Error while closing command context: NullPointerException

naeem · April 17, 2019, 5:08am

Hi. I have a TaskListener which needs to use the ContentEngine, the task’s form has an upload fieldType and when the task is completed the TaskListener is invoked:

<userTask id="fileUploadTask" name="File Upload Task" flowable:formKey="file_upload">
    <extensionElements>
        <flowable:taskListener
                event="complete"
                class="FileUploadToContentTaskListener" />
    </extensionElements>
</userTask>

The TaskListener gets a handle on the ContentEngine:

    ContentService contentService = ContentEngines.getDefaultContentEngine().getContentService();

and subsequently:

                InputStream inputStream = contentService.getContentItemData(value.toString());

When the TaskListener is done, then I get this exception:

ERROR org.flowable.engine.common.impl.interceptor.CommandContext - Error while closing command context
java.lang.NullPointerException
at org.flowable.content.engine.impl.util.CommandContextUtil.getContentItemEntityManager(CommandContextUtil.java:57)
at org.flowable.content.engine.impl.util.CommandContextUtil.getContentItemEntityManager(CommandContextUtil.java:53)
at org.flowable.content.engine.impl.cmd.CreateContentItemCmd.execute(CreateContentItemCmd.java:31)
at org.flowable.content.engine.impl.cmd.CreateContentItemCmd.execute(CreateContentItemCmd.java:25)
at org.flowable.engine.common.impl.interceptor.DefaultCommandInvoker.execute(DefaultCommandInvoker.java:10)
at org.flowable.engine.common.impl.interceptor.TransactionContextInterceptor.execute(TransactionContextInterceptor.java:53)
at org.flowable.engine.common.impl.interceptor.CommandContextInterceptor.execute(CommandContextInterceptor.java:72)
at org.flowable.engine.common.impl.interceptor.LogInterceptor.execute(LogInterceptor.java:30)
at org.flowable.engine.common.impl.cfg.CommandExecutorImpl.execute(CommandExecutorImpl.java:56)
at org.flowable.engine.common.impl.cfg.CommandExecutorImpl.execute(CommandExecutorImpl.java:51)
at org.flowable.content.engine.impl.ContentServiceImpl.newContentItem(ContentServiceImpl.java:33)
at FileUploadToContentTaskListener.notify(FileUploadToContentTaskListener.java:25)
at org.flowable.engine.impl.delegate.invocation.TaskListenerInvocation.invoke(TaskListenerInvocation.java:35)
at org.flowable.engine.impl.delegate.invocation.DelegateInvocation.proceed(DelegateInvocation.java:35)
at org.flowable.engine.impl.delegate.invocation.DefaultDelegateInterceptor.handleInvocation(DefaultDelegateInterceptor.java:26)
at org.flowable.engine.impl.bpmn.helper.ClassDelegate.notify(ClassDelegate.java:122)
at org.flowable.engine.impl.delegate.invocation.TaskListenerInvocation.invoke(TaskListenerInvocation.java:35)
at org.flowable.engine.impl.delegate.invocation.DelegateInvocation.proceed(DelegateInvocation.java:35)
at org.flowable.engine.impl.delegate.invocation.DefaultDelegateInterceptor.handleInvocation(DefaultDelegateInterceptor.java:26)
at org.flowable.engine.impl.bpmn.listener.ListenerNotificationHelper.executeTaskListeners(ListenerNotificationHelper.java:125)
at org.flowable.engine.impl.bpmn.listener.ListenerNotificationHelper.executeTaskListeners(ListenerNotificationHelper.java:106)
at org.flowable.engine.impl.util.TaskHelper.completeTask(TaskHelper.java:77)
at org.flowable.engine.impl.cmd.CompleteTaskCmd.execute(CompleteTaskCmd.java:64)
at org.flowable.engine.impl.cmd.CompleteTaskCmd.execute(CompleteTaskCmd.java:26)
at org.flowable.engine.impl.cmd.NeedsActiveTaskCmd.execute(NeedsActiveTaskCmd.java:58)
at org.flowable.engine.impl.interceptor.CommandInvoker$1.run(CommandInvoker.java:51)
at org.flowable.engine.impl.interceptor.CommandInvoker.executeOperation(CommandInvoker.java:93)
at org.flowable.engine.impl.interceptor.CommandInvoker.executeOperations(CommandInvoker.java:72)
at org.flowable.engine.impl.interceptor.CommandInvoker.execute(CommandInvoker.java:56)
at org.flowable.engine.impl.interceptor.BpmnOverrideContextInterceptor.execute(BpmnOverrideContextInterceptor.java:25)
at org.flowable.engine.common.impl.interceptor.TransactionContextInterceptor.execute(TransactionContextInterceptor.java:53)
at org.flowable.engine.common.impl.interceptor.CommandContextInterceptor.execute(CommandContextInterceptor.java:72)
at org.flowable.engine.common.impl.interceptor.LogInterceptor.execute(LogInterceptor.java:30)
at org.flowable.engine.common.impl.cfg.CommandExecutorImpl.execute(CommandExecutorImpl.java:56)
at org.flowable.engine.common.impl.cfg.CommandExecutorImpl.execute(CommandExecutorImpl.java:51)
at org.flowable.engine.impl.TaskServiceImpl.complete(TaskServiceImpl.java:215)
at FileUploadToContentTaskListenerTest.test(FileUploadToContentTaskListenerTest.java:74)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
at org.flowable.engine.test.FlowableRule$1.evaluate(FlowableRule.java:116)
at org.flowable.content.engine.test.FlowableContentRule$1.evaluate(FlowableContentRule.java:97)
at org.junit.rules.RunRules.evaluate(RunRules.java:20)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)

I’m running from a JUnit test using FlowableContentRule.

Not sure what’s wrong. Any advice please? Using Flowable 6.2.1

Thanks.

naeem · April 20, 2019, 12:10am

Hi. Any response please?

dbmalkovsky · April 20, 2019, 2:46pm

It would help if you provided the source code of the Junit test that you are using as it is hard to tell what is going on in FileUploadToContentTaskListener.

naeem · April 23, 2019, 12:18pm

Hi. I’m restricted on posting code from my org, but let me try and provide the essentials:

@Rule
public FlowableRule flowableRule = new FlowableRule();

@Rule
public FlowableContentRule rule = new FlowableContentRule();

private static ContentEngine cachedContentEngine;
private ContentService contentService;

@Before
public void initFormEngine() {
    if (cachedContentEngine == null) {
        cachedContentEngine = rule.getContentEngine();
    }
    this.contentService = cachedContentEngine.getContentService();
}

@Test
@Deployment(resources = {
        "file-upload.bpmn20.xml"
})
public void test() {
    ProcessInstance processInstance = flowableRule.getRuntimeService().startProcessInstanceByKey("fileUpload");
    Task task = flowableRule.getTaskService().createTaskQuery().singleResult();

    ContentItem contentItem = contentService.newContentItem();
    contentItem.setName("announcement.msg");
    contentItem.setMimeType("application/octet-stream");
    contentItem.setProcessInstanceId(processInstance.getId());
    contentItem.setTaskId(task.getId());
    contentService.saveContentItem(contentItem, FileUploadToContentTaskListener.class.getResourceAsStream("content/announcement.msg"));

    flowableRule.getTaskService().complete(task.getId());
}

naeem · April 24, 2019, 6:12am

And it works in deployment… just can’t get the unit test working without this error.

tijs · April 24, 2019, 6:50am

Hi,

The problem is that the content engine should be started together with the process engine. An example on how this can be done can be found here:

github.com

flowable/flowable-engine/blob/master/modules/flowable-cmmn-engine-configurator/src/test/resources/flowable.cfg.xml

<?xml version="1.0" encoding="UTF-8"?>

<beans xmlns="http://www.springframework.org/schema/beans"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://www.springframework.org/schema/beans   http://www.springframework.org/schema/beans/spring-beans.xsd">
  
    <bean id="processEngineConfiguration" class="org.flowable.engine.impl.cfg.StandaloneProcessEngineConfiguration">
        <property name="jdbcUrl" value="jdbc:h2:mem:flowable;DB_CLOSE_DELAY=1000;MVCC=TRUE" />
        <property name="jdbcDriver" value="org.h2.Driver" />
        <property name="jdbcUsername" value="sa" />
        <property name="jdbcPassword" value="" />
        <property name="databaseSchemaUpdate" value="true" />
        
        <property name="asyncExecutor" ref="processAsyncExecutor" />
        <property name="asyncExecutorActivate" value="false" />
        
        <property name="asyncFailedJobWaitTime" value="1" />
        
        <property name="enableEntityLinks" value="true" />
        <property name="enableProcessDefinitionInfoCache" value="true" />

This file has been truncated. show original

This is using Spring XML configuration, but the idea is the same for a Spring Java config. The CMMN engine is booted together with the process engine by adding a CmmnEngineConfigurator to the configurators of the process engine configuration.

You can do a similar thing with the SpringContentEngineConfigurator:

github.com

flowable/flowable-engine/blob/master/modules/flowable-content-spring-configurator/src/main/java/org/flowable/content/spring/configurator/SpringContentEngineConfigurator.java

/* 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.content.spring.configurator;

import org.flowable.common.engine.api.FlowableException;
import org.flowable.common.engine.impl.AbstractEngineConfiguration;
import org.flowable.common.spring.SpringEngineConfiguration;
import org.flowable.content.engine.ContentEngine;
import org.flowable.content.engine.configurator.ContentEngineConfigurator;
import org.flowable.content.spring.SpringContentEngineConfiguration;

This file has been truncated. show original

Best regards,

Tijs

naeem · April 24, 2019, 7:32am

Ok, thanks. That makes sense. But how do I get around this error:

org.springframework.beans.factory.BeanDefinitionStoreException: IOException parsing XML document from class path resource [flowable.content.cfg.xml]; nested exception is java.io.FileNotFoundException: class path resource [flowable.content.cfg.xml] cannot be opened because it does not exist

Caused at the last line:

@Before
public void initFormEngine() {
    if (cachedContentEngine == null) {
        cachedContentEngine = rule.getContentEngine();
    }
    this.contentService = cachedContentEngine.getContentService();
}

flowable.cfg.xml:

<bean id="processEngineConfiguration"
      class="org.flowable.engine.impl.cfg.StandaloneProcessEngineConfiguration" depends-on="flowableHelper">

    <property name="jdbcUrl" value="jdbc:h2:mem:flowable;DB_CLOSE_DELAY=1000;MVCC=TRUE"/>
    <property name="jdbcDriver" value="org.h2.Driver"/>
    <property name="jdbcUsername" value="sa"/>
    <property name="jdbcPassword" value=""/>

    <property name="databaseSchemaUpdate" value="true"/>

    <property name="configurators">
        <list>
            <ref bean="formEngineConfigurator"/>
            <ref bean="contentEngineConfigurator"/>
        </list>
    </property>

</bean>

<bean id="formEngineConfigurator" class="org.flowable.form.engine.configurator.FormEngineConfigurator">
    <property name="formEngineConfiguration" ref="formEngineConfiguration"/>
</bean>
<bean id="formEngineConfiguration" class="org.flowable.form.engine.impl.cfg.StandaloneFormEngineConfiguration">
</bean>

<bean id="contentEngineConfigurator" class="org.flowable.content.engine.configurator.ContentEngineConfigurator">
    <property name="contentEngineConfiguration" ref="contentEngineConfiguration"/>
</bean>
<bean id="contentEngineConfiguration" class="org.flowable.content.engine.impl.cfg.StandaloneContentEngineConfiguration">
    <property name="jdbcUrl" value="jdbc:h2:mem:flowablecontent;DB_CLOSE_DELAY=1000" />
    <property name="jdbcDriver" value="org.h2.Driver" />
    <property name="jdbcUsername" value="sa" />
    <property name="jdbcPassword" value="" />
</bean>

naeem · April 29, 2019, 10:55am

Hi. Could you please advise on a sample config xml that would get this working? Thanks.

naeem · May 3, 2019, 8:50am

Any help please? Still stuck on this.

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Error while closing command context: NullPointerException

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