fix - 修复部分场景下，已完成的实例，查实例数据会存在NPE

workflow-engine-core/src/main/java/org/flowable/engine/impl/variable/ParallelMultiInstanceLoopVariableType.java

@@ -0,0 +1,109 @@
+/* Licensed under the Apache License, Version 2.0 (the "License");
+ * 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.flowable.engine.impl.variable;
+
+import org.flowable.bpmn.model.BoundaryEvent;
+import org.flowable.common.engine.impl.interceptor.CommandContext;
+import org.flowable.engine.impl.cfg.ProcessEngineConfigurationImpl;
+import org.flowable.engine.impl.persistence.entity.ExecutionEntity;
+import org.flowable.engine.impl.persistence.entity.ExecutionEntityManager;
+import org.flowable.engine.impl.util.CommandContextUtil;
+import org.flowable.variable.api.types.ValueFields;
+import org.flowable.variable.api.types.VariableType;
+
+import java.util.List;
+
+/**
+ * @author Filip Hrisafov
+ */
+public class ParallelMultiInstanceLoopVariableType implements VariableType {
+
+    public static final String TYPE_NAME = "bpmnParallelMultiInstanceCompleted";
+    protected static final String NUMBER_OF_INSTANCES = "nrOfInstances";
+
+    protected final ProcessEngineConfigurationImpl processEngineConfiguration;
+
+    public ParallelMultiInstanceLoopVariableType(ProcessEngineConfigurationImpl processEngineConfiguration) {
+        this.processEngineConfiguration = processEngineConfiguration;
+    }
+
+    @Override
+    public String getTypeName() {
+        return TYPE_NAME;
+    }
+
+    @Override
+    public boolean isCachable() {
+        return false;
+    }
+
+    @Override
+    public boolean isAbleToStore(Object value) {
+        return value instanceof ParallelMultiInstanceLoopVariable;
+    }
+
+    @Override
+    public void setValue(Object value, ValueFields valueFields) {
+        if (value instanceof ParallelMultiInstanceLoopVariable) {
+            valueFields.setTextValue(((ParallelMultiInstanceLoopVariable) value).getExecutionId());
+            valueFields.setTextValue2(((ParallelMultiInstanceLoopVariable) value).getType());
+        } else {
+            valueFields.setTextValue(null);
+            valueFields.setTextValue2(null);
+        }
+    }
+
+    @Override
+    public Object getValue(ValueFields valueFields) {
+        CommandContext commandContext = CommandContextUtil.getCommandContext();
+        if (commandContext != null) {
+            return getValue(valueFields, commandContext);
+        } else {
+            return processEngineConfiguration.getCommandExecutor()
+                    .execute(context -> getValue(valueFields, context));
+        }
+    }
+
+    protected Object getValue(ValueFields valueFields, CommandContext commandContext) {
+        String multiInstanceRootId = valueFields.getTextValue();
+        String type = valueFields.getTextValue2();
+
+        ProcessEngineConfigurationImpl processEngineConfiguration = CommandContextUtil.getProcessEngineConfiguration(commandContext);
+        ExecutionEntityManager executionEntityManager = processEngineConfiguration.getExecutionEntityManager();
+        ExecutionEntity multiInstanceRootExecution = executionEntityManager.findById(multiInstanceRootId);
+        if (multiInstanceRootExecution == null) {
+            /**
+             *  @see https://github.com/flowable/flowable-engine/blob/main/modules/flowable-engine/src/main/java/org/flowable/engine/impl/variable/ParallelMultiInstanceLoopVariableType.java
+             */
+            return 0;
+        }
+        List<? extends ExecutionEntity> childExecutions = multiInstanceRootExecution.getExecutions();
+        int nrOfActiveInstances = (int) childExecutions.stream().filter(execution -> execution.isActive()
+                && !(execution.getCurrentFlowElement() instanceof BoundaryEvent)).count();
+        if (ParallelMultiInstanceLoopVariable.COMPLETED_INSTANCES.equals(type)) {
+            Object nrOfInstancesValue = multiInstanceRootExecution.getVariable(NUMBER_OF_INSTANCES);
+            int nrOfInstances = (Integer) (nrOfInstancesValue != null ? nrOfInstancesValue : 0);
+            return nrOfInstances - nrOfActiveInstances;
+        } else if (ParallelMultiInstanceLoopVariable.ACTIVE_INSTANCES.equals(type)) {
+            return nrOfActiveInstances;
+        } else {
+            //TODO maybe throw exception
+            return 0;
+        }
+    }
+
+    @Override
+    public boolean isReadOnly() {
+        return true;
+    }
+}