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Step 2: Setup the build system: JDK and Gradle

Ensure that JDK 20 is available to IntelliJ

Ensure you have a Java 20 SDK configured by navigating to File > Project Structure… > Platform Settings > SDKs.

Plattform Settings - SDKs
JDKs 11, 14, and 15 shown in available SDKs. JDK 20 is missing.

If there is another JDK than JDK 20 selected, click on the plus button and choose “Download JDK…”

Plattform Settings - SDKs - plus button - Download JDK...
Download JDK…

Select JDK version 20 and then Eclipse Temurin (showing JDK 18 as example).

Download Eclipse Temurin
Example for JDK 18 - Choose Eclipse Temurin

After clicking “Download”, IntelliJ installs Eclipse Temurin:

IntelliJ installs Eclipse Temurin
IntelliJ installs Eclipse Temurin

Navigate to Project Settings > Project and ensure that the projects’ SDK is Java 20

Project SDK is JDK 18
Project SDK is pinned to the downloaded SDK (showing JDK 18 as example)

Click “OK” to store the changes.

Configure the Build System

Navigate to File > Settings… > Build, Execution, Deployment > Build Tools > Gradle and select the “Project SDK” as the Gradle JVM at the bottom. If that does not exist, just select a JDK 20.

Gradle JVM is project SDK
Gradle JVM is project SDK (showing JDK 18 as example)

To prepare IntelliJ’s build system additional steps are required:

Navigate to Build, Execution, Deployment > Compiler > Java Compiler, and under “Override compiler parameters per-module”, click add ([+]) and choose JabRef.main:

Gradle JVM is project SDK
Choose JabRef.main

Then double click inside the cell “Compilation options” and enter following parameters:


Press Enter to have the value really stored. Otherwise, it seems like the setting is stored, but it is not there if you re-open this preference dialog. Then click on “Apply” to store the setting.

Overridden compiler parameters
Resulting settings for module JabRef.main

If this step is omited, you will get: java: package com.sun.javafx.scene.control is not visible (package com.sun.javafx.scene.control is declared in module javafx.controls, which does not export it to module org.jabref).

Enable annotation processors by navigating to Build, Execution, Deployment > Compiler > Annotation processors and check “Enable annotation processing”

Enable annotation processing
Enabled annotation processing

Using Gradle from within IntelliJ IDEA

Ensuring JabRef builds with Gradle should always the first step because, e.g. it generates additional sources that are required for compiling the code.

Open the Gradle Tool Window with the small button that can usually be found on the right side of IDEA or navigate to View > Tool Windows > Gradle. In the Gradle Tool Window, press the “Reload All Gradle Projects” button to ensure that all settings are up-to-date with the setting changes.

Highlighted reload button
Reload of Gradle project

After that, you can use the Gradle Tool Window to build all parts JabRef and run it. To do so, expand the JabRef project in the Gradle Tool Window and navigate to Tasks. From there, you can build and run JabRef by double-clicking JabRef > Tasks > application > run.

JabRef > Tasks > application > run
JabRef > Tasks > application > run

The Gradle run window opens, shows compilation and then the output of JabRef. The spinner will run as long as JabRef is opened.

Gradle run window
Gradle run Window

You can close JabRef again.

After that a new entry called “jabref [run]” appears in the run configurations. Now you can also select “jabref [run]” and either run or debug the application from within IntelliJ.

You can run any other development task in a similar way.

Using IntelliJ’s internal build system for tests

In File > Settings… > Build, Execution, Deployment > Build Tools > Gradle the setting “Run tests using:” is set to “IntelliJ IDEA”.

IntelliJ setting: Run tests using IntelliJ"
IntelliJ setting: Run tests using IntelliJ

In case there are difficulties later, this is the place to switch back to gradle.

Click “OK” to close the preference dialog.

In the menubar, select Build > Rebuild project.

IntelliJ now compiles JabRef. This should happen without any error.

Now you can use IntelliJ IDEA’s internal build system by using Build > Build Project.

Final build system checks (optional)

To run an example test from IntelliJ, we let IntelliJ create a launch configuration:

Locate the class BibEntryTest: Press Ctrl+N. Then, the “Search for classes dialog” pops up. Enter bibenrytest. Now, BibEntryTest should appear first:

IntelliJ search for class "BibEntryTest"
IntelliJ search for class “BibEntryTest”

Press Enter to jump to that class.

Hover on the green play button on testDefaultConstructor:

However on green play button
However on green play button

Then, click on it. A popup menu opens. Choose the first entry “Run testDefaultConstructor” and click on it.

Popup menu - Run testDefaultConstructor
Run testDefaultConstructor

Then, the single test starts.

You also have an entry in the Launch configurations to directly launch the test. You can also click on the debug symbol next to it to enable stopping at breakpoints.

Launch menu contains BibEntry test case
Launch menu contains BibEntry test case

The tests are green after the run. You can also use the play button there to re-execute the tests. A right-click on “BibEntryTests” enables to start the debugger.

Run window for the BibEntry test case
Run window for the BibEntry test case