WebSockets Support

从 4.1 版本开始，Spring Integration 支持 WebSocket。它基于 Spring Framework 的 web-socket`模块的架构、基础设施和 API。因此，Spring WebSocket 的许多组件（例如 `SubProtocolHandler`或 `WebSocketClient）和配置选项（例如 @EnableWebSocketMessageBroker）可以在 Spring Integration 中重复使用。有关详细信息，请参阅 Spring Framework 参考手册中的 Spring Framework WebSocket Support章节。

Starting with version 4.1, Spring Integration has WebSocket support. It is based on the architecture, infrastructure, and API from the Spring Framework’s web-socket module. Therefore, many of Spring WebSocket’s components (such as SubProtocolHandler or WebSocketClient) and configuration options (such as @EnableWebSocketMessageBroker) can be reused within Spring Integration. For more information, see the Spring Framework WebSocket Support chapter in the Spring Framework reference manual.

你需要将此依赖项包含在你的项目中：

You need to include this dependency into your project:

Maven
Gradle

<dependency>
    <groupId>org.springframework.integration</groupId>
    <artifactId>spring-integration-websocket</artifactId>
    <version>{project-version}</version>
</dependency>

compile "org.springframework.integration:spring-integration-websocket:{project-version}"

对于服务器端，org.springframework:spring-webmvc 依赖项必须显式包含。

For server side, the org.springframework:spring-webmvc dependency must be included explicitly.

Spring Framework WebSocket 基础设施基于 Spring 消息基础，并提供了一个基于 Spring Integration 使用的相同 MessageChannel 实现和 MessageHandler 实现（以及一些 POJO 方法注释映射）的基本消息框架。因此，即使没有 WebSocket 适配器，Spring Integration 也可以直接参与 WebSocket 流。为此，你可以使用适当的注释来配置一个 Spring Integration @MessagingGateway，如下面的示例所示：

The Spring Framework WebSocket infrastructure is based on the Spring messaging foundation and provides a basic messaging framework based on the same MessageChannel implementations and MessageHandler implementations that Spring Integration uses (and some POJO-method annotation mappings). Consequently, Spring Integration can be directly involved in a WebSocket flow, even without WebSocket adapters. For this purpose, you can configure a Spring Integration @MessagingGateway with appropriate annotations, as the following example shows:

@MessagingGateway
@Controller
public interface WebSocketGateway {

    @MessageMapping("/greeting")
    @SendToUser("/queue/answer")
    @Gateway(requestChannel = "greetingChannel")
    String greeting(String payload);

}

Overview

由于 WebSocket 协议按定义为流式，并且我们可以同时向和来自 WebSocket 发送和接收消息，因此可以处理适当的 WebSocketSession，无论是在客户端还是在服务器端。为了封装连接管理和 WebSocketSession 注册表，需通过 ClientWebSocketContainer 和 ServerWebSocketContainer 实现为 IntegrationWebSocketContainer 提供信息。借助 Spring 框架中的 WebSocket API 及其实现（包含许多扩展），在服务器端和客户端均使用相同的类（当然，这是从 Java 的角度来看的）。因此，在两端，大多数连接和 WebSocketSession 注册表选项都是相同的。这让我们可以重复使用许多配置项和基础架构挂钩，以便在服务器端和客户端上构建 WebSocket 应用程序。以下示例显示了组件如何同时服务于这两个目的：

Since the WebSocket protocol is streaming by definition, and we can send and receive messages to and from a WebSocket at the same time, we can deal with an appropriate WebSocketSession, regardless of being on the client or server side. To encapsulate the connection management and WebSocketSession registry, the IntegrationWebSocketContainer is provided with ClientWebSocketContainer and ServerWebSocketContainer implementations. Thanks to the WebSocket API and its implementation in the Spring Framework (with many extensions), the same classes are used on the server side as well as the client side (from a Java perspective, of course). Consequently, most connection and WebSocketSession registry options are the same on both sides. That lets us reuse many configuration items and infrastructure hooks to build WebSocket applications on the server side as well as on the client side. The following example shows how components can serve both purposes:

//Client side
@Bean
public WebSocketClient webSocketClient() {
    return new SockJsClient(Collections.singletonList(new WebSocketTransport(new JettyWebSocketClient())));
}

@Bean
public IntegrationWebSocketContainer clientWebSocketContainer() {
    return new ClientWebSocketContainer(webSocketClient(), "ws://my.server.com/endpoint");
}

//Server side
@Bean
public IntegrationWebSocketContainer serverWebSocketContainer() {
    return new ServerWebSocketContainer("/endpoint").withSockJs();
}

IntegrationWebSocketContainer 旨在实现双向消息传递，可以在入站和出站通道适配器之间共享（见下文），在使用单向（发送或接收）WebSocket 消息传递时只能从中一个引用它。它可以在没有任何通道适配器的情况下使用，但是，在这种情况下，IntegrationWebSocketContainer 仅充当 WebSocketSession 注册表。

The IntegrationWebSocketContainer is designed to achieve bidirectional messaging and can be shared between inbound and outbound channel adapters (see below), can be referenced from only one of them when using one-way (sending or receiving) WebSocket messaging. It can be used without any channel adapter, but, in this case, IntegrationWebSocketContainer only plays a role as the WebSocketSession registry.

ServerWebSocketContainer 实现 WebSocketConfigurer 以将内部 IntegrationWebSocketContainer.IntegrationWebSocketHandler 注册为 Endpoint。它在为目标供应商 WebSocket 容器的 ServletWebSocketHandlerRegistry 中提供的 paths 和其他服务器 WebSocket 选项（例如 HandshakeHandler 或 SockJS fallback）下进行此操作。此注册使用基础结构 WebSocketIntegrationConfigurationInitializer 组件实现，它与 @EnableWebSocket 注解的作用相同。这意味着，通过在应用程序上下文中使用 @EnableIntegration（或任何 Spring Integration 命名空间），您可以忽略 @EnableWebSocket 声明，因为 Spring Integration 基础结构会检测所有 WebSocket 端点。

The ServerWebSocketContainer implements WebSocketConfigurer to register an internal IntegrationWebSocketContainer.IntegrationWebSocketHandler as an Endpoint. It does so under the provided paths and other server WebSocket options (such as HandshakeHandler or SockJS fallback) within the ServletWebSocketHandlerRegistry for the target vendor WebSocket Container. This registration is achieved with an infrastructural WebSocketIntegrationConfigurationInitializer component, which does the same as the @EnableWebSocket annotation. This means that, by using @EnableIntegration (or any Spring Integration namespace in the application context), you can omit the @EnableWebSocket declaration, because the Spring Integration infrastructure detects all WebSocket endpoints.

从 6.1 版本开始，ClientWebSocketContainer 可通过提供的 URI 进行配置，而不是 uriTemplate 和 uriVariables 组合。在有些场景下需要对 URI 的某些部分进行自定义编码时，这种方式非常有用。较为便捷的方式是，参阅 UriComponentsBuilder API。

Starting with version 6.1, the ClientWebSocketContainer can be configured with a provided URI instead of uriTemplate and uriVariables combination. This is useful in cases when custom encoding is required for some parts of the uri. See an UriComponentsBuilder API for convenience.

WebSocket Inbound Channel Adapter

WebSocketInboundChannelAdapter 实现了 WebSocketSession 交互中的接收部分。你必须向它提供一个 IntegrationWebSocketContainer 并且该适配器将自己注册为一个 WebSocketListener 来处理传入的消息和 WebSocketSession 事件。

The WebSocketInboundChannelAdapter implements the receiving part of WebSocketSession interaction. You must supply it with a IntegrationWebSocketContainer, and the adapter registers itself as a WebSocketListener to handle incoming messages and WebSocketSession events.

只能在 IntegrationWebSocketContainer 中注册一个 WebSocketListener。

Only one WebSocketListener can be registered in the IntegrationWebSocketContainer.

为 WebSocket 子协议，WebSocketInboundChannelAdapter 可以通过 SubProtocolHandlerRegistry 进行配置，SubProtocolHandlerRegistry 为第二个构造函数参数。该适配器委托给 SubProtocolHandlerRegistry 来根据已接受的 WebSocketSession 判断恰当的 SubProtocolHandler，并将一个 WebSocketMessage 转换为一个 Message，具体取决于子协议的实现。

For WebSocket sub-protocols, the WebSocketInboundChannelAdapter can be configured with SubProtocolHandlerRegistry as the second constructor argument. The adapter delegates to the SubProtocolHandlerRegistry to determine the appropriate SubProtocolHandler for the accepted WebSocketSession and to convert a WebSocketMessage to a Message according to the sub-protocol implementation.

默认情况下，WebSocketInboundChannelAdapter 仅依赖于原始 PassThruSubProtocolHandler 实现，该实现将 WebSocketMessage 转换为 Message。

By default, the WebSocketInboundChannelAdapter relies only on the raw PassThruSubProtocolHandler implementation, which converts the WebSocketMessage to a Message.

WebSocketInboundChannelAdapter 仅接受和发送包含 SimpMessageType.MESSAGE 或一个空的 simpMessageType 头的 Message 实例到底层集成流。所有其他 Message 类型通过从 SubProtocolHandler 实现（如 StompSubProtocolHandler）发出的 ApplicationEvent 实例来处理。

The WebSocketInboundChannelAdapter accepts and sends to the underlying integration flow only Message instances that have SimpMessageType.MESSAGE or an empty simpMessageType header. All other Message types are handled through the ApplicationEvent instances emitted from a SubProtocolHandler implementation (such as StompSubProtocolHandler).

在服务器端，如果存在 @EnableWebSocketMessageBroker 配置，可以使用 useBroker = true 选项来配置 WebSocketInboundChannelAdapter。在这种情况下，所有 非 MESSAGE 的 Message 类型都将委托给提供的 AbstractBrokerMessageHandler。另外，如果代理中继使用 destination 前缀进行了配置，那么与代理目标匹配的消息会路由到 AbstractBrokerMessageHandler，而不是 WebSocketInboundChannelAdapter 的 outputChannel。

On the server side, if the @EnableWebSocketMessageBroker configuration is present, you can configure WebSocketInboundChannelAdapter with the useBroker = true option. In this case, all non-MESSAGE Message types are delegated to the provided AbstractBrokerMessageHandler. In addition, if the broker relay is configured with destination prefixes, those messages that match the Broker destinations are routed to the AbstractBrokerMessageHandler instead of to the outputChannel of the WebSocketInboundChannelAdapter.

如果 useBroker = false 且接收的消息类型是 SimpMessageType.CONNECT，那么 WebSocketInboundChannelAdapter 会立即向 WebSocketSession 发送一个 SimpMessageType.CONNECT_ACK 消息，而不会将它发送到通道。

If useBroker = false and the received message is of the SimpMessageType.CONNECT type, the WebSocketInboundChannelAdapter immediately sends a SimpMessageType.CONNECT_ACK message to the WebSocketSession without sending it to the channel.

Spring 的 WebSocket 支持只允许配置一个代理中继。因此，不需要 AbstractBrokerMessageHandler 引用。它在应用程序上下文中检测到。

Spring’s WebSocket Support allows the configuration of only one broker relay. Consequently, we do not require an AbstractBrokerMessageHandler reference. It is detected in the Application Context.

有关更多配置选项，请参见 WebSockets Namespace Support。

For more configuration options, see WebSockets Namespace Support.

WebSocket Outbound Channel Adapter

WebSocketOutboundChannelAdapter：

The WebSocketOutboundChannelAdapter:

Accepts Spring Integration messages from its MessageChannel
Determines the WebSocketSession id from the MessageHeaders
Retrieves the WebSocketSession from the provided IntegrationWebSocketContainer
Delegates the conversion and sending of WebSocketMessage work to the appropriate SubProtocolHandler from the provided SubProtocolHandlerRegistry.

在客户端，并不需要 WebSocketSession 的 id 消息头，因为 ClientWebSocketContainer 只处理单个连接和它各自的 WebSocketSession。

On the client side, the WebSocketSession id message header is not required, because ClientWebSocketContainer deals only with a single connection and its WebSocketSession respectively.

要使用 STOMP 子协议，你应该使用 StompSubProtocolHandler`配置该适配器。然后你可以使用 `StompHeaderAccessor.create(StompCommand…)`和 `MessageBuilder`将任何 STOMP 消息类型发送到该适配器，或者只使用 `HeaderEnricher（请参见 Header Enricher）。

To use the STOMP sub-protocol, you should configure this adapter with a StompSubProtocolHandler. Then you can send any STOMP message type to this adapter, using StompHeaderAccessor.create(StompCommand…) and a MessageBuilder, or just using a HeaderEnricher (see Header Enricher).

本章的剩余部分主要涵盖附加配置选项。

The rest of this chapter covers largely additional configuration options.

WebSockets Namespace Support

Spring Integration WebSocket 命名空间包括本章剩余部分描述的几个组件。要将它包含在你的配置中，在你的应用程序上下文配置文件中使用以下命名空间声明：

The Spring Integration WebSocket namespace includes several components described in the remainder of this chapter. To include it in your configuration, use the following namespace declaration in your application context configuration file:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xmlns:int="http://www.springframework.org/schema/integration"
  xmlns:int-websocket="http://www.springframework.org/schema/integration/websocket"
  xsi:schemaLocation="
    http://www.springframework.org/schema/beans
    https://www.springframework.org/schema/beans/spring-beans.xsd
    http://www.springframework.org/schema/integration
    https://www.springframework.org/schema/integration/spring-integration.xsd
    http://www.springframework.org/schema/integration/websocket
    https://www.springframework.org/schema/integration/websocket/spring-integration-websocket.xsd">
    ...
</beans>

`<int-websocket:client-container>` Attributes

以下清单展示了 <int-websocket:client-container> 元素可用的属性：

The following listing shows the attributes available for the <int-websocket:client-container> element:

<int-websocket:client-container
                  id=""                             1
                  client=""                         2
                  uri=""                            3
                  uri-variables=""                  4
                  origin=""                         5
                  send-time-limit=""                6
                  send-buffer-size-limit=""         7
                  send-buffer-overflow-strategy=""  8
                  auto-startup=""                   9
                  phase="">                        10
                <int-websocket:http-headers>
                  <entry key="" value=""/>
                </int-websocket:http-headers>      11
</int-websocket:client-container>

1	The component bean name.
2	The `WebSocketClient` bean reference.
3	The `uri` or `uriTemplate` to the target WebSocket service. If you use it as a `uriTemplate` with URI variable placeholders, the `uri-variables` attribute is required.
4	Comma-separated values for the URI variable placeholders within the `uri` attribute value. The values are replaced into the placeholders according to their order in the `uri`. See `UriComponents.expand(Object…uriVariableValues)`.
5	The `Origin` Handshake HTTP header value.
6	The WebSocket session 'send' timeout limit. Defaults to `10000`.
7	The WebSocket session 'send' message size limit. Defaults to `524288`.
8	The WebSocket session send buffer overflow strategy determines the behavior when a session’s outbound message buffer has reached the `send-buffer-size-limit`. See `ConcurrentWebSocketSessionDecorator.OverflowStrategy` for possible values and more details.
9	Boolean value indicating whether this endpoint should start automatically. Defaults to `false`, assuming that this container is started from the WebSocket inbound adapter.
10	The lifecycle phase within which this endpoint should start and stop. The lower the value, the earlier this endpoint starts and the later it stops. The default is `Integer.MAX_VALUE`. Values can be negative. See `SmartLifeCycle`.
11	A `Map` of `HttpHeaders` to be used with the Handshake request.

`<int-websocket:server-container>` Attributes

以下清单展示了 <int-websocket:server-container> 元素可用的属性：

The following listing shows the attributes available for the <int-websocket:server-container> element:

<int-websocket:server-container
          id=""                             1
          path=""                           2
          handshake-handler=""              3
          handshake-interceptors=""         4
          decorator-factories=""            5
          send-time-limit=""                6
          send-buffer-size-limit=""         7
          send-buffer-overflow-strategy=""  8
          allowed-origins="">               9
          <int-websocket:sockjs
            client-library-url=""          10
            stream-bytes-limit=""          11
            session-cookie-needed=""       12
            heartbeat-time=""              13
            disconnect-delay=""            14
            message-cache-size=""          15
            websocket-enabled=""           16
            scheduler=""                   17
            message-codec=""               18
            transport-handlers=""          19
            suppress-cors="true" />        20
</int-websocket:server-container>

1	The component bean name.
2	A path (or comma-separated paths) that maps a particular request to a `WebSocketHandler`. Supports exact path mapping URIs (such as `/myPath`) and ant-style path patterns (such as `/myPath/**`).
3	The `HandshakeHandler` bean reference. Defaults to `DefaultHandshakeHandler`.
4	List of `HandshakeInterceptor` bean references.
5	List of one or more factories (`WebSocketHandlerDecoratorFactory`) that decorate the handler used to process WebSocket messages. This may be useful for some advanced use cases (for example, to allow Spring Security to forcibly close the WebSocket session when the corresponding HTTP session expires). See the Spring Session Project for more information.
6	See the same option on the <<`<int-websocket:client-container>`,websocket-client-container-attributes>>.
7	See the same option on the <<`<int-websocket:client-container>`,websocket-client-container-attributes>>.
8	The WebSocket session send buffer overflow strategy determines the behavior when a session’s outbound message buffer has reached the `send-buffer-size-limit`. See `ConcurrentWebSocketSessionDecorator.OverflowStrategy` for possible values and more details.
9	The allowed origin header values. You can specify multiple origins as a comma-separated list. This check is mostly designed for browser clients. There is nothing preventing other types of client from modifying the origin header value. When SockJS is enabled and allowed origins are restricted, transport types that do not use origin headers for cross-origin requests (`jsonp-polling`, `iframe-xhr-polling`, `iframe-eventsource`, and `iframe-htmlfile`) are disabled. As a consequence, IE6 and IE7 are not supported, and IE8 and IE9 are supported only without cookies. By default, all origins are allowed.
10	Transports with no native cross-domain communication (such as `eventsource` and `htmlfile`) must get a simple page from the “foreign” domain in an invisible iframe so that code in the iframe can run from a domain local to the SockJS server. Since the iframe needs to load the SockJS javascript client library, this property lets you specify the location from which to load it. By default, it points to `https://d1fxtkz8shb9d2.cloudfront.net/sockjs-0.3.4.min.js`. However, you can also set it to point to a URL served by the application. Note that it is possible to specify a relative URL, in which case the URL must be relative to the iframe URL. For example, assuming a SockJS endpoint mapped to `/sockjs` and the resulting iframe URL is `/sockjs/iframe.html`, the relative URL must start with "../../" to traverse up to the location above the SockJS mapping. For prefix-based servlet mapping, you may need one more traversal.
11	Minimum number of bytes that can be sent over a single HTTP streaming request before it is closed. Defaults to `128K` (that is, 128*1024 or 131072 bytes).
12	The `cookie_needed` value in the response from the SockJs `/info` endpoint. This property indicates whether a `JSESSIONID` cookie is required for the application to function correctly (for example, for load balancing or in Java Servlet containers for the use of an HTTP session).
13	The amount of time (in milliseconds) when the server has not sent any messages and after which the server should send a heartbeat frame to the client in order to keep the connection from breaking. The default value is `25,000` (25 seconds).
14	The amount of time (in milliseconds) before a client is considered disconnected after not having a receiving connection (that is, an active connection over which the server can send data to the client). The default value is `5000`.
15	The number of server-to-client messages that a session can cache while waiting for the next HTTP polling request from the client. The default size is `100`.
16	Some load balancers do not support WebSockets. Set this option to `false` to disable the WebSocket transport on the server side. The default value is `true`.
17	The `TaskScheduler` bean reference. A new `ThreadPoolTaskScheduler` instance is created if no value is provided. This scheduler instance is used for scheduling heart-beat messages.
18	The `SockJsMessageCodec` bean reference to use for encoding and decoding SockJS messages. By default, `Jackson2SockJsMessageCodec` is used, which requires the Jackson library to be present on the classpath.
19	List of `TransportHandler` bean references.
20	Whether to disable automatic addition of CORS headers for SockJS requests. The default value is `false`.

`<int-websocket:outbound-channel-adapter>` Attributes

以下清单展示了 <int-websocket:outbound-channel-adapter> 元素可用的属性：

The following listing shows the attributes available for the <int-websocket:outbound-channel-adapter> element:

<int-websocket:outbound-channel-adapter
                          id=""                             1
                          channel=""                        2
                          container=""                      3
                          default-protocol-handler=""       4
                          protocol-handlers=""              5
                          message-converters=""             6
                          merge-with-default-converters=""  7
                          auto-startup=""                   8
                          phase=""/>                        9

1	The component bean name. If you do not provide the `channel` attribute, a `DirectChannel` is created and registered in the application context with this `id` attribute as the bean name. In this case, the endpoint is registered with the bean name `id` plus `.adapter`. And the `MessageHandler` is registered with the bean alias `id` plus `.handler`.
2	Identifies the channel attached to this adapter.
3	The reference to the `IntegrationWebSocketContainer` bean, which encapsulates the low-level connection and `WebSocketSession` handling operations. Required.
4	Optional reference to a `SubProtocolHandler` instance. It is used when the client did not request a sub-protocol or it is a single protocol-handler. If this reference or a `protocol-handlers` list is not provided, the `PassThruSubProtocolHandler` is used by default.
5	List of `SubProtocolHandler` bean references for this channel adapter. If you provide only a single bean reference and do not provide a `default-protocol-handler`, that single `SubProtocolHandler` is used as the `default-protocol-handler`. If you do not set this attribute or `default-protocol-handler`, the `PassThruSubProtocolHandler` is used by default.
6	List of `MessageConverter` bean references for this channel adapter.
7	Boolean value indicating whether the default converters should be registered after any custom converters. This flag is used only if `message-converters` is provided. Otherwise, all default converters are registered. Defaults to `false`. The default converters are (in order): `StringMessageConverter`, `ByteArrayMessageConverter`, and `MappingJackson2MessageConverter` (if the Jackson library is present on the classpath).
8	Boolean value indicating whether this endpoint should start automatically. Defaults to `true`.
9	The lifecycle phase within which this endpoint should start and stop. The lower the value, the earlier this endpoint starts and the later it stops. The default is `Integer.MIN_VALUE`. Values can be negative. See `SmartLifeCycle`.

`<int-websocket:inbound-channel-adapter>` Attributes

以下清单展示了 <int-websocket:outbound-channel-adapter> 元素可用的属性：

The following listing shows the attributes available for the <int-websocket:outbound-channel-adapter> element:

<int-websocket:inbound-channel-adapter
                            id=""  1
                            channel=""  2
                            error-channel=""  3
                            container=""  4
                            default-protocol-handler=""  5
                            protocol-handlers=""  6
                            message-converters=""  7
                            merge-with-default-converters=""  8
                            send-timeout=""  9
                            payload-type=""  10
                            use-broker=""  11
                            auto-startup=""  12
                            phase=""/>  13

1	The component bean name. If you do not set the `channel` attribute, a `DirectChannel` is created and registered in the application context with this `id` attribute as the bean name. In this case, the endpoint is registered with the bean name `id` plus `.adapter`.
2	Identifies the channel attached to this adapter.
3	The `MessageChannel` bean reference to which the `ErrorMessage` instances should be sent.
4	See the same option on the <<`<int-websocket:outbound-channel-adapter>`,websocket-outbound-channel-adapter-attributes>>.
5	See the same option on the <<`<int-websocket:outbound-channel-adapter>`,websocket-outbound-channel-adapter-attributes>>.
6	See the same option on the <<`<int-websocket:outbound-channel-adapter>`,websocket-outbound-channel-adapter-attributes>>.
7	See the same option on the <<`<int-websocket:outbound-channel-adapter>`,websocket-outbound-channel-adapter-attributes>>.
8	See the same option on the <<`<int-websocket:outbound-channel-adapter>`,websocket-outbound-channel-adapter-attributes>>.
9	Maximum amount of time (in milliseconds) to wait when sending a message to the channel if the channel can block. For example, a `QueueChannel` can block until space is available if its maximum capacity has been reached.
10	Fully qualified name of the Java type for the target `payload` to convert from the incoming `WebSocketMessage`. Defaults to `java.lang.String`.
11	Indicates whether this adapter sends `non-MESSAGE` `WebSocketMessage` instances and messages with broker destinations to the `AbstractBrokerMessageHandler` from the application context. When this attribute is `true`, the `Broker Relay` configuration is required. This attribute is used only on the server side. On the client side, it is ignored. Defaults to `false`.
12	See the same option on the <<`<int-websocket:outbound-channel-adapter>`,websocket-outbound-channel-adapter-attributes>>.
13	See the same option on the <<`<int-websocket:outbound-channel-adapter>`,websocket-outbound-channel-adapter-attributes>>.

Using `ClientStompEncoder`

从 4.3.13 版本开始，Spring Integration 提供 ClientStompEncoder （作为标准 StompEncoder 的扩展）以供在 WebSocket 信道适配器的客户端使用。为了正确准备客户端消息，您必须将 ClientStompEncoder 的实例注入 StompSubProtocolHandler。默认 StompSubProtocolHandler 的一个问题在于它是为服务器端设计的，因此它会将 SEND stompCommand 标头更新为 MESSAGE（这是服务器端 STOMP 协议的要求）。如果客户端不以正确的 SEND Web 套接字框架发送其消息，则部分 STOMP 代理不会接受它们。在这种情况下，ClientStompEncoder 的目的是覆盖 stompCommand 标头，并将其设置为 SEND 值，然后再将消息编码为 byte[]。

Starting with version 4.3.13, Spring Integration provides ClientStompEncoder (as an extension of the standard StompEncoder) for use on the client side of WebSocket channel adapters. For proper client side message preparation, you must inject an instance of the ClientStompEncoder into the StompSubProtocolHandler. One problem with the default StompSubProtocolHandler is that it was designed for the server side, so it updates the SEND stompCommand header into MESSAGE (as required by the STOMP protocol for the server side). If the client does not send its messages in the proper SEND web socket frame, some STOMP brokers do not accept them. The purpose of the ClientStompEncoder, in this case, is to override the stompCommand header and set it to the SEND value before encoding the message to the byte[].

Dynamic WebSocket Endpoints Registration

从 5.5 版本开始，WebSocket 服务器端点（基于 ServerWebSocketContainer 的信道适配器）现可在运行时注册（和移除） - 映射到 ServerWebSocketContainer 的 paths 通过 HandlerMapping 公开到 DispatcherServlet 中，并可供 WebSocket 客户端访问。Dynamic and Runtime Integration Flows 支持有助于以透明方式注册这些端点：

Starting with version 5.5, the WebSocket server endpoints (channel adapters based on a ServerWebSocketContainer) can now be registered (and removed) at runtime - the paths a ServerWebSocketContainer is mapped is exposed via HandlerMapping into a DispatcherServlet and accessible for WebSocket clients. The Dynamic and Runtime Integration Flows support helps to register these endpoints in a transparent manner:

@Autowired
IntegrationFlowContext integrationFlowContext;

@Autowired
HandshakeHandler handshakeHandler;
...
ServerWebSocketContainer serverWebSocketContainer =
       new ServerWebSocketContainer("/dynamic")
               .setHandshakeHandler(this.handshakeHandler);

WebSocketInboundChannelAdapter webSocketInboundChannelAdapter =
       new WebSocketInboundChannelAdapter(serverWebSocketContainer);

QueueChannel dynamicRequestsChannel = new QueueChannel();

IntegrationFlow serverFlow =
       IntegrationFlow.from(webSocketInboundChannelAdapter)
               .channel(dynamicRequestsChannel)
               .get();

IntegrationFlowContext.IntegrationFlowRegistration dynamicServerFlow =
       this.integrationFlowContext.registration(serverFlow)
               .addBean(serverWebSocketContainer)
               .register();
...
dynamicServerFlow.destroy();

在动态流注册中调用 .addBean(serverWebSocketContainer) 以将 ServerWebSocketContainer 实例添加到 ApplicationContext 中以进行端点注册非常重要。当动态流注册被销毁时，关联的 ServerWebSocketContainer 实例也会被销毁，以及相应的端点注册（包括 URL 路径映射）。

It is important to call .addBean(serverWebSocketContainer) on the dynamic flow registration to add the instance of ServerWebSocketContainer into an ApplicationContext for endpoint registration. When a dynamic flow registration is destroyed, the associated ServerWebSocketContainer instance is destroyed, too, as well as the respective endpoint registration, including URL path mappings.

动态 WebSocket 端点只能通过 Spring Integration 机制注册：当使用常规 Spring @EnableWebsocket 时，Spring Integration 配置会退出，不会注册用于动态端点的任何基础结构。

The dynamic Websocket endpoints can only be registered via Spring Integration mechanism: when regular Spring @EnableWebsocket is used, Spring Integration configuration backs off and no infrastructure for dynamic endpoints is registered.

WebSockets Support

Overview

WebSocket Inbound Channel Adapter

WebSocket Outbound Channel Adapter

WebSockets Namespace Support

<int-websocket:client-container> Attributes

<int-websocket:server-container> Attributes

<int-websocket:outbound-channel-adapter> Attributes

<int-websocket:inbound-channel-adapter> Attributes