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Seam core module for Seam framework integrated with JSF2
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/*
 * JBoss, Home of Professional Open Source
 *
 * Distributable under LGPL license.
 * See terms of license at gnu.org.
 */
package org.jboss.seam.bpm;

import java.lang.reflect.Method;

import org.jboss.seam.annotations.bpm.BeginTask;
import org.jboss.seam.annotations.bpm.CreateProcess;
import org.jboss.seam.annotations.bpm.EndTask;
import org.jboss.seam.annotations.bpm.ResumeProcess;
import org.jboss.seam.annotations.bpm.StartTask;
import org.jboss.seam.annotations.intercept.AroundInvoke;
import org.jboss.seam.annotations.intercept.Interceptor;
import org.jboss.seam.contexts.Contexts;
import org.jboss.seam.core.BijectionInterceptor;
import org.jboss.seam.core.Expressions;
import org.jboss.seam.core.Init;
import org.jboss.seam.intercept.AbstractInterceptor;
import org.jboss.seam.intercept.InvocationContext;
import org.jboss.seam.log.LogProvider;
import org.jboss.seam.log.Logging;
import org.jboss.seam.util.Strings;
import org.jboss.seam.web.Parameters;

/**
 * Implements annotation-based business-process demarcation.
 *
 * @author Steve Ebersole
 * @author Gavin King
 */
@Interceptor(stateless = true, around = BijectionInterceptor.class)
public class BusinessProcessInterceptor extends AbstractInterceptor {
	private static final long serialVersionUID = 758197867958840918L;

	private static final LogProvider log = Logging.getLogProvider(BusinessProcessInterceptor.class);

	public BusinessProcessInterceptor() {
		super();
	}
	
	@Override
	@AroundInvoke
	public Object aroundInvoke(InvocationContext invocation) throws Exception {
		if (!beforeInvocation(invocation)) {
			return null;
		} else {
			return afterInvocation(invocation, invocation.proceed());
		}
	}

	private boolean beforeInvocation(InvocationContext invocationContext) {
		Method method = invocationContext.getMethod();
		if (method.isAnnotationPresent(StartTask.class)) {
			log.trace("encountered @StartTask");
			StartTask tag = method.getAnnotation(StartTask.class);
			Long taskId = getProcessOrTaskId(tag.taskIdParameter(), tag.taskId());
			return BusinessProcess.instance().resumeTask(taskId);
		} else if (method.isAnnotationPresent(BeginTask.class)) {
			log.trace("encountered @BeginTask");
			BeginTask tag = method.getAnnotation(BeginTask.class);
			Long taskId = getProcessOrTaskId(tag.taskIdParameter(), tag.taskId());
			return BusinessProcess.instance().resumeTask(taskId);
		} else if (method.isAnnotationPresent(ResumeProcess.class)) {
			log.trace("encountered @ResumeProcess");
			ResumeProcess tag = method.getAnnotation(ResumeProcess.class);
			if ("".equals(tag.processKey())) {
				Long processId = getProcessOrTaskId(tag.processIdParameter(), tag.processId());
				return BusinessProcess.instance().resumeProcess(processId);
			} else {
				return BusinessProcess.instance().resumeProcess(tag.definition(), getProcessKey(tag.processKey()));
			}
		}
		if (method.isAnnotationPresent(EndTask.class)) {
			log.trace("encountered @EndTask");
			return BusinessProcess.instance().validateTask();
		} else {
			return true;
		}
	}

	private Object afterInvocation(InvocationContext invocation, Object result) {
		Method method = invocation.getMethod();
		if (result != null || method.getReturnType().equals(void.class)) //interpreted as "redisplay"
		{
			if (method.isAnnotationPresent(CreateProcess.class)) {
				log.trace("encountered @CreateProcess");
				CreateProcess tag = method.getAnnotation(CreateProcess.class);
				if ("".equals(tag.processKey())) {
					BusinessProcess.instance().createProcess(tag.definition());
				} else {
					BusinessProcess.instance().createProcess(tag.definition(), getProcessKey(tag.processKey()));
				}
			}
			if (method.isAnnotationPresent(StartTask.class)) {
				log.trace("encountered @StartTask");
				BusinessProcess.instance().startTask();
			}
			if (method.isAnnotationPresent(EndTask.class)) {
				log.trace("encountered @EndTask");
				BusinessProcess.instance().endTask(method.getAnnotation(EndTask.class).transition());
			}
			if (method.isAnnotationPresent(org.jboss.seam.annotations.bpm.Transition.class)) {
				log.trace("encountered @Transition");
				String transitionName = method.getAnnotation(org.jboss.seam.annotations.bpm.Transition.class).value();
				if ("".equals(transitionName)) {
					transitionName = method.getName();
				}
				BusinessProcess.instance().transition(transitionName);
			}
		}
		return result;
	}

	private String getProcessKey(String el) {
		Object key = Expressions.instance().createValueExpression(el).getValue();
		if (key == null) {
			throw new IllegalStateException("process business key may not be null");
		}
		return key.toString();
	}

	private Long getProcessOrTaskId(String paramName, String el) {
		Object id;
		if (Strings.isEmpty(paramName)) {
			id = Expressions.instance().createValueExpression(el).getValue();
		} else {
			String[] values = Parameters.instance().getRequestParameters().get(paramName);
			id = values != null && values.length == 1 ? values[0] : null;
		}

		if (id == null) {
			throw new IllegalStateException("task/process id may not be null");
		} else if (id instanceof Long) {
			return (Long) id;
		} else if (id instanceof String) {
			return Long.valueOf((String) id);
		} else {
			throw new IllegalArgumentException("task/process id must be a string or long");
		}
	}

	@Override
	public boolean isInterceptorEnabled() {
		return Contexts.isApplicationContextActive() && Init.instance().isJbpmInstalled();
	}

}