bpel-rest-extensions/src/main/java/org/apache/ode/bpel/extension/bpel4restlight/Bpel4RestLightUtil.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.ode.bpel.extension.bpel4restlight;

import java.io.IOException;

import org.apache.ode.bpel.common.FaultException;
import org.apache.ode.bpel.eapi.ExtensionContext;
import org.apache.ode.bpel.obj.OScope;
import org.apache.ode.bpel.obj.OScope.Variable;
import org.apache.ode.bpel.obj.OVarType;
import org.apache.ode.bpel.obj.OXsdTypeVarType;
import org.apache.ode.utils.DOMUtils;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.xml.sax.SAXException;

/**
 * This class provides some utility methods for the BPEL REST extension
 * activities.
 * 
 * @author Michael Hahn (mhahn.dev@gmail.com)
 * 
 */
public class Bpel4RestLightUtil {

	private static final String VARIABLE_VALUE_REFERENCE = "$bpelvar[";

	/**
	 * This method extracts the request message payload from the provided extension
	 * activity. This request payload is either provided through a specified BPEL
	 * variable ('request' attribute) or statically defined within the process model
	 * as the child node of the extension activity.
	 * 
	 * @param context
	 *            The extension context required to resolve variable values
	 * @param element
	 *            The extension activity DOM element containing the request payload
	 * @return The request message payload
	 * 
	 * @throws FaultException
	 */
	public static String extractRequestPayload(ExtensionContext context, Element element) throws FaultException {
		String requestPayload = null;

		String requestPayloadVariableName = getMethodAttributeValue(context, element,
				MethodAttribute.REQUEST_PAYLOAD_VARIABLE);

		// Check if a reference to a variable is specified
		if (requestPayloadVariableName != null && !requestPayloadVariableName.isEmpty()) {
			// Get the request variable value
			Node requestVariableNode = context.readVariable(requestPayloadVariableName);

			// Check if the specified variable provides data
			if (requestVariableNode != null) {
				requestPayload = variableData2String(requestVariableNode);
			}
		}

		// If no variable was specified or the variable doesn't provide data, we check
		// if a static request payload is specified as the child element of the
		// extension activity
		if (requestPayload == null) {
			Node request = DOMUtils.findChildByType(element, Node.ELEMENT_NODE);

			if (request != null) {
				requestPayload = DOMUtils.domToString(request);
			}
		}

		if (requestPayload == null) {
			throw new FaultException(Bpel4RestLightExtensionBundle.FAULT_QNAME,
					"REST extension activity does not specify any request payload.");
		}

		return requestPayload;
	}

	/**
	 * This method writes the response payload to a specified BPEL variable.
	 * 
	 * @param context
	 *            The extension context required to resolve a variable and write a
	 *            new value to it
	 * @param responsePayload
	 *            The payload of the response which will be written to the specified
	 *            variable
	 * @param processVariableName
	 *            The name of the variable to write to
	 * @throws FaultException
	 */
	public static void writeResponsePayload(ExtensionContext context, Object responsePayload,
			String processVariableName) throws FaultException {
		if (responsePayload != null && !responsePayload.toString().isEmpty()) {
			OScope.Variable bpelVariable = context.getVisibleVariables().get(processVariableName);

			// Create a new instance of the variables' type, to see if we need a wrapper
			Document doc = DOMUtils.newDocument();
			Node val = bpelVariable.getType().newInstance(doc);

			// Check if we need a temporary simple type wrapper
			if (val.getNodeType() == Node.TEXT_NODE) {
				// Create a wrapper element and add the response payload as text node
				Element tempwrapper = doc.createElementNS(null, "temporary-simple-type-wrapper");
				doc.appendChild(tempwrapper);
				tempwrapper.appendChild(val);

				// Set the response payload
				val.setTextContent(responsePayload.toString());

				// Return the wrapper element
				val = tempwrapper;
			} else {
				// Convert the structured XML response payload to DOM
				try {
					val = DOMUtils.stringToDOM(responsePayload.toString());
				} catch (SAXException e) {
					throw new FaultException(Bpel4RestLightExtensionBundle.FAULT_QNAME,
							"BPEL4REST: Writing the response payload to BPEL variable '" + processVariableName
									+ "' caused an exception: " + e.getMessage(),
							e);
				} catch (IOException e) {
					throw new FaultException(Bpel4RestLightExtensionBundle.FAULT_QNAME,
							"BPEL4REST: Writing the response payload to BPEL variable '" + processVariableName
									+ "' caused an exception: " + e.getMessage(),
							e);
				}
			}

			// Write the variable value
			context.writeVariable(bpelVariable, val);
		}
	}

	public static String extractAcceptHeader(ExtensionContext context, Element element) throws FaultException {
		return getMethodAttributeValue(context, element, MethodAttribute.ACCEPT_HEADER);
	}

	/**
	 * This method extracts special predefined attributes (see
	 * {@link MethodAttribute}) from an extension activity. Therefore, references to
	 * a variable value via '$bpelVar[varName]' are also automatically resolved.
	 * 
	 * @param context
	 *            The extension context required to resolve variable values
	 * @param element
	 *            The extension activity DOM element containing the attribute value
	 * @param methodAttribute
	 *            Attribute whose content has to be returned
	 * @return The value of the attribute
	 * @throws FaultException
	 */
	public static String getMethodAttributeValue(ExtensionContext context, Element element,
			MethodAttribute methodAttribute) throws FaultException {

		String result = "";

		switch (methodAttribute) {

		case REQUEST_URI:
			result = element.getAttribute("uri");

			if (result == null || result.isEmpty()) {
				result = element.getAttribute("requestUri");
			} else {
				// Resolve a possible variable value reference
				result = resolveVariableValueReference(context, result);
			}

			break;
		case REQUEST_PAYLOAD_VARIABLE:
			result = element.getAttribute("request");

			if (result == null || result.isEmpty()) {
				result = element.getAttribute("requestPayload");
			}
			break;
		case RESPONSE_PAYLOAD_VARIABLE:
			result = element.getAttribute("response");

			if (result == null || result.isEmpty()) {
				result = element.getAttribute("responsePayload");
			}
			break;
		case STATUS_CODE_VARIABLE:
			result = element.getAttribute("statusCode");
			break;
		case ACCEPT_HEADER:
			result = element.getAttribute("accept");

			// Resolve a possible variable value reference
			if (result != null && !result.isEmpty()) {
				result = resolveVariableValueReference(context, result);
			}

			break;
		}

		return result;
	}

	/**
	 * Resolves references to variable values specified in an extension activity via
	 * '$bpelVar[varName]'.
	 * 
	 * @param context
	 *            The extension context to lookup and resolve variables and their
	 *            values.
	 * @param variableValueReference
	 *            A potential variable value reference.
	 * 
	 * @return If the 'variableValueReference' parameter contains a variable value
	 *         reference ($bpelVar[varName]), the actual value of the variable is
	 *         returned, else the provided parameter value is returned.
	 * @throws FaultException
	 */
	public static String resolveVariableValueReference(ExtensionContext context, String variableValueReference)
			throws FaultException {
		String variableValue = variableValueReference;

		// Check if a concrete variable name ("varName") or a reference to the value of
		// a variable
		// is specified ("$bpelVar[varName]")
		if (variableValueReference.startsWith(VARIABLE_VALUE_REFERENCE)) {
			String variableName = variableValueReference.substring(variableValueReference.indexOf("[") + 1,
					variableValueReference.indexOf("]"));

			Variable variable = context.getVisibleVariables().get(variableName);

			// We only support simple type variables, therefore the value of the variable is
			// directly provided within a <temporary-simple-type-wrapper/> element.
			if (variable != null && isSimpleType(variable.getType())) {
				Node variableContent = context.readVariable(variableName);

				if (variableContent.getTextContent() != null) {
					variableValue = variableContent.getTextContent();
				}
			} else {
				throw new FaultException(Bpel4RestLightExtensionBundle.FAULT_QNAME,
						"References to the value of a BPEL variable using '$bpelVar[varName]' only support simple type variables.");
			}
		}

		return variableValue;
	}

	public static String variableData2String(Node variableData) {
		String result = null;

		if (variableData != null) {
			if ("temporary-simple-type-wrapper".equals(variableData.getLocalName())) {
				result = variableData.getTextContent();
			} else {
				result = DOMUtils.domToString(variableData);
			}
		}

		return result;
	}

	/**
	 * Checks if the type is a simple type or not.
	 * 
	 * @param type
	 *            to check
	 * 
	 * @return True, if the type is simple, False otherwise.
	 */
	private static boolean isSimpleType(OVarType type) {
		boolean result = false;

		if (type instanceof OXsdTypeVarType) {
			result = ((OXsdTypeVarType) type).isSimple();
		}

		return result;
	}
}