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| Original file line number | Diff line number | Diff line change |
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| --- | ||
| title: Fuseki Modules | ||
| --- | ||
|
|
||
| <em>Fuseki modules</em> are a mechanism to include extension code into a Fuseki | ||
| server. Modules are invoked during the process of building a [Fuseki | ||
| Main](./fuseki-main.html) server. The module can modify the server | ||
| configuration, add new functionality, or react to a server being built and | ||
| started. | ||
|
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| This feature was added in Jena version 4.3.0. | ||
|
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| Fuseki Modules are loaded use the JDK | ||
| [ServiceLoader](https://www.baeldung.com/java-spi) by being placing a jar file on the classpath, | ||
| together with any additional dependencies. The service loader looks for files | ||
| `META-INF/services/org.apache.jena.fuseki.main.sys.FusekiModule` in the jar | ||
| file. | ||
| This is often done by placing the file in the development code in | ||
| `src/main/resources/META-INF/services/`). | ||
| The file containing a line with the implementation full class name. If | ||
| [repacking](../notes/jena-repack.html) Fuseki with the maven-shade-plugin, make | ||
| sure the `ServicesResourceTransformer` is used. The module must have a no | ||
| argument constructor. | ||
|
|
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| If using Fuseki as an [embedded server](./fuseki-embedded.html), the module is | ||
| added in code as: | ||
|
|
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| ``` | ||
| FusekiModule module = new MyModule(); | ||
| FusekiModules.add(module); | ||
| ``` | ||
|
|
||
| The method `start` is called when the module is loaded. Custom operations can | ||
| be globally registered at this point (see the [Fuseki | ||
| examples](https://github.com/apache/jena/tree/main/jena-fuseki2/jena-fuseki-main/src/test/java/org/apache/jena/fuseki/main/examples) directory). | ||
|
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| The module lifecycle during creating a Fuseki server is: | ||
|
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| * `configuration` - access and modify the setup. | ||
| This is called after the server has been configured, just before the server is built. | ||
| * `server` - access the built server | ||
| * `serverBeforeStarting` - about to call "server.start()" | ||
| * `serverAfterStarting` - just after calling "server.start()" | ||
| * `serverStopped` - called as the server stop | ||
| (note, this is not always called because a server can simply exit the JVM). | ||
|
|
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| A Fuseki module does not need to implement all these steps, the default for all | ||
| of them is "do nothing". Usually, an extension will only be interested in | ||
| certain stpes, like the configuration and registry information of | ||
| `configuration`. | ||
|
|
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| During the configuration step, the Fuskei configuration file for the server is | ||
| available. If the server is built programmatically without a configuration file, | ||
| this is null. | ||
|
|
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| The configuration file can contain RDF information to build resources (e.g. | ||
| contains assembler descriptions not directly linked to the server). | ||
|
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| There is an [example Fuseki | ||
| Module](https://github.com/apache/jena/blob/main/jena-fuseki2/jena-fuseki-main/src/test/java/org/apache/jena/fuseki/main/examples/ExFusekiMain_3_FusekiModule.java) | ||
| in the Fuseki examples directory. | ||
|
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| `FusekiModule` interface: | ||
|
|
||
| ```java | ||
| /** | ||
| * Module interface for Fuseki. | ||
| * <p> | ||
| * A module is additional code, usually in a separate jar, | ||
| * but can also be part of the application code. | ||
| */ | ||
| public interface FusekiModule extends SubsystemLifecycle { | ||
| /** | ||
| * Unique (within this server) name to identify this module. | ||
| * The default is to generate an UUID. | ||
| */ | ||
| public String name(); | ||
|
|
||
| /** Module loaded */ | ||
| @Override | ||
| public default void start() {} | ||
|
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| // ---- Build cycle | ||
|
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| /** | ||
| * Called at the start of "build" step. The builder has been set according to the | ||
| * configuration. The "configModel" parameter is set if a configuration file was | ||
| * used otherwise it is null. | ||
| */ | ||
| public default void configuration(FusekiServer.Builder builder, DataAccessPointRegistry dapRegistry, Model configModel) {} | ||
|
|
||
| /** | ||
| * Built, not started, about to be returned to the builder caller. | ||
| */ | ||
| public default void server(FusekiServer server) { } | ||
|
|
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| /** | ||
| * Server starting - called just before server.start happens. | ||
| */ | ||
| public default void serverBeforeStarting(FusekiServer server) { } | ||
|
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| /** | ||
| * Server started - called just after server.start happens, and before server | ||
| * .start() returns to the application. | ||
| */ | ||
| public default void serverAfterStarting(FusekiServer server) { } | ||
|
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||
| /** Server stopping. | ||
| * Do not rely on this to clear up external resources. | ||
| * Usually there is no stop phase and the JVM just exits or is killed externally. | ||
| * | ||
| */ | ||
| public default void serverStopped(FusekiServer server) { } | ||
|
|
||
| /** Module unloaded */ | ||
| @Override | ||
| public default void stop() {} | ||
| } | ||
| ``` |