Repeating and Delaying Tasks
The ExecutorService Interface is not the end of Executors. The package provides another specialized interface ScheduledExecutorService which is capable of executing tasks after a certain delay, or...
View ArticleComponents in JPA
We have used components in Hibernate. They provide a very good technique for code reuse. They are also useful if we do now want to represent a particular table as Entity and give them their own...
View ArticleA Set of Enums
Why would I need a collection Of Enums? Consider that we do have a simple enum: public enum Rating { TOP, GOOD, PASSABLE, BAD, POOR, FAIL}Now if I want to get all the values I would call the...
View ArticleEnums as the key in Map
In the previous post we saw how EnumSet is an optimized collection built for use with Enums. While I genuinely struggled to come up with scenarios where I could need a set of enums, I have often come...
View ArticleThe Identity Hash Map
If we work with Maps in java than the keys need to implement equals and hashcode - Right ? Actually Wrong.The reason we need hashcode is all Map implementations that we know of are hash based...
View ArticleRemember Me... Spring Security
Login page in most web applications have a small check-box that says "Remember Me". Nothing new there. The cool part is spring security comes with this functionality ready made.I decided to use the...
View ArticleSpring Security And Authorization
In a Java Web application, where authorization is involved, roles come into the picture. If a request is authorized to access a particular resource, then only will the Servlet Container allow it to...
View ArticleDelegatingFilterProxy And Spring Security
We saw an example of the GenericFilterBean earlier. While the class included some nifty techniques from Spring, it isn't really a part of the Spring Environment. We saw how to get access to the Spring...
View ArticleListening for Session creation
With Spring security session creation and destruction is managed by the framework. Along with the session management code, we often tend to have some other activities performed. For e.g. I would like a...
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The Query Cache
In the previous posts we saw the Hibernate cache system and the Cache modes. We saw the query cache is disabled by default.The first step to getting the Query cache working is in the configuration...
View ArticleUpdate Timestamps Cache in Action
We saw the query cache in our previous post. We also learned about the UpdateTimestampsCache and its impact on query caching. I decided to try and bring it into play in this post.publicstatic void...
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Writing Logs to the Database
With loggers we have something called as an Appender. Simply defined an appender is a component responsible for taking a log request, building the log message in a suitable format and sending it to...
View ArticleHandlers and Interceptors in CXF - Are they related ?
I have been trying out some things in CXF (and also feeling pretty good about it :P ) The other day I needed to modify the message of more than one web service in a common manner. I achieved the same...
View ArticleWhich Log message belongs to which user ?
I created a very simple web application. In it any calls to URLs ending in ".do" reach the below servlet : publicclass SimpleServlet extends HttpServlet {privatestaticfinal Logger logger =...
View ArticleMapping a Filter directly to a Servlet
I guess we have all used filters in our web projects. The common approach that I have followed is specifying the URL patterns to be intercepted by the...
View ArticleSemaphores in Java
What exactly is a semaphore ? To use the wiki definition: In computer science, particularly in operating systems, a semaphore is a variable or abstract data type that is used for controlling access, by...
View ArticleViews in ModelAndView
We had an interesting scenario in our code. It all started out when we had this complex controller that included methods specific to a certain flow. In case of any exception, we used an error handler...
View ArticleWeak References in Java
I have been looking at the java.lang.ref package with a view to understanding references in java. It all started when I tried to understand WeakHashMap and its use in string pools. The various related...
View ArticleSoft References in Java
In the last post I looked at using weak references in my java code. As we saw Java has not just strong and weak but also soft and phantom references.Firstly, what are soft references ?I modified my...
View ArticleReference Queues
In the previous posts we had a look at weak and soft references. The java.lang.ref package also includes a class ReferenceQueue. As per the class documentation: Reference queues, to which registered...
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