Spring Integration：如何用HttpRequestExecutingMessageHandler传递JSON参数到API URL

你需要将JSON中的msg和mobileNo参数通过Spring Integration的HttpRequestExecutingMessageHandler传递到目标REST API的URL参数中，现针对你的代码给出修改方案：

现有代码模块 #

Controller代码 #

@RestController
@RequestMapping("/api")
public class NotificationController {

    @Autowired
    NotificationGateway notificationGateway;
    
    
    @PostMapping("/sendmsg")
    public String sendMsg(@RequestBody SMSData smsData) {
        return notificationGateway.sendMsg(smsData);
    }
}

Gateway代码 #

@MessagingGateway
public interface NotificationGateway {

    @Gateway(requestChannel = "httpOutRequest")
    String sendMsg(SMSData smsData);
}

原配置类代码 #

@Configuration
public class HTTPConfig {

    private final Logger log = LoggerFactory.getLogger(HTTPConfig.class);

    @Bean
    @ServiceActivator(inputChannel = "httpOutRequest")
    public MessageHandler outbound() {
        log.info("Inside HTTPConfig :: outbound() invoked ");
        HttpRequestExecutingMessageHandler handler = new HttpRequestExecutingMessageHandler(
                "http://localhost:9090/Gateway/rest?msg={msg}&mobileNo={mobileNo}", restTemplate());
        handler.setHttpMethod(HttpMethod.GET);
        handler.setExpectedResponseType(String.class);
        handler.setExpectReply(true);

        ExpressionParser expressionParser = new SpelExpressionParser();
        handler.setUriVariableExpressions(
                Collections.singletonMap("msg", expressionParser.parseExpression("headers['msg']")));
        handler.setUriVariableExpressions(
                Collections.singletonMap("mobileNo", expressionParser.parseExpression("headers['mobileNo']")));
        return handler;
    }

    @Bean
    public RestTemplateBuilder restTemplateBuilder() {
        log.info("Inside HTTPConfig :: restTemplateBuilder() invoked ");
        return new RestTemplateBuilder();
    }

    @Bean
    public RestTemplate restTemplate() {
        log.info("Inside HTTPConfig :: restTemplate() invoked ");
        RestTemplate restTemplate = new RestTemplate();
        return restTemplate;
    }

}

DTO代码 #

public class SMSData {
    public String msg;
    public String mobileNo; 
}

问题分析 #

1. 原配置中两次调用setUriVariableExpressions，第二次会直接覆盖第一次的参数映射，导致只有mobileNo的配置生效。
2. 原配置从消息头（headers）中获取参数，但NotificationGateway的sendMsg方法是将SMSData对象作为消息体（payload）传递，而非存入消息头，因此无法从headers中取到参数值。

修改后的核心配置 #

调整outbound()方法，修正参数映射的来源与映射方式：

@Bean
@ServiceActivator(inputChannel = "httpOutRequest")
public MessageHandler outbound() {
    log.info("Inside HTTPConfig :: outbound() invoked ");
    HttpRequestExecutingMessageHandler handler = new HttpRequestExecutingMessageHandler(
            "http://localhost:9090/Gateway/rest?msg={msg}&mobileNo={mobileNo}", restTemplate());
    handler.setHttpMethod(HttpMethod.GET);
    handler.setExpectedResponseType(String.class);
    handler.setExpectReply(true);

    ExpressionParser expressionParser = new SpelExpressionParser();
    // 构建完整的参数映射，从消息体（payload）中提取SMSData的属性值
    Map<String, Expression> uriVariables = new HashMap<>();
    uriVariables.put("msg", expressionParser.parseExpression("payload.msg"));
    uriVariables.put("mobileNo", expressionParser.parseExpression("payload.mobileNo"));
    handler.setUriVariableExpressions(uriVariables);
    
    return handler;
}

原理说明 #

• 调用NotificationGateway.sendMsg(smsData)时，smsData会被封装为Spring Integration的Message对象，其中smsData作为消息的payload。
• 通过SpEL表达式payload.msg和payload.mobileNo，直接从消息体中提取SMSData的属性值，填充到目标URL的参数占位符中。
• 最终目标REST API会收到GET请求，URL参数为msg=This is my message&mobileNo=00123456987，与你提供的JSON参数完全对应。

内容的提问来源于stack exchange，提问作者Sam