package com.qrsx.exam.web.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 com.qrsx.exam.dao.util.HibernateUtil;

/**
 * 用于進(jìn)行Hibernate事務(wù)處理的Servlet過濾器
 * 
 * @author galaxy
 */
public class HibernateFilter implements Filter {

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

    /**
     * 過濾器的主要方法 用于實(shí)現(xiàn)Hibernate事務(wù)的開始和提交
     */
    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {
        // 得到SessionFactory對象的實(shí)例
        SessionFactory sf = HibernateUtil.getSessionFactory();

        try {
            // 開始一個(gè)新的事務(wù)
            log.debug("Starting a database transaction");
            sf.getCurrentSession().beginTransaction();

            log.debug("Request Path:\t"
                    + ((HttpServletRequest) request).getServletPath());
            // Call the next filter (continue request processing)
            chain.doFilter(request, response);

            // 提交事務(wù)
            log.debug("Committing the database transaction");
            sf.getCurrentSession().getTransaction().commit();

        } catch (Throwable ex) {
            ex.printStackTrace();
            try {
                // 會(huì)滾事務(wù)
                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);
            }

            // 拋出異常
            throw new ServletException(ex);
        }
    }

    /**
     * Servlet過濾器的初始化方法 可以讀取配置文件中設(shè)置的配置參數(shù)
     */
    public void init(FilterConfig filterConfig) throws ServletException {
    }

    /**
     * Servlet的銷毀方法 用于釋放過濾器所申請的資源
     */
    public void destroy() {
    }

}