[英]How to hook begin and end of HTTP requests in JavaEE?
如何在ServletRequestListener.requestDestroyed期间获得ServletResponse ?
在 JavaEE 中,我想知道什么时候:
在 ASP.net 世界中,如果您想知道请求何时开始和结束,请编写IHttpModule
:
public class ExampleModuleForThisQuestion : IHttpModule
{
}
然后在 web xml 配置文件中注册您的“模块” :
web.config :
<system.webServer>
<modules>
<add name="DoesntMatter" type="ExampleModuleForThisQuestion "/>
</modules>
</system.webServer>
在您的模块中,您可以为以下内容注册回调处理程序:
然后,Web 服务器基础架构会调用您的Init
方法。 这是您注册希望在请求开始和请求结束时接收通知的机会:
public class ExampleModuleForThisQuestion : IHttpModule
{
public void Init(HttpApplication application)
{
application.BeginRequest += new EventHandler(beginRequest); //register the "BeginRequet" event
application.EndRequest += new EventHandler(endRequest); //register the "EndRequest" event
}
}
现在我们有了请求开始时的回调:
private void beginRequest(object sender, EventArgs e)
{
HttpApplication application = (HttpApplication)sender;
//Record the time the request started
application.Context.Items["RequestStartTime"] = DateTime.Now;
//We can even access the Request and Response objects
application.ContenxtLog(application.Context.Request.Headers["User-Agent"]);
}
当请求结束时我们有回调:
private void endRequest(object sender, EventArgs e)
{
HttpApplication application = (HttpApplication)sender;
//We can even access the Request and Response objects
//Get the response status code (e.g. 418 I'm a teapot)
int statusCode = application.Context.Response.StatusCode;
//Get the request method (e.g. GET, POST, BREW)
String method = application.context.Request.RequestType;
//Get the path from the request (e.g. /ViewCustomer)
String path = application.context.Request.AppRelativeCurrentExecutionFilePath'
//Get when the request started - that we recorded during "Begin Request"
DateTime requestStartTime = (DateTime)application.Context.Items["RequestStartTime"];
//And we can modify the response
if ((DateTime.Now - requestStartTime).TotalSeconds = 17)
application.Context.Response.StatusCode = 451;
}
在 Java 中,显然相应的技术是创建和实现ServletRequestListener接口的 object:
@WebListener
public class ExampleListenerForThisQuestion
implements javax.servlet.ServletRequestListener {
}
并将我们的侦听器注册到应用程序服务器,方法是将其包含在我们的 web xml 配置文件中:
web.xml
<listener>
<listener-class>ExampleListenerForThisQuestion</listener-class>
</listener>
现在我们可以实现requestInitialized和requestDestroyed方法来获取请求何时开始和结束:
public class ExampleListenerForThisQuestion
implements javax.servlet.ServletRequestListener {
@Override
public void requestInitialized(ServletRequestEvent sre) {
ServletRequest sr = sre.getServletRequest();
sr.setAttribute("requestStartTicks", getCurrentTickCount());
HttpServletRequest request = (HttpServletRequest) sr;
// e.g. "PUT /Customers/1234"
System.out.printf("%s %s\r\n", request.getMethod());
}
@Override
public void requestDestroyed(ServletRequestEvent sre) {
ServletRequest sr = sre.getServletRequest();
long requestStartTicks = (long)sr.getAttribute("requestStartTicks");
HttpServletResponse response = (HttpServletRequest)...nothing, because i don't know how...
// e.g. "226 IM Used"
System.out.printf("%d %s\r\n", response.getStatus(), response.getStatusDescription());
}
}
现在我在响应结束时收到通知,我需要该请求的结果:
424
)Failed Dependency
)您注意到我上面的代码中的行:
HttpServletResponse response = (HttpServletRequest)...nothing, because i don't know how...
我不知道如何得到回应; 这就是为什么我要问 Stackoverflow。
您可以创建过滤器而不是侦听器。
过滤器允许您围绕请求处理创建包装器。
对于 HTTP,您可以使用HTTPFilter 。 这可能如下所示:
@WebFilter("")//or via deployment descriptor
public class YourFilter extends HttpFilter{ //or just Filter for general (non-HTTP) processing
@Override
public void doFilter(HttpServletRequest req, HttpServletResponse res, FilterChain chain) {//for generic filters, use ServletRequest/ServletResponse instead
//before request processing
chain.doFilter(req, res, chain);//calls other filters and processes request
//after request processing
//you can use res here
}
}
如果不调用chain.doFilter
,其他过滤器和 servlet 将不会被执行。
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