package com.brothers.servlet;

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 javax.servlet.http.HttpServletResponse;

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

import com.brothers.hibernate.HibernateUtil;
import com.brothers.model.User;

/**
 * 用于進行Hibernate事務處理的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 用于實現Hibernate事務的開始和提交
	 */
	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
		// 得到SessionFactory對象的實例
		SessionFactory sf = HibernateUtil.getSessionFactory();

		try {
			// 開始一個新的事務
			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
			log.debug("Committing the database transaction");
			sf.getCurrentSession().getTransaction().commit();

		} catch (Throwable ex) {
			ex.printStackTrace();
			try {
				// 回滾事務
				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置的配置參數
	 */
	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() {
	}

}