Question

我正在尝试使用以下代码发送消息并接收响应

MessageProperties props    =MessagePropertiesBuilder.newInstance().setContentType(MessageProperties.CONTENT_TYPE_TEXT_PLAIN)
            .setMessageId("MSG12345").setHeader("type", "type1").setCorrelationId(UUID.randomUUID().toString().getBytes()).build();
 Message message = MessageBuilder.withBody(input.getBytes()).andProperties(props).build();
 Message response = (Message) template.convertSendAndReceive("key", message);

但是，它正在抛出ava.lang.ClassCastException：java.lang.String无法强制转换为org.springframework.amqp.core.Message

可能是因为，我使用java（spring-amqp）程序发送请求，接收器是python（pika）程序。 Recevier向我发送了一个以字符串格式转储的JSON对象，但我无法处理它。

Answer 1

您使用RabbitTemplate.convertSendAndReceive()的问题：

/**
 * Basic RPC pattern with conversion. Send a Java object converted to a message to a default exchange with a
 * specific routing key and attempt to receive a response, converting that to a Java object. Implementations will
 * normally set the reply-to header to an exclusive queue and wait up for some time limited by a timeout.
 *
 * @param routingKey the routing key
 * @param message a message to send
 * @return the response if there is one
 * @throws AmqpException if there is a problem
 */
Object convertSendAndReceive(String routingKey, Object message) throws AmqpException;

即使您的payload是Message，我们也有：

protected Message convertMessageIfNecessary(final Object object) {
    if (object instanceof Message) {
        return (Message) object;
    }
    return getRequiredMessageConverter().toMessage(object, new MessageProperties());
}

它将reply转换为body的目标对象：

return this.getRequiredMessageConverter().fromMessage(replyMessage);

并且不会按预期返回Message。

所以，你真的必须转发String并自己处理你的JSON。

无法处理从template.convertSendAndReceive（）收到的响应

1 个答案: