variableinstance.java

jBpm是一个灵活可扩展的工作流管理系统。作为jBpm运行时server输入的业务流程使用简单强大的语言表达并打包在流程档案中

/*
 * JBoss, Home of Professional Open Source
 * Copyright 2005, JBoss Inc., and individual contributors as indicated
 * by the @authors tag. See the copyright.txt in the distribution for a
 * full listing of individual contributors.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */
package org.jbpm.context.exe;

import java.io.Serializable;
import java.util.Iterator;

import org.jbpm.JbpmException;
import org.jbpm.context.exe.variableinstance.NullInstance;
import org.jbpm.context.exe.variableinstance.UnpersistableInstance;
import org.jbpm.context.log.VariableCreateLog;
import org.jbpm.graph.exe.ProcessInstance;
import org.jbpm.graph.exe.Token;

/**
 * is a jbpm-internal class that serves as a base class for classes 
 * that store variable values in the database.
 */
public abstract class VariableInstance implements Serializable {

  private static final long serialVersionUID = 1L;
  
  long id = 0;
  protected String name = null;
  protected Token token = null;
  protected TokenVariableMap tokenVariableMap = null;
  protected ProcessInstance processInstance = null;
  protected Converter converter = null;
  protected Object valueCache = null;
  protected boolean isValueCached = false;

  // constructors /////////////////////////////////////////////////////////////
  
  public VariableInstance() {
  }

  public static VariableInstance create(Token token,
                                        String name, 
                                        Object value) {

    VariableInstance variableInstance = null;
    if (value==null) {
      variableInstance = new NullInstance();
    } else {
      variableInstance = createVariableInstance(value);
    }
    
    variableInstance.token = token;
    variableInstance.name = name;
    variableInstance.processInstance = (token!=null ? token.getProcessInstance() : null );
    if (token!=null) {
      token.addLog(new VariableCreateLog(variableInstance));
    }
    variableInstance.setValue(value);
    return variableInstance;
  }

  public static VariableInstance createVariableInstance(Object value) {
    VariableInstance variableInstance = null;
    
    Iterator iter = JbpmType.getJbpmTypes().iterator();
    while ( (iter.hasNext())
            && (variableInstance==null) ){
      JbpmType jbpmType = (JbpmType) iter.next();
      
      if (jbpmType.matches(value.getClass())) {
        variableInstance = jbpmType.newVariableInstance();
      }
    }

    if (variableInstance==null) {
      variableInstance = new UnpersistableInstance();
    }
    
    return variableInstance;
  }

  
  // abstract methods /////////////////////////////////////////////////////////

  /**
   * is true if this variable-instance supports the given value, false otherwise.
   */
  public abstract boolean isStorable(Object value);
  /**
   * is the value, stored by this variable instance.
   */
  protected abstract Object getObject();
  /**
   * stores the value in this variable instance.
   */
  protected abstract void setObject(Object value);

  // variable management //////////////////////////////////////////////////////

  public boolean supports(Object value) {
    if (converter!=null) {
      return converter.supports(value);
    }
    return isStorable(value);
  }

  public void setValue(Object value) {
    valueCache = value;
    isValueCached = true;

    if (converter!=null) {
      if (! converter.supports(value)) {
        throw new JbpmException("the converter '"+converter.getClass().getName()+"' in variable instance '"+this.getClass().getName()+"' does not support values of type '"+value.getClass().getName()+"'.  to change the type of a variable, you have to delete it first");
      }
      value = converter.convert(value);
    }
    if ( (value!=null)
         && (! this.isStorable(value)) ) {
      throw new JbpmException("variable instance '"+this.getClass().getName()+"' does not support values of type '"+value.getClass().getName()+"'.  to change the type of a variable, you have to delete it first");
    }
    setObject(value);
  }

  public Object getValue() {
    if (isValueCached) {
      return valueCache;
    }
    Object value = getObject();
    if ( (value!=null)
         && (converter!=null) ) {
      value = converter.revert(value);
      valueCache = value;
      isValueCached = true;
    }
    return value;
  }
  
  public void removeReferences() {
    tokenVariableMap = null;
    token = null;
    processInstance = null;
  }

  // utility methods /////////////////////////////////////////////////////////

  public String toString() {
    return "${"+name+"}";
  }
  
  // getters and setters //////////////////////////////////////////////////////

  public String getName() {
    return name;
  }
  public ProcessInstance getProcessInstance() {
    return processInstance;
  }
  public Token getToken() {
    return token;
  }
  public void setTokenVariableMap(TokenVariableMap tokenVariableMap) {
    this.tokenVariableMap = tokenVariableMap;
  }

  // private static Log log = LogFactory.getLog(VariableInstance.class);
}