MyBatis（三）ThreadLocal

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.
2. 语法示例

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

3. 封装工具类

public class MyBatisUtil {
    //factory实例化的过程是一个比较耗费性能的过程.
    //保证有且只有一个factory
    private static SqlSessionFactory factory;
    private static ThreadLocal<SqlSession> tl = new ThreadLocal<>();
    static{
        try {
            InputStream is = Resources.getResourceAsStream("mybatis.xml");
            factory = new SqlSessionFactoryBuilder().build(is);
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    /**
     * 获取SqlSession的方法
     */
    public static SqlSession getSession(){
        SqlSession session = tl.get();
        if(session==null){
            tl.set(factory.openSession());
        }
        return tl.get();
    }
    
    public static void closeSession(){
        SqlSession session = tl.get();
        if(session!=null){
            session.close();
        }
        tl.set(null);
    }
}

4. 封装Filter类

package com.bjsxt.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.bjsxt.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
        
    }

}

5. 使用

public class LogServiceImpl implements LogService{

    @Override
    public int ins(Log log) {
        SqlSession session = MyBatisUtil.getSession();
        LogMapper mapper = session.getMapper(LogMapper.class);
        return mapper.ins(log);
    }

}