# Unknown property used in expression when using Java Delegate with Delegate Expression in BPMN

**URL:** <https://forum.flowable.org/t/unknown-property-used-in-expression-when-using-java-delegate-with-delegate-expression-in-bpmn/7221>\
**Category:** Flowable Engine\
**Created:** [December 15, 2020, 2:43pm UTC](https://forum.flowable.org/t/unknown-property-used-in-expression-when-using-java-delegate-with-delegate-expression-in-bpmn/7221 "2020-12-15T14:43:41Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![awk123123](https://avatars.discourse-cdn.com/v4/letter/a/a5b964/32.png) [@awk123123](https://forum.flowable.org/u/awk123123)\
**Post date:** [December 15, 2020, 2:43pm UTC](https://forum.flowable.org/t/unknown-property-used-in-expression-when-using-java-delegate-with-delegate-expression-in-bpmn/7221/1 "2020-12-15T14:43:41Z")

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Is anyone also having problem when using java delegate task in service task with delegate expression?  
It is ok when placing into class with “org.flowable.DelegateExpressionBean”

**Error Message**

> Forwarding to error page from request [/app/rest/process-instances] due to exception [Unknown property used in expression: ${delegateExpressionBean}]

**Java Class**

```
package org.flowable;

@Component
public class DelegateExpressionBean implements JavaDelegate {
    @Autowired
    ExternalService externalService;
    @Override
    public void execute(DelegateExecution delegateExecution) {
       ...
       externalService.call();
    }

```

**BPMN XML**

> \<serviceTask id=“DelegateExpressionBean” name=“Delegate Expression Bean” flowable:delegateExpression=“${delegateExpressionBean}”\>

---

<div class="post-metadata">

**Author:** ![filiphr](https://yyz1.discourse-cdn.com/flex035/user_avatar/forum.flowable.org/filiphr/32/315_2.png) [@filiphr](https://forum.flowable.org/u/filiphr)\
**Post date:** [December 23, 2020, 10:17am UTC](https://forum.flowable.org/t/unknown-property-used-in-expression-when-using-java-delegate-with-delegate-expression-in-bpmn/7221/2 "2020-12-23T10:17:05Z")

</div>

Hey @awk123123,

This seems a lot like the post you shared in [Executing Service Task from UI](https://forum.flowable.org/t/executing-service-task-from-ui/4350/7). Have a look at my [reply](https://forum.flowable.org/t/executing-service-task-from-ui/4350/8) there.

Cheers,  
Filip