1. Configuration

# Scan packages for Plugin and PluginInterface annotations
regards.plugins.packages-to-scan=fr.cnes.regards.plugins,fr.cnes.regards.plugins.utils

It is possible to add a new package to scan by using the the method addPluginPackage from the PluginService.

2. Autoconfiguration

3. How to

3.1. How to define a new plugin's type

Before creating a new Plugin, it is mandatory to define the corresponding plugin's type. To do so, you need to create a contract, defined by an interface annotated PluginInterface.

@PluginInterface(description = "hello sample plugin interface")
public interface ISamplePlugin {
    String echo(String pMessage);

    int add(int pFirst, int pSecond);
}

3.2. How to define a new Plugin

On a functionnal point of view, defining a new plugin is defining a new way to respect its contract. On a developper point of view, it means creating a new class annotated Plugin that implements an interface annotated PluginInterface

@Plugin(author = "CSSI", description = "Sample plugin test", id = "aSamplePlugin", version = "12345-6789-11")
public class SamplePlugin implements ISamplePlugin {

    @PluginParameter(description = "string parameter", name = "a suffix paramereter")
    private String suffix;

    @PluginParameter(description = "int parameter", name = "a coeff parameter")
    private Integer coef;

    @PluginParameter(description = "boolean parameter", name = "a boolean parameter")
    private Boolean isActive;

    @Override
    public String echo(final String pMessage) {
        final StringBuffer str = new StringBuffer();
        if (this.isActive) {
            str.append(this.getClass().getName() + " -> " + pMessage + " - " + this.suffix);
        } else {
            str.append(this.getClass().getName() + ":is not active");
        }
        return str.toString();
    }

    @Override
    public int add(final int pFist, final int pSecond) {
        final int res = this.coef * (pFist + pSecond);
        LOGGER.info("add result : " + res);
        return res;
    }

    @PluginInit
    private void aInit() {
        LOGGER.info("Init method call : " + this.getClass().getName() + "suffixe:" + this.suffix + "|active:"
                + this.isActive + "|coeff:" + this.coef);
    }

}

As we can see in the above example, SamplePlugin is a Plugin that respect its contract: ISamplePlugin. In this example, SamplePlugin needs parameters to help him respect its contract depending on the context. Those parameters are identified by the PluginParameter annotation which is detailed further below. SamplePlugin also needs to do some stuff while it is initialized, this method is identified by the PluginInit annotation.

To sum up on a more technical point of view:

• the class SamplePlugin is a plugin because it is annotated Plugin
• ISamplePlugin is SamplePlugin contract
• suffix, coef, isActive are plugin parameters given thanks a PluginConfiguration
• any thing that needs to be done before the plugin is fully ready to use and after the plugin parameters has been set must be in a method annotated PluginInit

3.2.1 How to define plugin parameters

PluginParameter annotation can be used to define different type of plugin parameters:

• Primitive types
• Plugins
• Objects
• Collections

The first one is pretty simple to use, just define a plugin parameter as in the example.

The plugins, here we directly provide you with an instance of the plugin wanted.

The objects and collections, they are jsonified so deserialization issues can appaer. In particular, our default JSON library is GSON and GSON does not always handle well deserialization of parametrized objects which is the case of collections, if you encounter issues with this, you can either:

• create a wrapper object
• use the type attribute from the PluginParameter annotation, provide the Class object representing the parameter of your collection and it should be good. For now, we do not handle "complex" collection which parameter is a parametrized object.( ie List<Some<Thing>>)

Note that attributes into objects will only be taken into account if they annotated PluginParameter

3.3 How to use the REGARDS plugin's module

To use a Plugin, it is necessary to create a PluginConfiguration to define the plugin's parameters.

The REGARDS's module plugins provide all the methods to managed the Plugin. It can be done with the PluginService in a REGARDS Java module, or with the REST API provided by the PluginController.

3.4 How to interact with plugins updates

You can be aware of plugin configuration modification by listening via AMQP to PluginConfigurationEvent. PluginConfigurationEvent contains the following attributes:

• pluginConfId: the plugin configuration id
• pluginType: the interface name the configuration is related to
• action: the action at the origin of the event : CREATE, ACTIVATE, DESACTIVATE, DELETE

3.5 How to generate a plugin jar

Plugins aren't deployed with microservices standard code. They are deployed thanks to a jar which will be scanned at the microservice launch. Plugin jars should not embed any of the microservice standard code. To do so, with maven, you can declare framework dependencies with the scope provided. Moreover, our maven configuration does not generate a self suffisent jar by itself, you need to instruct it to. Lets take the CatalogSecurityDelegation plugin example.

CatalogSecurityDelegation is a plugin used by the microservice rs-storage allowing to apply access rights defined in microservice rs-dam throught results returned by rs-catalog. This plugin is defined in the catalog-security-delegation module and within its pom we can find this:

<dependencies>
	<dependency>
		<groupId>fr.cnes.regards.modules.search</groupId>
		<artifactId>search-client</artifactId>
	</dependency>
	<dependency>
		<groupId>fr.cnes.regards.modules.accessrights</groupId>
		<artifactId>accessrights-client</artifactId>
	</dependency>
	<dependency>
		<groupId>fr.cnes.regards.modules.models</groupId>
		<artifactId>models-client</artifactId>
	</dependency>
	<dependency>
		<groupId>fr.cnes.regards.modules.entities</groupId>
		<artifactId>entities-gson</artifactId>
	</dependency>
	<!-- Provided: dependencies that are already included by the microservice -->
	<dependency>
		<groupId>fr.cnes.regards.framework</groupId>
		<artifactId>authentication-regards-starter</artifactId>
		<scope>provided</scope>
	</dependency>
	<dependency>
		<groupId>fr.cnes.regards.framework</groupId>
		<artifactId>feign-regards-starter</artifactId>
		<scope>provided</scope>
	</dependency>
	<dependency>
		<groupId>fr.cnes.regards.modules.storage</groupId>
		<artifactId>storage-dao</artifactId>
		<scope>provided</scope>
	</dependency>
	<!-- Tests -->
	<dependency>
		<groupId>fr.cnes.regards.framework.test</groupId>
		<artifactId>regards-integration-test</artifactId>
		<scope>test</scope>
	</dependency>
	<dependency>
		<groupId>fr.cnes.regards.framework.modules.plugins</groupId>
		<artifactId>plugins-service</artifactId>
		<scope>test</scope>
	</dependency>
	<dependency>
		<groupId>fr.cnes.regards.modules.storage</groupId>
		<artifactId>storage-service</artifactId>
		<scope>test</scope>
	</dependency>
	<dependency>
		<groupId>commons-io</groupId>
		<artifactId>commons-io</artifactId>
		<scope>test</scope>
	</dependency>
</dependencies>

<build>
	<plugins>
		<plugin>
			<groupId>org.apache.maven.plugins</groupId>
			<artifactId>maven-shade-plugin</artifactId>
		</plugin>
	</plugins>
</build>

CatalogSecurityDelegation being a plugin from rs-storage, all dependencies to rs-storage code are provided: storage-dao. Dependencies to the framework, feign-regards-starter and authentication-regards-starter, are also provided as they are being shipped with rs-storage. On the other hand, dependencies to rs-dam and rs-catalog are not provided, respecfully accessright-client, model-client, entities-gson and search-client. To embed these dependencies, we need to tell maven to use the maven-shade-plugin, here we are using our default maven-shade-plugin configuration which is defined in regards-parent pom in the pluginManagement section. In case this configuration is not suited for you, you can simply override it in your pom.

Considering we are using the default configuration, maven build will now generate one more jar: a shaded jar. This is what we called here a plugin jar. It, at least should, contains everything that your plugin needs to work properly within tis microservice.

Once generated, the shaded jar just needs to be put in the right directoy, the one pointed by loader.path Java property.