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Dynamic Provider Registration in JAX-RS

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Dynamic Provider Registration in JAX-RS

Wondering if it's possible to register providers dynamically in JEE? The answer is yes, it is possible! Read on to find out how it's done.

· Java Zone
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The DynamicFeature class in JAX-RS (2.0) allows you to register providers:

  • Dynamically i.e. without any pre-defined binding strategy (e.g. annotations).
  • Based on criteria i.e. to help decide which provider to bind to which JAX-RS resource(s).

The JAX-RS implementation detects and executes the DynamicFeature implementations at deployment time

Here is an example where we instruct the JAX-RS runtime to dynamically bind the AuthenticationFilter (a JAX-RS post construct filter) to be applied when a PUT is invoked on UserResource (which is a JAX-RS resource class):

@Provider
public class DynamicFilter implements DynamicFeature {
  @Override
  public void configure(ResourceInfo resInfo, FeatureContext ctx) {
    if (UserResource.class.equals(resInfo.getResourceClass()) &&
      resInfo.getResourceMethod().getName().contains("PUT")) {
      ctx.register(AuthenticationFilter.class);
    }
  }
}


Criteria-Based

Criteria are provided by ResourceInfo, and they're based on two attributes:

  • The resource class
  • The resource method

Dynamic

Dynamic registration is achieved using FeatureContext, whose register method can be used to bind the provider.

Note

  • @Provider is needed for automatic discovery by the JAX-RS runtime.
  • Applicable for: filters, interceptors and  any Feature
  • In case of filters, the following applicability criteria apply
    • Post matching (@PreMatching filters excluded).
    • Server side filters i.e. ClientRequestFilter and ClientResponseFilter cannot be registered using this method.
  • Once used, it overrides other bindings (static or using @NameBinding).

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Topics:
java ee ,java ,jax-rs ,dynamic provider ,registration

Published at DZone with permission of Abhishek Gupta, DZone MVB. See the original article here.

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