Groovy

Groovy Goodness: Easy Object Creation With Tap Method

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Hubert Klein Ikkink

Groovy 2.5.0 adds the tap method to all objects and changes the method signature of the with method. In a previous post we already learned about the with method. In Groovy 2.5.0 we can add an extra boolean argument to the with method. If the value is false (is default) the with method must return the same value as what the closure invocation returns. If the value is true the object instance on which the with method is invoked is returned. The new tap method is an alias for with(true), so it will always return the object instance.

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Groovy Goodness: Where Is My Class?

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Hubert Klein Ikkink

Groovy 2.5.0 makes it possible to get the location of a Class file by adding the method getLocation to the Class class. If the Class is part of the JDK the location returned is null, but otherwise we get the location of the JAR file or source file (if available) with the Class file.

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Groovy Goodness: Calculate MD5 And SHA Hash Values

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Hubert Klein Ikkink

Groovy adds a lot of useful methods to the String class. Since Groovy 2.5.0 we can even calculate MD5 and SHA hash values using the methods md5 and digest. The md5 method create a hash value using the MD5 algorithm. The digest method accepts the name of the algorithm as value. These values are dependent on the available algorithms on our Java platform. For example the algorithms MD2, MD5, SHA-1, SHA-256, SHA-384 and SHA-512 are by default available.

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Groovy Goodness: Java 8 Stream Enhancements

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Hubert Klein Ikkink

Groovy 2.5.0 adds several methods to make working with Java 8 Streams more Groovy. First of all the methods toList and toSet are added to the Stream class. These methods will convert the stream to a List and Set using the Stream.collect method with Collectors.toList and Collectors.toSet as argument. Furthermore we can convert any array object to a Stream using the stream method that is added to all array objects.

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Groovy Goodness: Using String Values In Ranges

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Hubert Klein Ikkink

We can use ranges in Groovy using an easy syntax where the start and end values of the range are separated by .. for an inclusive range and ..< for an exclusive range as we have seen in a previous post. The values of the range are mostly numbers or enum values. But we can also use String values to define a range. Groovy will check if the String values are the same length and if the values, except for the last character, are the same. Then the natural ordering of the last character of the String value, based on the character’s int value, is used to create the range values.

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Groovy Goodness: Use Range By Method To Set Steps Between Numbers

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Hubert Klein Ikkink

Groovy has support for defining ranges in the language. When we define a range of numbers the steps between the values in the range is 1 by default. We can change the step size using the step method. This method accepts a int value with a new step size. The result is a List object with the values. Since Groovy 2.5.0 the by method is added to ranges with numbers. The by method accepts also decimal numbers and the result of the method is a NumberRange object instead of a List.

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Groovy Goodness: Download Grab Dependencies In IntelliJ IDEA

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Hubert Klein Ikkink

In our Groovy scripts we can use the @Grab annotation. With this annotation we define dependencies for our script and they will be automatically downloaded and added to the class path when we run our script. When we use IntelliJ IDEA we can use a nice intention that is part of the IntelliJ IDEA Groovy support to download the dependencies from our IDE editor. IDEA downloads the dependencies and add it to the project module dependencies. This is useful, because this will also adds code completion for the classes in the dependency to our editor.

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Spocklight: Reuse Variables In Data Providers

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Hubert Klein Ikkink

Writing a parameterized specification in Spock is easy. We need to add the where: block and use data providers to specify different values. For each set of values from the data providers our specifications is run, so we can test for example very effectively multiple input arguments for a method and the expected outcome. A data provider can be anything that implements the Iterable interface. Spock also adds support for a data table. In the data table we define columns for each variable and in the rows values for each variable. Since Spock 1.1 we can reuse the value of the variables inside the data provider or data table. The value of the variable can only be reused in variables that are defined after the variable we want to reuse is defined.

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Spocklight: Group Assertions With verifyAll

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Hubert Klein Ikkink

We all know writing tests or specifications with Spock is fun. We can run our specifications and when one of our assertions in a feature method invalid, the feature method is marked as failed. If we have more than one assertion in our feature method, only the first assertion that fails is returned as an error. Any other assertion after a failing assertion are not checked. To let Spock execute all assertions and return all failing assertions at once we must use the verifyAll method. We pass a closure with all our assertions to the method. All assertions will be checked when use the verifyAll and if one or more of the assertions is invalid the feature method will fail.

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Ratpacked: Assert No Exceptions Are Thrown With RequestFixture

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Hubert Klein Ikkink

Writing unit tests for our handlers in Ratpack is easy with RequestFixture. We invoke the handle method and use a Handler or Chain we want to test as argument. We can provide extra details on the fixture instance with a second argument, for example adding objects to the registry or setting the request method. The handle method returns a HandlingResult object. This object has the method exception that we can use to see if an exception occurred in our code under test. The method throws a HandlerExceptionNotThrownException if the expected exception doesn’t occur.

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Groovy Goodness: Redirecting Print Methods In Scripts

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Hubert Klein Ikkink

To run external Groovy scripts in our Java or Groovy application is easy to do. For example we can use GroovyShell to evaluate Groovy code in our applications. If our script contains print methods like println we can redirect the output of these methods. The Script class, which is a base class to run script code, has an implementation for the print, printf and println methods. The implementation of the method is to look for a property out, either as part of a Script subclass or in the binding added to a Script class. If the property out is available than all calls to print, printf and println methods are delegated to the object assigned to the out property. When we use a PrintWriter instance we have such an object, but we could also write our own class with an implementation for the print methods. Without an assignment to the out property the fallback is to print on System.out.

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