Obtain HTTP headers using HttpHeaders objects

Use the JAX-RS HttpHeaders object to access request headers.

Injected HttpHeaders objects derive HTTP request header information. To indicate a context object is injected, use...

@javax.ws.rs.core.Context

The interface of the object to to inject is...

javax.ws.rs.core.HttpHeaders

Procedure...

1. Determine if the method signature can be modified.

   • For JAX-RS specific resource methods, we generally modify the method signature, and add parameters.

   • If the JAX-RS resource method was developed by re-using code and adapting existing classes and methods to add JAX-RS functionality, there might be constraints on the method signature by previously existing code that calls the method. In this case, you might not be able to modify the method signature.

2. If a resource method signature can be modified, add parameter...
   javax.ws.rs.core.HttpHeaders

   ...annotated with...

   @javax.ws.rs.core.Context

   ...to the method. When the resource method is invoked, the JAX-RS runtime environment passes an object that implements the HttpHeaders object; for example:

   @Path("/contextexample")
   public class RootResource 
   {
       @GET
       public String getResource(@Context HttpHeaders httpHeaders) 
       {
           /* Call a method on httpHeaders. */
           return "The client sent a header value of " + headers.getRequestHeaders().getFirst("CustomHeader") + " for CustomHeader";
       }
   }

3. If a resource method signature cannot be modified and the class is a root resource, add a javax.ws.rs.core.HttpHeaders field that is annotated with the @javax.ws.rs.core.Context annotation to the class. When the resource is instantiated for a request, an object that implements HttpHeaders is injected; for example:

   @Path("/contextexample")
   public class RootResource 
   {
        @Context
       HttpHeaders httpHeaders;
        @GET
       public String getResource() 
       {
           /* This calls a method on httpHeaders. */
           return "The client sent a header value of " + headers.getRequestHeaders().getFirst("CustomHeader") + " for CustomHeader";
       }
   }

Results

The resource method uses information from the HTTP headers that is sent in the request to determine an appropriate response.

Example

The following example illustrates a resource that returns a different greeting depending on the setting of the Accept-Language header.

In the following code snippet, the @Context HttpHeaders parameter is added to the method signature. Notice that the @Context annotation and the type declaration are in the parameters list of the getGreeting method.

import java.util.List;  
import java.util.Locale;
import javax.ws.rs.GET;  
import javax.ws.rs.Path;  
import javax.ws.rs.Produces;  
import javax.ws.rs.core.Context;  
import javax.ws.rs.core.HttpHeaders;  
import javax.ws.rs.core.MediaType;

@Path("/contexttest")  public class HelloWorldInMyLanguage 
{       /**
     *   @return Returns the string in the preferred language.  */

    @GET
    @Produces(MediaType.TEXT_PLAIN)
    public String getGreeting(@Context HttpHeaders httpHeaders) 
    {
        List<Locale> locales = httpHeaders.getAcceptableLanguages();
        if (locales.size() == 0) 
        {
            return "Hello!";
        }

        Locale locale = locales.get(0);
        if (locale.equals(Locale.FRENCH)) 
        {
            return "Bonjour!";
        } 
        else if (locale.equals(Locale.GERMAN)) 
        {
            return "Guten Tag!";
        } 
        else 
        {
            return "Hello!";
        }
    }
} 

Alternatively, we can choose to declare the @Context HttpHeaders httpHeaders property as a field in the class; for example:

import java.util.List;  
import java.util.Locale;
import javax.ws.rs.GET;  
import javax.ws.rs.Path;  
import javax.ws.rs.Produces;  
import javax.ws.rs.core.Context;  
import javax.ws.rs.core.HttpHeaders;  
import javax.ws.rs.core.MediaType;

@Path("/contexttest")  
public class HelloWorldInMyLanguage 
{       
    @Context
    HttpHeaders httpHeaders;

     /**
     * @return Returns the string in the preferred language.
     */
    @GET
    @Produces(MediaType.TEXT_PLAIN)
    public String getGreeting() 
    {
        List<Locale> locales = httpHeaders.getAcceptableLanguages();
        if (locales.size() == 0) 
        {
            return "Hello!";
        }

        Locale locale = locales.get(0);
        if (locale.equals(Locale.FRENCH)) 
        {
            return "Bonjour!";
        } 
        else if (locale.equals(Locale.GERMAN)) 
        {
            return "Guten Tag!";
        } 
        else 
       {
            return "Hello!";
        }
    }
}

Related tasks

Use JAX-RS context objects to obtain more information about requests

Obtain information about URIs using UriInfo objects

Evaluate request preconditions using Request objects

Determine security information using SecurityContext objects

Web services specifications and APIs