HttpServlet中的service方法

 

service方法是接口中的方法，servlet容器把所有请求发送到该方法，该方法默认行为是转发http请求到doXXX方法中，如果你重载了该方法，默认操作被覆盖，不再进行转发操作！
HttpServlet的实现其中关于service 的实现如下:
    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 logic
doGet(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);
}
    }