GrepCode: org.apache.wicket.model.LoadableDetachableModel (.java) - Class

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org.apache.wicket.model.LoadableDetachableModel
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  /*
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   * Licensed to the Apache Software Foundation (ASF) under one or more
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   * contributor license agreements.  See the NOTICE file distributed with
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   * this work for additional information regarding copyright ownership.
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   * The ASF licenses this file to You under the Apache License, Version 2.0
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   * (the "License"); you may not use this file except in compliance with
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   * the License.  You may obtain a copy of the License at
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   *
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   *      http://www.apache.org/licenses/LICENSE-2.0
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  *
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  * Unless required by applicable law or agreed to in writing, software
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  * distributed under the License is distributed on an "AS IS" BASIS,
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  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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  * See the License for the specific language governing permissions and
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  * limitations under the License.
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  */
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 package org.apache.wicket.model;
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 import org.apache.wicket.Component;
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 import org.apache.wicket.RequestCycle;
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 import org.slf4j.Logger;
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 import org.slf4j.LoggerFactory;


 Model that makes working with detachable models a breeze. LoadableDetachableModel holds a
 temporary, transient model object, that is set when AbstractReadOnlyModel.getObject(org.apache.wicket.Component) is called by
 calling abstract method 'load', and that will be reset/ set to null on detach().
 
 A usage example:
 
  LoadableDetachableModel venueListModel = new LoadableDetachableModel()
 {
  protected Object load()
  {
   return getVenueDao().findVenues();
  }
 };
 
 Though you can override methods onAttach() and onDetach() for additional
 attach/ detach behavior, the point of this class is to hide as much of the attaching/ detaching
 as possible. So you should rarely need to override those methods, if ever.
 
 Author(s):Eelco HilleniusIgor Vaynberg
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 public abstract class LoadableDetachableModel extends AbstractReadOnlyModel
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 {
	
 
 
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 	private static final long serialVersionUID = 1L;

	
Logger.
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 	private static final Logger log = LoggerFactory.getLogger(LoadableDetachableModel.class);

	
keeps track of whether this model is attached or detached
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 	private transient boolean attached = false;

	
temporary, transient object.
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 	private transient Object transientModelObject;

	
 Construct.
 
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 	public LoadableDetachableModel()
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 	{
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 	}

	
 This constructor is used if you already have the object retrieved and want to wrap it with a
 detachable model.
 
 
 Parameters:object
            retrieved instance of the detachable object
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 	public LoadableDetachableModel(Object object)
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 	{
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 		this.transientModelObject = object;
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 		attached = true;
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 	}

	
 See also:IDetachable.detach()
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 	public void detach()
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 	{
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 		if (attached)
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 		{
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 			attached = false;
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 			transientModelObject = null;
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 			if (log.isDebugEnabled())
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 			{
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 				log.debug("removed transient object for " + this + ", requestCycle " +
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						RequestCycle.get());
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			}
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			onDetach();
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		}
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	}

	
 See also:IModel.getObject()
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	public Object getObject()
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	{
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		if (!attached)
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		{
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			attached = true;
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			transientModelObject = load();
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			if (log.isDebugEnabled())
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			{
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				log.debug("loaded transient object " + transientModelObject + " for " + this +
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						", requestCycle " + RequestCycle.get());
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			}
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			onAttach();
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		}
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		return transientModelObject;
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	}

	
 Gets the attached status of this model instance
 
 
 Returns:true if the model is attached, false otherwise
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	public final boolean isAttached()
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	{
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		return attached;
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	}

	
 See also:java.lang.Object.toString()
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	public String toString()
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	{
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		StringBuffer sb = new StringBuffer(super.toString());
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		sb.append(":attached=").append(attached).append(":tempModelObject=[").append(
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				this.transientModelObject).append("]");
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		return sb.toString();
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	}

	
 Loads and returns the (temporary) model object.
 
 
 Returns:the (temporary) model object
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	protected abstract Object load();

	
 Attaches to the current request. Implement this method with custom behavior, such as loading
 the model object.
 
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	protected void onAttach()
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	{
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	}

	
 Detaches from the current request. Implement this method with custom behavior, such as
 setting the model object to null.
 
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	protected void onDetach()
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	{
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	}
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}