使用HttpEndpoint Options和http4的Apache骆驼

当你从传播的HTTP URI调用direct:parent到direct:a，但保持在一个嵌套的例外条款direct:parent，在抛出的异常direct:a是不向上传播到父路径。但是，您应该做的是将嵌套异常子句重构为全局异常子句。

我创建了一个简单的测试用例，它可以模拟在204消息上引发的异常，或者可以调用真实服务并在204响应的情况下失败：

import org.apache.camel.Produce;
import org.apache.camel.ProducerTemplate;
import org.apache.camel.builder.AdviceWithRouteBuilder;
import org.apache.camel.builder.RouteBuilder;
import org.apache.camel.http.common.HttpOperationFailedException;
import org.apache.camel.test.junit4.CamelTestSupport;
import org.junit.Test;

import java.util.HashMap;
import java.util.Map;

import static org.hamcrest.CoreMatchers.equalTo;
import static org.hamcrest.CoreMatchers.is;
import static org.hamcrest.CoreMatchers.nullValue;

public class Http4ExceptionHandlingTest extends CamelTestSupport {

  @Produce(uri = "direct:parent")
  protected ProducerTemplate template;

  @Override
  public boolean isUseAdviceWith() {
    return true;
  }

  @Override
  protected RouteBuilder createRouteBuilder() {
    return new RouteBuilder() {
      @Override
      public void configure() throws Exception {

        onException(HttpOperationFailedException.class)
            .onWhen(exchange -> {
              HttpOperationFailedException
                  exe = exchange.getException(HttpOperationFailedException.class);
              return 204 == exe.getStatusCode();
            })
            .log("HTTP exception handled")
            .handled(true)
            //.continued(true)
            .setBody(constant(null));

        from("direct:parent").routeId("parent")
//            .onException(HttpOperationFailedException.class)
//                .onWhen(exchange -> {
//                  HttpOperationFailedException
//                      exe = exchange.getException(HttpOperationFailedException.class);
//                  return 204 == exe.getStatusCode();
//                })
//                .setBody(constant(null))
//            .end()
            .log("Parent start");
            .to("direct:a")
            .log("Parent done");

        from("direct:a").routeId("a")
            .log("a start")
            .to("http4://localhost:8022/test/service?okStatusCodeRange=200-201")
            .convertBodyTo(String.class)
            .log("a done");
      }
    };
  }

  @Test
  public void testExceptionHandling() throws Exception {
    // comment the following line out if you want to invoke the real service instead!
    weaveRoute();

    context.start();

    Object response = template.requestBody("foo");

    assertThat(response, is(nullValue()));
  }

  @Test
  public void testSuccessfulResponse() throws Exception {
    // comment the following line out if you want to invoke the real service instead!
    weaveRoute();

    context.start();

    Object response = template.requestBody("bar");

    assertThat(response, is(equalTo("bar")));
  }

  private void weaveRoute() throws Exception {
    context.getRouteDefinition("a").adviceWith(context, new AdviceWithRouteBuilder() {
      @Override
      public void configure() throws Exception {
        this.interceptSendToEndpoint("http4*")
            .skipSendToOriginalEndpoint()
            .process(exchange -> {
              String body = exchange.getIn().getBody(String.class);
              if ("foo".equals(body)) {
                Map<String, String> headers = new HashMap<>();
                String location = "";
                HttpOperationFailedException exe =
                    new HttpOperationFailedException("http://bla", 204, "No Content", location,
                                                     headers, "response body");
                throw exe;
              }
            });
      }
    });
  }
}

我在父路由中保留了原始的嵌套异常子句，以便您可以比较结果。全局异常处理程序还有一条额外的.handled(true）`语句，它刚刚超出了当前路由。因此，文档指出以下内容：

如果handle为true，则将处理抛出的异常，并且Camel将不会继续沿原始路由进行路由，而是会中断。但是，您可以在onException中配置一个路由，该路由将被代替使用。如果您需要创建一些返回给调用者的自定义响应消息，或者执行其他任何处理（因为引发了该异常），则可以使用此路由。（来源）

不将捕获的异常设置为.handled(true)会导致堆栈跟踪的呈现，然后继续执行。

我添加了更多的日志语句以可视化异常处理中的行为。执行上面提供的代码后，您将获得类似以下的输出：

[INFO ] -  - Parent start [            ] [parent] [              ] [main] 
[INFO ] -  - a start [            ] [a] [              ] [main] 
[INFO ] -  - HTTP exception handled [            ] [a] [              ] [main] 

取而代之的是，.handled(true)您也可以使用.continued(true)以便按照记录进行执行：

如果continue为true，那么Camel将捕获该异常，并且实际上只是忽略该异常并继续沿原始路由进行路由。但是，如果在onException中配置了路由，它将先路由该路由，然后再继续在原始路由中路由。

在全局异常子句中启用.continued(true)和禁用测试的情况下运行测试.handled(true)将产生以下日志：

[INFO ] -  - Parent start [            ] [parent] [              ] [main] 
[INFO ] -  - a start [            ] [a] [              ] [main] 
[INFO ] -  - HTTP exception handled [            ] [a] [              ] [main] 
[ERROR] -  - Failed delivery for (MessageId: ...). Exhausted after delivery attempt: 1 caught: null. Handled and continue routing.

Message History
---------------------------------------------------------------------------------------------------------------------------------------
RouteId              ProcessorId          Processor                                                                        Elapsed (ms)
[parent            ] [parent            ] [direct://parent                                                               ] [         8]
[parent            ] [log9              ] [log                                                                           ] [         0]
[parent            ] [to4               ] [direct:a                                                                      ] [         8]
[a                 ] [log7              ] [log                                                                           ] [         1]
[a                 ] [to3               ] [http4://localhost:8022/test/service?okStatusCodeRange=200-201                 ] [         8]
[                  ] [process2          ] [Processor@0x3c7f66c4                                                          ] [         8]
[a                 ] [log6              ] [log                                                                           ] [         1]
[a                 ] [setBody2          ] [setBody[{null}]                                                               ] [         0]

Stacktrace
--------------------------------------------------------------------------------------------------------------------------------------- [            ] [o.a.c.p.DefaultErrorHandler] [              ] [main] 
org.apache.camel.http.common.HttpOperationFailedException: HTTP operation failed invoking http://bla with statusCode: 204, redirectLocation: 
    at at.erpel.messaginghub.services.unit.routes.rest.Http4ExceptionHandlingTest$2.lambda$configure$1(Http4ExceptionHandlingTest.java:103)
    at org.apache.camel.processor.DelegateSyncProcessor.process(DelegateSyncProcessor.java:63)
    ...
[INFO ] -  - a done [            ] [a] [              ] [main] 
[INFO ] -  - Parent done [            ] [parent] [              ] [main] 

从简化的日志中可以看出，.continued(true)尽管会记录一条消息历史记录以及被忽略异常的堆栈跟踪信息，但不会超出路由范围。

如果父路由中有嵌套异常子句，而子路由确实遇到异常，则在嵌套异常子句中添加.handled(true)或.continuted(true)无效，因为子路由中捕获的实际异常不会传播到父嵌套异常子句，并且因此根本没有处理。

我已经针对模拟和真实服务测试了代码示例，该真实服务返回了204接收到foo正文的200响应以及接收到其他内容的响应。?okStatusCodeRange=200-201因此，在我的情况下，配置参数可以按预期工作。对于完整性：我正在使用Camel 2.17.0。