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Author Archives: Michael Scharhag

Michael Scharhag
Michael Scharhag is a Java Developer, Blogger and technology enthusiast. Particularly interested in Java related technologies including Java EE, Spring, Groovy and Grails.

Java can finally join strings

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I am sure you were in a situation in which you wanted to join multiple strings. If you were using a programming language other than Java you probably used the join() function provided by the programming language. If you were using Java you could not do this. There was no join() method. The Java Standard Class Library provided you tools ...

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How you can benefit from Groovy Shell

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This is a post about the Groovy Shell and how it can help you with your daily work (as long as you are working as software developer). You can benefit from the Groovy Shell no matter what programming language(s) or technologies you are using. The only real requirement is that you are able to write (and read) small pieces of ...

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A deeper look into the Java 8 Date and Time API

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Within this post we will have a deeper look into the new Date/Time API we get with Java 8 ( JSR 310). Please note that this post is mainly driven by code examples that show the new API functionality. I think the examples are self-explanatory so I did not spent much time writing text around them :-) Let’s get started! ...

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Java 8 Type Annotations

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Lambda expressions are by far the most discussed and promoted feature of Java 8. While I agree that Lambdas are a large improvement I think that some other Java 8 feature go a bit short because of the Lambda hype. In this post I want to show a number of examples from another nice Java 8 feature: Type Annotations. Type ...

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Java: Exception translation with AspectJ

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Within this blog post I describe how you can use AspectJ to automatically translate one type of exception to another. The problem Sometimes we are in situations where we have to convert an exception (often thrown by a third-party library) to another type of exception. Assume you are using a persistence framework like hibernate and you do not want to ...

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Using database views in Grails

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This post is a quick explanation on how to use database views in Grails. For an introduction I tried to summarize what database views are. However, I noticed I cannot describe it better than it is already done on Wikipedia. Therefore I will just quote the Wikipedia summary of View (SQL) here:           In database theory, ...

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Grails: Using Hibernate Filters

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The Grails Hibernate Filters plugin makes it possible to use Hibernate Filters with GORM. Hibernate Filters provide additional restriction rules that can be applied to classes and collections. The Hibernate Filters plugin makes it possible to use this functionality with GORM inside Grails applications. Let’s look at an example to see how filters can help us. Assume we have the ...

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Java: Using the specification pattern with JPA

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This article is an introduction to using the specification pattern in Java. We also will see how we can combine classic specifications with JPA Criteria queries to retrieve objects from a relational database. Within this post we will use the following Poll class as an example entity for creating specifications. It represents a poll that has a start and end ...

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Java: Moving conditions into Message files

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The Java classes ResourceBundle and MessageFormat provide a nice toolset for resolving localized messages inside Java applications. This post provides a small example on how you can move simple message related conditions from your Java code into message files using ChoiceFormat. If you already know ChoiceFormat I do not think you will learn anything new in this post. However, in ...

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Two things to remember when using Java RMI

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This is a short blog post about two common pitfalls you should be aware of when using Java RMI. Setting java.rmi.server.hostname If you are getting strange Connection refused to host: error messages on the RMI client and you are sure the connection should work (you double checked all the standard things like network configuration etc.) the RMI system property java.rmi.server.hostname is ...

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