How do I add query parameters to a GetMethod (using Java commons-httpclient)?

Question

Using Apache's commons-httpclient for Java, what's the best way to add query parameters to a GetMethod instance? If I'm using PostMethod, it's very straightforward:

PostMethod method = new PostMethod();
method.addParameter("key", "value");

GetMethod doesn't have an "addParameter" method, though. I've discovered that this works:

GetMethod method = new GetMethod("http://www.example.com/page");
method.setQueryString(new NameValuePair[] {
    new NameValuePair("key", "value")
});

However, most of the examples I've seen either hard-code the parameters directly into the URL, e.g.:

GetMethod method = new GetMethod("http://www.example.com/page?key=value");

or hard-code the query string, e.g.:

GetMethod method = new GetMethod("http://www.example.com/page");
method.setQueryString("?key=value");

Is one of these patterns to be preferred? And why the API discrepancy between PostMethod and GetMethod? And what are all those other HttpMethodParams methods intended to be used for?

Middleoftheroader

Answer 1

Post methods have post parameters, but get methods do not.

Query parameters are embedded in the URL. The current version of HttpClient accepts a string in the constructor. If you wanted to add the key, value pair above, you could use:

String url = "http://www.example.com/page?key=value";
GetMethod method = new GetMethod(url);

A good starting tutorial can be found on the Apache Jakarta Commons page.

Update: As suggested in the comment, NameValuePair works.

GetMethod method = new GetMethod("example.com/page"); 
method.setQueryString(new NameValuePair[] { 
    new NameValuePair("key", "value") 
}); 

Courcy

I discovered that this works: GetMethod method = new GetMethod("example.com/page"); method.setQueryString(new NameValuePair[] { new NameValuePair("key", "value") }); This isn't mentioned on the tutorial page, however. Should this pattern be avoided? – Middleoftheroader

Hm, apparently you can't put code blocks in comments, so I've edited my question to add that example and others. – Middleoftheroader

Answer 2

It's not just a matter of personal preference. The pertinent issue here is URL-encoding your parameter values, so that the values won't get corrupted or misinterpreted as extra delimiters, etc.

As always, it is best to read the API documentation in detail: HttpClient API Documentation

Reading this, you can see that setQueryString(String) will NOT URL-encode or delimit your parameters & values, whereas setQueryString(NameValuePair[]) will automatically URL-encode and delimit your parameter names and values. This is the best method whenever you are using dynamic data, because it might contain ampersands, equal signs, etc.

Hypomania

Answer 3

Try it this way:

    URIBuilder builder = new URIBuilder("https://graph.facebook.com/oauth/access_token")
            .addParameter("client_id", application.getKey())
            .addParameter("client_secret", application.getSecret())
            .addParameter("redirect_uri", callbackURL)
            .addParameter("code", code);

    HttpPost method = new HttpPost(builder.build());

Bissonnette

what package is UrlBuilder in? – Karrikarrie

I think it should be: "GetMethod(builder.build())" – Excrement

URIBuilder can be found at: org.apache.http.client.utils.URIBuilder; – Pals

URIBuilder is Apache HttpClient 4.5.x onwards. Older versions are out of luck and may have to rely on method.setQueryString(new nameValuePair[]{ new NameValuePair("theKey", "theValue" }); – Ferula