Getting Started

This section will walk through the croquet-example, a simple CRM site to show off the various features of Croquet. For more detailed information, see the User Manual section.

Croquet Dependency

The easiest way to get started with Croquet is to use Maven and simply add the croquet-core dependency. It can be added to your project like this:

That’s it! Croquet will bring in the proper versions of Wicket, Jetty, Hibernate, Guice, and a few other common libraries.


Croquet is configured through a YAML file and via code. This may seem confusing at first as there are two places to look for configurations; however, we felt that some configurations are just easier (for example when needing to specify full classpaths) through code. Also, Guice is inherently configured via code, and we didn’t want to reinvent the wheel by making Guice configurable via a file.

Why have a file at all then? Simply because when you’re changing environments (from staging to production for example), it’s very easy to change the file Croquet runs with. So we’ve put those things you might want to change from environment to environment (database, log level, etc) into the YAML file, and those things that aren’t likely to change (home page, Guice modules) are configured via code.

Configuration File

There are 3 main sections to the YAML file: top-level, db, logging. The top-level section configures Wicket and Jetty. The db section configures Hibernate. Finally, the logging section configures logback.

You can provide custom settings in the configuration file by specifying a settings class. You can see this in the croquet-example‘s application.yml file:

# custom settings, see
current-user: Joe User
mail-user: test-user
mail-pass: test-pass

    - style.css
    - style-2.css
    - //

    - script.js
    - script-2.js
    - //

port: 8080


development: true

    # persistence-unit: croquet-example # uncomment this, and comment the lines below to use a persistence.xml file
    driver: org.hsqldb.jdbcDriver
    jdbc_url: jdbc:hsqldb:file:db/crm
    user: SA

        "com.metrink.croquet": DEBUG
        "org.hibernate": WARN
        enabled: true
        currentLogFilename: ./croquet.log
        archivedLogFilenamePattern: ./croquet-%d.log.gz


The rest of Croquet is configured via code using the CroquetBuilder class. This class uses the Builder design pattern to construct a Croquet object. The Croquet object has additional methods to configure how Croquet runs. Why the two-step building/configuring? Because we want the user to have access to their custom settings from the configuration file. The CroquetBuilder class parses the configuration file returning a Croquet object that can provide the custom settings. This is often useful when constructing Guice modules or Managed modules (see below).

The croquet-example‘s Main class shows how the CroquetBuilder class is used to configure a Croquet object:

final Croquet<CrmSettings> croquet =
        CroquetBuilder.create(CrmSettings.class, args)
                      .addPageMount("/people", PeoplePage.class)
                      .addPageMount("/company", CompanyPage.class)
                      .addHealthCheck("/statuscheck", HealthCheck.class)

Adding Modules

Croquet supports two types of modules: Guice modules and ManagedModules. These modules are added to the Croquet instance created by the CroquetBuilder. You can access any custom settings via the Croquet.getSettings() method. This is often useful when creating modules.

Guice Modules

Guice modules are used to configure additional bindings in Guice. Any modules that extends Module can be added to Croquet via the addGuiceModule() method. The example adds 1 binding and creates 2 AssistedInject factories. For more information on creating Guice modules, see the Guice documentation.

protected void configure() {
    bind(String.class).annotatedWith(Names.named("current-user")).toInstance("Metrink User");

    install(new FactoryModuleBuilder().build(PeopleDataProviderFactory.class));
    install(new FactoryModuleBuilder().build(new TypeLiteral<GenericDataProviderFactory<CompanyBean>>(){}));

Managed Modules

Managed modules are classes that extend the ManagedModule interface provided by Croquet. These classes are started after Jetty has started and are shutdown after Jetty has shutdown. These modules are useful for dependencies (an HTTP Client for example) your application might have that require startup and shutdown.

If there are managed modules that you find yourself implementing (or copying) over-and-over again, create a pull request with your code and we’ll try to get it into the next release of Croquet.

The Croquet class only adds Managed modules via the public void addManagedModule(final Class<? extends ManagedModule> module) method. You might be wondering how to pass settings into a Managed when the method only accepts a Class<? extends ManagedModule> parameter. The answer is via a Guice module. You should bind any settings that need to be passed into a Managed module in your Guice module. You can use the @Named annotation to aid in disambiguating common types like strings. Or you can simply inject your entire custom settings class:

public EmailModule(final CrmSettings settings) {
    this.settings = settings;

Building Your Croquet Application

The easiest way to build a Croquet application is by bundling everything together into one big JAR file. This is most easily done with the Maven Shade plugin. The croquet-example‘s pom.xml file show how to create such a JAR file:


You might find you need to add transformers to the shade configuration to remove any signatures from packages.

There can be issues with using the Maven Shade plugin when multiple packages pull in different versions of common dependencies. One way around this is to use the exclude directive in your pom. Another avenue is to use the Maven Dependency plugin in concert with the Maven JAR plugin. This is a bit more tricky, so try and get Maven Shade working when possible.

Running Your Croquet Application

Running a Croquet application that is bundled into a single JAR is as easy as:

java -jar croquet-example.jar application.yml

Because everything is packaged into a single JAR, you do not need to fuss with classpaths. The desired configuration file is passed as a command line argument to your Croquet application. This makes it very easy to change between configurations; simply pass a different YAML file.

When your Croquet application is up and running, it will drop a PID file (if specified in code or config file) to let you know everything is working. This is useful for tools like Monit to ensure your process is always running.