Spicy Spring: Customize error JSON response with ErrorAttributes

The default JSON error body of Spring Boot can be customized or extended by defining our own ErrorAttributes implementation. In Spring Boot we get an error response JSON format for free. Any thrown Exception is automatically translated to this JSON format and returned with a corresponding HTTP status.

Default implementation

As soon as we throw an Exception in a @RequestMapping annotated method of a @Controller, the thrown Exception is translated to a HTTP status and a JSON error body.

The default JSON error body looks like:

Write your own ErrorAttributes implementation

What if we want extra attributes in this JSON error body?

Just define an implementation for ErrorAttributes and register it as a Spring @Component. The following example will result in a customized JSON error response body with the cause of the exception included.

Our resulting body will now look like:

Happy developing!

Groovy Goodness: Make Class Cloneable With @AutoClone

Groovy has many AST annotations that add code to our class (the Abstract Syntax Tree – AST) before it is compiled. So the compiled class file contains the code added by the AST annotation. With the @AutoClone annotation a clone method is added and the class implements the Cloneable interface. We have different strategies to choose from to support cloning for our class.

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Spicy Spring: Creating a Fully Executable Jar

With a Spring (Boot/Cloud) application you can create a fully executable JAR, where the jar can be run from the command-line by just calling ./my-own-jar-0.0.1.jar.
My colleague Mr. Haki wrote a nice blog about creating a fully executable JAR for Grails.

Together with the famous one-liner of Josh Long in mind: “Make JAR not WAR!”, create a JAR whenever you develop a Spring Boot/Cloud application. As described in Mr. Haki’s blog, it is very easy to make our Spring application executable:

Maven configuration

Gradle configuration

You can find the description in the Spring Reference guide.

Happy Developing! And remember, “Make JAR not WAR!”

Grails Goodness: Creating A Fully Executable Jar

With Grails 3 we can create a so-called fat jar or war file. To run our application we only have to use java -jar followed by our archive file name and the application starts. Another option is to create a fully executable jar or war file, which adds a shell script in front of the jar or war file so we can immediately run the jar or war file. We don’t have to use java -jar anymore to run our Grails application. The fully executable JAR file can only run on Unix-like systems and it is ready to be used as service using init.d or systemd.

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Generic Code Formatting with EditorConfig example

I love code. I take care of my code and I like my code to be formatted nicely. No matter if I’m on Eclipse, Netbeans or IntelliJ, I want my code to be formatted the same.

Nowadays we have EditorConfig. In the source code we can place a file .editorconfig with formatting instructions. These instructions can be read by many Tools like Eclipse, Netbeans, IntelliJ and VisualStudio. If we create an .editorconfig file with formatting instructions, these rules are automatically applied.


An example of an .editorconfig file looks like:

As you see you can define specific formatting rules for different file types.

Happy coding and formatting!

Grails Goodness: Add Git Commit Information To Info Endpoint

We know Grails 3 is based on Spring Boot. This means we can use Spring Boot features in our Grails application. For example a default Grails application has a dependency on Spring Boot Actuator, which means we have a /info endpoint when we start the application. We add the Git commit id and branch to the /info endpoint so we can see which Git commit was used to create the running application.

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Ratpacked: Use TestHttpClient For External HTTP Services

Ratpack has a very useful class: TestHttpClient. This is a blocking HTTP client that we normally use for testing our Ratpack applications. For example we use MainClassApplicationUnderTest or GroovyRatpackMainApplicationUnderTest in a test and invoke the getHttpClient method to get an instance of TestHttpClient. The class has a lot of useful methods to make HTTP requests with a nice DSL. TestHttpClient is also very useful as a standalone HTTP client in other applications.

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