Chapter 22. Process Server capabilities and extensions

The capabilities in Process Server are determined by plug-in extensions that you can enable, disable, or further extend to meet your business needs. Process Server supports the following default capabilities and extensions:

Table 22.1. Process Server capabilities and extensions

Capability nameExtension nameDescription

KieServer

KieServer

Provides the core capabilities of Process Server, such as creating and disposing KIE containers on your server instance

BRM

Drools

Provides the Business Rule Management (BRM) capabilities, such as inserting facts and executing business rules

BPM

jBPM

Provides the Business Process Management (BPM) capabilities, such as managing user tasks and executing business processes

BPM-UI

jBPM-UI

Provides additional user-interface capabilities related to business processes, such as rendering XML forms and SVG images in process diagrams

CaseMgmt

Case-Mgmt

Provides the case management capabilities for business processes, such as managing case definitions and milestones

BRP

OptaPlanner

Provides the Business Resource Planning (BRP) capabilities, such as implementing solvers

DMN

DMN

Provides the Decision Model and Notation (DMN) capabilities, such as managing DMN data types and executing DMN models

Swagger

Swagger

Provides the Swagger web-interface capabilities for interacting with the Process Server REST API

To view the supported extensions of a running Process Server instance, send a GET request to the following REST API endpoint and review the XML or JSON server response:

Base URL for GET request for Process Server information

http://SERVER:PORT/kie-server/services/rest/server

Example JSON response with Process Server information

{
  "type": "SUCCESS",
  "msg": "Kie Server info",
  "result": {
    "kie-server-info": {
      "id": "test-kie-server",
      "version": "7.26.0.20190818-050814",
      "name": "test-kie-server",
      "location": "http://localhost:8080/kie-server/services/rest/server",
      "capabilities": [
        "KieServer",
        "BRM",
        "BPM",
        "CaseMgmt",
        "BPM-UI",
        "BRP",
        "DMN",
        "Swagger"
      ],
      "messages": [
        {
          "severity": "INFO",
          "timestamp": {
            "java.util.Date": 1566169865791
          },
          "content": [
            "Server KieServerInfo{serverId='test-kie-server', version='7.26.0.20190818-050814', name='test-kie-server', location='http:/localhost:8080/kie-server/services/rest/server', capabilities=[KieServer, BRM, BPM, CaseMgmt, BPM-UI, BRP, DMN, Swagger]', messages=null', mode=DEVELOPMENT}started successfully at Sun Aug 18 23:11:05 UTC 2019"
          ]
        }
      ],
      "mode": "DEVELOPMENT"
    }
  }
}

To enable or disable Process Server extensions, configure the related *.server.ext.disabled Process Server system property. For example, to disable the BRM capability, set the system property org.drools.server.ext.disabled=true. For all Process Server system properties, see Chapter 21, Process Server system properties.

By default, Process Server extensions are exposed through REST or JMS data transports and use predefined client APIs. You can extend existing Process Server capabilities with additional REST endpoints, extend supported transport methods beyond REST or JMS, or extend functionality in the Process Server client.

This flexibility in Process Server functionality enables you to adapt your Process Server instances to your business needs, instead of adapting your business needs to the default Process Server capabilities.

Important

If you extend Process Server functionality, Red Hat does not support the custom code that you use as part of your custom implementations and extensions.

22.1. Extending an existing Process Server capability with a custom REST API endpoint

The Process Server REST API enables you to interact with your KIE containers and business assets (such as business rules, processes, and solvers) in Red Hat Process Automation Manager without using the Business Central user interface. The available REST endpoints are determined by the capabilities enabled in your Process Server system properties (for example, org.drools.server.ext.disabled=false for the BRM capability). You can extend an existing Process Server capability with a custom REST API endpoint to further adapt the Process Server REST API to your business needs.

As an example, this procedure extends the Drools Process Server extension (for the BRM capability) with the following custom REST API endpoint:

Example custom REST API endpoint

/server/containers/instances/{containerId}/ksession/{ksessionId}

This example custom endpoint accepts a list of facts to be inserted into the working memory of the decision engine, automatically executes all rules, and retrieves all objects from the KIE session in the specified KIE container.

Procedure

  1. Create an empty Maven project and define the following packaging type and dependencies in the pom.xml file for the project:

    Example pom.xml file in the sample project

    <packaging>jar</packaging>
    
    <properties>
      <version.org.kie>7.18.0.Final-redhat-00002</version.org.kie>
    </properties>
    
    <dependencies>
      <dependency>
        <groupId>org.kie</groupId>
        <artifactId>kie-api</artifactId>
        <version>${version.org.kie}</version>
      </dependency>
      <dependency>
        <groupId>org.kie</groupId>
        <artifactId>kie-internal</artifactId>
        <version>${version.org.kie}</version>
      </dependency>
      <dependency>
        <groupId>org.kie.server</groupId>
        <artifactId>kie-server-api</artifactId>
        <version>${version.org.kie}</version>
      </dependency>
      <dependency>
        <groupId>org.kie.server</groupId>
        <artifactId>kie-server-services-common</artifactId>
        <version>${version.org.kie}</version>
      </dependency>
      <dependency>
        <groupId>org.kie.server</groupId>
        <artifactId>kie-server-services-drools</artifactId>
        <version>${version.org.kie}</version>
      </dependency>
      <dependency>
        <groupId>org.kie.server</groupId>
        <artifactId>kie-server-rest-common</artifactId>
        <version>${version.org.kie}</version>
      </dependency>
      <dependency>
        <groupId>org.drools</groupId>
        <artifactId>drools-core</artifactId>
        <version>${version.org.kie}</version>
      </dependency>
      <dependency>
        <groupId>org.drools</groupId>
        <artifactId>drools-compiler</artifactId>
        <version>${version.org.kie}</version>
      </dependency>
      <dependency>
        <groupId>org.slf4j</groupId>
        <artifactId>slf4j-api</artifactId>
        <version>1.7.25</version>
      </dependency>
    </dependencies>

  2. Implement the org.kie.server.services.api.KieServerApplicationComponentsService interface in a Java class in your project, as shown in the following example:

    Sample implementation of the KieServerApplicationComponentsService interface

    public class CusomtDroolsKieServerApplicationComponentsService implements KieServerApplicationComponentsService {  1
    
        private static final String OWNER_EXTENSION = "Drools";  2
    
        public Collection<Object> getAppComponents(String extension, SupportedTransports type, Object... services) {  3
            // Do not accept calls from extensions other than the owner extension:
            if ( !OWNER_EXTENSION.equals(extension) ) {
                return Collections.emptyList();
            }
    
            RulesExecutionService rulesExecutionService = null;  4
            KieServerRegistry context = null;
    
            for( Object object : services ) {
                if( RulesExecutionService.class.isAssignableFrom(object.getClass()) ) {
                    rulesExecutionService = (RulesExecutionService) object;
                    continue;
                } else if( KieServerRegistry.class.isAssignableFrom(object.getClass()) ) {
                    context = (KieServerRegistry) object;
                    continue;
                }
            }
    
            List<Object> components = new ArrayList<Object>(1);
            if( SupportedTransports.REST.equals(type) ) {
                components.add(new CustomResource(rulesExecutionService, context));  5
            }
    
            return components;
        }
    
    }

    1
    Delivers REST endpoints to the Process Server infrastructure that is deployed when the application starts.
    2
    Specifies the extension that you are extending, such as the Drools extension in this example.
    3
    Returns all resources that the REST container must deploy. Each extension that is enabled in your Process Server instance calls the getAppComponents method, so the if ( !OWNER_EXTENSION.equals(extension) ) call returns an empty collection for any extensions other than the specified OWNER_EXTENSION extension.
    4
    Lists the services from the specified extension that you want to use, such as the RulesExecutionService and KieServerRegistry services from the Drools extension in this example.
    5
    Specifies the transport type for the extension, either REST or JMS (REST in this example), and the CustomResource class that returns the resource as part of the components list.
  3. Implement the CustomResource class that the Process Server can use to provide the additional functionality for the new REST resource, as shown in the following example:

    Sample implementation of the CustomResource class

    // Custom base endpoint:
    @Path("server/containers/instances/{containerId}/ksession")
    public class CustomResource {
    
        private static final Logger logger = LoggerFactory.getLogger(CustomResource.class);
    
        private KieCommands commandsFactory = KieServices.Factory.get().getCommands();
    
        private RulesExecutionService rulesExecutionService;
        private KieServerRegistry registry;
    
        public CustomResource() {
    
        }
    
        public CustomResource(RulesExecutionService rulesExecutionService, KieServerRegistry registry) {
            this.rulesExecutionService = rulesExecutionService;
            this.registry = registry;
        }
    
        // Supported HTTP method, path parameters, and data formats:
        @POST
        @Path("/{ksessionId}")
        @Consumes({MediaType.APPLICATION_XML, MediaType.APPLICATION_JSON})
        @Produces({MediaType.APPLICATION_XML, MediaType.APPLICATION_JSON})
        public Response insertFireReturn(@Context HttpHeaders headers,
                @PathParam("containerId") String id,
                @PathParam("ksessionId") String ksessionId,
                String cmdPayload) {
    
            Variant v = getVariant(headers);
            String contentType = getContentType(headers);
    
            // Marshalling behavior and supported actions:
            MarshallingFormat format = MarshallingFormat.fromType(contentType);
            if (format == null) {
                format = MarshallingFormat.valueOf(contentType);
            }
            try {
                KieContainerInstance kci = registry.getContainer(id);
    
                Marshaller marshaller = kci.getMarshaller(format);
    
                List<?> listOfFacts = marshaller.unmarshall(cmdPayload, List.class);
    
                List<Command<?>> commands = new ArrayList<Command<?>>();
                BatchExecutionCommand executionCommand = commandsFactory.newBatchExecution(commands, ksessionId);
    
                for (Object fact : listOfFacts) {
                    commands.add(commandsFactory.newInsert(fact, fact.toString()));
                }
                commands.add(commandsFactory.newFireAllRules());
                commands.add(commandsFactory.newGetObjects());
    
                ExecutionResults results = rulesExecutionService.call(kci, executionCommand);
    
                String result = marshaller.marshall(results);
    
    
                logger.debug("Returning OK response with content '{}'", result);
                return createResponse(result, v, Response.Status.OK);
            } catch (Exception e) {
                // If marshalling fails, return the `call-container` response to maintain backward compatibility:
                String response = "Execution failed with error : " + e.getMessage();
                logger.debug("Returning Failure response with content '{}'", response);
                return createResponse(response, v, Response.Status.INTERNAL_SERVER_ERROR);
            }
    
        }
    }

    In this example, the CustomResource class for the custom endpoint specifies the following data and behavior:

    • Uses the base endpoint server/containers/instances/{containerId}/ksession
    • Uses POST HTTP method
    • Expects the following data to be given in REST requests:

      • The containerId as a path argument
      • The ksessionId as a path argument
      • List of facts as a message payload
    • Supports all Process Server data formats:

      • XML (JAXB, XStream)
      • JSON
    • Unmarshals the payload into a List<?> collection and, for each item in the list, creates an InsertCommand instance followed by FireAllRules and GetObject commands.
    • Adds all commands to the BatchExecutionCommand instance that calls to the decision engine.
  4. To make the new endpoint discoverable for Process Server, create a META-INF/services/org.kie.server.services.api.KieServerApplicationComponentsService file in your Maven project and add the fully qualified class name of the KieServerApplicationComponentsService implementation class within the file. For this example, the file contains the single line org.kie.server.ext.drools.rest.CusomtDroolsKieServerApplicationComponentsService.
  5. Build your project and copy the resulting JAR file into the ~/kie-server.war/WEB-INF/lib directory of your project. For example, on Red Hat JBoss EAP, the path to this directory is EAP_HOME/standalone/deployments/kie-server.war/WEB-INF/lib.
  6. Start the Process Server and deploy the built project to the running Process Server. You can deploy the project using either the Business Central interface or the Process Server REST API (a PUT request to http://SERVER:PORT/kie-server/services/rest/server/containers/{containerId}).

    After your project is deployed on a running Process Server, you can start interacting with your new REST endpoint.

    For this example, you can use the following information to invoke the new endpoint:

    • Example request URL: http://localhost:8080/kie-server/services/rest/server/containers/instances/demo/ksession/defaultKieSession
    • HTTP method: POST
    • HTTP headers:

      • Content-Type: application/json
      • Accept: application/json
    • Example message payload:

      [
        {
          "org.jbpm.test.Person": {
            "name": "john",
            "age": 25
          }
        },
        {
          "org.jbpm.test.Person": {
            "name": "mary",
            "age": 22
          }
        }
      ]
    • Example server response: 200 (success)
    • Example server log output:

      13:37:20,347 INFO  [stdout] (default task-24) Hello mary
      13:37:20,348 INFO  [stdout] (default task-24) Hello john

22.2. Extending Process Server to use a custom data transport

By default, Process Server extensions are exposed through REST or JMS data transports. You can extend Process Server to support a custom data transport to adapt Process Server transport protocols to your business needs.

As an example, this procedure adds a custom data transport to Process Server that uses the Drools extension and that is based on Apache MINA, an open-source Java network-application framework. The example custom MINA transport exchanges string-based data that relies on existing marshalling operations and supports only JSON format.

Procedure

  1. Create an empty Maven project and define the following packaging type and dependencies in the pom.xml file for the project:

    Example pom.xml file in the sample project

    <packaging>jar</packaging>
    
    <properties>
      <version.org.kie>7.18.0.Final-redhat-00002</version.org.kie>
    </properties>
    
    <dependencies>
      <dependency>
        <groupId>org.kie</groupId>
        <artifactId>kie-api</artifactId>
        <version>${version.org.kie}</version>
      </dependency>
      <dependency>
        <groupId>org.kie</groupId>
        <artifactId>kie-internal</artifactId>
        <version>${version.org.kie}</version>
      </dependency>
      <dependency>
        <groupId>org.kie.server</groupId>
        <artifactId>kie-server-api</artifactId>
        <version>${version.org.kie}</version>
      </dependency>
      <dependency>
        <groupId>org.kie.server</groupId>
        <artifactId>kie-server-services-common</artifactId>
        <version>${version.org.kie}</version>
      </dependency>
      <dependency>
        <groupId>org.kie.server</groupId>
        <artifactId>kie-server-services-drools</artifactId>
        <version>${version.org.kie}</version>
      </dependency>
      <dependency>
        <groupId>org.drools</groupId>
        <artifactId>drools-core</artifactId>
        <version>${version.org.kie}</version>
      </dependency>
      <dependency>
        <groupId>org.drools</groupId>
        <artifactId>drools-compiler</artifactId>
        <version>${version.org.kie}</version>
      </dependency>
      <dependency>
        <groupId>org.slf4j</groupId>
        <artifactId>slf4j-api</artifactId>
        <version>1.7.25</version>
      </dependency>
      <dependency>
        <groupId>org.apache.mina</groupId>
        <artifactId>mina-core</artifactId>
        <version>2.1.3</version>
      </dependency>
    </dependencies>

  2. Implement the org.kie.server.services.api.KieServerExtension interface in a Java class in your project, as shown in the following example:

    Sample implementation of the KieServerExtension interface

    public class MinaDroolsKieServerExtension implements KieServerExtension {
    
        private static final Logger logger = LoggerFactory.getLogger(MinaDroolsKieServerExtension.class);
    
        public static final String EXTENSION_NAME = "Drools-Mina";
    
        private static final Boolean disabled = Boolean.parseBoolean(System.getProperty("org.kie.server.drools-mina.ext.disabled", "false"));
        private static final String MINA_HOST = System.getProperty("org.kie.server.drools-mina.ext.port", "localhost");
        private static final int MINA_PORT = Integer.parseInt(System.getProperty("org.kie.server.drools-mina.ext.port", "9123"));
    
        // Taken from dependency on the `Drools` extension:
        private KieContainerCommandService batchCommandService;
    
        // Specific to MINA:
        private IoAcceptor acceptor;
    
        public boolean isActive() {
            return disabled == false;
        }
    
        public void init(KieServerImpl kieServer, KieServerRegistry registry) {
    
            KieServerExtension droolsExtension = registry.getServerExtension("Drools");
            if (droolsExtension == null) {
                logger.warn("No Drools extension available, quiting...");
                return;
            }
    
            List<Object> droolsServices = droolsExtension.getServices();
            for( Object object : droolsServices ) {
                // If the given service is null (not configured), continue to the next service:
                if (object == null) {
                    continue;
                }
                if( KieContainerCommandService.class.isAssignableFrom(object.getClass()) ) {
                    batchCommandService = (KieContainerCommandService) object;
                    continue;
                }
            }
            if (batchCommandService != null) {
                acceptor = new NioSocketAcceptor();
                acceptor.getFilterChain().addLast( "codec", new ProtocolCodecFilter( new TextLineCodecFactory( Charset.forName( "UTF-8" ))));
    
                acceptor.setHandler( new TextBasedIoHandlerAdapter(batchCommandService) );
                acceptor.getSessionConfig().setReadBufferSize( 2048 );
                acceptor.getSessionConfig().setIdleTime( IdleStatus.BOTH_IDLE, 10 );
                try {
                    acceptor.bind( new InetSocketAddress(MINA_HOST, MINA_PORT) );
    
                    logger.info("{} -- Mina server started at {} and port {}", toString(), MINA_HOST, MINA_PORT);
                } catch (IOException e) {
                    logger.error("Unable to start Mina acceptor due to {}", e.getMessage(), e);
                }
    
            }
        }
    
        public void destroy(KieServerImpl kieServer, KieServerRegistry registry) {
            if (acceptor != null) {
                acceptor.dispose();
                acceptor = null;
            }
            logger.info("{} -- Mina server stopped", toString());
        }
    
        public void createContainer(String id, KieContainerInstance kieContainerInstance, Map<String, Object> parameters) {
            // Empty, already handled by the `Drools` extension
    
        }
    
        public void disposeContainer(String id, KieContainerInstance kieContainerInstance, Map<String, Object> parameters) {
          // Empty, already handled by the `Drools` extension
    
        }
    
        public List<Object> getAppComponents(SupportedTransports type) {
            // Nothing for supported transports (REST or JMS)
            return Collections.emptyList();
        }
    
        public <T> T getAppComponents(Class<T> serviceType) {
    
            return null;
        }
    
        public String getImplementedCapability() {
            return "BRM-Mina";
        }
    
        public List<Object> getServices() {
            return Collections.emptyList();
        }
    
        public String getExtensionName() {
            return EXTENSION_NAME;
        }
    
        public Integer getStartOrder() {
            return 20;
        }
    
        @Override
        public String toString() {
            return EXTENSION_NAME + " KIE Server extension";
        }
    }

    The KieServerExtension interface is the main extension interface that Process Server can use to provide the additional functionality for the new MINA transport. The interface consists of the following components:

    Overview of the KieServerExtension interface

    public interface KieServerExtension {
    
        boolean isActive();
    
        void init(KieServerImpl kieServer, KieServerRegistry registry);
    
        void destroy(KieServerImpl kieServer, KieServerRegistry registry);
    
        void createContainer(String id, KieContainerInstance kieContainerInstance, Map<String, Object> parameters);
    
        void disposeContainer(String id, KieContainerInstance kieContainerInstance, Map<String, Object> parameters);
    
        List<Object> getAppComponents(SupportedTransports type);
    
        <T> T getAppComponents(Class<T> serviceType);
    
        String getImplementedCapability();  1
    
        List<Object> getServices();
    
        String getExtensionName();  2
    
        Integer getStartOrder();  3
    }

    1
    Specifies the capability that is covered by this extension. The capability must be unique within Process Server.
    2
    Defines a human-readable name for the extension.
    3
    Determines when the specified extension should be started. For extensions that have dependencies on other extensions, this setting must not conflict with the parent setting. For example, in this case, this custom extension depends on the Drools extension, which has StartOrder set to 0, so this custom add-on extension must be greater than 0 (set to 20 in the sample implementation).

    In the previous MinaDroolsKieServerExtension sample implementation of this interface, the init method is the main element for collecting services from the Drools extension and for bootstrapping the MINA server. All other methods in the KieServerExtension interface can remain with the standard implementation to fulfill interface requirements.

    The TextBasedIoHandlerAdapter class is the handler on the MINA server that reacts to incoming requests.

  3. Implement the TextBasedIoHandlerAdapter handler for the MINA server, as shown in the following example:

    Sample implementation of the TextBasedIoHandlerAdapter handler

    public class TextBasedIoHandlerAdapter extends IoHandlerAdapter {
    
        private static final Logger logger = LoggerFactory.getLogger(TextBasedIoHandlerAdapter.class);
    
        private KieContainerCommandService batchCommandService;
    
        public TextBasedIoHandlerAdapter(KieContainerCommandService batchCommandService) {
            this.batchCommandService = batchCommandService;
        }
    
        @Override
        public void messageReceived( IoSession session, Object message ) throws Exception {
            String completeMessage = message.toString();
            logger.debug("Received message '{}'", completeMessage);
            if( completeMessage.trim().equalsIgnoreCase("quit") || completeMessage.trim().equalsIgnoreCase("exit") ) {
                session.close(false);
                return;
            }
    
            String[] elements = completeMessage.split("\\|");
            logger.debug("Container id {}", elements[0]);
            try {
                ServiceResponse<String> result = batchCommandService.callContainer(elements[0], elements[1], MarshallingFormat.JSON, null);
    
                if (result.getType().equals(ServiceResponse.ResponseType.SUCCESS)) {
                    session.write(result.getResult());
                    logger.debug("Successful message written with content '{}'", result.getResult());
                } else {
                    session.write(result.getMsg());
                    logger.debug("Failure message written with content '{}'", result.getMsg());
                }
            } catch (Exception e) {
    
            }
        }
    }

    In this example, the handler class receives text messages and executes them in the Drools service.

    Consider the following handler requirements and behavior when you use the TextBasedIoHandlerAdapter handler implementation:

    • Anything that you submit to the handler must be a single line because each incoming transport request is a single line.
    • You must pass a KIE container ID in this single line so that the handler expects the format containerID|payload.
    • You can set a response in the way that it is produced by the marshaller. The response can be multiple lines.
    • The handler supports a stream mode that enables you to send commands without disconnecting from a Process Server session. To end a Process Server session in stream mode, send either an exit or quit command to the server.
  4. To make the new data transport discoverable for Process Server, create a META-INF/services/org.kie.server.services.api.KieServerExtension file in your Maven project and add the fully qualified class name of the KieServerExtension implementation class within the file. For this example, the file contains the single line org.kie.server.ext.mina.MinaDroolsKieServerExtension.
  5. Build your project and copy the resulting JAR file and the mina-core-2.0.9.jar file (which the extension depends on in this example) into the ~/kie-server.war/WEB-INF/lib directory of your project. For example, on Red Hat JBoss EAP, the path to this directory is EAP_HOME/standalone/deployments/kie-server.war/WEB-INF/lib.
  6. Start the Process Server and deploy the built project to the running Process Server. You can deploy the project using either the Business Central interface or the Process Server REST API (a PUT request to http://SERVER:PORT/kie-server/services/rest/server/containers/{containerId}).

    After your project is deployed on a running Process Server, you can view the status of the new data transport in your Process Server log and start using your new data transport:

    New data transport in the server log

    Drools-Mina KIE Server extension -- Mina server started at localhost and port 9123
    Drools-Mina KIE Server extension has been successfully registered as server extension

    For this example, you can use Telnet to interact with the new MINA-based data transport in Process Server:

    Starting Telnet and connecting to Process Server on port 9123 in a command terminal

    telnet 127.0.0.1 9123

    Example interactions with Process Server in a command terminal

    Trying 127.0.0.1...
    Connected to localhost.
    Escape character is '^]'.
    
    # Request body:
    demo|{"lookup":"defaultKieSession","commands":[{"insert":{"object":{"org.jbpm.test.Person":{"name":"john","age":25}}}},{"fire-all-rules":""}]}
    
    # Server response:
    {
      "results" : [ {
        "key" : "",
        "value" : 1
      } ],
      "facts" : [ ]
    }
    
    demo|{"lookup":"defaultKieSession","commands":[{"insert":{"object":{"org.jbpm.test.Person":{"name":"mary","age":22}}}},{"fire-all-rules":""}]}
    {
      "results" : [ {
        "key" : "",
        "value" : 1
      } ],
      "facts" : [ ]
    }
    
    demo|{"lookup":"defaultKieSession","commands":[{"insert":{"object":{"org.jbpm.test.Person":{"name":"james","age":25}}}},{"fire-all-rules":""}]}
    {
      "results" : [ {
        "key" : "",
        "value" : 1
      } ],
      "facts" : [ ]
    }
    exit
    Connection closed by foreign host.

    Example server log output

    16:33:40,206 INFO  [stdout] (NioProcessor-2) Hello john
    16:34:03,877 INFO  [stdout] (NioProcessor-2) Hello mary
    16:34:19,800 INFO  [stdout] (NioProcessor-2) Hello james

22.3. Extending the Process Server client with a custom client API

Process Server uses predefined client APIs that you can interact with to use Process Server services. You can extend the Process Server client with a custom client API to adapt Process Server services to your business needs.

As an example, this procedure adds a custom client API to Process Server to accommodate a custom data transport (configured previously for this scenario) that is based on Apache MINA, an open-source Java network-application framework.

Procedure

  1. Create an empty Maven project and define the following packaging type and dependencies in the pom.xml file for the project:

    Example pom.xml file in the sample project

    <packaging>jar</packaging>
    
    <properties>
       <version.org.kie>7.18.0.Final-redhat-00002</version.org.kie>
     </properties>
    
     <dependencies>
       <dependency>
         <groupId>org.kie.server</groupId>
         <artifactId>kie-server-api</artifactId>
         <version>${version.org.kie}</version>
       </dependency>
       <dependency>
          <groupId>org.kie.server</groupId>
          <artifactId>kie-server-client</artifactId>
          <version>${version.org.kie}</version>
        </dependency>
       <dependency>
         <groupId>org.drools</groupId>
         <artifactId>drools-compiler</artifactId>
         <version>${version.org.kie}</version>
       </dependency>
     </dependencies>

  2. Implement the relevant ServicesClient interface in a Java class in your project, as shown in the following example:

    Sample RulesMinaServicesClient interface

    public interface RulesMinaServicesClient extends RuleServicesClient {
    
    }

    A specific interface is required because you must register client implementations based on the interface, and you can have only one implementation for a given interface.

    For this example, the custom MINA-based data transport uses the Drools extension, so this example RulesMinaServicesClient interface extends the existing RuleServicesClient client API from the Drools extension.

  3. Implement the RulesMinaServicesClient interface that the Process Server can use to provide the additional client functionality for the new MINA transport, as shown in the following example:

    Sample implementation of the RulesMinaServicesClient interface

    public class RulesMinaServicesClientImpl implements RulesMinaServicesClient {
    
        private String host;
        private Integer port;
    
        private Marshaller marshaller;
    
        public RulesMinaServicesClientImpl(KieServicesConfiguration configuration, ClassLoader classloader) {
            String[] serverDetails = configuration.getServerUrl().split(":");
    
            this.host = serverDetails[0];
            this.port = Integer.parseInt(serverDetails[1]);
    
            this.marshaller = MarshallerFactory.getMarshaller(configuration.getExtraJaxbClasses(), MarshallingFormat.JSON, classloader);
        }
    
        public ServiceResponse<String> executeCommands(String id, String payload) {
    
            try {
                String response = sendReceive(id, payload);
                if (response.startsWith("{")) {
                    return new ServiceResponse<String>(ResponseType.SUCCESS, null, response);
                } else {
                    return new ServiceResponse<String>(ResponseType.FAILURE, response);
                }
            } catch (Exception e) {
                throw new KieServicesException("Unable to send request to KIE Server", e);
            }
        }
    
        public ServiceResponse<String> executeCommands(String id, Command<?> cmd) {
            try {
                String response = sendReceive(id, marshaller.marshall(cmd));
                if (response.startsWith("{")) {
                    return new ServiceResponse<String>(ResponseType.SUCCESS, null, response);
                } else {
                    return new ServiceResponse<String>(ResponseType.FAILURE, response);
                }
            } catch (Exception e) {
                throw new KieServicesException("Unable to send request to KIE Server", e);
            }
        }
    
        protected String sendReceive(String containerId, String content) throws Exception {
    
            // Flatten the content to be single line:
            content = content.replaceAll("\\n", "");
    
            Socket minaSocket = null;
            PrintWriter out = null;
            BufferedReader in = null;
    
            StringBuffer data = new StringBuffer();
            try {
                minaSocket = new Socket(host, port);
                out = new PrintWriter(minaSocket.getOutputStream(), true);
                in = new BufferedReader(new InputStreamReader(minaSocket.getInputStream()));
    
                // Prepare and send data:
                out.println(containerId + "|" + content);
                // Wait for the first line:
                data.append(in.readLine());
                // Continue as long as data is available:
                while (in.ready()) {
                    data.append(in.readLine());
                }
    
                return data.toString();
            } finally {
                out.close();
                in.close();
                minaSocket.close();
            }
        }
    }

    This example implementation specifies the following data and behavior:

    • Uses socket-based communication for simplicity
    • Relies on default configurations from the Process Server client and uses ServerUrl for providing the host and port of the MINA server
    • Specifies JSON as the marshalling format
    • Requires received messages to be JSON objects that start with an open bracket {
    • Uses direct socket communication with a blocking API while waiting for the first line of the response and then reads all lines that are available
    • Does not use stream mode and therefore disconnects the Process Server session after invoking a command
  4. Implement the org.kie.server.client.helper.KieServicesClientBuilder interface in a Java class in your project, as shown in the following example:

    Sample implementation of the KieServicesClientBuilder interface

    public class MinaClientBuilderImpl implements KieServicesClientBuilder {  1
    
        public String getImplementedCapability() {  2
            return "BRM-Mina";
        }
    
        public Map<Class<?>, Object> build(KieServicesConfiguration configuration, ClassLoader classLoader) {  3
            Map<Class<?>, Object> services = new HashMap<Class<?>, Object>();
    
            services.put(RulesMinaServicesClient.class, new RulesMinaServicesClientImpl(configuration, classLoader));
    
            return services;
        }
    
    }

    1
    Enables you to provide additional client APIs to the generic Process Server client infrastructure
    2
    Defines the Process Server capability (extension) that the client uses
    3
    Provides a map of the client implementations, where the key is the interface and the value is the fully initialized implementation
  5. To make the new client API discoverable for the Process Server client, create a META-INF/services/org.kie.server.client.helper.KieServicesClientBuilder file in your Maven project and add the fully qualified class name of the KieServicesClientBuilder implementation class within the file. For this example, the file contains the single line org.kie.server.ext.mina.client.MinaClientBuilderImpl.
  6. Build your project and copy the resulting JAR file into the ~/kie-server.war/WEB-INF/lib directory of your project. For example, on Red Hat JBoss EAP, the path to this directory is EAP_HOME/standalone/deployments/kie-server.war/WEB-INF/lib.
  7. Start the Process Server and deploy the built project to the running Process Server. You can deploy the project using either the Business Central interface or the Process Server REST API (a PUT request to http://SERVER:PORT/kie-server/services/rest/server/containers/{containerId}).

    After your project is deployed on a running Process Server, you can start interacting with your new Process Server client. You use your new client in the same way as the standard Process Server client, by creating the client configuration and client instance, retrieving the service client by type, and invoking client methods.

    For this example, you can create a RulesMinaServiceClient client instance and invoke operations on Process Server through the MINA transport:

    Sample implementation to create the RulesMinaServiceClient client

    protected RulesMinaServicesClient buildClient() {
        KieServicesConfiguration configuration = KieServicesFactory.newRestConfiguration("localhost:9123", null, null);
        List<String> capabilities = new ArrayList<String>();
        // Explicitly add capabilities (the MINA client does not respond to `get-server-info` requests):
        capabilities.add("BRM-Mina");
    
        configuration.setCapabilities(capabilities);
        configuration.setMarshallingFormat(MarshallingFormat.JSON);
    
        configuration.addJaxbClasses(extraClasses);
    
        KieServicesClient kieServicesClient =  KieServicesFactory.newKieServicesClient(configuration);
    
        RulesMinaServicesClient rulesClient = kieServicesClient.getServicesClient(RulesMinaServicesClient.class);
    
        return rulesClient;
    }

    Sample configuration to invoke operations on Process Server through the MINA transport

    RulesMinaServicesClient rulesClient = buildClient();
    
    List<Command<?>> commands = new ArrayList<Command<?>>();
    BatchExecutionCommand executionCommand = commandsFactory.newBatchExecution(commands, "defaultKieSession");
    
    Person person = new Person();
    person.setName("mary");
    commands.add(commandsFactory.newInsert(person, "person"));
    commands.add(commandsFactory.newFireAllRules("fired"));
    
    ServiceResponse<String> response = rulesClient.executeCommands(containerId, executionCommand);
    Assert.assertNotNull(response);
    
    Assert.assertEquals(ResponseType.SUCCESS, response.getType());
    
    String data = response.getResult();
    
    Marshaller marshaller = MarshallerFactory.getMarshaller(extraClasses, MarshallingFormat.JSON, this.getClass().getClassLoader());
    
    ExecutionResultImpl results = marshaller.unmarshall(data, ExecutionResultImpl.class);
    Assert.assertNotNull(results);
    
    Object personResult = results.getValue("person");
    Assert.assertTrue(personResult instanceof Person);
    
    Assert.assertEquals("mary", ((Person) personResult).getName());
    Assert.assertEquals("JBoss Community", ((Person) personResult).getAddress());
    Assert.assertEquals(true, ((Person) personResult).isRegistered());