Maven best practice

littlegrid is available from Maven central, simply add the following dependency to your POM file - littlegrid should be set to test scope.


littlegrid doesn’t have any dependencies on other frameworks, it simply requires a version of Coherence to be available in your project.


littlegrid is used on a lot of Maven projects and so the below is a quick list of best practice to help you get going easily and quickly

  1. Ensure littlegrid is set to test scope.

  2. Create a separate Maven module for the functional/integration tests (basically those using littlegrid to start a Coherence cluster). This module will typically have your tests for things like: entry processors, cache stores, triggers, backing map access etc.

    Typical names for this module might be something like: my-project-datagrid-cluster-integration-tests

  3. Configure Surefire to allocate more memory to your functional/integration tests and allow for class-reloading (littlegrid loads classes into separate class-loaders for each Coherence cluster members).


this Surefire configuration is only required for your littlegrid functional/integration test module(s).

                    Set the forkMode to 'once' if you have many tests and you intend
                    to use the reusable cluster member group functionality that
                    littlegrid can provide.

                    Set the forkMode to 'always' if you're just getting started -
                    after you've got littlegrid embedded into your build, then look
                    to change this to 'once' and also use the littlegrid
                    reusable cluster member group functionality.
                <!-- <forkMode>always</forkMode> -->
                <argLine>-Xmx768m -Xms768m -XX:MaxPermSize=384m</argLine>

  1. Use a common way to start and shutdown littlegrid, typically littlegrid and your Coherence cluster controlled by littlegrid are started within something like JUnit’s @BeforeClass and typically shutdown in an @AfterClass


Often a base class is used which performs the starting up and shutting down of littlegrid, typical examples might be a base class for storage-disabled client tests using one or two storage-enabled cache servers. Other examples are an Extend client, connecting to an Extend proxy and one or more cache servers.

  1. Most projects can utilise littlegrid’s reusable cluster member group - this basically tells littlegrid to try and use the same established cluster for all your tests, this Reusable cluster member group avoids the delay of starting up and shutting down the Coherence cluster members for each test class

  2. If your project also uses Extend, then it is recommended that a separate Maven module is introduced just for the Extend tests.

    Typical names for this module might be something like: my-project-datagrid-remote-client-integration-tests

Again, configure Surefire for this module to use specific memory settings (see above) and also to use the reusable cluster member group.

So, here’s how the project might look:


Actual code for entry processors, cache stores etc. Any standard unit tests (i.e. not integration tests).


littlegrid integration tests for entry processors, cache stores etc. typically as storage-disabled client and using one or more storage-enabled members.


Actual code for Extend remote client, perhaps Spring configuration/wrapper around Coherence etc.


littlegrid integration tests connecting as an Extend client with one or more storage-enabled members and one or more Extend proxies.