mybatis的快速入门

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

　　

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。

　　

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

　　

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);

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

　　

二：案例二

1.程序最终目录

　　

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》');

　　

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