Welcome to Geoff Hayward's Weblog

JSP: Embed the Application Root for JavaScript
02 May 2018

There are several ways to embed the root of a deployed application into a JSP page for JavaScript to phone home with. However in some server environments some methods work better than others. This short post explains the problem that load balancing can course to the Request object and gives a simple workaround for finding the application's root from its JavaScript.

The most common suggestion for embedding an application's seems to be the following. However, the following does not work when a load balancer forwards HTTPS request to the application's server via HTTP (a.k.a. SSL Off Loading).

function root() { // Bad example
       return "${pageContext.request.scheme}://${pageContext.request.serverName}:${pageContext.request.serverPort}${pageContext.request.contextPath}";}";
}

When the application server receives a proxied request via HTTP the JSP will embed the HTTP scheme along with the application server's configured HTTP port.

The simple workaround is to ask JavaScript for its origin and append only the context path from the JSP. Here is a working example:

function root() { // Good example
       return window.location.origin + "${pageContext.request.contextPath}";
}

Hope this helps.

Docker: Delete Containers and Images Using GREP
20 April 2018

Here is a handy way of deleting Docker containers using GREP.

docker rm -f $(docker ps | grep <grep term> | awk ‘{print $1}’)

And here is a handy way of deleting Docker images using GREP.

docker rmi -f $(docker images | grep <grep term> | awk ‘{print $3}’)

Finished my MSc dissertation
10 April 2018

I just wanted to say, I finished my MSc dissertation and have handed it in for marking. It's time to catch up with life.

I might get time to post to my blog now.

Java JUnit: Reset a singleton
28 February 2018

Java singleton's are hard to unit test because the state of the singleton is altered as each test runs. But for testing sake you can reset the singleton's state use reflection. Here is an example that worked for me.

@Before
public void setup() throws NoSuchFieldException, IllegalAccessException {
        Field instance = RemoteMessageTranslation.class.getDeclaredField("set");
        instance.setAccessible(true);
        instance.setBoolean(null, false);
}

I hope this helps

Java Regex Pattern Within a String
01 February 2018

Here is how to find a Java regex pattern within a string.

@Test
public void stringContainsRegexPattern() {
	assertTrue(Pattern.compile("pattern(?:\\s[a-z]+){2}\\setc\\.").matcher("Here is the pattern and that etc.").find());
}