Spring Integration入站适配器自动端口

Question

加里·罗素（Gary Russell）友善地回答了我以前关于Spring Integration udp flow的问题。 从那里出发，我偶然发现了端口问题。

Spring Integration文档说， 您可以将0设置为入站通道适配器端口，并且OS将为适配器选择一个可用端口 ，可以在运行时调用适配器对象上的getPort（）来检索该端口。 问题是，如果我尝试以编程方式检索端口，则在运行时我只会得到0 。 这是“我的”代码（即Russel对我先前正在使用的有关Spring Integration 4.3.12的先前问题的回答的稍作修改的版本）。

@SpringBootApplication
public class  TestApp  {

private final Map<Integer, IntegrationFlowRegistration> registrations = new HashMap<>();

@Autowired
private IntegrationFlowContext flowContext;

public static void main(String[] args) {
    SpringApplication.run(TestApp.class, args);
}

@Bean
public PublishSubscribeChannel channel() {
    return new PublishSubscribeChannel();
}

@Bean
public TestData test() {
    return new TestData();
}

@Bean
public ApplicationRunner runner() {     
    return args -> {
        UnicastReceivingChannelAdapter source;
        source = makeANewUdpInbound(0);
        makeANewUdpOutbound(source.getPort());
         Thread.sleep(5_000);
         channel().send(MessageBuilder.withPayload("foo\n").build());
         this.registrations.values().forEach(r -> {
           r.stop();
           r.destroy();
         });
         this.registrations.clear();

         makeANewUdpInbound(1235);
         makeANewUdpOutbound(1235);
         Thread.sleep(5_000);
         channel().send(MessageBuilder.withPayload("bar\n").build());
         this.registrations.values().forEach(r -> {
           r.stop();
           r.destroy();
         });
         this.registrations.clear();
    };
}

public UnicastSendingMessageHandler makeANewUdpOutbound(int port) {
    System.out.println("Creating an adapter to send to port " + port);
    UnicastSendingMessageHandler adapter = new UnicastSendingMessageHandler("localhost", port);
    IntegrationFlow flow = IntegrationFlows.from(channel())
            .handle(adapter)
            .get();
    IntegrationFlowRegistration registration = flowContext.registration(flow).register();
    registrations.put(port, registration);
    return adapter;
}

public UnicastReceivingChannelAdapter makeANewUdpInbound(int port) {
    System.out.println("Creating an adapter to receive from port " + port);
    UnicastReceivingChannelAdapter source = new UnicastReceivingChannelAdapter(port);
    IntegrationFlow flow = IntegrationFlows.from(source)
            .<byte[], String>transform(String::new)
            .handle(System.out::println)
            .get();
    IntegrationFlowRegistration registration = flowContext.registration(flow).register();
    registrations.put(port, registration);
    return source;
}
}

我读的输出是

Creating an adapter to receive from port 0
Creating an adapter to send to port 0
Creating an adapter to receive from port 1235
Creating an adapter to send to port 1235
GenericMessage [payload=bar, headers={ip_packetAddress=127.0.0.1/127.0.0.1:54374, ip_address=127.0.0.1, id=c95d6255-e63a-433d-3723-c389fe66b060, ip_port=54374, ip_hostname=127.0.0.1, timestamp=1517220716983}]

我怀疑该库确实在OS选择的免费端口上创建了适配器，但是我无法检索分配的端口。

Answer 1

端口是异步分配的； 您需要等待，直到实际分配了端口。 就像是...

int n = 0;
while (n++ < 100 && ! source.isListening()) {
    Thread.sleep(100;
}
if (!source.isListening()) {
    // failed to start in 10 seconds.
}

我们可能应该增强适配器以在端口准备好时发出事件。 随时打开“改进” JIRA问题 。