Spring Integration HTTP出站消息头转换策略与优化

Header "errorChannel" with value [reference to hash Object] will not be set since it is not a String and no Converter is available. Consider registering a Converter with ConversionService

import org.springframework.core.convert.converter.Converter;
import org.springframework.integration.annotation.IntegrationConverter;
import org.springframework.messaging.MessageChannel;

/**
 * 自定义转换器，将MessageChannel转换为String。
 * 这里简单地返回一个空字符串，或者可以返回通道的名称。
 */
@IntegrationConverter
public class MessageChannelToStringConverter implements Converter<MessageChannel, String> {

    @Override
    public String convert(MessageChannel source) {
        // 可以根据需要返回通道的名称，例如：
        // if (source instanceof NamedChannel) {
        //     return ((NamedChannel) source).getBeanName();
        // }
        // 或者简单返回一个空字符串，表示该内部通道不应作为HTTP头传递
        return ""; 
    }
}

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.integration.dsl.IntegrationFlow;
import org.springframework.integration.dsl.IntegrationFlows;
import org.springframework.integration.http.dsl.Http;
import org.springframework.integration.http.HttpHeaders;
import org.springframework.integration.mapping.Default  HttpHeaderMapper;

@Configuration
public class HttpOutboundConfig {

    @Bean
    public IntegrationFlow myHttpOutboundFlow() {
        return IntegrationFlows.from("inputChannel")
                .handle(Http.outboundGateway("http://localhost:8080/api/resource")
                        .httpMethod(org.springframework.http.HttpMethod.POST)
                        // 明确指定需要映射的请求头，排除内部通道
                        .mappedRequestHeaders("Content-Type", "Accept", "X-Custom-Header", "correlationId")
                        // 如果需要自定义HeaderMapper，可以注入一个
                        .headerMapper(customHttpHeaderMapper()) 
                )
                .get();
    }

    @Bean
    public DefaultHttpHeaderMapper customHttpHeaderMapper() {
        DefaultHttpHeaderMapper mapper = new DefaultHttpHeaderMapper();
        // 设置需要映射的请求头，例如只映射标准HTTP头和特定的自定义头
        mapper.setOutboundRequestHeaders(new String[]{
            HttpHeaders.CONTENT_TYPE, 
            HttpHeaders.ACCEPT, 
            "X-Custom-Header", 
            "correlationId"
            // 明确排除 "replyChannel", "errorChannel"
        });
        // 也可以设置不映射的头
        // mapper.setExcludedOutboundRequestHeaders("replyChannel", "errorChannel"); 
        return mapper;
    }
}

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.integration.dsl.IntegrationFlow;
import org.springframework.integration.dsl.IntegrationFlows;
import org.springframework.integration.dsl.Transformers;
import org.springframework.integration.http.dsl.Http;
import org.springframework.integration.transformer.HeaderEnricher;
import org.springframework.integration.transformer.support.HeaderValueMessageProcessor;
import org.springframework.integration.transformer.support.ExpressionEvaluatingHeaderValueMessageProcessor;

@Configuration
public class HttpOutboundEnricherConfig {

    @Bean
    public IntegrationFlow myHttpOutboundFlowWithEnricher() {
        return IntegrationFlows.from("inputChannel")
                // 在发送到HTTP网关之前，使用HeaderEnricher处理消息头
                .enrichHeaders(h -> h
                    // 将replyChannel转换为一个String类型的头 'x-reply-channel-name'
                    .header("x-reply-channel-name", new ExpressionEvaluatingHeaderValueMessageProcessor<String>("headers.replyChannel.beanName"), true)
                    // 将errorChannel转换为一个String类型的头 'x-error-channel-name'
                    .header("x-error-channel-name", new ExpressionEvaluatingHeaderValueMessageProcessor<String>("headers.errorChannel.beanName"), true)
                    // 如果原始的replyChannel和errorChannel不再需要，可以将其移除
                    .headerChannelsRemoved("replyChannel", "errorChannel")
                )
                .handle(Http.outboundGateway("http://localhost:8080/api/resource")
                        .httpMethod(org.springframework.http.HttpMethod.POST)
                        // 此时，HTTP网关将发送 'x-reply-channel-name' 和 'x-error-channel-name'
                        // 并且原始的replyChannel和errorChannel已被移除或不会被映射
                        .mappedRequestHeaders("Content-Type", "Accept", "x-reply-channel-name", "x-error-channel-name")
                )
                .get();
    }
}