feat UrlResolver

clients/java/client/src/main/java/org/camunda/bpm/client/ExternalTaskClientBuilder.java

@@ -34,11 +34,45 @@ public interface ExternalTaskClientBuilder {
   /**
    * Base url of the Camunda BPM Platform REST API. This information is mandatory.
    *
+   * If this method is used, it will create a permanent url resolver with the given baseUrl.
+   *
    * @param baseUrl of the Camunda BPM Platform REST API
    * @return the builder
    */
   ExternalTaskClientBuilder baseUrl(String baseUrl);
 
+
+  /**
+   * Url resolver of the Camunda BPM Platform REST API. This information is mandatory.
+   *
+   * If the server is in a cluster or you are using spring cloud, you can create a class which implements UrlResolver..
+   *
+   * this is a sample for spring cloud DiscoveryClient
+   *
+   * public class CustomUrlResolver implements UrlResolver{
+   *
+   *    protected String serviceId;
+   *
+   *    protected DiscoveryClient discoveryClient;
+   *
+   *    protected String getRandomServiceInstance() {
+   *      List<ServiceInstance> serviceInstances = discoveryClient.getInstances(serviceId);
+   *      Random random = new Random();
+   *      return serviceInstances.get(random.nextInt(serviceInstances.size())).getUri().toString();
+   *    }
+   *
+   *    @Override
+   *    public String getBaseUrl() {
+   *      return getRandomServiceInstance();
+   *    }
+   * }
+   *
+   *
+   * @param urlResolver of the Camunda BPM Platform REST API
+   * @return the builder
+   */
+  ExternalTaskClientBuilder urlResolver(UrlResolver urlResolver);
+
   /**
    * A custom worker id the Workflow Engine is aware of. This information is optional.
    * Note: make sure to choose a unique worker id

clients/java/client/src/main/java/org/camunda/bpm/client/UrlResolver.java

@@ -0,0 +1,25 @@
+/*
+ * Copyright Camunda Services GmbH and/or licensed to Camunda Services GmbH
+ * under one or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership. Camunda licenses this file to you under the Apache License,
+ * Version 2.0; you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.camunda.bpm.client;
+
+/**
+ * Get service url of the Camunda server
+ */
+public interface UrlResolver {
+
+    String getBaseUrl();
+}

clients/java/client/src/main/java/org/camunda/bpm/client/impl/EngineClient.java

@@ -20,6 +20,7 @@
 import java.util.List;
 import java.util.Map;
 
+import org.camunda.bpm.client.UrlResolver;
 import org.camunda.bpm.client.task.OrderingConfig;
 import org.camunda.bpm.client.task.ExternalTask;
 import org.camunda.bpm.client.task.impl.ExternalTaskImpl;
@@ -56,7 +57,7 @@ public class EngineClient {
   public static final String PROCESS_INSTANCE_ID_RESOURCE_PATH = PROCESS_INSTANCE_RESOURCE_PATH + "/" + ID_PATH_PARAM;
   public static final String GET_BINARY_VARIABLE =
       PROCESS_INSTANCE_ID_RESOURCE_PATH + "/variables/" + NAME_PATH_PARAM + "/data";
-  protected String baseUrl;
+  protected UrlResolver urlResolver;
   protected String workerId;
   protected int maxTasks;
   protected boolean usePriority;
@@ -65,40 +66,57 @@ public class EngineClient {
   protected RequestExecutor engineInteraction;
   protected TypedValues typedValues;
 
-  public EngineClient(String workerId, int maxTasks, Long asyncResponseTimeout, String baseUrl, RequestExecutor engineInteraction) {
-    this(workerId, maxTasks, asyncResponseTimeout, baseUrl, engineInteraction, true, OrderingConfig.empty());
-  }
-
-  public EngineClient(String workerId, int maxTasks, Long asyncResponseTimeout, String baseUrl, RequestExecutor engineInteraction,
-                      boolean usePriority, OrderingConfig orderingConfig) {
-    this.workerId = workerId;
-    this.asyncResponseTimeout = asyncResponseTimeout;
-    this.maxTasks = maxTasks;
-    this.usePriority = usePriority;
-    this.engineInteraction = engineInteraction;
-    this.baseUrl = baseUrl;
-    this.orderingConfig = orderingConfig;
-  }
+    public EngineClient(String workerId, int maxTasks, Long asyncResponseTimeout, String baseUrl, RequestExecutor engineInteraction) {
+        this(workerId, maxTasks, asyncResponseTimeout, baseUrl, engineInteraction, true, OrderingConfig.empty());
+    }
+
+    public EngineClient(String workerId, int maxTasks, Long asyncResponseTimeout, String baseUrl, RequestExecutor engineInteraction,
+                        boolean usePriority, OrderingConfig orderingConfig) {
+        this.workerId = workerId;
+        this.asyncResponseTimeout = asyncResponseTimeout;
+        this.maxTasks = maxTasks;
+        this.usePriority = usePriority;
+        this.engineInteraction = engineInteraction;
+        this.urlResolver = new PermanentUrlResolver(baseUrl);
+        this.orderingConfig = orderingConfig;
+    }
+
+
+    public EngineClient(String workerId, int maxTasks, Long asyncResponseTimeout,  UrlResolver urlResolver, RequestExecutor engineInteraction) {
+        this(workerId, maxTasks, asyncResponseTimeout, urlResolver, engineInteraction, true, OrderingConfig.empty());
+    }
+
+
+    public EngineClient(String workerId, int maxTasks, Long asyncResponseTimeout, UrlResolver urlResolver, RequestExecutor engineInteraction,
+                        boolean usePriority, OrderingConfig orderingConfig) {
+        this.workerId = workerId;
+        this.asyncResponseTimeout = asyncResponseTimeout;
+        this.maxTasks = maxTasks;
+        this.usePriority = usePriority;
+        this.engineInteraction = engineInteraction;
+        this.urlResolver = urlResolver;
+        this.orderingConfig = orderingConfig;
+    }
 
   public List<ExternalTask> fetchAndLock(List<TopicRequestDto> topics)  {
     FetchAndLockRequestDto payload = new FetchAndLockRequestDto(workerId, maxTasks, asyncResponseTimeout,
         topics, usePriority, orderingConfig);
 
-    String resourceUrl = baseUrl + FETCH_AND_LOCK_RESOURCE_PATH;
+    String resourceUrl = getBaseUrl() + FETCH_AND_LOCK_RESOURCE_PATH;
     ExternalTask[] externalTasks = engineInteraction.postRequest(resourceUrl, payload, ExternalTaskImpl[].class);
     return Arrays.asList(externalTasks);
   }
 
   public void lock(String taskId, long lockDuration)  {
     LockRequestDto payload = new LockRequestDto(workerId, lockDuration);
     String resourcePath = LOCK_RESOURCE_PATH.replace("{id}", taskId);
-    String resourceUrl = baseUrl + resourcePath;
+    String resourceUrl = getBaseUrl() + resourcePath;
     engineInteraction.postRequest(resourceUrl, payload, Void.class);
   }
 
   public void unlock(String taskId)  {
     String resourcePath = UNLOCK_RESOURCE_PATH.replace("{id}", taskId);
-    String resourceUrl = baseUrl + resourcePath;
+    String resourceUrl = getBaseUrl() + resourcePath;
     engineInteraction.postRequest(resourceUrl, null, Void.class);
   }
 
@@ -108,15 +126,15 @@ public void complete(String taskId, Map<String, Object> variables, Map<String, O
 
     CompleteRequestDto payload = new CompleteRequestDto(workerId, typedValueDtoMap, localTypedValueDtoMap);
     String resourcePath = COMPLETE_RESOURCE_PATH.replace("{id}", taskId);
-    String resourceUrl = baseUrl + resourcePath;
+    String resourceUrl = getBaseUrl() + resourcePath;
     engineInteraction.postRequest(resourceUrl, payload, Void.class);
   }
 
   public void setVariables(String processId, Map<String, Object> variables)  {
     Map<String, TypedValueField> typedValueDtoMap = typedValues.serializeVariables(variables);
     SetVariablesRequestDto payload = new SetVariablesRequestDto(workerId, typedValueDtoMap);
     String resourcePath = SET_VARIABLES_RESOURCE_PATH.replace("{id}", processId);
-    String resourceUrl = baseUrl + resourcePath;
+    String resourceUrl = getBaseUrl() + resourcePath;
     engineInteraction.postRequest(resourceUrl, payload, Void.class);
   }
 
@@ -127,35 +145,35 @@ public void failure(String taskId, String errorMessage, String errorDetails, int
 
     FailureRequestDto payload = new FailureRequestDto(workerId, errorMessage, errorDetails, retries, retryTimeout, typedValueDtoMap, localTypedValueDtoMap);
     String resourcePath = FAILURE_RESOURCE_PATH.replace("{id}", taskId);
-    String resourceUrl = baseUrl + resourcePath;
+    String resourceUrl = getBaseUrl() + resourcePath;
     engineInteraction.postRequest(resourceUrl, payload, Void.class);
   }
 
   public void bpmnError(String taskId, String errorCode, String errorMessage, Map<String, Object> variables)  {
     Map<String, TypedValueField> typeValueDtoMap = typedValues.serializeVariables(variables);
     BpmnErrorRequestDto payload = new BpmnErrorRequestDto(workerId, errorCode, errorMessage, typeValueDtoMap);
     String resourcePath = BPMN_ERROR_RESOURCE_PATH.replace("{id}", taskId);
-    String resourceUrl = baseUrl + resourcePath;
+    String resourceUrl = getBaseUrl() + resourcePath;
     engineInteraction.postRequest(resourceUrl, payload, Void.class);
   }
 
   public void extendLock(String taskId, long newDuration)  {
     ExtendLockRequestDto payload = new ExtendLockRequestDto(workerId, newDuration);
     String resourcePath = EXTEND_LOCK_RESOURCE_PATH.replace("{id}", taskId);
-    String resourceUrl = baseUrl + resourcePath;
+    String resourceUrl = getBaseUrl() + resourcePath;
     engineInteraction.postRequest(resourceUrl, payload, Void.class);
   }
 
   public byte[] getLocalBinaryVariable(String variableName, String executionId)  {
-    String resourcePath = baseUrl + GET_BINARY_VARIABLE
+    String resourcePath =  getBaseUrl()  + GET_BINARY_VARIABLE
             .replace(ID_PATH_PARAM, executionId)
             .replace(NAME_PATH_PARAM, variableName);
 
     return engineInteraction.getRequest(resourcePath);
   }
 
   public String getBaseUrl() {
-    return baseUrl;
+    return this.urlResolver.getBaseUrl();
   }
 
   public String getWorkerId() {