mybatis学习（一）

如今的持久化框架中，Hibernate和mybatis可以说是各自占据了半壁江山，所以我们不能单独只了解Hibernate，还得学习mybatis，今天就首先来入门mybatis

要使用mybatis只需下载mybatis然后将mybatis-3.0.4.jar导入到工程中，要使用mybatis就必须先了解他的配置文件，在这里我们来看看mybatis的核心配置文件，名字可以随意命名，configuration,xml

<?xml version="1.0" encoding="GBK"?>
  <!DOCTYPE configuration
    PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
   "http://mybatis.org/dtd/mybatis-3-config.dtd">
 <configuration>
 
   <!-- 指定properties配置文件， 我这里面配置的是数据库相关 -->
   
   <!-- 指定Mybatis使用log4j -->
   <environments default="development">
     <environment id="development">
       <transactionManager type="JDBC"/>
       <dataSource type="POOLED">
           
        <!--   如果上面没有指定数据库配置的properties文件，那么此处可以这样直接配置  -->
         <property name="driver" value="com.mysql.jdbc.Driver"/>
         <property name="url" value="jdbc:mysql://localhost:3306/express_door"/>
         <property name="username" value="root"/>
         <property name="password" value="root"/>
         
          
          <!-- 上面指定了数据库配置文件， 配置文件里面也是对应的这四个属性 -->
       <!--   <property name="driver" value="${driver}"/>
          <property name="url" value="${url}"/>
          <property name="username" value="${username}"/>
          <property name="password" value="${password}"/> -->
          
       </dataSource>
     </environment>
   </environments>
   
  <!-- 映射文件，mybatis精髓， 后面才会细讲 -->
   <mappers>
     <mapper resource="main/java/conf/userDao-mapping.xml"/>
   </mappers>
   
 </configuration>

 在这里我们定义它的environments，在这个节点里面我们可以配置多个environment，这个使用多个环境的时候就可以用到，随后就是定义他的dataSource,就是一般的驱动，数据库，用户名和密码,配置完之后，我们还需要配置映射文件，如我们这里有个userDao-mapping.xml

接着就是这个userDao-mapping.xml

内容如下：

<?xml version="1.0" encoding="GBK"?>  
  <!DOCTYPE mapper   
  PUBLIC "-//ibatis.apache.org//DTD Mapper 3.0//EN"  
  "http://ibatis.apache.org/dtd/ibatis-3-mapper.dtd"> 
  <mapper namespace="main.java.com.mybatis.UserDao">
   <select id="findUserById" resultType="main.java.com.mybatis.User" > 
      select * from user_t where id = #{id}
    </select>
	
 </mapper>

 可以看到，首先配置了mapper，虽然现在不知道是什么鬼，但是可以看到就是一个执行数据库操作的一个接口，然后可以看到定义了一个查询 resultType是一个实体类

在这里需要注意的是这个查询的id需要和接口中的方法名一致，还有这样配置的缺点是数据库列名必须和实体名保持一致，要想自定义的话我们可以在上面定义一个resultMap

这样配置文件就变成了如下：

<?xml version="1.0" encoding="GBK"?>  
  <!DOCTYPE mapper   
  PUBLIC "-//ibatis.apache.org//DTD Mapper 3.0//EN"  
  "http://ibatis.apache.org/dtd/ibatis-3-mapper.dtd"> 
  <mapper namespace="main.java.com.mybatis.UserDao">
 	<resultMap id ="userMap" type="main.java.com.mybatis.User">
 		<result  column="id" property ="id"/>
 		<result  column="user_name" property ="userName"/>
 		<result  column="user_type" property ="userType"/>
 	</resultMap>
   <select id="findUserById" resultMap="userMap" > 
      select * from user_t where id = #{id}
    </select>
	
 </mapper>

我们的实体类为：

package main.java.com.mybatis;

public class User {
	private int id ; 
	private String userName ; 
	private String userType ;
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getUserName() {
		return userName;
	}
	public void setUserName(String userName) {
		this.userName = userName;
	}
	public String getUserType() {
		return userType;
	}
	public void setUserType(String userType) {
		this.userType = userType;
	}
	@Override
	public String toString() {
		return "User [id=" + id + ", userName=" + userName + ", userType="
				+ userType + "]";
	}
	
	
}

  

 

定义好了配置文件，我们就需要来写一个数据库执行类，UserDao

package main.java.com.mybatis;

import java.util.List;

public interface UserDao {
	public void insert(User user);
	
	public User findUserById(int userId);
	
	public List<User> findAllUsers();
}

可以看到这就是一个接口，然后定义了一些方法。

最后来测试一下吧

 

package main.java;

import java.io.IOException;

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 main.java.com.mybatis.User;
import main.java.com.mybatis.UserDao;
import main.java.com.mybatis.UserDaoImp;

public class Main {
	public static void main(String[] args) {
		SqlSession sqlSession =  getSessionFactory().openSession();
		UserDao userMapper = sqlSession.getMapper(UserDao.class);
		User user = userMapper.findUserById(2);
		System.out.println(user);
	}
	private static SqlSessionFactory getSessionFactory() {  
        SqlSessionFactory sessionFactory = null;  
       String resource = "main/java/conf/configuration.xml";  
        try {  
           sessionFactory = new SqlSessionFactoryBuilder().build(Resources  
                    .getResourceAsReader(resource));
        } catch (IOException e) {  
            e.printStackTrace();  
       }  
       return sessionFactory;  
   }
}

 输出为：

SLF4J: Class path contains multiple SLF4J bindings.

SLF4J: Found binding in [jar:file:/D:/JettyProject/SpringStudyPro/WebContent/WEB-INF/lib/activemq-all-5.14.1.jar!/org/slf4j/impl/StaticLoggerBinder.class]

SLF4J: Found binding in [jar:file:/D:/JettyProject/SpringStudyPro/WebContent/WEB-INF/lib/slf4j-jdk14-1.6.1.jar!/org/slf4j/impl/StaticLoggerBinder.class]

SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.

SLF4J: Actual binding is of type [org.slf4j.impl.Log4jLoggerFactory]

User [id=2, userName=dss, userType=dsa]

 

这就是一个简单的mybatis的实用例子，很简单吧

 

 下面贴出使用mybatis实现增删改查的例子：

先贴出mapping配置文件：

userDao-mapping.xml

<?xml version="1.0" encoding="GBK"?>  
  <!DOCTYPE mapper   
  PUBLIC "-//ibatis.apache.org//DTD Mapper 3.0//EN"  
  "http://ibatis.apache.org/dtd/ibatis-3-mapper.dtd"> 
  <mapper namespace="main.java.com.mybatis.UserDao">
 	<resultMap id ="userMap" type="main.java.com.mybatis.User">
 		<result  column="id" property ="id"/>
 		<result  column="user_name" property ="userName"/>
 		<result  column="user_type" property ="userType"/>
 	</resultMap>
   <select id="findUserById" parameterType="java.lang.Integer" resultMap="userMap" > 
      select * from user_t where id = #{id}
    </select>
    <select id="findUserByName" parameterType="java.lang.String" resultMap="userMap" > 
      select * from user_t where user_name like '%${value}%'
    </select>
    <insert id="insertUser" parameterType="java.lang.String">
    	insert into user_t(user_name , user_type) values (#{userName} , #{userType}) 
    </insert>
    <delete id="deleteUserById" parameterType="int">
       delete from user_t where id=#{id}
    </delete>
    <update id="updateUser" parameterType="main.java.com.mybatis.User">
       update user_t set user_name=#{userName},user_type=#{userType}  where id=#{id}
    </update>
	<insert id="insertBatch" parameterType="java.util.List"> 
 		insert user_t(user_name , user_type) 
 		values 
 		<foreach collection="list" item="obj" index="index" separator="," > 
   		 (#{userName} , #{userType})
 		</foreach> 
 	</insert>
 </mapper>

 实现类：

userDaoImp

package main.java.com.mybatis;

import java.io.IOException;
import java.util.List;

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 UserDaoImp  {
	
	public void updateUserById(){
		User user = findUserById(3);
		user.setUserName("updateDengwei");
		SqlSession sqlSession = getSessionFactory().openSession();
		sqlSession.update("updateUser", user);
		sqlSession.commit();
		
	}
	
	public void deleteUserById(int id){
		SqlSession sqlSession = getSessionFactory().openSession() ;
		sqlSession.delete("deleteUserById", id);
		sqlSession.commit();
	}
	public void insertUser(User user){
		SqlSession sqlSession =  getSessionFactory().openSession();
		UserDao userMapper = sqlSession.getMapper(UserDao.class);
		sqlSession.insert("insertUser", user);
		sqlSession.commit();
		System.out.println("OK");
	}
	public User findUserById(int userId) {
		SqlSession sqlSession =  getSessionFactory().openSession();
		UserDao userMapper = sqlSession.getMapper(UserDao.class);
		User user = userMapper.findUserById(userId);
		System.out.println(user);
		return user;
	}
	public List<User> findUserByName(String name){
		SqlSession session = getSessionFactory().openSession() ;
		UserDao userMappper = session.getMapper(UserDao.class);
		List<User> list = userMappper.findUserByName(name);
		return list ;
	}
	public List<User> findAllUsers() {
		SqlSession sqlSession =  getSessionFactory().openSession();
		UserDao userMapper = sqlSession.getMapper(UserDao.class);
		List<User> users = userMapper.findAllUsers();
		for(User user : users){
			System.out.println(user);
		}
		return null;
	}
	
	 private static SqlSessionFactory getSessionFactory() {  
		          SqlSessionFactory sessionFactory = null;  
		         String resource = "main/java/conf/configuration.xml";  
		          try {  
		             sessionFactory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsReader(resource));
		          } catch (IOException e) {  
		              e.printStackTrace();  
		         }  
		         return sessionFactory;  
		     }
}