId(int id) {

         this.id = id;

     }

     public String getName() {

         return name;

     }

     public void setName(String name) {

         this.name = name;

     }

     public int getAge() {

         return age;

     }

     public void setAge(int age) {

         this.age = age;

     }

     @Override

     public String toString() {

         return "User [id=" + id + ", name=" + name + ", age=" + age + "]";

     }

 }

6.新建配置文件--Configuration.xml　

resource="users.xml"，注意的是，这个不需要加/。
 <?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>

   <environments default="development">

     <environment id="development">

       <transactionManager type="JDBC">

         <property name="" value=""/>

       </transactionManager>

       <dataSource type="UNPOOLED">

         <property name="driver" value="com.mysql.jdbc.Driver"/>

         <property name="url" value="jdbc:mysql://127.0.0.1:3308/mybatis"/>

         <property name="username" value="root"/>

         <property name="password" value="123456"/>

       </dataSource>

     </environment>

   </environments>

    <mappers>

       <mapper resource="users.xml"/>

    </mappers>

 </configuration>

7.新建映射文件--users.xml

　　在这个映射文件中，需要注意的是，需要写result Map，不然找不到返回值。

 <?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="quickFirst">

     <resultMap type="com.test.User" id="User">

         <id column="ID" jdbcType="INTEGER" property="id"/>

         <result column="NAME" jdbcType="VARCHAR" property="name"/>

         <result column="AGE" jdbcType="INTEGER" property="age"/>

     </resultMap>

     <select id="selectUser" parameterType="int" resultMap="User">

         SELECT * From users where id = #{id};

     </select>

 </mapper>

8.测试类--TestSelectById.java

　　这个类中使用的是反射的形式来获取配置文件。

　　需要注意的是：String resources="/Configuration.xml"，这个需要增加/。

 package com.test;

 import java.io.InputStream;

 import org.apache.ibatis.session.SqlSession;

 import org.apache.ibatis.session.SqlSessionFactory;

 import org.apache.ibatis.session.SqlSessionFactoryBuilder;

 public class TestSelectById {

     public static void main(String[] regs) {

         String resources="/Configuration.xml";

         InputStream is=TestSelectById.class.getResourceAsStream(resources);

         SqlSessionFactory sqlSessionFactory=new SqlSessionFactoryBuilder().build(is);

         SqlSession sqlSession=sqlSessionFactory.openSession();

         String statement="quickFirst.selectUser";

         User user=sqlSession.selectOne(statement, 1);

         System.out.println(user);

     }

 }

9.效果图

　　mybatis的快速入门

二：案例二

1.程序最终目录

　　mybatis的快速入门

2.新建表

 DROP TABLE IF EXISTS `message`;

 CREATE TABLE `message` (

   `ID` int(20) AUTO_INCREMENT COMMENT '主键',

   `COMMAND` varchar(16) DEFAULT NULL COMMENT '指令名称',

   `DESCRIPTION` varchar(32) DEFAULT NULL COMMENT '描述',

   `CONTENT` varchar(2048) DEFAULT NULL COMMENT '内容',

   PRIMARY KEY (`ID`)

 ) ENGINE=InnoDB AUTO_INCREMENT=10 DEFAULT CHARSET=utf8;

 INSERT INTO `message` VALUES ('', '查看', '精彩内容', '精彩内容');

 INSERT INTO `message` VALUES ('', '段子', '精彩段子', '如果你的月薪是3000块钱');

 INSERT INTO `message` VALUES ('', '新闻', '今日头条', '7月17日，马来西亚一架载有298人');

 INSERT INTO `message` VALUES ('', '娱乐', '娱乐新闻', '昨日，邓超在微博分享了自己和孙俪的书法。');

 INSERT INTO `message` VALUES ('', '电影', '近日上映大片', '《忍者神龟》');

　　mybatis的快速入门

3.新建Message.java

 package com.cao.bean;

 /**

  * message��

  * @author dell

  *

  */

 public class Message {

     private int id;

     private String command;

     private String description;

     private String content;

     public Message() {}

     public Message(int id, String command, String description, String content) {

         super();

         this.id = id;

         this.command = command;

         this.description = description;

         this.content = content;

     }

     public int getId() {

         return id;

     }

     public void setId(int id) {

         this.id = id;

     }

     public String getCommand() {

         return command;

     }

     public void setCommand(String command) {

         this.command = command;

     }

     public String getDescription() {

         return description;

     }

     public void setDescription(String description) {

         this.description = description;

     }

     public String getContent() {

         return content;

     }

     public void setContent(String content) {

         this.content = content;

     }

 }

4.新建配置文件

 <?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>

   <environments default="development">

     <environment id="development">

       <transactionManager type="JDBC">

         <property name="" value=""/>

       </transactionManager>

       <dataSource type="UNPOOLED">

         <property name="driver" value="com.mysql.jdbc.Driver"/>

         <property name="url" value="jdbc:mysql://127.0.0.1:3308/mybatis"/>

         <property name="username" value="root"/>

         <property name="password" value="123456"/>

       </dataSource>

     </environment>

   </environments>

    <mappers>

       <mapper resource="com/cao/config/Message.xml"/>

    </mappers>

 </configuration>

5.新建映射文件

 <?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="Message">

   <resultMap type="com.cao.bean.Message" id="MessageResult">

     <id column="ID" jdbcType="INTEGER" property="id"/>

     <result column="COMMAND" jdbcType="VARCHAR" property="command"/>

     <result column="DESCRIPTION" jdbcType="VARCHAR" property="description"/>

     <result column="CONTENT" jdbcType="VARCHAR" property="content"/>

   </resultMap>

   <select id="queryMessageList" parameterType="com.cao.bean.Message" resultMap="MessageResult">

     SELECT ID,COMMAND,DESCRIPTION,CONTENT FROM message WHERE 1=1

   </select>

 </mapper>

6.新建DBAccess.java，链接数据库

 package com.cao.db;

 import java.io.IOException;

 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 DBAccess {

     public SqlSession getSqlSession() throws Exception {

         //获取数据库的连接信息

         Reader reader=Resources.getResourceAsReader("com/cao/config/Configuration.xml");

         //

         SqlSessionFactory sqlSessionFactory=new SqlSessionFactoryBuilder().build(reader);

         //

         SqlSession sqlSession=sqlSessionFactory.openSession();

         System.out.println(sqlSession);

         return sqlSession;

     }

 }

7.新建Dao，操作数据库

 package com.cao.dao;

 import java.sql.Connection;

 import java.sql.DriverManager;

 import java.sql.PreparedStatement;

 import java.sql.ResultSet;

 import java.sql.SQLException;

 import java.util.ArrayList;

 import java.util.List;

 import org.apache.ibatis.session.SqlSession;

 import com.cao.bean.Message;

 import com.cao.db.DBAccess;

 /**

  * 和message相关的dao

  * @author dell

  *

  */

 public class MessageDao {

     /**

      * 查询以及包括条件查询

      * @param command

      * @param description

      * @return

      */

     public List<Message> queryMessageList()  {

         List<Message> messageList=new ArrayList<>();

         SqlSession sqlSession=null;

         /**

          * MyBatis

          */

         DBAccess dbAccess=new DBAccess();

         try {

             //封装，方便将参数传进到xml中

             Message message=new Message();

             sqlSession=dbAccess.getSqlSession();

             messageList=sqlSession.selectList("Message.queryMessageList",message);

         } catch (Exception e) {

             e.printStackTrace();

         }finally {

             sqlSession.close();

         }

         return messageList;

     }

 }

8.新建service，数据处理层

 package com.cao.service;

 import java.util.List;

 import com.cao.bean.Message;

 import com.cao.dao.MessageDao;

 /**

  * 列表相关的业务功能

  * @author dell

  *

  */

 public class ListService {

     public List<Message> queryMessageList() {

         MessageDao messageDao=new MessageDao();

         return messageDao.queryMessageList();

     }

 }

9.测试类

 package com.cao.main;

 import java.util.Iterator;

 import java.util.List;

 import com.cao.bean.Message;

 import com.cao.service.ListService;

 public class TestSelectList {

     public static void main(String[] args) {

         ListService listService=new ListService();

         List messageList=listService.queryMessageList();

         Iterator it=messageList.iterator();

         while(it.hasNext()) {

             Message message=(Message)it.next();

             String com=message.getCommand();

             System.out.println(com);

         }

     }

 }

10，结果

　　mybatis的快速入门

　　

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