Using UriTemplate to change path parameters in a URI

I have been recently working on a client generator in the wadl.java.net project and I was solving a bug where I wanted to change path parameter on a URI. This turned out to be quite easy with existing classes that are part of the Jersey project.

First of all you need a instance of UriTemplate, depending on the very of Jersey this is in a slightly different package - you IDE's automatic import will do the work for you.

  String template = "http://example.com/name/{name}/age/{age}";
  UriTemplate uriTemplate = new UriTemplate(template);

Then you use match(...) to extract them:

  String uri = "http://example.com/name/Bob/age/47";
  Map<String, String> parameters = new HashMap<>();

  // Not this method returns false if the URI doesn't match, ignored
  // for the purposes of the this blog.
  uriTemplate.match(uri, parameters);

Then you can replace the parameters at will and rebuild the URI:

  parameters.put("name","Arnold");

  UriBuilder builder = UriBuilder.fromPath(template);
  URI output = builder.build(parameters);

A little temporal feedback when running tests

I have been working a lot recently with a bunch of test jobs that are intermittently getting stuck. Now it is possible to work out the point where the problem is occurring by looking at the date labels on the LOG output; but it is hard visually to pick these discontinuities out.

In order improve the output in a way that my brain can really quickly parse and identify I thought I would try my hand a bit of simple ASCII animation. I wrote a simple fixture that writes out a line every 1 minute while the test is running, here is a very simple implementation - I am sure there are better ways to do the animation!

import java.util.Timer;
import java.util.TimerTask;
import java.util.concurrent.TimeUnit;

public class TickTockFixture
{
   private Timer timer;
   

   @Before
   public void setUp()
   {
      // Clean out any old timers
      tearDown();
      
      // Start a new timer
      
      timer = new Timer();
      timer.scheduleAtFixedRate(new TimerTask()
      {
         int counter = 0;
         
         @Override
         public void run()
         {
            StringBuilder sb = new StringBuilder(". TickTock : ");
            int animation = counter++ % 10;
            boolean direction = animation < 5;
            int count = direction ?  animation : 9 - animation;
            sb.append("     ", 0, count);
            sb.append(direction ? "/" : "\\");
            sb.append("     ",0, 5-count);
            sb.append(counter);
            sb.append(" min(s)");
            System.err.println(sb);
         }
      }, 0, TimeUnit.MINUTES.toMillis(1));
      
   }

   @After
   public void tearDown()
   {
      if (timer!=null)
      {
         timer.cancel();
         timer = null;
      }
   }
}

So does this help, well take a look at the - made up example - output below and try to spot the section of the log output where everything slows down. It is a lot easier with the ticking output which I think sticks out better because of the animation.

22-Feb-2013 11:54:30 Items in drs, going to tidy up
22-Feb-2013 11:54:40 Removing file:/scratch/gdavison/view_storage/gdavison_lt/oracle/jdeveloper/system12.1.2.0.40.65.92/o.j2ee/drs/Application1/Project1WebApp.war/WEB-INF/weblogic.xml
22-Feb-2013 11:54:40 Removing file:/scratch/gdavison/view_storage/gdavison_lt/oracle/jdeveloper/system12.1.2.0.40.65.92/o.j2ee/drs/Application1/Project1WebApp.war/WEB-INF/web.xml
22-Feb-2013 11:54:40 Removing file:/scratch/gdavison/view_storage/gdavison_lt/oracle/jdeveloper/system12.1.2.0.40.65.92/o.j2ee/drs/Application1/Project1WebApp.war/WEB-INF/classes/project1/Hello.class
22-Feb-2013 11:54:40 Removing file:/scratch/gdavison/view_storage/gdavison_lt/oracle/jdeveloper/system12.1.2.0.40.65.92/o.j2ee/drs/Application1/Project1WebApp.war/WEB-INF/classes/project1/
22-Feb-2013 11:54:40 Removing file:/scratch/gdavison/view_storage/gdavison_lt/oracle/jdeveloper/system12.1.2.0.40.65.92/o.j2ee/drs/Application1/Project1WebApp.war/WEB-INF/classes/
22-Feb-2013 11:54:40 Removing file:/scratch/gdavison/view_storage/gdavison_lt/oracle/jdeveloper/system12.1.2.0.40.65.92/o.j2ee/drs/Application1/Project1WebApp.war/WEB-INF/
22-Feb-2013 11:54:40 Removing file:/scratch/gdavison/view_storage/gdavison_lt/oracle/jdeveloper/system12.1.2.0.40.65.92/o.j2ee/drs/Application1/Project1WebApp.war/
22-Feb-2013 11:54:40 Removing file:/scratch/gdavison/view_storage/gdavison_lt/oracle/jdeveloper/system12.1.2.0.40.65.92/o.j2ee/drs/Application1/.module_marker
22-Feb-2013 11:54:40 Removing file:/scratch/gdavison/view_storage/gdavison_lt/oracle/jdeveloper/system12.1.2.0.40.65.92/o.j2ee/drs/Application1/META-INF/weblogic-application.xml
22-Feb-2013 11:54:40 Removing file:/scratch/gdavison/view_storage/gdavison_lt/oracle/jdeveloper/system12.1.2.0.40.65.92/o.j2ee/drs/Application1/META-INF/application.xml
22-Feb-2013 11:54:40 Removing file:/scratch/gdavison/view_storage/gdavison_lt/oracle/jdeveloper/system12.1.2.0.40.65.92/o.j2ee/drs/Application1/META-INF/
22-Feb-2013 11:54:40 Removing file:/scratch/gdavison/view_storage/gdavison_lt/oracle/jdeveloper/system12.1.2.0.40.65.92/o.j2ee/drs/Application1/.adrs-module.properties
22-Feb-2013 11:54:40 Removing file:/scratch/gdavison/view_storage/gdavison_lt/oracle/jdeveloper/system12.1.2.0.40.65.92/o.j2ee/drs/Application1/
22-Feb-2013 11:54:53 oracle.jdevimpl.webservices.tcpmonitor.config.AnalyzerInstance stop
WARNING: AnalyzerInstance aborting a stop as already appears to be stopped
22-Feb-2013 11:54:53 weblogic.logging.ServerLoggingHandler publish
WARNING: Container weblogic.wsee.jaxws.WLSContainer$BasicContainer@1232e17 doesn't support class com.sun.xml.ws.api.server.Module
22-Feb-2013 11:54:53 weblogic.logging.ServerLoggingHandler publish
WARNING: Container weblogic.wsee.jaxws.WLSContainer$BasicContainer@1232e17 doesn't support class com.sun.xml.ws.api.server.Module
trigger seeding of SecureRandom
. TickTock :  \    9 min(s)
. TickTock : \     10 min(s)
. TickTock : /     11 min(s)
. TickTock :  /    12 min(s)
. TickTock :   /   13 min(s)
22-Feb-2013 11:59:50 done seeding SecureRandom
22-Feb-2013 11:59:53 weblogic.logging.ServerLoggingHandler publish
WARNING: Container weblogic.wsee.jaxws.WLSContainer$BasicContainer@1232e17 doesn't support class com.sun.xml.ws.api.server.Module
22-Feb-2013 12:00:01 Removing file:/scratch/gdavison/view_storage/gdavison_lt/oracle/jdeveloper/system12.1.2.0.40.65.92/o.j2ee/drs/Application1/Project1WebApp.war/WEB-INF/classes/project1/Hello.class
22-Feb-2013 12:00:01 Removing file:/scratch/gdavison/view_storage/gdavison_lt/oracle/jdeveloper/system12.1.2.0.40.65.92/o.j2ee/drs/Application1/Project1WebApp.war/WEB-INF/classes/project1/
22-Feb-2013 12:00:01 Removing file:/scratch/gdavison/view_storage/gdavison_lt/oracle/jdeveloper/system12.1.2.0.40.65.92/o.j2ee/drs/Application1/Project1WebApp.war/WEB-INF/classes/
22-Feb-2013 12:00:01 Removing file:/scratch/gdavison/view_storage/gdavison_lt/oracle/jdeveloper/system12.1.2.0.40.65.92/o.j2ee/drs/Application1/Project1WebApp.war/WEB-INF/
22-Feb-2013 12:00:01 Removing file:/scratch/gdavison/view_storage/gdavison_lt/oracle/jdeveloper/system12.1.2.0.40.65.92/o.j2ee/drs/Application1/Project1WebApp.war/

Proxying a request to localhost in Java

It can be very convenient when developing to server based application to run them using "localhost" in order to maintain consistency between developer machines. This is normally a good idea but there is a small case where this can cause problems.

Consider if you are running a local http proxy on your machine in order to capture your HTTP traffic. (Cough perhaps even the one in JDeveloper I work on). Then you might run into Java bug 6737819. Basically by default JDK 1.6 was hard coded not to send any request to localhost via a proxy which of course was a bit of a pain. Luckily a workaround was put in where you could put the string "~localhost" in your nonProxyHosts entry to turn of this feature:

java -client -classpath classes -Dhttp.proxyHost=localhost -Dhttp.proxyPort=8099 -Dhttp.nonProxyHosts=~localhost -Dhttps.proxyHost=localhost -Dhttps.proxyPort=8099 client.Example

Now moving forward to JDK 1.7 this workaround no longer works; but you need to take care to define nonProxyHosts as an empty string:

java -client -classpath classes -Dhttp.proxyHost=localhost -Dhttp.proxyPort=8099 -Dhttp.nonProxyHosts= -Dhttps.proxyHost=localhost -Dhttps.proxyPort=8099 client.Example

If you define this any anything other than an empty string the DefaultProxySelector though beware because internally it will append / or use the http.nonProxyHosts value from ../jre/lib/net.properties".

Just a minor complication that is not obvious from the published API.