java - 当 RequestHandler 抛出异常时 Jetty 重试请求

Question

我注意到每当handle抛出异常时，Jetty就会重试调用指定的Handler。

这是不受欢迎的行为，但我似乎找不到阻止它的配置设置。

我已经使用 Jetty 一段时间了，但最近升级了我的环境以使用 9.4.9.v20180320。这可能是也可能不是新行为，但我从未注意到它。

下面是一个简单的用例来说明我的问题。请注意，输出中有两行指示正文内容，但令人困惑的是，在第二次尝试时，正文为空。

public class JettyTest extends AbstractHandler
{
    @Override
    public void handle(String arg0, Request arg1, HttpServletRequest arg2, HttpServletResponse arg3)
    throws IOException
    {
        //read request body into string
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        //apache commons copy
        IOUtils.copy(arg1.getInputStream(), bos);
        String body = new String(bos.toByteArray());
        System.out.println("request body: " + body);
        throw new NullPointerException();
    }

    public static void main(String args[])
    throws Exception
    {
        Server server = new Server();
        server.setHandler(new JettyTest());
        LocalConnector localConnector = new LocalConnector(server);
        server.addConnector(localConnector);
        server.start();
        String simpleRequest = "GET / http/1.1\r\nHost: localhost:0\r\nContent-Type: text/plain\r\nContent-Length: 2\r\n\r\nhi";
        String response = localConnector.getResponse(simpleRequest);
        server.join();
    }

}

输出

2018-03-26 19:47:49.590:INFO:oejs.Server:main: Started @327ms

request body: hi

2018-03-26 19:47:49.660:WARN:oejs.HttpChannel:qtp1349277854-12: /
java.lang.NullPointerException
    at test.JettyTest.handle(JettyTest.java:28)
    at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:132)
    at org.eclipse.jetty.server.Server.handle(Server.java:531)
    at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:352)
    at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:260)
    at org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:281)
    at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:102)
    at org.eclipse.jetty.io.ByteArrayEndPoint$1.run(ByteArrayEndPoint.java:78)
    at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:754)
    at org.eclipse.jetty.util.thread.QueuedThreadPool$2.run(QueuedThreadPool.java:672)
    at java.lang.Thread.run(Thread.java:748)

request body: 

Answer 1

你有很多事情正在发生。

1. 您没有处理该请求(您的代码库中没有任何内容使用 Request.setHandled(true))
2. 您没有 ERROR 调度处理。
3. 您没有 ErrorHandler 设置。

所以发生的事情是......

1. 你的 JettyTest.handle() 被调用，异常流出。
2. 请求现在处于 ERROR 调度模式。
3. 现在，错误调度请求会再次发送到处理程序中以进行错误处理。

如果您只是对此进行更改...

package jetty.errors;

import java.io.ByteArrayOutputStream;
import java.io.IOException;

import javax.servlet.DispatcherType;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.eclipse.jetty.server.LocalConnector;
import org.eclipse.jetty.server.Request;
import org.eclipse.jetty.server.Server;
import org.eclipse.jetty.server.handler.AbstractHandler;
import org.eclipse.jetty.util.IO;

public class HandlerWithError extends AbstractHandler
{
    @Override
    public void handle(String s, Request request, HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse) throws IOException
    {
        if (DispatcherType.REQUEST.equals(httpServletRequest.getDispatcherType()))
        {
            // read request body into string
            ByteArrayOutputStream bos = new ByteArrayOutputStream();
            // apache commons copy
            IO.copy(httpServletRequest.getInputStream(), bos);
            String body = new String(bos.toByteArray());
            System.out.println("request body: " + body);
            throw new NullPointerException();
        }
        else
        {
            System.out.println("Now in DispatchType: " + httpServletRequest.getDispatcherType());
        }
    }

    public static void main(String args[])
            throws Exception
    {
        Server server = new Server();
        server.setHandler(new HandlerWithError());
        LocalConnector localConnector = new LocalConnector(server);
        server.addConnector(localConnector);
        server.start();
        String simpleRequest = "GET / http/1.1\r\n" +
                "Host: localhost:0\r\n" +
                "Connection: close\r\n" +
                "Content-Type: text/plain\r\n" +
                "Content-Length: 2\r\n\r\nhi";
        String response = localConnector.getResponse(simpleRequest);
        server.join();
    }
}

你会得到结果...

2018-03-27 06:47:40.074:INFO::main: Logging initialized @429ms to org.eclipse.jetty.util.log.StdErrLog
2018-03-27 06:47:40.148:INFO:oejs.Server:main: jetty-9.4.9.v20180320; built: 2018-03-20T07:21:10-05:00; git: 1f8159b1e4a42d3f79997021ea1609f2fbac6de5; jvm 9.0.4+11
2018-03-27 06:47:40.182:INFO:oejs.AbstractConnector:main: Started LocalConnector@2f490758{HTTP/1.1,[http/1.1]}
2018-03-27 06:47:40.183:INFO:oejs.Server:main: Started @548ms
2018-03-27 06:47:40.287:WARN:oejs.HttpChannel:qtp2104545713-16: /
java.lang.NullPointerException
    at jetty.errors.HandlerWithError.handle(HandlerWithError.java:29)
    at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:132)
    at org.eclipse.jetty.server.Server.handle(Server.java:531)
    at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:352)
    at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:260)
    at org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:281)
    at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:102)
    at org.eclipse.jetty.io.ByteArrayEndPoint$1.run(ByteArrayEndPoint.java:78)
    at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:754)
    at org.eclipse.jetty.util.thread.QueuedThreadPool$2.run(QueuedThreadPool.java:672)
    at java.base/java.lang.Thread.run(Thread.java:844)
request body: hi
Now in DispatchType: ERROR

了解了这一切后，您可以通过以下方式更改您的实现以利用此 ERROR 调度。

package jetty.errors;

import java.io.ByteArrayOutputStream;
import java.io.IOException;

import javax.servlet.DispatcherType;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.eclipse.jetty.http.HttpTester;
import org.eclipse.jetty.server.LocalConnector;
import org.eclipse.jetty.server.Request;
import org.eclipse.jetty.server.Server;
import org.eclipse.jetty.server.handler.AbstractHandler;
import org.eclipse.jetty.server.handler.DefaultHandler;
import org.eclipse.jetty.server.handler.HandlerList;
import org.eclipse.jetty.util.IO;

public class HandlerWithError
{
    public static class MyRequestHandler extends AbstractHandler
    {
        @Override
        public void handle(String target, Request baseRequest, HttpServletRequest request, HttpServletResponse response) throws IOException
        {
            System.out.println("MyRequestHandler.handle() - DispatcherType: " + request.getDispatcherType());
            // only work with REQUEST Dispatches
            if (!DispatcherType.REQUEST.equals(request.getDispatcherType()))
            {
                // skip this handler
                return;
            }

            // Set handled (by this handler), don't let other handlers operate on this request
            baseRequest.setHandled(true);
            // read request body into string
            ByteArrayOutputStream bos = new ByteArrayOutputStream();
            // apache commons copy
            IO.copy(request.getInputStream(), bos);
            String body = new String(bos.toByteArray());
            System.out.println("request body: " + body);
            throw new NullPointerException();
        }
    }

    public static class MyErrorHandler extends AbstractHandler
    {
        @Override
        public void handle(String target, Request baseRequest, HttpServletRequest request, HttpServletResponse response) throws IOException
        {
            System.out.println("MyErrorHandler.handle() - DispatcherType: " + request.getDispatcherType());
            if(!DispatcherType.ERROR.equals(request.getDispatcherType()))
            {
                // skip this handler
                return;
            }

            baseRequest.setHandled(true);
            response.setStatus(HttpServletResponse.SC_SERVICE_UNAVAILABLE);
            response.setContentType("text/plain");
            response.getWriter().println("Go away, you silly NPE fool");
        }
    }

    public static void main(String args[])
            throws Exception
    {
        Server server = new Server();
        HandlerList handlers = new HandlerList();
        // Add your ERROR Dispatch handler first to handle dispatches for errors
        handlers.addHandler(new MyErrorHandler());
        // Add your handlers here (can be more then one)
        handlers.addHandler(new MyRequestHandler());
        // Always add DefaultHandler last, to ensure that something in your handler
        // list is calling baseRequest.setHandled(true)
        handlers.addHandler(new DefaultHandler());
        server.setHandler(handlers);
        LocalConnector localConnector = new LocalConnector(server);
        server.addConnector(localConnector);
        server.start();

        try
        {
            String simpleRequest = "GET / http/1.1\r\n" +
                    "Host: localhost:0\r\n" +
                    "Connection: close\r\n" +
                    "Content-Type: text/plain\r\n" +
                    "Content-Length: 2\r\n\r\nhi";
            HttpTester.Response response = HttpTester.parseResponse(
                    localConnector.getResponse(simpleRequest));
            System.out.println("Response: " + response);
            System.out.println(response.getContent());
        }
        catch (Throwable t)
        {
            t.printStackTrace();
        }
        finally
        {
            server.stop();
        }
    }
}

输出看起来像这样......

2018-03-27 07:03:25.220:INFO::main: Logging initialized @320ms to org.eclipse.jetty.util.log.StdErrLog
2018-03-27 07:03:25.288:INFO:oejs.Server:main: jetty-9.4.9.v20180320; built: 2018-03-20T07:21:10-05:00; git: 1f8159b1e4a42d3f79997021ea1609f2fbac6de5; jvm 9.0.4+11
2018-03-27 07:03:25.309:INFO:oejs.AbstractConnector:main: Started LocalConnector@4ba2ca36{HTTP/1.1,[http/1.1]}
2018-03-27 07:03:25.310:INFO:oejs.Server:main: Started @417ms
MyErrorHandler.handle() - DispatcherType: REQUEST
MyRequestHandler.handle() - DispatcherType: REQUEST
request body: hi
2018-03-27 07:03:25.399:WARN:oejs.HttpChannel:qtp525571-15: /
java.lang.NullPointerException
    at jetty.errors.HandlerWithError$MyRequestHandler.handle(HandlerWithError.java:41)
    at org.eclipse.jetty.server.handler.HandlerList.handle(HandlerList.java:61)
    at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:132)
    at org.eclipse.jetty.server.Server.handle(Server.java:531)
    at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:352)
    at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:260)
    at org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:281)
    at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:102)
    at org.eclipse.jetty.io.ByteArrayEndPoint$1.run(ByteArrayEndPoint.java:78)
    at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:754)
    at org.eclipse.jetty.util.thread.QueuedThreadPool$2.run(QueuedThreadPool.java:672)
    at java.base/java.lang.Thread.run(Thread.java:844)
MyErrorHandler.handle() - DispatcherType: ERROR
Response: HTTP/1.1 503 Service Unavailable
Connection: close
Content-Type: text/plain;charset=ISO-8859-1
Content-Length: 29
Server: Jetty(9.4.9.v20180320)

Go away, you silly NPE fool

2018-03-27 07:03:25.423:INFO:oejs.AbstractConnector:main: Stopped LocalConnector@4ba2ca36{HTTP/1.1,[http/1.1]}