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   package com.fc.taglibs.castor;
   
   import java.io.*;
   import java.util.ArrayList;
   import javax.naming.*;
   import javax.servlet.jsp.*;
   import javax.servlet.jsp.tagext.*;
   import org.apache.taglibs.standard.lang.support.*;
   
  import org.exolab.castor.jdo.DataObjects;
  import org.exolab.castor.jdo.Database;
  import org.exolab.castor.jdo.ClassNotPersistenceCapableException;
  import org.exolab.castor.jdo.TransactionNotInProgressException;
  import org.exolab.castor.jdo.PersistenceException;
  
  public class CastorLoadTag extends BodyTagSupport
  {
  	
  	/***
  	* The name of this tag
  	*/
  	private static String _tagName = "CastorLoadTag";
  	
  	/***
  	* The object to load
  	*/
  	private Object data = null;
  	
  	/***
  	* The Class of the object to load
  	*/
  	private Class c = null;
  	
  	/***
  	* The database to perform the update
  	*/
  	private Database db = null;
  	
  	/***
  	* The id by which we will refer to the data object in the JSP page.
  	*/
  	private String id;
  	
  	/***
  	* The fully qualified class name of the bean returned
  	*/
  	private String className;
  
  	/***
  	* The primary key of the bean in the database
  	*/
  	private String key;
  	
  		
  	/***
  	* The scope the bean will be placed in.
  	* Default to page scope
  	*/
  	private String scope = "page";
  	
  	/***
  	* For determining access mode
  	*/
  	private boolean accessModeSet = false;
  	private short _accessMode = Database.Shared;
  	private String accessMode = null;
  	
  	/***
     	* Sets the name of the page scoped attribute
  	* that is the bean we are deleting/updating
     	*/
    	public void setId(String _id)
    	{
      	this.id = _id;
    	}
  	
  	/***
     	* Sets the classname
     	*/
    	public void setClassName(String _class)
    	{
      	this.className = _class;
    	}
  
  	
  	/***
  	* Sets the primary key
  	*/
  	public void setKey(String _key)
  	{
  		this.key = _key;
  	}
  	
  	/***
  	* Sets the scope of the bean
  	*/
  	public void setScope(String _scope)
  	{
  		this.scope = _scope;
 	}
 	
 	/***
 	* Sets the access mode string
 	*/
 	public void setAccessMode(String _accessModeStr)
 	{
 		this.accessModeSet = true;
 		this.accessMode = _accessModeStr;
 	}
 	
 	/***
    	* Do the start tag bit
    	*/
 	public int doStartTag() throws JspException
 	{
 		
 		try 
 		{	
 			/***
 			* Determine the accessmode
 			*/
 			if (this.accessModeSet)
 			{
 				if (this.accessMode.equals("DbLocked"))
 					this._accessMode = Database.DbLocked;
 				else if (this.accessMode.equals("Exclusive"))
 					this._accessMode = Database.Exclusive;
 				else if (this.accessMode.equals("Shared"))
 					this._accessMode = Database.Shared;
 				else if (this.accessMode.equals("ReadOnly"))
 					this._accessMode = Database.ReadOnly;
 				else
 				{
 					String msg = "Invalid Access Mode set.";
 					log(msg , null);
 					throw new JspTagException(msg);
 				}
 			}
 			
 			
 			/*
 			* Check to see if this tag is nested within a transactional tag
 			* Get the transaction. Exception if no Transaction parent tag found.
 			*/
 			CastorTransactionInitiator t = (CastorTransactionInitiator)findAncestorWithClass(this, CastorTransactionInitiator.class);
 			if (t!=null) 
 			{
 				db = t.getDatabase();
 				log ("Got transaction from parent tag", null);
 				
 				/*
 				* Evaluate the primary key
 				*/
 				Object pk = null; 
 				if (this.key != null)
 				{
 	    			pk = (Object)ExpressionEvaluatorManager.evaluate("dataSource",this.key, Object.class, this, pageContext);
 				}
 				
 				/*
 				* Create an instance of the Class we are retrieving
 				*/
 				c = Class.forName(this.className);
 
 				/*
 				* Attempt to load the object only if the key is not null
 				*/
 				log("Loading object of type " + c + " with key " + pk, null);
 				
 					if (pk!=null)			
 						data = db.load(c,pk,_accessMode);
 					else
 						data = c.newInstance();
 				/*	
 				* Put the returned object in the 
 				* specified scope.
 				*/
 				
 				if (this.scope.equals("request")) 
 					pageContext.setAttribute(this.id, data, PageContext.REQUEST_SCOPE);	
 				else if (this.scope.equals("page"))
 					pageContext.setAttribute(this.id, data, PageContext.PAGE_SCOPE);
 				else if (this.scope.equals("session"))
 					pageContext.setAttribute(this.id, data, PageContext.SESSION_SCOPE);
 				else if (this.scope.equals("application"))
 					pageContext.setAttribute(this.id, data, PageContext.APPLICATION_SCOPE);
 				
 			}
 			else
 			{	
 				String msg = "Tag not nested within a CastorTransactionTag.";
 				log(msg,null);
 				throw new Exception(msg);	
 			}	
 		}
 		catch(TransactionNotInProgressException  e)
 		{
 			log(e.getMessage() , e);
 			throw new JspTagException(e.getMessage());
 		}
 		catch(PersistenceException  e)
 		{
 			log(e.getMessage() , e);
 			throw new JspTagException(e.getMessage());
 		}
 		catch(Exception  e)
 		{
 			log(e.getMessage() , e);
 			throw new JspTagException(e.getMessage());
 		}
 		
 		return EVAL_PAGE;
 	}
 	
 	private void log(String msg,Exception e)
 	{	
 		if (e!=null)
 		{
 			System.err.println(_tagName + ": " + msg);
 			e.printStackTrace();
 		}
 		else
 		{
 			System.out.println(_tagName + ": " + msg);
 		}
 	}
 
 }