How do I set the proxy to be used by the JVM

Question

Many times, a Java app needs to connect to the Internet. The most common example happens when it is reading an XML file and needs to download its schema.

I am behind

Answer 1

This is a minor update, but since Java 7, proxy connections can now be created programmatically rather than through system properties. This may be useful if:

1. Proxy needs to be dynamically rotated during the program's runtime
2. Multiple parallel proxies need to be used
3. Or just make your code cleaner :)

Here's a contrived example in groovy:

// proxy configuration read from file resource under "proxyFileName"
String proxyFileName = "proxy.txt"
String proxyPort = "1234"
String url = "http://www.promised.land"
File testProxyFile = new File(proxyFileName)
URLConnection connection

if (!testProxyFile.exists()) {

    logger.debug "proxyFileName doesn't exist.  Bypassing connection via proxy."
    connection = url.toURL().openConnection()

} else {
    String proxyAddress = testProxyFile.text
    connection = url.toURL().openConnection(new Proxy(Proxy.Type.HTTP, new InetSocketAddress(proxyAddress, proxyPort)))
}

try {
    connection.connect()
}
catch (Exception e) {
    logger.error e.printStackTrace()
}

Full Reference: http://docs.oracle.com/javase/7/docs/technotes/guides/net/proxies.html