Apache Camel：發布請求正文時出現問題

Question

我有一個服務器和客戶端應用程序，它們都使用 Apache Camel 來配置和管理它們的路由。 我正在嘗試使用 REST 組件從客戶端向服務器發出 POST 請求，並在請求正文中發送消息。 似乎正在調用 REST 端點，但主體沒有通過。 我想我要么錯過了一些步驟，要么我做錯了。

另一件要提的是，我使用的是通用消息 class，它基本上可以包含任何 object（包括字節或字符的 arrays）。 也許這是我遇到的問題背后的部分（或全部）原因。

通用消息.java：

public class GenericMessage<T extends Object> {
  private T payload;

  public GenericMessage(T payload) {
    this.payload = payload;
  }

  public T getPayload() {
    return payload;
  }

  public void setPayload(T payload) {
    this.payload = payload;
  }

  @Override
  public String toString() {
    return "GenericMessage [payload=" + payload + "]";
  }
}

服務器

駱駝上下文.xml：

  <camelContext id="camel-context" xmlns="http://camel.apache.org/schema/spring">
    <restConfiguration component="jetty" bindingMode="json"
      contextPath="/" host="localhost" port="9100">
      <dataFormatProperty key="prettyPrint" value="true" />
    </restConfiguration>

    <rest>
      <get uri="/data?size={size}" produces="JSON">
        <route id="get-data-by-size">
          <log loggingLevel="INFO" message="start - get-data-by-size" />
          <process ref="get-request-processor" />
          <log loggingLevel="INFO" message="end - get-data-by-size" />
        </route>
      </get>

      <post uri="post-data" consumes="json">
        <route id="post-data">
          <log loggingLevel="INFO" message="start - post-data" />
          <process ref="post-request-processor" />
          <log loggingLevel="INFO" message="end - post-data" />
        </route>
      </post>
    </rest>
  </camelContext>

GetRequestProcessor.java：

@Component("get-request-processor")
public class GetRequestProcessor implements Processor {
  @Autowired
  private DataProvider provider;

  public void process(Exchange exchange) throws Exception {
    int size = exchange.getIn().getHeader("size", Integer.class);
    // TODO currently only sends char[] data
    GenericMessage<?> data = provider.getCharData(size);
    exchange.getMessage().setBody(data, GenericMessage.class);
  }
}

PostRequestProcessor.java：

@Component("post-request-processor")
public class PostRequestProcessor implements Processor {
  private final Logger logger = LoggerFactory.getLogger(PostRequestProcessor.class);

  public void process(Exchange exchange) throws Exception {
    GenericMessage<?> data = exchange.getIn().getBody(GenericMessage.class);

    if (data != null) {
      logger.info("process: object received: {}", data);
    } else {
      logger.warn("process: null object");
    }
  }
}

數據提供者.java：

@Component
public class DataProvider {
  private final Logger logger = LoggerFactory.getLogger(DataProvider.class);

  public GenericMessage<?> getByteData(final int size) {
    logger.info("getByteData: size={}", size);
    return new GenericMessage<byte[]>(DataGenerator.generateByteArray(size));
  }

  public GenericMessage<?> getCharData(final int size) {
    logger.info("getCharData: size={}", size);
    return new GenericMessage<char[]>(DataGenerator.generateCharArray(size));
  }
}

客戶

駱駝上下文.xml：

  <camelContext id="camel-context" xmlns="http://camel.apache.org/schema/spring">
    <restConfiguration component="jetty" bindingMode="json"
      contextPath="/" host="{{http-client.server.host}}"
      port="{{http-client.server.port}}">
      <dataFormatProperty key="prettyPrint" value="true" />
    </restConfiguration>

    <route id="rest-get">
      <from
        uri="timer:{{http-client.timers.http-get.name}}?delay={{http-client.timers.http-get.start-delay}}&amp;fixedRate=true&amp;period={{http-client.timers.http-get.period}}&amp;repeatCount={{http-client.timers.http-get.repeat-count}}" />
      <log loggingLevel="INFO" message="start - rest-get" />
      <to uri="rest:get:{{http-client.endpoints.http-get}}" />
      <process ref="process-get-response" />
      <log loggingLevel="INFO" message="end - rest-get" />
    </route>

    <route id="rest-post">
      <from
        uri="timer:{{http-client.timers.http-post.name}}?delay={{http-client.timers.http-post.start-delay}}&amp;fixedRate=true&amp;period={{http-client.timers.http-post.period}}&amp;repeatCount={{http-client.timers.http-post.repeat-count}}" />
      <log loggingLevel="INFO" message="start - rest-post" />
      <process ref="add-post-body" />
      <to uri="rest:post:{{http-client.endpoints.http-post}}" />
      <log loggingLevel="INFO" message="end - rest-post" />
    </route>
  </camelContext>

AddPostRequestBody.java：

@Component("add-post-body")
public class AddPostRequestBody implements Processor {
  private final Logger logger = LoggerFactory.getLogger(AddPostRequestBody.class);

  @Autowired
  private DataProvider provider;

  @Override
  public void process(Exchange exchange) throws Exception {
    GenericMessage<?> data = null;
    int intValue = RandomUtil.generateInt(1);

    switch (intValue) {
      case 0:
        data = provider.produceByteArrayData();
        break;
      case 1:
        data = provider.produceCharArrayData();
        break;
      default:
        break;
    }

    logger.info("adding POST request body:\n{}", data);

    exchange.getMessage().setHeader(Exchange.HTTP_METHOD, "POST");
    exchange.getMessage().setHeader(Exchange.CONTENT_TYPE, "application/json");
    exchange.getMessage().setBody(data, GenericMessage.class);
  }
}

GetResponseProcessor.java：

@Component("process-get-response")
public class GetResponseProcessor implements Processor {
  private final Logger logger = LoggerFactory.getLogger(GetResponseProcessor.class);

  @Override
  public void process(Exchange exchange) throws Exception {
    GenericMessage<?> body = (GenericMessage<?>) exchange.getIn().getBody();
    logger.info("body: {}", body);
  }
}

數據提供者.java：

@Component
public class DataProvider {
  private final Logger logger = LoggerFactory.getLogger(DataProvider.class);

  public GenericMessage<byte[]> produceByteArrayData() {
    int size = RandomUtil.generateInt(1000, 20000000);
    byte[] bytes = DataGenerator.generateByteArray(size);
    logger.info("produceByteArrayData: generated {} bytes", size);
    GenericMessage<byte[]> data = new GenericMessage<>(bytes);
    return data;
  }

  public GenericMessage<char[]> produceCharArrayData() {
    int size = RandomUtil.generateInt(1000, 20000000);
    char[] chars = DataGenerator.generateCharArray(size);
    logger.info("produceCharArrayData: generated {} characters", size);
    GenericMessage<char[]> data = new GenericMessage<>(chars);
    return data;
  }
}

我將其配置為從客戶端執行一個 POST 請求。 有散布的日志語句可以讓您了解正在發生的事情。

客戶端控制台：

2020-04-13 13:23:39.805  INFO 17464 --- [           main] o.a.c.i.e.AbstractCamelContext           : Route: rest-get started and consuming from: timer://http-get
2020-04-13 13:23:39.806  INFO 17464 --- [           main] o.a.c.i.e.AbstractCamelContext           : Route: rest-post started and consuming from: timer://http-post
2020-04-13 13:23:39.812  INFO 17464 --- [           main] o.a.c.i.e.AbstractCamelContext           : Total 2 routes, of which 2 are started
2020-04-13 13:23:39.812  INFO 17464 --- [           main] o.a.c.i.e.AbstractCamelContext           : Apache Camel 3.1.0 (CamelContext: RESTClient) started in 1.679 seconds
2020-04-13 13:23:42.308  INFO 17464 --- [mer://http-post] rest-post                                : start - rest-post
2020-04-13 13:23:42.312  INFO 17464 --- [mer://http-post] e.m.l.m.s.DataProvider                   : produceCharArrayData: generated 1039 characters
2020-04-13 13:23:42.313  INFO 17464 --- [mer://http-post] e.m.l.m.p.AddPostRequestBody             : CLIENT: Adding POST request body:
GenericMessage [payload=[C@2124c204]
2020-04-13 13:23:42.408  INFO 17464 --- [mer://http-post] rest-post                                : end - rest-post

服務器控制台：

2020-04-13 13:23:10.846  INFO 23260 --- [           main] o.a.c.i.e.AbstractCamelContext           : Route: get-data-by-size started and consuming from: jetty:http://localhost:9100/data
2020-04-13 13:23:10.847  INFO 23260 --- [           main] o.a.c.i.e.AbstractCamelContext           : Route: post-data started and consuming from: jetty:http://localhost:9100/post-data
2020-04-13 13:23:10.852  INFO 23260 --- [           main] o.a.c.i.e.AbstractCamelContext           : Total 2 routes, of which 2 are started
2020-04-13 13:23:10.853  INFO 23260 --- [           main] o.a.c.i.e.AbstractCamelContext           : Apache Camel 3.1.0 (CamelContext: RESTServer) started in 0.314 seconds
2020-04-13 13:23:42.395  INFO 23260 --- [tp1276761134-37] post-data                                : start - post-data
2020-04-13 13:23:42.396  INFO 23260 --- [tp1276761134-37] e.m.l.m.p.PostRequestProcessor           : SERVER: Processing POST request
2020-04-13 13:23:42.400  WARN 23260 --- [tp1276761134-37] e.m.l.m.p.PostRequestProcessor           : null object
2020-04-13 13:23:42.400  INFO 23260 --- [tp1276761134-37] post-data                                : end - post-data

Answer 1

Camel 不知道您的GenericMessage class，因此它不知道如何與它進行轉換。

Camel 使用可插入類型轉換器來告訴它如何在不同類型的對象之間轉換消息（正文）。

內置類型轉換器涵蓋了很多常見情況（例如，字符串到 Integer，迭代器到 ArrayList 等），但它們不知道如何轉換為您編寫的任何自定義類或從您編寫的任何自定義類轉換。

這就是服務器處理器中的這一行返回 null 的原因：

GenericMessage<?> data = exchange.getIn().getBody(GenericMessage.class);

因為當時，Body 是 Stream，但 Camel 不知道如何將其轉換為您要求的GenericMessage 。

（如果無法轉換， getBody(Class<T>)的默認行為是返回null 。如果您希望拋出異常，請嘗試使用getMandatoryBody(Class<T>) 。）

在客戶端：您如何獲得作為GenericMessage的響應？ 您需要使用unmarshalling 。 您首先將 JSON 解組為 Java object。 正是在這一點上，您需要向 Camel 提示要解組到哪個 class。

<dataFormats>
    <json id="myGeneric" .... unmarshalTypeName="....GenericMessage"/>
</dataFormats>

...
<unmarshal><custom ref="myGeneric"/></unmarshal>

然后 Body 將是您的GenericMessage類型。

請注意，在 Camel 中，類型轉換和編組/解組是兩件不同的事情。

On the Server side: Camel will try to unmarshal a request from JSON to a simple Java object (eg a HashMap, etc.) automatically. 要告訴它解組到特定的 POJO，請在 REST 動詞定義上設置一個type ，例如：

<post uri="post-data" consumes="json" type="com.example.demo.GenericMessage">

您還可以使用相同的方法來定義outType （用於將響應編組回 JSON）