hibernatefilter.java

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package cn.hxex.vote.filter;

import java.io.IOException;

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.http.HttpServletRequest;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.hibernate.SessionFactory;

import cn.hxex.vote.util.HibernateUtil;


/**
 * 用于进行Hibernate事务处理的Servlet过滤器
 *
 * @author galaxy
 */
public class HibernateFilter implements Filter {

    private static Log log = LogFactory.getLog(HibernateFilter.class);

    /**
     * 过滤器的主要方法
     * 用于实现Hibernate事务的开始和提交
     */
    public void doFilter(ServletRequest request,
                         ServletResponse response,
                         FilterChain chain)
            throws IOException, ServletException 
    {
    	// 得到SessionFactory对象的实例
    	SessionFactory sf = HibernateUtil.getSessionFactory();

        try 
        {
        	// 开始一个新的事务
            log.debug("Starting a database transaction");
            sf.getCurrentSession().beginTransaction();

            log.debug( "Request Path:\t" + ((HttpServletRequest)request).getServletPath() );
            
            // 设置用户请求的编码格式
            request.setCharacterEncoding( "gb2312" );
            
            // Call the next filter (continue request processing)
            chain.doFilter(request, response);

            // 提交事务
            log.debug("Committing the database transaction");
            sf.getCurrentSession().getTransaction().commit();
            
        } 
        catch (Throwable ex) 
        {
        	ex.printStackTrace();
            try 
            {
            	// 会滚事务
                log.debug("Trying to rollback database transaction after exception");
                sf.getCurrentSession().getTransaction().rollback();
            } 
            catch (Throwable rbEx) 
            {
                log.error("Could not rollback transaction after exception!", rbEx);
            }

            // 抛出异常
            throw new ServletException(ex);
        }
    }

    /**
     * Servlet过滤器的初始化方法
     * 可以读取配置文件中设置的配置参数
     */
    public void init(FilterConfig filterConfig) throws ServletException {}

    /**
     * Servlet的销毁方法
     * 用于释放过滤器所申请的资源
     */
    public void destroy() {}

}