工具类：mybatis中使用Threadlocal开启session及关闭session

1、线程容器,给线程绑定一个Object 内容,后只要线程不变,可以随时取出.

1.1 改变线程,无法取出内容.

 final ThreadLocal threadLocal = new ThreadLocal<>();
 threadLocal.set("测试");
 new Thread(){
     public void run() {
         String result = threadLocal.get();
         System.out.println("结果:"+result);
     };
 }.start();

2、使用Threadlocal简化开发

2.1定义工具类

    将SqlSession创建出来，存放到Threadlocal中，需要时再从中取出

 package com.test.util;

 import java.io.IOException;
 import java.io.InputStream;

 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 MybatisUtil {

     //工厂
     private static SqlSessionFactory factory;
     //线程容器
     private static ThreadLocal<SqlSession> tl = new ThreadLocal<>();

     static{
         try {
             InputStream is = Resources.getResourceAsStream("mybatis.xml");
             factory = new SqlSessionFactoryBuilder().build(is);
         } catch (IOException e) {
             e.printStackTrace();
         }
     }
     /**
      * 获取session
      * 从线程容器中获取，没有则创建session在存放到线程容器中
      * @return
      */
     public static SqlSession getSession(){
         SqlSession sqlSession = tl.get();
         if(sqlSession == null){
             sqlSession = factory.openSession();
             tl.set(sqlSession);
         }
         return tl.get();
     }

     /**
      * 关闭session
      * 从容器线程中获取session，有则关闭，且将线程容器的session清空
      */
     public static void closeSession(){
         SqlSession sqlSession = tl.get();
         if(sqlSession != null){
             sqlSession.close();
         }
         tl.set(null);
     }
 }

将工厂的产生改成单例模式

 package com.text.util;

 import java.io.IOException;
 import java.io.InputStream;
 import java.util.logging.Level;
 import java.util.logging.Logger;

 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 MybatisUtil {

     //工厂
     private static SqlSessionFactory factory;
     //类线程锁
     private static final Class CLASS_LOCK = MybatisUtil.class;
     //线程容器
     private static ThreadLocal<SqlSession> tl = new ThreadLocal<>();
     //构造器私有化
     private MybatisUtil(){}

     public static SqlSessionFactory initSqlSessionFactory(){
         String resource = "mybatis.xml";
         InputStream is = null;
         try {
             is = Resources.getResourceAsStream(resource);
         } catch (IOException e) {
             Logger.getLogger(MybatisUtil.class.getName()).log(Level.SEVERE, null, e);
         }
         synchronized (CLASS_LOCK) {
             if(null == factory){
                 factory = new SqlSessionFactoryBuilder().build(is);
             }
         }
         return factory;
     }

     /**
      * 获取session
      * 从线程容器中获取，没有则创建session在存放到线程容器中
      * @return
      */
     public static SqlSession getSession(){
         SqlSession sqlSession = tl.get();
         if(sqlSession == null){
             if(factory == null){
                 initSqlSessionFactory();
             }
             sqlSession = factory.openSession();
             tl.set(sqlSession);
         }
         return tl.get();
     }

     /**
      * 关闭session
      * 从容器线程中获取session，有则关闭，且将线程容器的session清空
      */
     public static void closeSession(){
         SqlSession sqlSession = tl.get();
         if(sqlSession != null){
             sqlSession.close();
         }
         tl.set(null);
     }
 }

 

2.2 定义过滤器

    过滤器可以在调用方法前及方法后添加代码

 package com.test.filter;

 import java.io.IOException;

 import java.io.InputStream;

 import javax.servlet.Filter;
 import javax.servlet.FilterChain;
 import javax.servlet.FilterConfig;
 import javax.servlet.ServletException;
 import javax.servlet.ServletRequest;
 import javax.servlet.ServletResponse;
 import javax.servlet.annotation.WebFilter;

 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 com.test.util.MyBatisUtil;

 /**
  * 最开始是由Spring框架提出的.整合Hibernate框架是使用的是OpenSessionInView
  *
  *
  * @author Administrator
  *
  */
 @WebFilter("/*")
 public class OpenSessionInView implements Filter{

     @Override
     public void init(FilterConfig filterconfig) throws ServletException {
         // TODO Auto-generated method stub
     }

     @Override
     public void doFilter(ServletRequest servletrequest, ServletResponse servletresponse, FilterChain filterchain)
             throws IOException, ServletException {
 //        InputStream is = Resources.getResourceAsStream("mybatis.xml");
 //        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(is);
 //        SqlSession session = factory.openSession();
         SqlSession session = MyBatisUtil.getSession();
         try {
             filterchain.doFilter(servletrequest, servletresponse);
             session.commit();
         } catch (Exception e) {
             session.rollback();
             e.printStackTrace();
         }finally{
             MyBatisUtil.closeSession();
         }
 //        session.commit();
 //        session.close();
     }

     @Override
     public void destroy() {
         // TODO Auto-generated method stub
     }
 }