All persistent entities managed by the process engine (Process Instances, Tasks, …) have unique Ids. These Ids uniquely identify an individual task, process instance, etc. When these entities are persisted to the database, the ids are used as primary keys in the corresponding database tables.

Out of the box, the process engine provides two Id generator implementations.

The Database Id Generator

The Database Id Generator is implemented using a sequence Generator on top of the ACT_RU_PROPERTY table.

This id generator is good for debugging and testing since it generates human readable ids.

The UUID Generator

The StrongUuidGenerator uses a UUID generator which uses the Java UUID Generator (JUG) library internally.

In the Camunda BPM Full Distributions, the StrongUuidGenerator is preconfigured and the default Id Generator used by the process engine.

If you use an embedded process engine configuration and configure the process engine using Spring, you need to add the following lines to the Spring configuration to enable the StrongUuidGenerator:

<bean id="processEngineConfiguration" class="org.camunda.bpm.engine.impl.cfg.StandaloneInMemProcessEngineConfiguration">

  [...]

  <property name="idGenerator">
    <bean class="org.camunda.bpm.engine.impl.persistence.StrongUuidGenerator" />
  </property>

</bean>

Additionally, you need the following maven dependency:

<dependency>
  <groupId>com.fasterxml.uuid</groupId>
  <artifactId>java-uuid-generator</artifactId>
  <scope>provided</scope>
  <version>3.1.2</version>
</dependency>