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?

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.

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.