JSON deserialize error

[Thuy Le]

Hi,

I configured camunda engine to serialize object by default.

In my process, I created a class named Department. This class consists of a attribute called employeeList which comprise a list of Employee object.

The data object is serialized to json as following (see in cockpit):

Value Info:

Object type name: com.gtel.hrworks.model.Department

Serialization Data Format: application/json

Value (Serialized): dept

{"department_id":null,"department_name":"Công nghệ thông tin","employeeList":[{"date":"12/08/2015","employee_id":"01432","employee_name":"Ta Tuan Anh","dept_name":"Công nghệ thông tin","come_default":"8:00","leave_default":"17:00","come":"7:14","leave":"0:00","reason":"5","hr_approved":true}]}

However, cockpit cannot deserialize above variable.

I also try with below java code in delegation class:

Department dept  = (Department) execution.getVariableTyped("dept");

and I met this error:

Deserialization Error: 

Cannot deserialize object in variable 'dept': SPIN/JACKSON-JSON-01007 Cannot construct java type from string 'com.gtel.hrworks.model.Department' 

Anyone have similar issue with this? Please kindly advise. 

Thank you in advance

[thorben....@camunda.com]

Hi,

If your class com.gtel.hrworks.model.Department is not in Cockpit's classpath, then Cockpit can't deserialize the JSON String to an instance of that. That's why Cockpit displays the serialized JSON value as well. Is there a specific reason you need to access the deserialized value in Cockpit for?

As for the issue in your delegate, could you please post the entire exception stack trace?

Cheers,
Thorben

[Thuy Le]

Hi Thorben,

In fact, I would like to retrieve a variable we set before, but when we call 

Department dept  = (Department) execution.getVariableTyped("dept");

I got below error message: Deserialization Error: 

Cannot deserialize object in variable 'dept': SPIN/JACKSON-JSON-01007 Cannot construct java type from string 'com.gtel.hrworks.model.Department' 

I found work around for it: override toString() function in all of the model class (Department and Employee). It works well now.

I don't know how this help actually as I don't call it anywhere.

My function:

public String toString() {

     return "EmployeeRecord "

       + "[date=" + date + ", employee_id=" + employee_id 

       + ", employee_name=" + employee_name + ", dept_name=" + dept_name 

       + ", come_default=" + come_default + ", leave_default=" + leave_default 

       + ", come=" + come + ", leave=" + leave 

       + ", reason=" + reason + ", hr_approved=" + hr_approved +

       "]";

   }

Thank you.

[thorben....@camunda.com]

Hi,

This sounds odd. Are you able to provide a failing test case or a simplified process application project that reproduces the error?

Cheers,
Thorben

[Thuy Le]

Hi Thorben,

Please see attached file for my project. Please remember that I set engine to serialize objects using JSON format by default.

Thank you in advance,

Thuy Le

[Thuy Le]

With this project, I cannot get dept using this code: Department dept  = (Department) execution.getVariableTyped("dept");

[thorben....@camunda.com]

Hi,

Thanks for the code. Which application server do you use?

Cheers,
Thorben

[Thuy Le]

Hi,

I am using Tomcat, shared engine.

 

Thank you and best regards,
Thuy Le

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[thorben....@camunda.com]

Hi Thuy Le,

I slightly modified the process (removed the calls to the mailing library) and wasn't able to reproduce the problem. I get the error only in Cockpit when I access the deserialized variable value which is expected behavior. Could it be that you mistook the error you got in Cockpit to originate from the listener?

Cheers,
Thorben

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[Thuy Le]

Hi Thorben,

 

It is so strange, I tried again and no problem occurred.

I removed the toString() function in models, no problem found as well.

I don’t know what happened.

 

By the way, in case that I configure the engine to serialize objects using JSON, could you please advise I should use which of following way to retrieve engine variable?

 

Department dept  = (Department) execution.getVariable("dept");

or

ObjectValue typedDept= execution.getVariableTyped("dept");                  

Department dept = (Department) typedDept.getValue();

 

Thank you for supporting.

Thuy Le

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[thorben....@camunda.com]

Hi Thuy Le,

In the case that you want to access the variable as an instance of the Java type "Department", the two APIs are equivalent. In both cases, the JSON object is deserialized to an instance of "Department" when you call the execution#getVariable* method. The typed value API (the second code snippet you posted) provides additional metadata for the variable and allows to fetch a variable without deserializing it (by calling execution.getVariableTyped("dept", false)). See the section in our user guide on the typed value API [1] for more details.

Cheers,
Thorben

[1] https://docs.camunda.org/manual/7.3/guides/user-guide/#process-engine-process-variables-typed-value-api

[Thuy Le]

Hi Thorben,

I got your point. Thanks again for your help.

Best regards,
Thuy Le

 

 

From: thorben....@camunda.com
Sent: Tuesday, October 6, 2015 4:58 PM
To: camunda BPM users
Subject: Re: [camunda-bpm-users] Re: JSON deserialize error

 

 

Hi Thuy Le,

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