Activiti custom serialization of process variables.

appcontext.xml

  <bean id="configurationService"
		class="ConfigurationService" init-method="init">
		<property name="voVars">
			<list>
				<bean id="leaveProcVarType" class="..CustomVariableType">
					<constructor-arg type="java.lang.String" value="Leave" />
					<constructor-arg type="java.lang.Class"	value="..Leave" />
				</bean>
			</list>
		</property>
		<property name="processEngineConfigurationImpl" ref="processEngineConfiguration" />
	</bean>

ConfigurationService.java

public class ConfigurationService {
	/** 
	 * The process engine configuration impl. 
	 **/
	private ProcessEngineConfigurationImpl processEngineConfigurationImpl;
	/**
	 * The Custom vars. 
	 */
	private List<CustomVariableType> CustomVars;
	/**
	 * init method for this service bean
	 */
	public void init(){
		logger.debug("inside init");
		for(CustomVariableType varType : CustomVars) {
			logger.debug("adding type {}", varType.getTypeName());
			if(processEngineConfigurationImpl.getVariableTypes() == null){
				processEngineConfigurationImpl.setVariableTypes(new DefaultVariableTypes());
			}
			processEngineConfigurationImpl.getVariableTypes().addType(varType, 0);
			
			Context.setProcessEngineConfiguration(processEngineConfigurationImpl);
		}
	}
	/**
	 * @return the processEngineConfigurationImpl
	 */
	public ProcessEngineConfigurationImpl getProcessEngineConfigurationImpl() {
		return processEngineConfigurationImpl;
	}
	/**
	 * @param processEngineConfigurationImpl the processEngineConfigurationImpl to set
	 */
	public Customid setProcessEngineConfigurationImpl(
			ProcessEngineConfigurationImpl processEngineConfigurationImpl) {
		this.processEngineConfigurationImpl = processEngineConfigurationImpl;
	}
	/**
	 * @return the CustomVars
	 */
	public List<CustomVariableType> getCustomVars() {
		return CustomVars;
	}
	/**
	 * @param CustomVars the CustomVars to set
	 */
	public void setCustomVars(List<CustomVariableType> CustomVars) {
		this.CustomVars = CustomVars;
	}
}

CustomVar.java

/**
 * @author ajjain
 * 
 * Markup interface which represent an item which can be used as process variable
 * Serialization and Deserialization of such objects in work list application shall be managed independently. 
 */
public interface CustomVar {

}

CustomVariableType.java

/**
 * @author ajjain
 * 
 * Represents Custom variable type in Activiti. This supports serializing process variables as JSON strings
 * as byte arrays. 
 */
public class CustomVariableType extends ByteArrayType {

	/** The type name. */
	protected String typeName;

	/** The class. */
	protected Class<? extends CustomVar> theClass;
	/**
	 * represents the JSON mapper object
	 */
	private static final ObjectMapper jsonMapper = new ObjectMapper();
	/**
	 * Instantiates a new view object variable type.
	 *
	 * @param typeName the type name
	 * @param theClass the the class
	 */
	public CustomVariableType(String typeName, Class<? extends WorklistProcVar> theClass) {
		logger.trace("constructing custom variable type name {}, class {}", typeName, theClass);
		this.typeName = typeName;
		this.theClass = theClass;
	}
	/**
	 * @return the typeName
	 */
	@Override
	public String getTypeName() {
		return typeName;
	}

	@Override
	public Object getValue(ValueFields valueFields) {
		logger.trace("CustomVariableType.getValue valueFields {}", valueFields);

		byte[] bytes = (byte[]) super.getValue(valueFields);

		Object result;
		try {
			result = jsonMapper.readValue(bytes, this.getTheClass());
			logger.trace("getValue returning object {}", result);
			return result;
		}
		catch (Throwable e) {
			logger.warn("error in deserializing the output", e);
			throw new ActivitiException("Couldn't deserialize object in variable '"+valueFields.getName()+"'", e);
		}
	}
	@Override
	public boolean isCachable() {
		return false;
	}
	@Override
	public boolean isAbleToStore(Object value) {
		logger.trace("isAbleToStore value {}", value, value instanceof WorklistProcVar);
		return (value instanceof WorklistProcVar) && (theClass.isAssignableFrom(value.getClass()));
	}

	@Override
	public void setValue(Object value, ValueFields valueFields) {
		byte[] byteArray = serialize(value, valueFields);
		super.setValue(byteArray, valueFields);	
	}

	/**
	 * Serialize.
	 *
	 * @param value the value
	 * @param valueFields the value fields
	 * @return the byte[]
	 */
	public static byte[] serialize(Object value, ValueFields valueFields) {
		if (value == null) {
			return null;
		}
		try {
			byte[] valueBytes = jsonMapper.writeValueAsBytes(value);
			
			return valueBytes;
		} catch (Exception e) {
			throw new ActivitiException("Couldn't serialize value '"+value+"' in variable '"+valueFields.getName()+"'", e);
		} 
	}
	/**
	 * @return the theClass
	 */
	public Class<?> getTheClass() {
		return theClass;
	}

	/**
	 * @param theClass the theClass to set
	 */
	public void setTheClass(Class<? extends WorklistProcVar> theClass) {
		this.theClass = theClass;
	}

	/**
	 * @param typeName the typeName to set
	 */
	public void setTypeName(String typeName) {
		this.typeName = typeName;
	}
	/** The logger. */
	private Logger logger = LoggerFactory.getLogger(CustomVariableType.class);
	/**
	 * @return the json mapper
	 */
	public static ObjectMapper getJsonmapper() {
		return jsonMapper;
	}
}