Java连接到Http使用哪种方法？

Question

I have been looking around at different ways to connect to URLs and there seem to be a few.

My requirements are to do POST and GET queries on a URL and retrieve the result.

I have seen

URL class
DefaultHttpClient class
HttpClient - apache commons

which method is best?

Answer 1

My rule of thumb and recommendation: Don't introduce dependencies and 3rd party libraries if it's fairly easy to get away without.

In this case I would say, if you need efficiency such as multiple requests per established connection session handling or cookie support etc, go for HTTPClient .

If you only need to perform an HTTP get, this will suffice:

Getting Text from a URL

try {
    // Create a URL for the desired page
    URL url = new URL("http://hostname:80/index.html");

    // Read all the text returned by the server
    BufferedReader in = new BufferedReader(new InputStreamReader(url.openStream()));
    String str;
    while ((str = in.readLine()) != null) {
        // str is one line of text; readLine() strips the newline character(s)
    }
    in.close();
} catch (MalformedURLException e) {
} catch (IOException e) {
}

Sending a POST Request Using a URL

try {
    // Construct data
    String data = URLEncoder.encode("key1", "UTF-8") + "=" + URLEncoder.encode("value1", "UTF-8");
    data += "&" + URLEncoder.encode("key2", "UTF-8") + "=" + URLEncoder.encode("value2", "UTF-8");

    // Send data
    URL url = new URL("http://hostname:80/cgi");
    URLConnection conn = url.openConnection();
    conn.setDoOutput(true);
    OutputStreamWriter wr = new OutputStreamWriter(conn.getOutputStream());
    wr.write(data);
    wr.flush();

    // Get the response
    BufferedReader rd = new BufferedReader(new InputStreamReader(conn.getInputStream()));
    String line;
    while ((line = rd.readLine()) != null) {
        // Process line...
    }
    wr.close();
    rd.close();
} catch (Exception e) {
}

Both methods work great. (I've even done manual gets/posts with cookies.)

Answer 2

HTTPClient is the way to go if your needs go past trivial URL connection (eg proxy authentication such as NTLM). There are at least a comparison here between standard HTTP client functionality between libraries provided by the JRE, Apache HTTP Client and others.

Answer 3

If you are using JDK versions earlier to (including 1.4) and have a fairly large data in your post requests, like large file uploads, the default HTTPURLConnection that comes with the JRE is bound to go Out of memory at some point since it buffers the entire data before posting. Additionally it does not support some advanced HTTP headers like chunked encoding, etc.

So I'd recommend it only if your request are trivial and you are not posting large data as aioobe did.