jersey 2: How to create custom HTTP param binding

grizzly, java, jersey-2.0

Solution

If all you want is to pass value directly from the header to the method you don't need to create custom annotations. Let's say you have a header `Authorization`, then you can easily access it by declaring your method like this:

@GET
public String authFromHeader(@HeaderParam("Authorization") String authorization) {
    return "Header Value: " + authorization + "\n";
}

You can test it by calling `curl`, e.g.

$ curl --header "Authorization: 1234" http://localhost:8080/rest/resource
Header Value: 1234

Given that the answer to your question, how to create custom binding is as follows.

First you have to declare your annotation like this:

@java.lang.annotation.Target(PARAMETER)
@java.lang.annotation.Retention(RUNTIME)
@java.lang.annotation.Documented
public @interface UserAuthHeaderParam {
}

Having your annotation declared you have to define how it will be resolved. Declare the Value Factory Provider (this is where you'll have access to the header parameters - see my comment):

@Singleton
public class UserAuthHeaderParamValueFactoryProvider extends AbstractValueFactoryProvider {

    @Inject
    protected UserAuthHeaderParamValueFactoryProvider(MultivaluedParameterExtractorProvider mpep, ServiceLocator locator) {
        super(mpep, locator, Parameter.Source.UNKNOWN);
    }

    @Override
    protected Factory<?> createValueFactory(Parameter parameter) {
        Class<?> classType = parameter.getRawType();

        if (classType == null || (!classType.equals(String.class))) {
            return null;
        }

        return new AbstractHttpContextValueFactory<String>() {
            @Override
            protected String get(HttpContext httpContext) {
                // you can get the header value here
                return "testString";
            }
        };
    }
}

Now declare an injection resolver

public class UserAuthHeaderParamResolver extends ParamInjectionResolver<UserAuthHeaderParam> {
    public UserAuthHeaderParamResolver() {
        super(UserAuthHeaderParamValueFactoryProvider.class);
    }
}

and a Binder for your configuration

public class HeaderParamResolverBinder extends AbstractBinder {

    @Override
    protected void configure() {
        bind(UserAuthHeaderParamValueFactoryProvider.class)
                .to(ValueFactoryProvider.class)
                .in(Singleton.class);

        bind(UserAuthHeaderParamResolver.class)
                .to(new TypeLiteral<InjectionResolver<UserAuthHeaderParam>>() {})
                .in(Singleton.class);
    }
}

now the last thing, in your ResourceConfig add `register(new HeaderParamResolverBinder())`, like this

@ApplicationPath("rest")
public class MyApplication extends ResourceConfig {
    public MyApplication() {
        register(new HeaderParamResolverBinder());
        packages("your.packages");
    }
}

Given that, you should be now able to use the value as you wanted:

@GET
public String getResult(@UserAuthHeaderParam String param) {
    return "RESULT: " + param;
}

I hope this helps.

Problem

Original source

Related problems

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