设计模式与源码

最近在看JBPM4.4的源码，一直有一种想法，把Tomcat，Spring，Structs，Ext，Hibernate的源码中的23种设计模式进行整理出来，便于部门内学习。把设计的理论结合到源码中进行。

今天先看一下模板模式
/*
* 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.jpdl.internal.activity;

import org.w3c.dom.Element;

import org.jbpm.jpdl.internal.xml.JpdlParser;
import org.jbpm.pvm.internal.model.ActivityImpl;
import org.jbpm.pvm.internal.util.TagBinding;
import org.jbpm.pvm.internal.util.XmlUtil;
import org.jbpm.pvm.internal.xml.Parse;
import org.jbpm.pvm.internal.xml.Parser;

/**
* @author Tom Baeyens
*/
public abstract class JpdlBinding extends TagBinding {
 
  public JpdlBinding(String tagName) {
    super(tagName, null, null);
  }

  public abstract Object parseJpdl(Element element, Parse parse, JpdlParser parser);

  public final Object parse(Element element, Parse parse, Parser parser) {
    return parseJpdl(element, parse, (JpdlParser) parser);
  }

  public void parseName(Element element, ActivityImpl activity, Parse parse) {
    String name = XmlUtil.attribute(element, "name", isNameRequired() ? parse : null);
   
    if (name!=null) {
      // basic name validation
      if (name.length()==0) {
        parse.addProblem(XmlUtil.errorMessageAttribute(element, "name", name, "is empty"), element);
      }
      activity.setName(name);
    }
  }

  public boolean isNameRequired() {
    return true;
  }
}


父类中这个方法  public abstract Object parseJpdl(Element element, Parse parse, JpdlParser parser);

在子类中实现，但在父类中已经进行使用。

/*
* 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.jpdl.internal.activity;

import org.jbpm.jpdl.internal.xml.JpdlParser;
import org.jbpm.pvm.internal.model.ScopeElementImpl;
import org.jbpm.pvm.internal.task.TaskDefinitionImpl;
import org.jbpm.pvm.internal.xml.Parse;
import org.w3c.dom.Element;

/**
* @author Tom Baeyens
*/
public class TaskBinding extends JpdlBinding {

  private static final String TAG = "task";

  public TaskBinding() {
    super(TAG);
  }

  public Object parseJpdl(Element element, Parse parse, JpdlParser parser) {
    TaskActivity taskActivity = new TaskActivity();

    ScopeElementImpl scopeElement = parse.contextStackFind(ScopeElementImpl.class);
    TaskDefinitionImpl taskDefinition = parser.parseTaskDefinition(element, parse, scopeElement);
    taskActivity.setTaskDefinition(taskDefinition);
   
    return taskActivity;
  }
}