Java的MyBatis框架项目搭建与hellow world示例

新建项目（我使用的是maven项目）mybatis-study-01

一、加入mybatis与mysql-connector依赖包到pom文件

 4.0.0

 mybatis
 mybatis-study-01
 0.0.1-SNAPSHOT
 jar

 mybatis-01
 http://maven.apache.org

 
 UTF-8
  

 
 
  junit
  junit
  4.10
  test
 
 
 
 org.mybatis
 mybatis
 3.2.3
 
 
  
 mysql
 mysql-connector-java
 5.1.27
 
   
  
 

二、创建数据库mybatis-test
新建一张user表用于测试。建表sql如下：

CREATE TABLE `user` (
 `id` int(11) NOT NULL auto_increment,
 `password` varchar(255) default NULL,
 `user_name` varchar(50) default NULL,
 `user_age` int(11) default NULL,
 `user_address` varchar(200) default NULL,
 PRIMARY KEY (`id`),
 UNIQUE KEY `userName` (`user_name`)
) EN

插入一条数据

INSERT INTO `user` VALUES ('1', '123131', 'summer', '100', 'shanghai,pudong');

三、在项目中编写pojo对象。

package com.zf.mybatis.pojo;

public class User {

 private int id;
 private String password ;
 private String userName;
 private String userAge;
 private String userAddress;

 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 getUserAge() {
 return userAge;
 }
 public void setUserAge(String userAge) {
 this.userAge = userAge;
 }
 public String getUserAddress() {
 return userAddress;
 }
 public void setUserAddress(String userAddress) {
 this.userAddress = userAddress;
 }
 public String getPassword() {
 return password;
 }
 public void setPassword(String password) {
 this.password = password;
 }

}

四、编写pojo对应的映射文件User.xml

 
 
 id , password , user_name as userName , user_age as userAge , user_address as userAddress
 
 
 
  select 
   
  from `user` where id = #{id}
 
 
 
  insert into `user`
  (password , user_name , user_age , user_address)
  values(#{password} , #{userName} , #{userAge} , #{userAddress} )
 
 
 
 update `user`
 set password = #{password} , user_name = #{userName}, user_age = #{userAge}, user_address = #{userAddress}
 where id = #{id}
 
 
 
  delete from `user` where id = #{id}
 
 
 

注意：上面的namespace的值为com.zf.mybatis.pojo.UserMapper，可以自定义 ，UserMapper不是一个类，不需要存在的。
另外，mybatis会将从数据库查询出来的记录根据列名与pojo中的字段进行匹配， 所以上面的user_name，user_age ,user_address这几个字段都取了别名，跟pojo中的字段相对应。 如果不起别名， 查询出来的对象，这几个字段是没有值的。

五、编写mybatis的配置文件mybatis-config.xml

在该配置文件中配置了数据库的链接方式，以及注册所有的映射文件，还可以设置mybatis的一些参数。

现在就可以编写测试类了。来测试一下。

package com.zf.mybatis;

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;
import org.junit.Before;
import org.junit.Test;

import com.zf.mybatis.pojo.User;

public class TestMyBatis {
 
 private SqlSessionFactory sqlSessionFactory;
 private Reader reader; 

 @Before
 public void init(){
 try {
 reader = Resources.getResourceAsReader("mybatis-config.xml");
 sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
 } catch (IOException e) {
 e.printStackTrace();
 }
 }
 
 @Test
 public void testQueryUser(){
 SqlSession session = sqlSessionFactory.openSession();
 try {
 User user = (User) session.selectOne("com.zf.mybatis.pojo.UserMapper.selectByID" ,1);
 System.out.println(user.getUserAddress());
 System.out.println(user.getUserName());
 } finally {
 session.close();
 }
 }
 
 @Test
 public void testInsertUser(){
 SqlSession session = sqlSessionFactory.openSession();
 try {
 User user = new User() ;
 user.setUserName("abcde");
 user.setUserAge(15) ;
 user.setUserAddress("hangzhou/zhejiang");
 user.setPassword("123456");
 //返回值是记录条数
 int resultCount = session.insert("com.zf.mybatis.pojo.UserMapper.add", user );
 session.commit() ;
 System.out.printf("userID:%d,总记录条数:%d" , user.getId() , resultCount); //获取插入对象的id
 } finally {
 session.close();
 }
 }
 
 @Test
 public void testUpdateUser(){
 SqlSession session = sqlSessionFactory.openSession();
 try {
 User user = new User() ;
 user.setId(5) ;
 user.setUserName("updateName");
 user.setUserAge(101) ;
 user.setUserAddress("shenzhen/guangdong");
 user.setPassword("000000");
 //返回值是修改条数
 int updateCount = session.update("com.zf.mybatis.pojo.UserMapper.update", user );
 session.commit() ;
 System.out.printf("修改条数:%d" ,updateCount); 
 } finally {
 session.close();
 }
 }
 
 @Test
 public void testDelete(){
 SqlSession session = sqlSessionFactory.openSession();
 try {
 //返回值是删除条数
 int deleteCount = session.update("com.zf.mybatis.pojo.UserMapper.deleteById", 4 );
 session.commit() ;
 System.out.printf("删除条数:%d" ,deleteCount ); 
 } finally {
 session.close();
 }
 }


}

运行testQueryUser结果如下：

shanghai,pudong
summer

到此，一个mybatis的helloworld类型的小程序就出来了。

PS：MyBaits配置文件报错解决
Mybaits的配置文件校验很诡异，节点的位置还有要求
如下，会报错：

The content of element type "configuration" must match "(properties?,settings?,typeAliases?,typeHandlers?,objectFactory?,objectWrapperFactory?,plugins?,environments?,mappers?)". 

 
 
 
 
  
  
   
    
    
     
     
     
     
    
   
  
  
  
   
  
  
  
   
  
  
 

 
把typeAliases放到最上面就好了说：