Implementing issue apache#2167 : Create a new REST API (nav, doc upda…

…te and DELETE metadata element service)

docs/hop-user-manual/modules/ROOT/nav.adoc

@@ -441,6 +441,7 @@ under the License.
 ** xref:hop-server/rest-api.adoc[REST api]
 ** xref:hop-server/web-service.adoc[Web Service]
 * xref:hop-tools/index.adoc[Hop Tools]
+* xref:hop-rest/index.adoc[Hop REST Web Application]
 ** xref:hop-tools/hop-conf/hop-conf.adoc[hop-conf]
 ** xref:hop-tools/hop-encrypt.adoc[hop-encrypt]
 ** xref:hop-tools/hop-gui.adoc[hop-gui]

docs/hop-user-manual/modules/ROOT/pages/hop-rest/index.adoc

@@ -24,12 +24,38 @@ under the License.
 
 == Description
 
-The Hop REST web application is deployed as a WAR file `hop-rest-<version>.war`.  You can put this archive in the `webapps` folder of your favorite server (e.g. Apache Tomcat).  We suggest that you rename it to `hop.war` or that you unzip it in a `hop` folder.
+The Hop REST web application is deployed as a WAR file `hop-rest-<version>.war`.
+You can put this archive in the `webapps` folder of your favorite server (e.g. Apache Tomcat).
+We suggest that you rename it to `hop.war` or that you unzip it in a `hop` folder.
 
 == The base URL
 
 When deployed under a `webapps/hop` folder you will get the services, detailed below, under the base URL of `/hop/api/v1/`.
 
+== Configuration
+
+When the web application starts it will look for an environment variable called `HOP_REST_CONFIG_FOLDER` to determine where it will look for a file called `hop-rest.properties`.
+This file can contain the following properties to determine the configuration of the application:
+
+[cols="1,2"]
+|===
+|Property|Description
+
+|`logLevel`
+|The logging level to use, one of `NOTHING`, `ERROR`, `MINIMAL`,
+`BASIC`, `DETAILED`, `DEBUG`, or `ROWLEVEL`.
+
+|`metadataExportFile`
+|The metadata to use for the web application in the form of a single JSON 'export' file.  Use the GUI tools menu or `sh hop-conf.sh --export-metadata` to export metadata to a single file.
+
+|`environmentName`
+|In case the `projects` plugin is available it will enable this environment and the underlying project (to be configured on the system, point to a configuration with `HOP_CONFIG_FOLDER`) before starting the application.
+
+|`projectName`
+|In case the `projects` plugin is available it will enable this project (to be configured on the system, point to a configuration with `HOP_CONFIG_FOLDER`) before starting the application.
+
+|===
+
 == Metadata services
 
 The metadata services are deployed under sub-path `metadata/`.
@@ -130,6 +156,29 @@ The metadata services are deployed under sub-path `metadata/`.
 
 |===
 
+=== Delete a metadata element
+
+[cols="1,2"]
+|===
+|Type
+|`DELETE`
+
+|Path
+|`metadata/{key}/{name}`
+
+|Arguments
+|`key` : the key of the metadata type to save. `name` : the name of the metadata element to delete.
+
+|Produces
+|`application/json`
+
+|Example call
+|`curl -X DELETE http://localhost:8080/hop/api/v1/metadata/pipeline-run-configuration/Flink/`
+
+|Output
+|`Flink`
+
+|===
 
 == Plugins services
 
@@ -226,8 +275,6 @@ The body to post can contain the following options (see also: the example above)
 * `variables`: a map with variables (or parameters) with their names and values
 * `bodyContent`: this will be set as a variable using the body content variable option in the Web Service metadata.
 
-
-
 == Execution Information Location services
 
 The execution information location services are deployed under sub-path `location/`.

rest/src/main/java/org/apache/hop/rest/v1/resources/MetadataResource.java

@@ -20,6 +20,7 @@
 
 import com.fasterxml.jackson.core.JsonFactory;
 import com.fasterxml.jackson.core.JsonParser;
+import jakarta.ws.rs.DELETE;
 import jakarta.ws.rs.GET;
 import jakarta.ws.rs.POST;
 import jakarta.ws.rs.Path;
@@ -128,4 +129,30 @@ public Response saveElement(@PathParam("key") String key, String metadataJson)
       return getServerError("Error saving element of type " + key, e, true);
     }
   }
+
+  /**
+   * Save a metadata element
+   *
+   * @param key The key of the type of metadata to delete
+   * @param elementName The name of the element to delete
+   * @return
+   * @throws HopException
+   */
+  @DELETE
+  @Path("/{key}/{elementName}")
+  @Produces(MediaType.APPLICATION_JSON)
+  public Response deleteElement(
+      @PathParam("key") String key, @PathParam("elementName") String elementName)
+      throws HopException {
+    try {
+      IHopMetadataProvider provider = hop.getMetadataProvider();
+      Class<IHopMetadata> metadataClass = provider.getMetadataClassForKey(key);
+      IHopMetadataSerializer<IHopMetadata> serializer = provider.getSerializer(metadataClass);
+      serializer.delete(elementName);
+      return Response.ok().entity(elementName).build();
+    } catch (Exception e) {
+      return getServerError(
+          "Error deleting element of type " + key + " with name " + elementName, e, true);
+    }
+  }
 }