The API key and value will be sent as a request header along with the HTTP GET requests. These values are stored in a constants file URLConstants.java. In order to cover the most common scenarios we will look at examples of sending asynchronous HTTP GET request and synchronous POST request fot each type of client.įor HTTP GET requests, we will invoke an API: with API keys created from the API portal. Spring WebClient for Spring Boot applications.Apache HTTPClient from Apache HttpComponents project. ‘HttpClient’ included from Java 11 for applications written in Java 11 and above.We will look at the following HTTP clients in this post : This article is accompanied by a working code example on GitHub. This article provides an overview of some of the major libraries which are used as HTTP clients in Java applications for making HTTP calls. Applications built with Java rely on some form of HTTP client to make API invocations on other applications.Ī wide array of alternatives exist for choosing an HTTP client. It is a commonly used protocol for communication between applications that publish their capabilities in the form of REST APIs. As mentioned, these examples are heavily based on the Apache HttpClient samples, and I recommend looking at that code for more examples.Hypertext Transfer Protocol (HTTP) is an application-layer protocol for transmitting hypermedia documents, such as HTML, and API payloads in a standard format like JSON and XML. I hope these examples of creating Java REST (RESTful) clients using the Apache HttpClient have been helpful. Java REST clients using the Apache HttpClient library HttpClient.getConnectionManager().shutdown() Header headers = httpResponse.getAllHeaders() įor (int i = 0 i < headers.length i++) HttpEntity entity = httpResponse.getEntity() HttpResponse httpResponse = httpclient.execute(target, getRequest) HttpGet getRequest = new HttpGet("/forecastrss?p=80020&u=f") HttpHost target = new HttpHost("", 80, "http") * Try this Twitter API URL for another example (it returns JSON results):ĭefaultHttpClient httpclient = new DefaultHttpClient() * This executes a call against the Yahoo Weather API service, which is * A simple Java REST GET example using the Apache HTTP library. Here's the source code for this first example class. Hopefully you can try this against different URLs where you can examine the header information in more detail. I wish I could have provided this demo with the OpenSSO demos I wrote a few years ago (see my PHP OpenSSO REST API examples), because the OpenSSO REST API made extensive use of header information. It also shows how to get all of the headers from the web service you're calling. This REST client uses the following Apache HttpClient classes: That service actually returns information in an RSS format, but if you don't mind parsing that XML, it's an easy way to get weather updates. This first example shows a combination of these Apache HttpClient classes used to get information from the Yahoo Weather API. But hopefully these examples will make other POST or other RESTful examples easier to read. The REST client examples I share here are based on the examples on the HttpClient website I've mostly just tried to make them a little easier to read, and add some additional documentation to them.Īlso, I'm just focusing on HTTP GET requests in this article, because I'm writing real-world code to hit the Twitter REST API, and all I need right now are GET requests. In this article I share some source code for some simple Java REST clients that use the Apache HttpClient project. I started writing some Java REST (RESTful) clients lately, and in doing so, I've been looking at several different ways to do this, including using the Apache HttpClient project, the Jersey project, Apache CXF, and more.
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