研究Servlet族

protected void service(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException    {String method = req.getMethod();if (method.equals(METHOD_GET)) {    long lastModified = getLastModified(req);    if (lastModified == -1) {// servlet doesn't support if-modified-since, no reason// to go through further expensive logicdoGet(req, resp);    } else {long ifModifiedSince = req.getDateHeader(HEADER_IFMODSINCE);if (ifModifiedSince < (lastModified / 1000 * 1000)) {    // If the servlet mod time is later, call doGet()                    // Round down to the nearest second for a proper compare                    // A ifModifiedSince of -1 will always be less    maybeSetLastModified(resp, lastModified);    doGet(req, resp);} else {    resp.setStatus(HttpServletResponse.SC_NOT_MODIFIED);}    }} else if (method.equals(METHOD_HEAD)) {    long lastModified = getLastModified(req);    maybeSetLastModified(resp, lastModified);    doHead(req, resp);} else if (method.equals(METHOD_POST)) {    doPost(req, resp);    } else if (method.equals(METHOD_PUT)) {    doPut(req, resp);    } else if (method.equals(METHOD_DELETE)) {    doDelete(req, resp);    } else if (method.equals(METHOD_OPTIONS)) {    doOptions(req,resp);    } else if (method.equals(METHOD_TRACE)) {    doTrace(req,resp);    } else {    //    // Note that this means NO servlet supports whatever    // method was requested, anywhere on this server.    //    String errMsg = lStrings.getString("http.method_not_implemented");    Object[] errArgs = new Object[1];    errArgs[0] = method;    errMsg = MessageFormat.format(errMsg, errArgs);        resp.sendError(HttpServletResponse.SC_NOT_IMPLEMENTED, errMsg);}    }@overridepublic void service(ServletRequest req, ServletResponse res)throws ServletException, IOException    {HttpServletRequestrequest;HttpServletResponseresponse;try {    request = (HttpServletRequest) req;    response = (HttpServletResponse) res;} catch (ClassCastException e) {    throw new ServletException("non-HTTP request or response");}service(request, response);    }

这是javax.servlet.http.HttpServlet中的两个service方法。