Jersey 1.1.5.1 User Guide

Create the following Java class in your project:

    // The Java class will be hosted at the URI path "/helloworld"
    @Path("/helloworld")
    public class HelloWorldResource {
    
        // The Java method will process HTTP GET requests
        @GET 
        // The Java method will produce content identified by the MIME Media
        // type "text/plain"
        @Produces("text/plain")
        public String getClichedMessage() {
            // Return some cliched textual content
            return "Hello World";
        }
    }

The HelloWorldResource class is a very simple Web resource. The URI path of the resource is "/helloworld" (line 2), it supports the HTTP GET method (line 6) and produces cliched textual content (line 12) of the MIME media type "text/plain" (line 9).

Notice the use of Java annotations to declare the URI path, the HTTP method and the media type. This is a key feature of JSR 311.

The root resource will be deployed using the Grizzly Web container.

Create the following Java class in your project:

public class Main {
          
     public static void main(String[] args) throws IOException {
             
         final String baseUri = "http://localhost:9998/";
         final Map<String, String> initParams = 
	                       new HashMap<String, String>();
 
         initParams.put("com.sun.jersey.config.property.packages", 
                 "com.sun.jersey.samples.helloworld.resources");

        System.out.println("Starting grizzly...");
        SelectorThread threadSelector = 
	          GrizzlyWebContainerFactory.create(baseUri, initParams);
        System.out.println(String.format(
          "Jersey app started with WADL available at %sapplication.wadl\n” + 
          “Try out %shelloworld\nHit enter to stop it...", baseUri, baseUri));
        System.in.read();
        threadSelector.stopEndpoint();
        System.exit(0);
    }    
}

The Main class deploys the HelloWorldResource using the Grizzly Web container.

Lines 9 to 10 creates an initialization parameter that informs the Jersey runtime where to search for root resource classes to be deployed. In this case it assumes the root resource class in the package com.sun.jersey.samples.helloworld.resources (or in a sub-package of).

Lines 13 to 14 deploys the root resource to the base URI "http://localhost:9998/" and returns a Grizzly SelectorThread. The complete URI of the Hello World root resource is "http://localhost:9998/helloworld".

Notice that no deployment descriptors were needed and the root resource was setup in a few statements of Java code.

Goto the URI http://localhost:9998/helloworld in your favourite browser.

Or, from the command line use curl:

> curl http://localhost:9998/helloworld

The example code presented above is shipped as the HelloWorld sample in the Java.Net maven repository.

For developers wishing to get started by deploying a Web application an equivalent sample, as a Web application, is shipped as the HelloWorld-WebApp sample.

Root resource classes are POJOs (Plain Old Java Objects) that are annotated with @Path have at least one method annotated with @Path or a resource method designator annotation such as @GET, @PUT, @POST, or @DELETE. Resource methods are methods of a resource class annotated with a resource method designator. This section shows how to use Jersey to annotate Java objects to create RESTful web services.

The following code example is a very simple example of a root resource class using JAX-RS annotations. The example code shown here is from one of the samples that ships with Jersey, the zip file of which can be found in the maven repository here.

package com.sun.ws.rest.samples.helloworld.resources;

import javax.ws.rs.GET;
import javax.ws.rs.Produces;
import javax.ws.rs.Path;

// The Java class will be hosted at the URI path "/helloworld"
@Path("/helloworld")
public class HelloWorldResource {

    // The Java method will process HTTP GET requests
    @GET
    // The Java method will produce content identified by the MIME Media
    // type "text/plain"
    @Produces("text/plain")
    public String getClichedMessage() {
        // Return some cliched textual content
        return "Hello World";
    }
}

Let's look at some of the JAX-RS annotations used in this example.

@Path("/users/{username}")

@Path("/users/{username}")
public class UserResource {

    @GET
    @Produces("text/xml")
    public String getUser(@PathParam("username") String userName) {
        ...
    }
}

@Path("users/{username: [a-zA-Z][a-zA-Z_0-9]}")

@PUT
public Response putContainer() {
    System.out.println("PUT CONTAINER " + container);

    URI uri =  uriInfo.getAbsolutePath();
    Container c = new Container(container, uri.toString());

    Response r;
    if (!MemoryStore.MS.hasContainer(c)) {
        r = Response.created(uri).build();
    } else {
        r = Response.noContent().build();
    }

    MemoryStore.MS.createContainer(c);
    return r;
}

@Path("/myResource")
@Produces("text/plain")
public class SomeResource {
    @GET
    public String doGetAsPlainText() {
        ...
    }

    @GET
    @Produces("text/html")
    public String doGetAsHtml() {
        ...
    }
}

Accept: text/plain

Accept: text/plain;q=0.9, text/html

@GET
@Produces({"application/xml", "application/json"})
public String doGetAsXmlOrJson() {
    ...
}

@POST
@Consumes("text/plain")
public void postClichedMessage(String message) {
    // Store the message
}

JAX-RS provides the deployment agnostic abstract class Application for declaring root resource and provider classes, and root resource and provider singleton instances. A Web service may extend this class to declare root resource and provider classes. For example,

public class MyApplicaton extends Application {
    public Set<Class<?>> getClasses() {
        Set<Class<?>> s = new HashSet<Class<?>>();
        s.add(HelloWorldResource.class);
        return s;
    }
}

Alternatively it is possible to reuse one of Jersey's implementations that scans for root resource and provider classes given a classpath or a set of package names. Such classes are automatically added to the set of classes that are returned by getClasses. For example, the following scans for root resource and provider classes in packages "org.foo.rest", "org.bar.rest" and in any sub-packages of those two:

public class MyApplication extends PackagesResourceConfig {
    public MyApplication() {
        super("org.foo.rest;org.bar.rest");
    }
}

For servlet deployments JAX-RS specifies that a class that implements Application may be declared instead of a servlet class in <servlet-class> element of a web.xml, but as of writing this is not currently supported for Jersey. Instead it is necessary to declare the Jersey specific servlet and the Application class as follows:

<web-app>
    <servlet>
        <servlet-name>Jersey Web Application</servlet-name>
        <servlet-class>com.sun.jersey.spi.container.servlet.ServletContainer</servlet-class>
        <init-param>
            <param-name>javax.ws.rs.Application</param-name>
            <param-value>MyApplication</param-value>
        </init-param>
    </servlet>
    ....

Alternatively a simpler approach is to let Jersey choose the PackagesResourceConfig implementation automatically by declaring the packages as follows:

<web-app>
    <servlet>
        <servlet-name>Jersey Web Application</servlet-name>
        <servlet-class>com.sun.jersey.spi.container.servlet.ServletContainer</servlet-class>
        <init-param>
            <param-name>com.sun.jersey.config.property.packages</param-name>
            <param-value>org.foo.rest;org.bar.rest</param-value>
        </init-param>
    </servlet>
    ....

JAX-RS also provides the ability to obtain a container specific artifact from an Application instance. For example, Jersey supports using Grizzly as follows:

SelectorThread st = RuntimeDelegate.createEndpoint(new MyApplication(), SelectorThread.class);

Jersey also provides Grizzly helper classes to deploy the ServletThread instance at a base URL for in-process deployment.

The Jersey samples provide many examples of Servlet-based and Grizzly-in-process-based deployments.

Parameters of a resource method may be annotated with parameter-based annotations to extract information from a request. A previous example presented the use @PathParam to extract a path parameter from the path component of the request URL that matched the path declared in @Path.

@QueryParam is used to extract query parameters from the Query component of the request URL. The following example is an extract from the sparklines sample:

@Path("smooth")
@GET
public Response smooth(
        @DefaultValue("2") @QueryParam("step") int step,
        @DefaultValue("true") @QueryParam("min-m") boolean hasMin,
        @DefaultValue("true") @QueryParam("max-m") boolean hasMax,
        @DefaultValue("true") @QueryParam("last-m") boolean hasLast,           
        @DefaultValue("blue") @QueryParam("min-color") ColorParam minColor,
        @DefaultValue("green") @QueryParam("max-color") ColorParam maxColor,
        @DefaultValue("red") @QueryParam("last-color") ColorParam lastColor
        ) { ... }

If a query parameter "step" exists in the query component of the request URI then the "step" value will be will extracted and parsed as a 32 bit signed integer and assigned to the step method parameter. If "step" does not exist then a default value of 2, as declared in the @DefaultValue annotation, will be assigned to the step method parameter. If the "step" value cannot be parsed as an 32 bit signed integer then a 400 (Client Error) response is returned. User defined Java types such as ColorParam may be used, which as implemented as follows:

public class ColorParam extends Color {
    public ColorParam(String s) {
        super(getRGB(s));
    }

    private static int getRGB(String s) {
        if (s.charAt(0) == '#') {
            try {
                Color c = Color.decode("0x" + s.substring(1));
                return c.getRGB();
            } catch (NumberFormatException e) {
                throw new WebApplicationException(400);
            }
        } else {
            try {
                Field f = Color.class.getField(s);
                return ((Color)f.get(null)).getRGB();
            } catch (Exception e) {
                throw new WebApplicationException(400);
            }
        }
    }
}

In general the Java type of the method parameter may:

Sometimes parameters may contain more than one value for the same name. If this is the case then types in 4) may be used to obtain all values.

If the @DefaultValue is not used on conjuction with @QueryParam and the query parameter is not present in the request then value will be an empty collection for List, Set or SortedSet, null for other object types, and the Java-defined default for primitive types.

The @PathParam and the other parameter-based annotations, @MatrixParam, @HeaderParam, @CookieParam and @FormParam obey the same rules as @QueryParam. @MatrixParam extracts information from URL path segments. @HeaderParam extracts information from the HTTP headers. @CookieParam extracts information from the cookies declared in cookie related HTTP headers.

@FormParam is slightly special because it extracts information from a request representation that is of the MIME media type "application/x-www-form-urlencoded" and conforms to the encoding specified by HTML forms, as described here. This parameter is very useful for extracting information that is POSTed by HTML forms, for example the following extracts the form parameter named "name" from the POSTed form data:

@POST
@Consumes("application/x-www-form-urlencoded")
public void post(@FormParam("name") String name) {
    // Store the message
}

If it is necessary to obtain a general map of parameter name to values then, for query and path parameters it is possible to do the following:

@GET
public String get(@Context UriInfo ui) {
    MultivaluedMap<String, String> queryParams = ui.getQueryParameters();
    MultivaluedMap<String, String> pathParams = ui.getPathParameters();
}

For header and cookie parameters the following:

@GET
public String get(@Context HttpHeaders hh) {
    MultivaluedMap<String, String> headerParams = hh.getRequestHeaders();
    Map<String, Cookie> pathParams = hh.getCookies();
}

In general @Context can be used to obtain contextual Java types related to the request or response. For form parameters it is possible to do the following:

@POST
@Consumes("application/x-www-form-urlencoded")
public void post(MultivaluedMap<String, String> formParams) {
    // Store the message
}

Previous sections on @Produces and @Consumes referred to MIME media types of representations and showed resource methods that consume and produce the Java type String for a number of different media types. However, String is just one of many Java types that are required to be supported by JAX-RS implementations.

Java types such as byte[], java.io.InputStream, java.io.Reader and java.io.File are supported. In addition JAXB beans are supported. Such beans are JAXBElement or classes annotated with @XmlRootElement or @XmlType. The samples jaxb and json-from-jaxb show the use of JAXB beans.

Unlike method parameters that are associated with the extraction of request parameters, the method parameter associated with the representation being consumed does not require annotating. A maximum of one such unannotated method parameter may exist since there may only be a maximum of one such representation sent in a request.

The representation being produced corresponds to what is returned by the resource method. For example JAX-RS makes it simple to produce images that are instance of File as follows:

@GET
@Path("/images/{image}")
@Produces("image/*")
public Response getImage(@PathParam("image") String image) {
    File f = new File(image);

    if (!f.exists()) {
        throw new WebApplicationException(404);
    }

    String mt = new MimetypesFileTypeMap().getContentType(f);
    return Response.ok(f, mt).build();
}

A File type can also be used when consuming, a temporary file will be created where the request entity is stored.

The Content-Type (if not set, see next section) can be automatically set from the MIME media types declared by @Produces if the most acceptable media type is not a wild card (one that contains a *, for example "application/" or "/*"). Given the following method:

@GET
@Produces({"application/xml", "application/json"})
public String doGetAsXmlOrJson() {
    ...
}

if "application/xml" is the most acceptable then the Content-Type of the response will be set to "application/xml".

Sometimes it is necessary to return additional information in response to a HTTP request. Such information may be built and returned using Response and Response.ResponseBuilder. For example, a common RESTful pattern for the creation of a new resource is to support a POST request that returns a 201 (Created) status code and a Location header whose value is the URI to the newly created resource. This may be acheived as follows:

@POST
@Consumes("application/xml")
public Response post(String content) {
    URI createdUri = ...
    create(content);
    return Response.created(createdUri).build();
}

In the above no representation produced is returned, this can be achieved by building an entity as part of the response as follows:

@POST
@Consumes("application/xml")
public Response post(String content) {
    URI createdUri = ...
    String createdContent = create(content);
    return Response.created(createdUri).entity(createdContent).build();
}

Response building provides other functionality such as setting the entity tag and last modified date of the representation.

@Path may be used on classes and such classes are referred to as root resource classes. @Path may also be used on methods of root resource classes. This enables common functionality for a number of resources to be grouped together and potentially reused.

The first way @Path may be used is on resource methods and such methods are referred to as sub-resource methods. The following example shows the method signatures for a root resource class from the jmaki-backend sample:

@Singleton
@Path("/printers")
public class PrintersResource {

    @GET
    @Produces({"application/json", "application/xml"})
    public WebResourceList getMyResources() { ... }
   
    @GET @Path("/list")
    @Produces({"application/json", "application/xml"})
    public WebResourceList getListOfPrinters() { ... }

    @GET @Path("/jMakiTable")
    @Produces("application/json")
    public PrinterTableModel getTable() { ... }

    @GET @Path("/jMakiTree")
    @Produces("application/json")
    public TreeModel getTree() { ... }

    @GET @Path("/ids/{printerid}")
    @Produces({"application/json", "application/xml"})
    public Printer getPrinter(@PathParam("printerid") String printerId) { ... }

    @PUT @Path("/ids/{printerid}")
    @Consumes({"application/json", "application/xml"})
    public void putPrinter(@PathParam("printerid") String printerId,  Printer printer) { ... }

    @DELETE @Path("/ids/{printerid}")
    public void deletePrinter(@PathParam("printerid") String printerId) { ... }
}

If the path of the request URL is "printers" then the resource methods not annotated with @Path will be selected. If the request path of the request URL is "printers/list" then first the root resource class will be matched and then the sub-resource methods that match "list" will be selected, which in this case is the sub-resource method getListOfPrinters. So in this example hierarchical matching on the path of the request URL is performed.

The second way @Path may be used is on methods not annotated with resource method designators such as @GET or @POST. Such methods are referred to as sub-resource locators. The following example shows the method signatures for a root resource class and a resource class from the optimistic-concurrency sample:

@Path("/item")
public class ItemResource {
    @Context UriInfo uriInfo;

    @Path("content")
    public ItemContentResource getItemContentResource() {
        return new ItemContentResource();
    }

    @GET
    @Produces("application/xml")
    public Item get() { ... }
}

public class ItemContentResource {

    @GET
    public Response get() { ... }

    @PUT
    @Path("{version}")
    public void put(
            @PathParam("version") int version,
            @Context HttpHeaders headers,
            byte[] in) { ... }
}

The root resource class ItemResource contains the sub-resource locator method getItemContentResource that returns a new resource class. If the path of the request URL is "item/content" then first of all the root resource will be matched, then the sub-resource locator will be matched and invoked, which returns an instance of the ItemContentResource resource class. Sub-resource locators enable reuse of resource classes.

In addition the processing of resource classes returned by sub-resource locators is performed at runtime thus it is possible to support polymorphism. A sub-resource locator may return different sub-types depending on the request (for example a sub-resource locator could return different sub-types dependent on the role of the principle that is authenticated).

Note that the runtime will not manage the life-cycle or perform any field injection onto instances returned from sub-resource locator methods. This is because the runtime does not know what the life-cycle of the instance is.

A very important aspects of REST is hyperlinks, URIs, in representations that clients can use to transition the Web service to new application states (this is otherwise known as "hypermedia as the engine of application state"). HTML forms present a good example of this in practice.

Building URIs and building them safely is not easy with java.net.URI, which is why JAX-RS has the UriBuilder class that makes it simple and easy to build URIs safely.

UriBuilder can be used to build new URIs or build from existing URIs. For resource classes it is more than likely that URIs will be built from the base URI the Web service is deployed at or from the request URI. The class UriInfo provides such information (in addition to further information, see next section).

The following example shows URI building with UriInfo and UriBuilder from the bookmark sample:

@Path("/users/")
public class UsersResource {

    @Context UriInfo uriInfo;

    ...

    @GET
    @Produces("application/json")
    public JSONArray getUsersAsJsonArray() {
        JSONArray uriArray = new JSONArray();
        for (UserEntity userEntity : getUsers()) {
            UriBuilder ub = uriInfo.getAbsolutePathBuilder();
            URI userUri = ub.
                    path(userEntity.getUserid()).
                    build();
            uriArray.put(userUri.toASCIIString());
        }
        return uriArray;
    }
}

UriInfo is obtained using the @Context annotation, and in this particular example injection onto the field of the root resource class is performed, previous examples showed the use of @Context on resource method parameters.

UriInfo can be used to obtain URIs and associated UriBuilder instances for the following URIs: the base URI the application is deployed at; the request URI; and the absolute path URI, which is the request URI minus any query components.

The getUsersAsJsonArray method constructs a JSONArrray where each element is a URI identifying a specific user resource. The URI is built from the absolute path of the request URI by calling uriInfo.getAbsolutePathBuilder(). A new path segment is added, which is the user ID, and then the URI is built. Notice that it is not necessary to worry about the inclusion of '/' characters or that the user ID may contain characters that need to be percent encoded. UriBuilder takes care of such details.

UriBuilder can be used to build/replace query or matrix parameters. URI templates can also be declared, for example the following will build the URI "http://localhost/segment?name=value":

UriBuilder.fromUri("http://localhost/").
    path("{a}").
    queryParam("name", "{value}").
    build("segment", "value");

Previous sections have shown how to return HTTP responses and it is possible to return HTTP errors using the same mechanism. However, sometimes when programming in Java it is more natural to use exceptions for HTTP errors.

The following example shows the throwing of a NotFoundException from the bookmark sample:

@Path("items/{itemid}/")
public Item getItem(@PathParam("itemid") String itemid) {
    Item i = getItems().get(itemid);
    if (i == null)
        throw new NotFoundException("Item, " + itemid + ", is not found");

    return i;
}

This exception is a Jersey specific exception that extends WebApplicationException and builds a HTTP response with the 404 status code and an optional message as the body of the response:

public class NotFoundException extends WebApplicationException {

    /**
     * Create a HTTP 404 (Not Found) exception.
     */
    public NotFoundException() {
        super(Responses.notFound().build());
    }

    /**
     * Create a HTTP 404 (Not Found) exception.
     * @param message the String that is the entity of the 404 response.
     */
    public NotFoundException(String message) {
        super(Response.status(Responses.NOT_FOUND).
                entity(message).type("text/plain").build());
    }

}

In other cases it may not be appropriate to throw instances of WebApplicationException, or classes that extend WebApplicationException, and instead it may be preferable to map an existing exception to a response. For such cases it is possible to use the ExceptionMapper interface. For example, the following maps the EntityNotFoundException to a 404 (Not Found) response:

@Provider
public class EntityNotFoundMapper implements
        ExceptionMapper<javax.persistence.EntityNotFoundException> {
    public Response toResponse(javax.persistence.EntityNotFoundException ex) {
        return Response.status(404).
            entity(ex.getMessage()).
            type("text/plain").
            build();
    }
}

The above class is annotated with @Provider, this declares that the class is of interest to the JAX-RS runtime. Such a class may be added to the set of classes of the Application instance that is configured. When an application throws an EntityNotFoundException the toResponse method of the EntityNotFoundMapper instance will be invoked.

Conditional GETs are a great way to reduce bandwidth, and potentially server-side peformance, depending on how the information used to determine conditions is calculated. A well-designed web site may return 304 (Not Modified) responses for the many of the static images it serves.

JAX-RS provides support for conditional GETs using the contextual interface Request.

The following example shows conditional GET support from the sparklines sample:

public SparklinesResource(
        @QueryParam("d") IntegerList data,
        @DefaultValue("0,100") @QueryParam("limits") Interval limits,
        @Context Request request,
        @Context UriInfo ui) {
    if (data == null)
        throw new WebApplicationException(400);

    this.data = data;

    this.limits = limits;

    if (!limits.contains(data))
        throw new WebApplicationException(400);

    this.tag = computeEntityTag(ui.getRequestUri());
    if (request.getMethod().equals("GET")) {
        Response.ResponseBuilder rb = request.evaluatePreconditions(tag);
        if (rb != null)
            throw new WebApplicationException(rb.build());
    }
}

The constructor of the SparklinesResouce root resource class computes an entity tag from the request URI and then calls the request.evaluatePreconditions with that entity tag. If a client request contains an If-None-Match header with a value that contains the same entity tag that was calculated then the evaluatePreconditions returns a pre-filled out response, with the 304 status code and entity tag set, that may be built and returned. Otherwise, evaluatePreconditions returns null and the normal response can be returned.

Notice that in this example the constructor of a resource class can be used perform actions that may otherwise have to be duplicated to invoked for each resource method.

By default the life-cycle of root resource classes is per-request, namely that a new instance of a root resource class is created every time the request URI path matches the root resource. This makes for a very natural programming model where constructors and fields can be utilized (as in the previous section showing the constructor of the SparklinesResource class) without concern for multiple concurrent requests to the same resource.

In general this is unlikely to be a cause of performance issues. Class construction and garbage collection of JVMs has vastly improved over the years and many objects will be created and discarded to serve and process the HTTP request and return the HTTP response.

Instances of singleton root resource classes can be declared by an instance of Application.

Jersey supports two further life-cycles using Jersey specific annotations. If a root resource class is annotated with @Singleton then only one instance is created per-web applcation. If a root resource class is annotated with @PerSession then one instance is created per web session and stored as a session attribute.

Security information is available by obtaining the SecurityContext using @Context, which is essentially the equivalent functionality available on the HttpServletRequest.

SecurityContext can be used in conjunction with sub-resource locators to return different resources if the user principle is included in a certain role. For example, a sub-resource locator could return a different resource if a user is a preferred customer:

@Path("basket")
public ShoppingBasketResource get(@Context SecurityContext sc) {
    if (sc.isUserInRole("PreferredCustomer") {
       return new PreferredCustomerShoppingBaskestResource();
    } else {
       return new ShoppingBasketResource();
    }
}

Previous sections have presented examples of annotated types, mostly annotated method parameters but also annotated fields of a class, for the injection of values onto those types.

This section presents the rules of injection of values on annotated types. Injection can be performed on fields, constructor parameters, resource/sub-resource/sub-resource locator method parameters and bean setter methods. The following presents an example of all such injection cases:

@Path("id: \d+")
public class InjectedResource {
    // Injection onto field
    @DefaultValue("q") @QueryParam("p")
    private String p;

    // Injection onto constructor parameter
    public InjectedResource(@PathParam("id") int id) { ... }

    // Injection onto resource method parameter
    @GET
    public String get(@Context UriInfo ui) { ... }

    // Injection onto sub-resource resource method parameter
    @Path("sub-id")
    @GET
    public String get(@PathParam("sub-id") String id) { ... }

    // Injection onto sub-resource locator method parameter
    @Path("sub-id")
    public SubResource getSubResource(@PathParam("sub-id") String id) { ... }

    // Injection using bean setter method
    @HeaderParam("X-header")
    public void setHeader(String header) { ... }
}

There are some restrictions when injecting on to resource classes with a life-cycle other than per-request. In such cases it is not possible to injected onto fields for the annotations associated with extraction of request parameters. However, it is possible to use the @Context annotation on fields, in such cases a thread local proxy will be injected.

The @FormParam annotation is special and may only be utilized on resource and sub-resource methods. This is because it extracts information from a request entity.

Previous sections have introduced the use of @Context. Chapter 5 of the JAX-RS specification presents all the standard JAX-RS Java types that may be used with @Context.

When deploying a JAX-RS application using servlet then ServletConfig, ServletContext, HttpServletRequest and HttpServletResponse are available using @Context.

For a list of the annotations specified by JAX-RS see Appendix A of the specification.

This section introduces the client API and some features such as filters and how to use them with security features in the JDK. The Jersey client API is a high-level Java based API for interoperating with RESTful Web services. It makes it very easy to interoperate with RESTful Web services and enables a developer to concisely and efficiently implement a reusable client-side solution that leverages existing and well established client-side HTTP implementations.

The Jersey client API can be utilized to interoperate with any RESTful Web service, implemented using one of many frameworks, and is not restricted to services implemented using JAX-RS. However, developers familiar with JAX-RS should find the Jersey client API complementary to their services, especially if the client API is utilized by those services themselves, or to test those services.

The goals of the Jersey client API are threefold:

The Jersey Client API supports a pluggable architecture to enable the use of different underlying HTTP client implementations. Two such implementations are supported and leveraged: the Http(s)URLConnection classes supplied with the JDK; and the Apache HTTP client.

The uniform interface constraint bounds the architecture of RESTful Web services so that a client, such as a browser, can utilize the same interface to communicate with any service. This is a very powerful concept in software engineering that makes Web-based search engines and service mash-ups possible. It induces properties such as:

Further constraints are required:

The above process repeated over and again should be familiar to anyone who has used a browser to fill in HTML forms and follow links. That same process is applicable to non-browser based clients.

Many existing Java-based client APIs, such as the Apache HTTP client API or java.net.HttpURLConnection supplied with the JDK place too much focus on the Client-Server constraint for the exchanges of request and responses rather than a resource, identified by a URI, and the use of a fixed set of HTTP methods.

A resource in the Jersey client API is an instance of the Java class WebResource, and encapsulates a URI. The fixed set of HTTP methods are methods on WebResource or if using the builder pattern (more on this later) are the last methods to be called when invoking an HTTP method on a resource. The representations are Java types, instances of which, may contain links that new instances of WebResource may be created from.

Since a resource is represented as a Java type it makes it easy to configure, pass around and inject in ways that is not so intuitive or possible with other client-side APIs.

The Jersey Client API reuses many aspects of the JAX-RS and the Jersey implementation such as:

Some APIs, like the Apache HTTP client or java.net.HttpURLConnection, can be rather hard to use and/or require too much code to do something relatively simple.

This is why the Jersey Client API provides support for wrapping HttpURLConnection and the Apache HTTP client. Thus it is possible to get the benefits of the established implementations and features while getting the ease of use benefit.

It is not intuitive to send a POST request with form parameters and receive a response as a JAXB object with such an API. For example with the Jersey API this is very easy:

Form f = new Form();
f.add(“x”, “foo”);
f.add(“y”, “bar”);

Client c = Client.create();
WebResource r = c.resource(“http://localhost:8080/form”);

JAXBBean bean = r.
    type(MediaType.APPLICATION_FORM_URLENCODED_TYPE)
    .accept(MediaType.APPLICATION_JSON_TYPE)
    .post(JAXBBean.class, f);

In the above code a Form is created with two parameters, a new WebResource instance is created from a Client then the Form instance is POSTed to the resource, identified with the form media type, and the response is requested as an instance of a JAXB bean with an acceptable media type identifying the Java Script Object Notation (JSON) format. The Jersey client API manages the serialization of the Form instance to produce the request and de-serialization of the response to consume as an instance of a JAXB bean.

If the code above was written using HttpURLConnection then the developer would have to write code to serialize the form sent in the POST request and de-serialize the response to the JAXB bean. In addition further code would have to be written to make it easy to reuse the same resource “http://localhost:8080/form” that is encapsulated in the WebResource type.

Refer to the dependencies chapter, and specifically the Core client section, for details on the dependencies when using the Jersey client with Maven and Ant.

Refer to the Java API documentation for details on the Jersey client API packages and classes.

Refer to the Java API Apache HTTP client documentation for details on how to use the Jersey client API with the Apache HTTP client.

To utilize the client API it is first necessary to create an instance of a Client, for example:

    Client c = Client.create();

    c.getProperties().put(
        ClientConfig.PROPERTY_FOLLOW_REDIRECTS, true);

    c.setFollowRedirects(true);

    ClientConfig cc = new DefaultClientConfig();
    cc.getProperties().put(
        ClientConfig.PROPERTY_FOLLOW_REDIRECTS, true);
    Client c = Client.create(cc);

    WebResource r = c.resource(“http://localhost:8080/xyz”);

    String response = r.accept(
        MediaType.APPLICATION_JSON_TYPE,
        MediaType.APPLICATION_XML_TYPE).
        header(“X-FOO”, “BAR”).
        get(String.class);

    String request = “content”;
    String response = r.accept(
        MediaType.APPLICATION_JSON_TYPE,
        MediaType.APPLICATION_XML_TYPE).
        header(“X-FOO”, “BAR”).
        post(String.class, request);

    String response = r.accept(
         MediaType.APPLICATION_JSON_TYPE,
         MediaType.APPLICATION_XML_TYPE).
         header(“X-FOO”, “BAR”).
         type(MediaType.TEXT_PLAIN_TYPE).
         post(String.class, request);

    String response = r.accept(
         MediaType.APPLICATION_JSON_TYPE,
         MediaType.APPLICATION_XML_TYPE).
         header(“X-FOO”, “BAR”).
         entity(request, MediaType.TEXT_PLAIN_TYPE).
         post(String.class);

    ClientResponse response = r.get(ClientResponse.class);
    EntityTag e = response.getEntityTag();
    String entity = response.getEntity(String.class);

    try {
        String entity = r.get(String.class);
    } catch (UniformInterfaceException ue) {
        ClientResponse response = ue.getResponse();
    }

    WebResource r = c.resource(“http://localhost:8080/xyz”);

    MultivaluedMap<String, String> params = MultivaluedMapImpl();
    params.add(“foo”, “x”);
    params.add(“bar”, “y”);
    
    String response = r.path(“abc”).
        queryParams(params).
        get(String.class);

    InputStream in = r.get(InputStream.class);
    // Read from the stream
    in.close();

    File f = ...
    String response = r.post(String.class, f);

The support for new application-defined representations as Java types requires the implementation of the same provider-based interfaces as for the server side JAX-RS API, namely MessageBodyReader and MessageBodyWriter, respectively, for request and response entities (or inbound and outbound representations). Refer to the entity provider sample for such implementations utilized on the server side.

Classes or implementations of the provider-based interfaces need to be registered with a ClientConfig and passed to the Client for creation. The following registers a provider class MyReader which will be instantiated by Jersey:

    ClientConfig cc = new DefaultClientConfig();
    cc.getClasses().add(MyReader.class);
    Client c = Client.create(cc);

The following registers an instance or singleton of MyReader:

    ClientConfig cc = new DefaultClientConfig();
    MyReader reader = ...
    cc.getSingletons().add(reader);
    Client c = Client.create(cc);

Filtering requests and responses can provide useful functionality that is hidden from the application layer of building and sending requests, and processing responses. Filters can read/modify the request URI, headers and entity or read/modify the response status, headers and entity.

The Client and WebResource classes extend from Filterable and that enables the addition of ClientFilter instances. A WebResource will inherit filters from its creator, which can be a Client or another WebResource. Additional filters can be added to a WebResource after it has been created. For requests, filters are applied in order, starting with inherited filters and followed by the filters added to the WebResource. All filters are applied in the order in which they were added. For responses, filters are applied in reverse order, starting with the WebResource filters and then moving to the inherited filters. For instance, in the following example the Client has two filters added, filter1 and filter2, in that order, and the WebResource has one filter added, filter3:

    ClientFilter filter1 = ...
    ClientFilter filter2 = ...
    Client c = Client.create();
    c.addFilter(filter1);
    c.addFilter(filter2);
    
    ClientFilter filter3 = ...
    WebResource r = c.resource(...);
    r.addFilter(filter3);

After a request has been built the request is filtered by filter1, filter2 and filter3 in that order. After the response has been received the response is filtered by filter3, filter2 and filter1 in that order, before the response is returned.

Filters are implemented using the “russian doll” stack-based pattern where a filter is responsible for calling the next filter in the ordered list of filters (or the next filter in the “chain” of filters). The basic template for a filter is as follows:

    class AppClientFilter extends ClientFilter {
        public ClientResponse handle(ClientRequest cr) {
            // Modify the request
            ClientRequest mcr = modifyRequest(cr);
            // Call the next filter
            ClientResponse resp = getNext().handle(mcr);
            // Modify the response
            return modifyResponse(resp);
        }
    }

The filter modifies the request (if required) by creating a new ClientRequest or modifying the state of the passed ClientRequest before calling the next filter. The call to the next request will return the response, a ClientResponse. The filter modifies the response (if required) by creating a new ClientResponse or modifying the state of the returned ClientResponse. Then the filter returns the modified response. Filters are re-entrant and may be called by multiple threads performing requests and processing responses.

The Jersey client API was originally developed to aid the testing of the Jersey server-side, primarily to make it easier to write functional tests in conjunction with the JUnit framework for execution and reporting. It is used extensively and there are currently over 1000 tests.

Embedded servers, Grizzly and a special in-memory server, are utilized to deploy the test-based services. Many of the Jersey samples contain tests that utilize the client API to server both for testing and examples of how to use the API. The samples utilize Grizzly or embedded Glassfish to deploy the services.

The following code snippets are presented from the single unit test HelloWorldWebAppTest of the helloworld-webapp sample. The setUp method, called before a test is executed, creates an instance of the Glassfish server, deploys the application, and a WebResource instance that references the base resource:

    @Override
    protected void setUp() throws Exception {
        super.setUp();

        // Start Glassfish
        glassfish = new GlassFish(BASE_URI.getPort());
        
        // Deploy Glassfish referencing the web.xml
        ScatteredWar war = new ScatteredWar(
            BASE_URI.getRawPath(), new File("src/main/webapp"),
            new File("src/main/webapp/WEB-INF/web.xml"),
            Collections.singleton(
                new File("target/classes").
                    toURI().toURL()));
        glassfish.deploy(war);
        
        Client c = Client.create();
        r = c.resource(BASE_URI);
    }

The tearDown method, called after a test is executed, stops the Glassfish server.

    @Override
   protected void tearDown() throws Exception {
        super.tearDown();
        glassfish.stop();
   }

The testHelloWorld method tests that the response to a GET request to the Web resource returns “Hello World”:

    public void testHelloWorld() throws Exception {
       String responseMsg = r.path("helloworld").
           get(String.class);
       assertEquals("Hello World", responseMsg);
   }

Note the use of the path method on the WebResource to build from the base WebResource.

Taking this approach will save you a lot of time, if you want to easily produce/consume both JSON and XML data format. Because even then you will still be able to use a unified Java model. Another advantage is simplicity of working with such a model, as JAXB leverages annotated POJOs and these could be handled as simple Java beans

A disadvantage of JAXB based approach could be if you need to work with a very specific JSON format. Then it could be difficult to find a proper way to get such a format produced and consumed. This is a reason why a lot of configuration options are provided, so that you can control how things get serialized out and deserialized back.

Following is a very simple example of how a JAXB bean could look like.

@XmlRootElement
public class MyJaxbBean {
  public String name;
  public int age;
      
  public MyJaxbBean() {} // JAXB needs this

  public MyJaxbBean(String name, int age) {
    this.name = name;
    this.age = age;
  }
}

Using the above JAXB bean for producing JSON data format from you resource method, is then as simple as:

@GET @Produces("application/json")
public MyJaxbBean getMyBean() {
   return new MyJaxbBean("Agamemnon", 32);
}

Notice, that JSON specific mime type is specified in @Produces annotation, and the method returns an instance of MyJaxbBean, which JAXB is able to process. Resulting JSON in this case would look like:

    {"name":"Agamemnon", "age":"32"}

@XmlRootElement
public class MyJaxbBean {
  
    @XmlElement(name="king")
    public String name;
  
    @XmlTransient
    public int age;
 
    // several lines removed       
}

@Provider
public class JAXBContextResolver implements ContextResolver<JAXBContext> {

    private JAXBContext context;
    private Class[] types = {MyJaxbBean.class};

    public JAXBContextResolver() throws Exception {
        this.context = 
	  new JSONJAXBContext( 
	    JSONConfiguration.natural().build(), types); 
    }

    public JAXBContext getContext(Class<?> objectType) {
        for (Class type : types) {
            if (type == objectType) {
                return context;
            }
        }
        return null;
    }
}

@XmlRootElement
public class Address {
    public String street;
    public String town;

    public Address(){}

    public Address(String street, String town) {
        this.street = street;
        this.town = town;
    }
}

@XmlRootElement
public class Contact {

    public int id;
    public String name;
    public List<Address> addresses;

    public Contact() {};

    public Contact(int id, String name, List<Address> addresses) {
        this.name = name;
        this.id = id;
        this.addresses = 
	        (addresses != null) ? new LinkedList<Address>(addresses) : null;
    }
}

final Address[] addresses = {new Address("Long Street 1", "Short Village")};
Contact contact = new Contact(2, "Bob", Arrays.asList(addresses));

JSONConfiguration.mapped().build()

{ "id":"2" 
 ,"name":"Bob"
 ,"addresses":{"street":"Long Street 1"
                    ,"town":"Short Village"}}

contact.addresses.add(new Address("Short Street 1000", "Long Village"));

{ "id":"2" 
 ,"name":"Bob"
 ,"addresses":[{"street":"Long Street 1","town":"Short Village"}
              ,{"street":"Short Street 1000","town":"Long Village"}]}

JSONConfiguration.mapped().arrays("addresses").build()

JSONConfiguration.mapped().arrays("addresses").nonStrings("id").build()

  ...
  @XmlAttribute
  public int id;
  ...

{"@id":"2" ...

JSONConfiguration.mapped().attributeAsElement("id").build()

JSONConfiguration.mapped().rootUnwrapping(false).build()

{"contact":{ "id":"2" 
 ,"name":"Bob"
 ,"addresses":{"street":"Long Street 1"
                    ,"town":"Short Village"}}}

        Map<String,String> ns2json = new HashMap<String, String>();
        ns2json.put("http://example.com", "example");
        context = new JSONJAXBContext(
	      JSONConfiguration.mapped()
	           .xml2JsonNs(ns2json).build(), types);

JSONConfiguration.natural().build()

{ "id":2
 ,"name":"Bob"
 ,"addresses":[{"street":"Long Street 1"
                     ,"town":"Short Village"}]}

JSONConfiguration.natural().rootUnwrapping(false).build()

JSONConfiguration.mappedJettison().build()

{ "contact:{"id":2
              ,"name":"Bob"
              ,"addresses":{"street":"Long Street 1"
                                 ,"town":"Short Village"}}

  ...
  @XmlElement(namespace="http://example.com")
  public int id;
  ...

        Map<String,String> ns2json = new HashMap<String, String>();
        ns2json.put("http://example.com", "example");
        context = new JSONJAXBContext(
	      JSONConfiguration.mappedJettison()
	           .xml2JsonNs(ns2json).build(), types);

{ "contact:{"example.id":2
              ,"name":"Bob"
              ,"addresses":{"street":"Long Street 1"
                                 ,"town":"Short Village"}}

JSONConfiguration.badgerFish().build()

{"contact":{"id":{"$":"2"}
              ,"name":{"$":"Bob"}
              ,"addresses":{"street":{"$":"Long Street 1"}
                                 ,"town":{"$":"Short Village"}}}}

Using this approach means you will be using JSONObject and/or JSONArray classes for your data representations. These classes are actually taken from Jettison project, but conform to the description provided at http://www.json.org/java/index.html.

The biggest advantage here is, that you will gain full control over the JSON format produced and consumed. On the other hand, dealing with your data model objects will probably be a bit more complex, than when taking the JAXB based approach. Differencies are depicted at the following code snipets.

MyJaxbBean myBean = new MyJaxbBean("Agamemnon", 32);

Above you construct a simple JAXB bean, which could be written in JSON as {"name":"Agamemnon", "age":32}

Now to build an equivalent JSONObject (in terms of resulting JSON expression), you would need several more lines of code.

JSONObject myObject = new JSONObject();
myObject.JSONObject myObject = new JSONObject();
try {
  myObject.put("name", "Agamemnon");
  myObject.put("age", 32);
} catch (JSONException ex) {
  LOGGER.log(Level.SEVERE, "Error ...", ex);
}

Maven developers require a dependency on the jersey-server module. The following dependency needs to be added to the pom:

<dependency>
    <groupId>com.sun.jersey</groupId>
    <artifactId>jersey-server</artifactId>
    <version>1.1.5.1</version>
</dependency>

And the following repositories need to be added to the pom:

<repository>
    <id>maven2-repository.dev.java.net</id>
    <name>Java.net Repository for Maven</name>
    <url>http://download.java.net/maven/2/</url>
    <layout>default</layout>
</repository> 
<repository>
    <id>maven-repository.dev.java.net</id>
    <name>Java.net Maven 1 Repository (legacy)</name>
    <url>http://download.java.net/maven/1</url>
    <layout>legacy</layout>
</repository>

Non-maven developers require:

or, if using the jersey-bundle:

For Ant developers the Ant Tasks for Maven may be used to add the following to the ant document such that the dependencies do not need to be downloaded explicitly:

<artifact:dependencies pathId="dependency.classpath">
  <dependency groupId="com.sun.jersey" 
              artifactId="jersey-server"
              version="1.1.5.1"/>
  <artifact:remoteRepository id="maven2-repository.dev.java.net"
                             url="http://download.java.net/maven/2/" />
  <artifact:remoteRepository id="maven-repository.dev.java.net"
                             url="http://download.java.net/maven/1" 
                             layout="legacy" />
</artifact:dependencies>

The path id “dependency.classpath” may then be referenced as the classpath to be used for compiling or executing. Specifically the asm.jar dependency is required when either of the following com.sun.jersey.api.core.ResourceConfig implementations are utilized:

By default Jersey will utilize the ClasspathResourceConfig if an alternative is not specified. If an alternative is specified that does not depend on the asm.jar then it is no longer necessary to include the asm.jar in the minimum set of required jars.

Maven developers require a dependency on the jersey-client module. The following dependency needs to be added to the pom:

<dependency>
    <groupId>com.sun.jersey</groupId>
    <artifactId>jersey-client</artifactId>
    <version>1.1.5.1</version>
</dependency>

Non-maven developers require:

or, if using the jersey-bundle:

The use of client with the Apache HTTP client to make HTTP request and receive HTTP responses requires a dependency on the jersey-apache-client module. The following dependency needs to be added to the pom:

<dependency>
    <groupId>com.sun.jersey.contribs</groupId>
    <artifactId>jersey-apache-client</artifactId>
    <version>1.1.5.1</version>
</dependency>

By default WADL for resource classes is generated dynamically at runtime. WADL support requires a dependency on the JAXB reference implementation version 2.x or higher. Deploying an application for WADL support with Java SE 6 requires no additional dependences, since Java SE 6 ships with JAXB 2.x support.

Maven developers, using Java SE 5, require a dependency on the jaxb-impl module.

Non-maven developers require:

If the above dependencies are not present then WADL generation is disabled and a warning will be logged.

The WADL ant task requires the same set of dependences as those for runtime WADL support.

Maven developers, using Spring 2.0.x or Spring 2.5.x, require a dependency on the jersey-spring module. The following dependency needs to be added to the pom:

<dependency>
    <groupId>com.sun.jersey.contribs</groupId>
    <artifactId>jersey-spring</artifactId>
    <version>1.1.5.1</version>
</dependency>

See the Java documentation here on how to integrate Jersey-based Web applications with Spring.

Maven developers, using Guice 2.0, require a dependency on the jersey-guice module. The following dependency needs to be added to the pom:

<dependency>
    <groupId>com.sun.jersey.contribs</groupId>
    <artifactId>jersey-guice</artifactId>
    <version>1.1.5.1</version>
</dependency>

See the Java documentation here on how to integrate Jersey-based Web applications with Guice.

Guice support depends on the Guice artifacts distributed with GuiceyFruit a set of extensions on top of Guice 2.0, such as support for Java EE artifacts like @PostConstruct/@PreDestroy, @Resource and @PersistenceContext. To avail of GuiceyFruit features add the following dependency and repository to the pom:

<dependency>
    <groupId>org.guiceyfruit</groupId>
    <artifactId>guiceyfruit</artifactId>
    <version>2.0-beta-6</version>
</dependency>
...
<repository>
    <id>guice-maven</id>
    <name>guice maven</name>
    <url>http://guiceyfruit.googlecode.com/svn/repo/releases</url>
</repository>

NOTE that breaking changes have occurred between 1.1.1-ea and 1.1.2-ea. See the end of this section for details.

Jersey Test Framework allows you to test your RESTful Web Services on a wide range of containers. It supports light-weight containers such as Grizzly, Embedded GlassFish, and the Light Weight HTTP Server in addition to regular web containers such as GlassFish and Tomcat. Developers may plug in their own containers.

A developer may write tests using the Junit 4.x framework can extend from the abstract JerseyTest class.

Maven developers require a dependency on the jersey-test-framework module. The following dependency needs to be added to the pom:

<dependency>
    <groupId>com.sun.jersey</groupId>
    <artifactId>jersey-test-framework</artifactId>
    <version>1.1.5.1</version>
    <scope>test</scope>
</dependency>

When utilizing an embedded container this framework can manage deployment and testing of your web services. However, the framework currently doesn't support instantiating and deploying on external containers.

The test framework provides the following test container factories:

The system property test.containerFactory is utilized to declare the default test container factory that shall be used for testing, the value of which is the fully qualified class name of a test container factory class. If the property is not declared then the GrizzlyWebTestContainerFactory is utilized as default test container factory.

To test a maven-based web project with an external container such as GlassFish, create the war file then deploy as follows (assuming that the pom file is set up for deployment):

mvn clean package -Dmaven.test.skip=true

Then execute the tests as follows:

mvn test \ -Dtest.containerFactory=com.sun.jersey.test.framework.spi.container.external.ExternalTestContainerFactory \
-DJERSEY_HTTP_PORT=<HTTP_PORT>

Breaking changes from 1.1.1-ea to 1.1.2-ea

The maven project groupId has changed from com.sun.jersey.test.framework to com.sun.jersey

The extending of Jersey unit test and configuration has changed. See here for an example.

See the blog entry on Jersey Test Framework for detailed instructions on how to use 1.1.1-ea version of the framework in your application.