Eclipse IDE Setup

The use of Maven submodules to build a Multi Release JAR was motivated by its compatibility with popular IDEs. There are two configuration properties to be aware of when configuring your local development environment:

1. Java compiler versions
2. Compiler arguments for JPMS

Java compiler versions

Settings are usually synchronized with Maven Toolchain configuration, otherwise the Java version for a Maven module should be set as follows:

Maven submodule	JDK
datasketches-memory	8
datasketches-memory-java8	8
datasketches-memory-java11	11

Compiler arguments for JPMS

In order to compile Maven modules in Java versions 11 and above, it is necessary to provide the following arguments to the compiler. These are usually synchronized with the pom.xml configuration:

    <compilerArgs>
        <arg>--add-exports</arg>
        <arg>java.base/jdk.internal.ref=org.apache.datasketches.memory</arg>
    </compilerArgs>

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Running Datasketches-Memory in Eclipse

Note that the following configuration was verified using Eclipse Version: 2020-12 (4.18.0)

The eclipse maven plugin

The Eclipse Maven plugin is used to generate Eclipse IDE files. In order to run the eclipse plugin use:

$ mvn clean eclipse:eclipse -DskipTests=true

More information about using the eclipse plugin with multi-module Maven builds can be found in the Maven Multiple Module Projects document.

Please note that this plugin is retired and no longer maintained!

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Importing the project into eclipse

From the Package Explorer View:

• Right-click on a blank space in the view
• Select Import/Maven/Existing Maven Projects
• Select Next, and browse to the project directory
• Click Open

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Setting compiler arguments for JPMS

Although these should be set automatically, the Eclipse IDE does not currently configure these settings according to the pom.xml - see this Eclipse Bug. Ensure that the required JPMS arguments are set for the compiler (Java 11 only).

• First, right-click on the datasketches-memory-java11 project, and select Properties/Java Build Path.
• Next, open the Module Dependencies tab and select the java.base package.
• Click on Configured details, followed by Expose package.
• In the dialog box, enter package: jdk.internal.ref, and org.apache.datasketches.memory as the target module.
• Ensure that the exports checkbox is selected.

• Finally, click Apply and Close:

Note: These arguments need only be supplied for datasketches-memory-java11.

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Setting Java compiler settings

This should be set automatically by the IDE. However, you may ensure that the correct Java compliance level is set for each module by using the Eclipse Java Compiler dialog.

• Open the Java Compiler dialog, and ensure Enable project specific settings is checked:

You might need to verify this for each module, making sure the correct compliance level is used:

• datasketches-memory-java11 should use level 11 compliance.
• datasketches-memory-java8 should use level 1.8 compliance.

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Setting JRE library versions

This should be set automatically by the IDE. However, you may ensure that the correct JRE is used for each module by using the Eclipse Java Build Path dialog.

• First, open the project properties dialog for the datasketches-memory-java11 project, and click on Java Build Path.
• Next, open the Libraries tab and select the JRE System Library under Modulepath.
• Click Edit and ensure that the Execution Environment is selected and set to Java 11:

• Lastly, for all other modules, verify that the Execution Environment is selected and set to the Java 8 JRE:

Running unit tests

• Under the datasketches-memory-java8 module, right-click on the src/test/java directory.
• Select Run-As / TestNG Test
• It should open a new window and run over 400 tests without error.