Spring integration 筛选从http出站网关获取200状态的消息

我有一个消息流，如果GET HTTP调用（通过HTTP:outbound gateway）的结果是状态码200（即案例已经存在），我想在其中过滤/删除消息。换句话说，如果调用得到404（未找到），则流应该继续。理想情况下，任何其他状态代码或异常都应该转到errorHandler（现在）

我尝试调用一个使用http链的网关：带有请求处理程序建议链的出站网关，认为我可以捕获404，然后让事情继续，就好像它不是错误一样，然后在“过滤器”中测试状态码404。然而，有几个问题

onFailureExpression表达式未检测到状态代码404，日志显示HttpClientErrorException，所以可能未捕获异常

我应该从onFailureExpression返回什么值？空或有效载荷还是#有效载荷？理想情况下，我希望HTTP调用之前的负载保持原样

我需要TrapeException true吗

奇怪没有更简单的方法？shame不能只在http:outbound gateway httpStatusCodes上声明允许的和被视为正常的代码。我认为错误通道和错误处理程序不是正确的方法，因为如果404状态代码为，我希望原始流继续。因此，将想要的常规行为放在错误流中，并且已经有了更高级别的错误处理程序，这看起来很奇怪

2020-11-24 10:46:45060[main]调试org.springframework.web.client.restemplate-获取“的请求”http://localhost:9095/ccacase/V1/case/challenge/CHG123456789“导致404（未找到）；调用错误处理程序
2020-11-24 10:46:45134[main]DEBUG org.springframework.integration.channel.DirectChannel-postSend（sent=true）在“getChallengeCaseChannel”频道上，消息：GenericMessage[payload=uk.gov.voa.integration.ccacasecheck.json。CdbEvent@624b3544[id=22，eventType=MIGRATE\u CHALLENGE\u CASE，asstRef=，ccaCaseRef=CHG123456789，assessmentStatus=，settlementCode=，eventDateTime=2020-11-23T12:05，uarn=，sourceActivityId=，activityAction=，additionalProperties={}，标头={replyChannel=org.springframework.messaging.core.GenericMessageTemplate$TemporaryReplyChannel@54f6b629，errorChannel=org.springframework.messaging.core.GenericMessageTemplate$TemporaryReplyChannel@54f6b629，originalPayload=uk.gov.voa.integration.ccacasecheck.json。CdbEvent@624b3544[id=22，eventType=MIGRATE\u CHALLENGE\u CASE，asstRef=，ccaCaseRef=CHG123456789，assessmentStatus=，settlementCode=，eventDateTime=2020-11-23T12:05，uarn=，sourceActivityId=，activityAction=，additionalProperties={}]，message_id=22，history=cdbEventsAMQPChannel，routeEventChain，MigrateCallengeCaseEventChannel，MigrateCallengeCaseEventChain，statusFlow，GetChallengeCaseCaseChannel，id=6d99e890-fc56-74a8-1187-fbc3457685c8，timestamp=1606214804576}]
2020-11-24 10:46:45135[main]DEBUG org.springframework.integration.handler.expressionevaluationMessageProcessor-SpEL表达式求值失败，出现异常。org.springframework.web.client.httpclienterror异常：404未找到
原因：org.springframework.MessagingException:转换消息头失败；嵌套异常为org.springframework.messaging.MessageHandlingException:表达式计算失败：@statusFlow.exchange（#root）.headers[http#u statusCode]；嵌套异常为org.springframework.web.client.HttpClientErrorException:404未找到
位于org.springframework.integration.transformer.HeaderEnricher.transform（HeaderEnricher.java:128）
位于org.springframework.integration.transformer.MessageTransformingHandler.HandlerRequestMessage（MessageTransformingHandler.java:89）
…还有72个
原因：org.springframework.messaging.MessageHandlingException:表达式计算失败：@statusFlow.exchange（#root）.headers[http_statusCode]；嵌套异常为org.springframework.web.client.HttpClientErrorException:404未找到
位于org.springframework.integration.util.AbstractExpressionEvaluator.evaluateExpression（AbstractExpressionEvaluator.java:143）
位于org.springframework.integration.handler.ExpressionEvaluationMessageProcessor.processMessage（ExpressionEvaluationMessageProcessor.java:72）
位于org.springframework.integration.transformer.support.expressionEvaluationHeaderValueMessageProcessor.processMessage（expressionEvaluationHeaderValueMessageProcessor.java:71）
位于org.springframework.integration.transformer.HeaderEnricher.transform（HeaderEnricher.java:119）
…还有73个
原因：org.springframework.web.client.HttpClientErrorException:404未找到
位于org.springframework.web.client.DefaultResponseErrorHandler.handleError（DefaultResponseErrorHandler.java:91）

使用的解决方案是实现一个自定义ErrorHandler，它扩展默认值并覆盖hasError

/**
 * To be used with an 'int-http:outbound-gateway' to make a HTTP call and allow a statusCode 404 
 * response to be treated as normal (as well as a 200 statusCode). 
 * Normally a statusCode 404 would throw a 
 * org.springframework.web.client.HttpClientErrorException: 404 Not Found
 * and expect the caller to deal with an error-channel.  
 * This allows processing to continue and subsequently test for a 404 response
 * and route differently 
 *
 */
public class Allow404StatusCodeResponseHandler extends DefaultResponseErrorHandler  {

    /**
     * OVERRIDEN 
     * 
     * Indicate whether the given response has any errors.
     * <p>Implementations will typically inspect the
     * {@link ClientHttpResponse#getStatusCode() HttpStatus} of the response.
     * @param response the response to inspect
     * @return {@code true} if the response indicates an error; {@code false} otherwise
     * @throws IOException in case of I/O errors
     */
    @Override
    public boolean hasError(ClientHttpResponse response) throws IOException {
        int rawStatusCode = response.getRawStatusCode();
        return (rawStatusCode == 404 || rawStatusCode == 200) ? false : true;  // 404 to be treated as normal and testable downstream
    }

}

/**
*与“int http:outbound gateway”一起使用，以进行http调用并允许状态码404
*响应被视为正常（以及200状态代码）。
*通常情况下，状态码404会抛出
*org.springframework.web.client.HttpClientErrorException:未找到404
*并期望调用者处理错误通道。
*这允许处理继续并随后测试404响应
*而且路线不同
*
*/
公共类Allow404StatusCodeResponseHandler扩展了DefaultResponseErrorHandler{
/**
*凌驾
* 
*指示给定的响应是否有任何错误。
<int:chain id="migrateChallengeCaseEventChain" input-channel="migrateChallengeCaseEventChannel">

        <int:header-enricher>                                
            <int:header name="caseStatusCode" expression="@statusFlow.exchange(#root).headers[http_statusCode]" />    
        </int:header-enricher>
        
        <!-- to check http_statusCode header and drop any message with found 200 statusCode -->
        <int:filter ref="status200Filter"/>  
        
        <int:transformer ref="migrateChallengeCaseTransformer" />
        <int:transformer ref="jsonValidationTransformer" />
        <int:object-to-json-transformer object-mapper="springJacksonObjectMapper" />
        <int:header-enricher>
             <int:header name="contentType" value="application/json;charset=UTF-8" overwrite="true"/>
        </int:header-enricher>  
        <int-amqp:outbound-channel-adapter 
            amqp-template="amqpTemplate" exchange-name="cdbEvents.exchange" 
            routing-key="migrateCdbCcaChallengeCase.request.queue.binding" />
    </int:chain>    
    
    <int:gateway id="statusFlow" default-request-channel="getChallengeCaseChannel" />  
    
    <int:channel id="getChallengeCaseChannel" />
    
    <!-- Call API to see if Case already exists, 200 status code we want to filter/drop message   -->
    <int:chain id="getChallengeCaseChain" input-channel="getChallengeCaseChannel">
        <int-http:outbound-gateway id="httpOutboundGatewayChallengeCaseGet"     
                            expected-response-type="java.lang.String"                                           
                            http-method="GET"   charset="UTF-8"
                            extract-request-payload="true"  
                            request-factory="httpRequestFactory"                    
                            url="${mule.case.data.service.uri}/${case.challenge.subpath}/{ccaCaseRefValue}">
            <int-http:uri-variable name="ccaCaseRefValue" expression="headers['originalPayload'].ccaCaseRef"/>  
            <int-http:request-handler-advice-chain>
                    <bean class="org.springframework.integration.handler.advice.ExpressionEvaluatingRequestHandlerAdvice">
                        <!-- If true, the result of evaluating the onFailureExpression will be returned as the result -->
                        <property name="returnFailureExpressionResult" value="true" />
                        <property name="onSuccessExpression" value="payload" />
                        <!-- If true, any exception will be caught and null returned. Default false -->
                         <property name="trapException" value="true" /> 
                        <!-- Set the expression to evaluate against the root message after a failed handler invocation. The exception is available as the variable #exception. Defaults to payload, if failureChannel is configured. -->
                        <property name="onFailureExpression"  value="#exception.cause.statusCode == 404 ? payload : #exception"/> 
                        <!-- Set the channel name to which to send the ErrorMessage after evaluating the failure expression. -->
                        <!-- <property name="failureChannel" ref="#headers['replyChannel']" />  -->
                    </bean>
                </int-http:request-handler-advice-chain>
        </int-http:outbound-gateway>
    
    </int:chain>    

/**
 * To be used with an 'int-http:outbound-gateway' to make a HTTP call and allow a statusCode 404 
 * response to be treated as normal (as well as a 200 statusCode). 
 * Normally a statusCode 404 would throw a 
 * org.springframework.web.client.HttpClientErrorException: 404 Not Found
 * and expect the caller to deal with an error-channel.  
 * This allows processing to continue and subsequently test for a 404 response
 * and route differently 
 *
 */
public class Allow404StatusCodeResponseHandler extends DefaultResponseErrorHandler  {

    /**
     * OVERRIDEN 
     * 
     * Indicate whether the given response has any errors.
     * <p>Implementations will typically inspect the
     * {@link ClientHttpResponse#getStatusCode() HttpStatus} of the response.
     * @param response the response to inspect
     * @return {@code true} if the response indicates an error; {@code false} otherwise
     * @throws IOException in case of I/O errors
     */
    @Override
    public boolean hasError(ClientHttpResponse response) throws IOException {
        int rawStatusCode = response.getRawStatusCode();
        return (rawStatusCode == 404 || rawStatusCode == 200) ? false : true;  // 404 to be treated as normal and testable downstream
    }

}

/**
 * Spring's default implementation of the {@link ResponseErrorHandler} interface.
 *
 * <p>This error handler checks for the status code on the
 * {@link ClientHttpResponse}. Any code in the 4xx or 5xx series is considered
 * to be an error. This behavior can be changed by overriding
 * {@link #hasError(HttpStatus)}. Unknown status codes will be ignored by
 * {@link #hasError(ClientHttpResponse)}.
 *
 * <p>See {@link #handleError(ClientHttpResponse)} for more details on specific
 * exception types.
 *
 * @author Arjen Poutsma
 * @author Rossen Stoyanchev
 * @author Juergen Hoeller
 * @since 3.0
 * @see RestTemplate#setErrorHandler
 */
public class DefaultResponseErrorHandler implements ResponseErrorHandler {