Configuring WebSocket Server Endpoints
In this post we take a look at how to configure WebSocket server endpoints in Java EE and their related options. Read on for more details.
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Join For FreeBefore we dive into the details, here is a quick snapshot of the related interfaces
| Class/Interface | Description |
|---|---|
| ServerEndpointConfig | A derivative of EndpointConfig interface which is specific for configuration related to server side WebSocket endpoints |
| ServerEndpointConfig.Configurator | An interface whose custom implementation allows sharing of global (for all endpoints) available logic/state as well opportunity to intercept the WebSocket handshake process (via method override) |
| ServerEndpointConfig.Builder | Used only for programmatic server endpoints to build a ServerEndpointConfig instance |
From here on, we’ll explore the configuration strategies for annotated and programmatic server endpoints
Configuring Annotated Server Endpoints
Annotated server endpoints are configured implicitly via the elements of the @ServerEndpoint annotation. The WebSocket container picks up the value from the annotation elements and creates an instance of EndpointConfig behind the scenes. This instance is automatically injected (at run time by the WebSocket container) as a parameter of the @OnOpen method
Configuring Programmatic Server Endpoints
Programmatic endpoints need (explicit) coding as far as configuration is concerned. This is because of the fact that programmatic endpoints are deployed differently and need an instance of ServerEndpointConfig
Please look at this blog post for details of the deployment aspects for programmatic WebSocket endpoints
Here is where the fluent builder ServerEndpointConfig.Builder comes into picture. Let’s look at an example which deomnstrates its usage
The Big Picture
Annotated and programmatic endpoint configuration are handled differently, but the end result is the same. Below is a table which shows the mapping b/w corresponding element of the @ServerEndpoint annotation, the corresponding method in ServerEndpointConfig as well as appropriate the method in the ServerEndpointConfig.Builder
| @ServerEndpoint annotation element | ServerEndpointConfig method | ServerEndpointConfig.Builder method |
|---|---|---|
| value | getPath() | create(Class<?> endpointClass, String path) |
| configurator | getConfigurator() | configurator(ServerEndpointConfig.Configurator serverEndpointConfigurator) |
| decoders | getDecoders() | decoders(List<Class<? extends Decoder>> decoders) |
| encoders | getEncoders() | encoders(List<Class<? extends Encoder>> encoders) |
| subprotocols | getSubprotocols() | subprotocols(List<String> subprotocols) |
Cheers!
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