Configuring Eclipse to allow Fiddler to intercept requests

HttpClient needs to be made aware of the proxy information. Several approaches can be used:

See 2.7 in HTTP Component's documentation:

1. "Connect to the target host via a proxy is by setting the default proxy parameter"

   DefaultHttpClient httpclient = new DefaultHttpClient();
   
   HttpHost proxy = new HttpHost("127.0.0.1", 8888);
   
   httpclient.getParams().setParameter(ConnRoutePNames.DEFAULT_PROXY, proxy);
   

2. Using "the standard JRE proxy selector to obtain proxy information"

   DefaultHttpClient httpclient = new DefaultHttpClient();
   
   ProxySelectorRoutePlanner routePlanner = new ProxySelectorRoutePlanner(
               httpclient.getConnectionManager().getSchemeRegistry(), ProxySelector.getDefault());
   
   httpclient.setRoutePlanner(routePlanner);
   

   and then adding the following as VM arguments:

   -Dhttp.proxyHost=127.0.0.1 -Dhttp.proxyPort=8888 -Dhttps.proxyHost=127.0.0.1 -Dhttps.proxyPort=8888
   

3. Custom RoutePlanner implementation (I did not explore this option)

You have many possibility to configure proxy in java :

1. Using system properties
   • via VM arguments (assuming you want to enable proxy for http and https traffic) :

java -Dhttp.proxyHost=127.0.0.1 -Dhttp.proxyPort=8888 -Dhttps.proxyHost=127.0.0.1 -Dhttps.proxyPort=8888

• via System properties :

  // Get system properties
  Properties sysProperties = System.getProperties();
  // Specify proxy settings
  sysProperties.put("https.proxyHost", "127.0.0.1");
  sysProperties.put("https.proxyPort", "8888");
  sysProperties.put("http.proxyHost", "127.0.0.1");
  sysProperties.put("http.proxyPort", "8889");   
  

The "disavdantage" of this method : once the proxy is set for a protocol, all connection for that protocol will use the proxy

2. java.net.Proxy : available since java 1.5. Allow you to specify a proxy configuration to use for opening a connection

   SocketAddress addr = new  InetSocketAddress("127.0.0.1", 8888);
   Proxy proxy = new Proxy(Proxy.Type.HTTP, addr);
   URL url = new URL("http://stackoverflow.com/");
   InputStream in = url.openConnection(proxy).getInputStream();
   

3. ProxySelector class : available since Java 1.5. allow you to select a proxy by URI ! It's an abstract class, a simple implementation returning your proxy for all http and https connection looks like :

   public static class MyProxySelector extends ProxySelector {
       private List<Proxy> proxy;
       private List<Proxy> noProxy;
   
       MyProxySelector() {
           proxy = new ArrayList<Proxy>();
           SocketAddress addr = new  InetSocketAddress("127.0.0.1", 8888);
           proxy.add(new Proxy(Proxy.Type.HTTP, addr));
   
           noProxy = new ArrayList<Proxy>();
           noProxy.add(Proxy.NO_PROXY);
       }
   
       public List<Proxy> select(URI uri) {
           System.err.println("Connection to the proxy for uri :"+uri);
           if (uri == null) {
               throw new IllegalArgumentException("URI can't be null.");
           }
           String protocol = uri.getScheme();
   
           if ("http".equalsIgnoreCase(protocol) || "https".equalsIgnoreCase(protocol)) {
               //if http or https connection, return our proxy config
               return proxy;
           } else {
               // Otherwise don't use a proxy
               return noProxy;
           }
       }
   
       @Override
       public void connectFailed(URI uri, SocketAddress sa, IOException ioe) {
           System.err.println("Connection to the proxy failed !");
           //throw exception or do some stuff...
       }
   }
   

And set your proxy selector as default proxy selector

    public static void main(String[] args){
     ProxySelector.setDefault(new MyProxySelector());
     //...
    }

I prefer this last mechanism because you can put some logging and see wath Java is doing !

Important remark :

By default, Fiddler captures only traffic coming from web-browsers !! Change that to capture traffic of all processes :
_{(source: comexis.eu)}

The second method should work, however the properties are http.proxyHost and http.proxyPort.