Using Camunda HTTP-Connector

Hi there!

We can use the HTTP Connector in Camunda to call the relevant REST Endpoint from service tasks in the bpmn diagram. According to the below diagram, "Dummy Service 1 and 2"  are service tasks which will invoke the Rest endpoints.

A generic API exists to set parameters of a request. The following parameters are available.

In order to pass the Authorization key as a http header to the REST Endpoint, we have to check whether the auth key has more than 4000 characters. If so, the camunda engine will throw a jdbc exception. https://stackoverflow.com/questions/53471783/how-to-alter-camunda-database-to-accept-long-string-variables

To avoid the exception, you have to use java serialization for persisting the long string value.

RuntimeService runtimeService = processEngine.getRuntimeService();

VariableMap variables = Variables.createVariables();
variables.putValueTyped("var", Variables
          .objectValue(aLongStringValue)
              // tells the engine to use java serialization for persisting the value 
          .serializationDataFormat(SerializationDataFormats.JAVA)  
          .create());

// Start a process instance
ProcessInstance processInstance = runtimeService.startProcessInstanceByKey("testProcess", variables);

Limitations of this approach are:

1. You cannot use this variable in queries, for example runtimeService.createVariableInstanceQuery().variableValueEquals("var", aLongStringValue).list() would not find the variable
2. Whenever you fetch the variable, you will have to use the API that returns deserialized values (e.g. RuntimeService.getVariable("name") or RuntimeService.getVariableTyped("name", true)) to get the actual value. This can be a problem if you rely on the feature that the engine can serve variables in their serialized format (which is for a regular String variable just the plain String value; for a Java-serialized Object value, it is a base64-encoded String of the byte representation).

Ashen Jayasinghe

Software Developer 

DMS