WAS v8.5 > End-to-end paths > Web services - RESTful services > Use JAX-RS context objects to obtain more information about requests > Step 4. Add context fields and parameters to obtain information about requests.

Obtain information about URIs using UriInfo objects

Using Java API for RESTful Web Services (JAX-RS), we can use the UriInfo object to access request headers. The UriInfo object provides methods to enable you to find or build URI information of a request. Using an injected UriInfo object by the JAX-RS runtime environment, the relative and absolute uniform resource identifier (URI) information is known and available for modification.  The @javax.ws.rs.core.Context annotation indicates that a context object is injected. The javax.ws.rs.core.UriInfo interface is the interface of the object to inject. We can use the UriInfo object to build absolute and relative URLs using the UriBuilder class.

• If a resource method signature can be modified, add the @javax.ws.rs.core.Context javax.ws.rs.core.UriInfo parameter to the method. When the resource method is invoked, the JAX-RS runtime environment passes an object that implements the UriInfo object; for example:

  @Path("/contextexample")
  public class RootResource {
      @GET
      public String getResource(@Context UriInfo uriInfo) {
          /* This calls a method on the uriInfo object. */
          return "The client used this URI to reach this resource method: " + uriinfo.getAbsolutePath().toASCIIString();
      }}

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

  @Path("/contextexample")
  public class RootResource {
  
      @Context
      UriInfo uriInfo;
  
     @GET
      public String getResource() {
          /* This calls a method on the uriInfo object. */
          return "The client used this URI to reach this resource method: " + uriinfo.getAbsolutePath().toASCIIString();
      }}

Results

The resource method can use the URI and then build URI information using the UriInfo object

Example

In the following example, a list of books resource is available at the following URL: http://host:port/<context root>/<servlet path>/books.  Suppose you need another resource to reference the books resource.  Instead of hardcoding the URL into the application, use the UriInfo object to return a UriBuilder class that dynamically builds the URI to resources in the application.

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.UriInfo; 
import   javax.ws.rs.core.MediaType; 
  
@Path ( "/books" ) 
public   class  BookListResource   { 
  
     @GET
     @Produces(MediaType.TEXT_PLAIN)
     public   String  getBookList()   {
        return "a list of books";
      }} 

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.UriInfo; 
import   javax.ws.rs.core.MediaType; 
  
@Path ( "/allitems" ) 
public   class  AllItemsListResource   { 
  
     @GET
     @Produces(MediaType.TEXT_PLAIN)
     public   String   getLocationOfAllItems(@Context UriInfo uriInfo)   { 
        URI bookListURI = uriInfo.getBaseUriBuilder().path(BookListResource.class).build();
        return Response.ok("The URI to the book list is: " + bookListURI..toASCIIString()).build();
      }}

Related

Use JAX-RS context objects to obtain more information about requests
Obtain HTTP headers using HttpHeaders objects
Evaluate request preconditions using Request objects
Determine security information using SecurityContext objects

Reference:

Web services specifications and APIs

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