How do you create a REST client for Java?

Yaba_7524 0
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With JSR 311 and its implementations we have a powerful standard for exposing Java objects via REST. However on the client side there seems to be something missing that is comparable to Apache Axis for SOAP - something that hides the web service and marshals the data transparently back to Java objects.

How do you create Java RESTful clients? Using HTTPConnection and manual parsing of the result? Or specialized clients for e.g. Jersey or Apache CXR?

client rest java
18 Answers

This is an old question (2008) so there are many more options now than there were then:

UPDATES (projects still active in 2020):

  • Apache HTTP Components (4.2) Fluent adapter - Basic replacement for JDK, used by several other candidates in this list. Better than old Commons HTTP Client 3 and easier to use for building your own REST client. You'll have to use something like Jackson for JSON parsing support and you can use HTTP components URIBuilder to construct resource URIs similar to Jersey/JAX-RS Rest client. HTTP components also supports NIO but I doubt you will get better performance than BIO given the short requestnature of REST. Apache HttpComponents 5 has HTTP/2 support.
  • OkHttp - Basic replacement for JDK, similar to http components, used by several other candidates in this list. Supports newer HTTP protocols (SPDY and HTTP2). Works on Android. Unfortunately it does not offer a true reactor-loop based async option (see Ning and HTTP components above). However if you use the newer HTTP2 protocol this is less of a problem (assuming connection count is problem).
  • Ning Async-http-client - provides NIO support. Previously known as Async-http-client by Sonatype.
  • Feign wrapper for lower level http clients (okhttp, apache httpcomponents). Auto-creates clients based on interface stubs similar to some Jersey and CXF extensions. Strong spring integration.
  • Retrofit - wrapper for lower level http clients (okhttp). Auto-creates clients based on interface stubs similar to some Jersey and CXF extensions.
  • Volley wrapper for jdk http client, by google
  • google-http wrapper for jdk http client, or apache httpcomponents, by google
  • Unirest wrapper for jdk http client, by kong
  • Resteasy JakartaEE wrapper for jdk http client, by jboss, part of jboss framework
  • jcabi-http wrapper for apache httpcomponents, part of jcabi collection
  • restlet wrapper for apache httpcomponents, part of restlet framework
  • rest-assured wrapper with asserts for easy testing

A caveat on picking HTTP/REST clients. Make sure to check what your framework stack is using for an HTTP client, how it does threading, and ideally use the same client if it offers one. That is if your using something like Vert.x or Play you may want to try to use its backing client to participate in whatever bus or reactor loop the framework provides... otherwise be prepared for possibly interesting threading issues.

user_3181740

As I mentioned in this thread I tend to use Jersey which implements JAX-RS and comes with a nice REST client. The nice thing is if you implement your RESTful resources using JAX-RS then the Jersey client can reuse the entity providers such as for JAXB/XML/JSON/Atom and so forth - so you can reuse the same objects on the server side as you use on the client side unit test.

For example here is a unit test case from the Apache Camel project which looks up XML payloads from a RESTful resource (using the JAXB object Endpoints). The resource(uri) method is defined in this base class which just uses the Jersey client API.

e.g. 

    clientConfig = new DefaultClientConfig();
    client = Client.create(clientConfig);

    resource = client.resource("http://localhost:8080");
    // lets get the XML as a String
    String text = resource("foo").accept("application/xml").get(String.class);

BTW I hope that future version of JAX-RS add a nice client side API along the lines of the one in Jersey

James_Strachan_20682110

You can also check Restlet which has full client-side capabilities, more REST oriented that lower-level libraries such as HttpURLConnection or Apache HTTP Client (which we can leverage as connectors).

Best regards, Jerome Louvel

Jerome_Louvel_300680

I use Apache HTTPClient to handle all the HTTP side of things.

I write XML SAX parsers for the XML content that parses the XML into your object model. I believe that Axis2 also exposes XML -> Model methods (Axis 1 hid this part, annoyingly). XML generators are trivially simple.

It doesn't take long to code, and is quite efficient, in my opinion.

JeeBee_178320
user_48651170
user_33024240

I am currently using https://github.com/kevinsawicki/http-request I like their simplicity and the way examples are shown, but mostly I was sold when I read:

What are the dependencies?

None. The goal of this library is to be a single class class with some inner static classes. The test project does require Jetty in order to test requests against an actual HTTP server implementation.

which sorted out some problems on a java 1.6 project. As for decoding json into objects gson is just invincible :)

user_4360850
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