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Comparing JARs with Groovy

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It can sometimes be useful to compare the contents of two JARs. In this blog post, I demonstrate a Groovy script that acts like a simple “diff” tool for comparing two JAR files. The Groovy script shown here, jarDiff.groovy, can undoubtedly be improved upon, but does perform what I wanted it to. The script compare two provided JARs in the ...

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We Don’t Need That Documentation

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“We must write more documentation”. Have you heard that? I have, many times in many companies. Most people feel guilty for not writing documentation and agree. I don’t. There are two types of documentation – in-code and external. In-code documentation consists of javadoc (or whatever language/tool you are using to describe what classes and their methods do) and comments. External ...

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Spring MVC Custom Validation Annotations

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Last tutorial, I showed how to validate a form using annotations. This works great for simple validations, but eventually, you’ll need to validate some custom rules that aren’t available in the out-of-the-box annotations. For example, what if you need to validate that a user is over 21 years old, calculated based off their input birthdate, or, maybe you need to ...

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Auditing a Spring MVC Webapp with AspectJ. Part 2

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Now, this is the blog you want to read if you’re interested in creating a Spring MVC Webapp that uses Aspect Oriented Programming (AOP) in the form of Aspectj’s @Aspect and @Before annotations to audit a user’s visit to a screen. As I said in my last blog auditing a user’s visits to a screen is one of those few ...

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su and sudo in Spring Security applications

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Long time ago I worked on a project that had a quite powerful feature. There were two roles: user and supervisor. Supervisor could change any document in the system in any way while users were much more limited to workflow constraints. When a normal user had some issue with the document currently being edited and stored in HTTP session, supervisor ...

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Macro lifecycle in Clojure

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If you still struggle to understand what are macros in Clojure and why are they so useful, I will guide you through another example today. We will learn when macros are recognized, evaluated, expanded and executed. I believe the most important concept is their similarity to normal functions. As I described last time, macros are ordinary functions but executed at ...

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Micro jitter, busy waiting and binding CPUs

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Performance profiling a new machine When I work on a new machine, I like to get an understanding of it’s limitations.  In this post I am looking at the jitter on the machine and the impact of busy waiting for a new PC I built this weekend. The specs for the machine are interesting but not the purpose of the ...

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Java EE EJB Interceptors tutorial and example

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In this example we are going to see how to use Interceptors in an EJB and test it using a simple Web Application. 1. Introduction Interceptors are used, as the name suggests, when you want to intercept calls to EJB methods. If you declare an Interceptor for a Bean, every time a method of that Bean is invoked, it will ...

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LINQ and Java

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LINQ has been quite a successful, but also controversial addition to the .NET ecosystem. Many people are looking for a comparable solution in the Java world. To better understand what a comparable solution could be, let’s have a look at the main problem that LINQ solves: Query languages are often declarative programming languages with many keywords. They offer few control-flow ...

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Apache Server and JMeter debugging

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I had been using JMeter to generate load for my production server to test my application. The test-plan has 13+ HTTP sampler to make different request and one Regular Expression extractor to extract some value from the response. This value was used in consecutive HTTP Sampler. This test case simple and straight forward. Initially I used 200 JMeter threads to ...

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