collectionfunctions.java

JoSQL 1.5的源代码。JoSQL(SQL for Java Objects)为Java开发者提供运用SQL语句来操作Java对象集的能力.利用JoSQL可以像操作数据库中的数据一样对任何Java

	    } catch (Exception e) {

		throw new QueryExecutionException ("Unable to execute expression: \"" +
						   exp +
						   " on object at index: " +
						   i +
						   " from the list of objects.",
						   e);

	    }

	}

	if (saveValueName != null)
	{

	    this.q.setSaveValue (saveValueName,
				 retVals);

	}

	// Reset the current object.
	this.q.setCurrentObject (co);

	return retVals;

    }

    public List collect (Expression exp)
	                 throws     QueryExecutionException
    {

	return this.collect ((List) this.q.getVariable (Query.ALL_OBJS_VAR_NAME),
			    exp);

    }    

    public List collect (List       allobjs,
			 Expression exp)
                         throws     QueryExecutionException
    {

	return this.collect (allobjs,
			     exp,
			     null);

    }

    public List toList (Expression exp)
	                throws     QueryExecutionException
    {

	return this.toList ((List) this.q.getVariable (Query.ALL_OBJS_VAR_NAME),
			    exp);

    }    

    public List toList (List       allobjs,
			Expression exp)
                        throws     QueryExecutionException
    {

	return this.collect (allobjs,
			     exp,
			     null);

    }

    public List foreach (Expression exp)
	                 throws     QueryExecutionException
    {

	return this.foreach ((List) this.q.getVariable (Query.ALL_OBJS_VAR_NAME),
			     exp);

    }    

    public List foreach (List       allobjs,
			 Expression exp)
	                 throws     QueryExecutionException
    {

	if (allobjs == null)
	{

	    return null;

	}

	List res = new ArrayList ();

	int s = allobjs.size (); 

	for (int i = 0; i < s; i++)
	{

	    Object o = allobjs.get (i);

	    this.q.setCurrentObject (o);

	    res.add (exp.getValue (o,
				   this.q));

	}

	return res;

    }

    private void fillMap (Object o,
			  Getter k,
			  Getter v)
                          throws QueryExecutionException
    {

	

    }

    /*
    public Map toMap (Object o,
		      Getter k,
		      Getter v)
	              throws QueryExecutionException
    {



    }

    public Map toMap (Object o,
		      Getter k,
		      Getter v,
		      String type)
	              throws QueryExecutionException
    {

	// Try and create the correct "Map" type.

    }
    */

    /**
     * Given a list of objects, execute the expression against each one and return
     * those objects that return a <code>true</code> value for the expression.
     * In effect this is equivalent to executing the WHERE clause of a JoSQL statement
     * against each object (which in fact is what happens internally).  The class
     * for the objects if found by examining the list passed in.
     *
     * @param objs The list of objects.
     * @param exp The expression (basically a where clause, it is ok for the expression
     *            to start with "WHERE", case-insensitive) to execute for each of the
     *            objects.
     * @return The list of matching objects.
     */
    public List foreach (List   objs,
			 String exp)
	                 throws QueryExecutionException
    {

	List l = new ArrayList ();

	if ((objs == null)
	    ||
	    (objs.size () == 0)
	   )
	{

	    return l;

	}

	Query q = null;

	// See if we have the expression in our cache.
	if (this.foreachQueryCache != null)
	{

	    q = (Query) this.foreachQueryCache.get (exp);

	}

	if (q == null)
	{

	    // Init our query.
	    Class c = null;

	    Object o = objs.get (0);

	    if (o == null)
	    {

		int s = objs.size () - 1;

		// Bugger now need to cycle until we get a class.
		for (int i = s; s > -1; i--)
		{

		    o = objs.get (i);

		    if (o != null)
		    {

			c = o.getClass ();
			break;

		    }

		}

	    } else {
		    
		c = o.getClass ();
		    
	    }

	    if (exp.toLowerCase ().trim ().startsWith ("where"))
	    {

		exp = exp.trim ().substring (5);

	    }

	    String query = "SELECT * FROM " + c.getName () + " WHERE " + exp;

	    q = new Query ();

	    try
	    {

		q.parse (query);

	    } catch (Exception e) {

		throw new QueryExecutionException ("Unable to create statement using WHERE clause: " +
						   exp +
						   " and class: " +
						   c.getName () + 
						   " (gained from objects in list passed in)",
						   e);

	    }

	    // Cache it.
	    if (this.foreachQueryCache == null)
	    {

		this.foreachQueryCache = new HashMap ();

	    }

	    this.foreachQueryCache.put (exp,
					q);

	}

	return q.execute (objs).getResults ();

    }

    public List foreach (Expression listFunction,
			 Expression exp)
	                 throws     QueryExecutionException
    {

	// Execute the list function.
	Object o = listFunction.getValue (this.q.getCurrentObject (),
					  this.q);

	if (!(o instanceof List))
	{

	    throw new QueryExecutionException ("Expected expression: " + 
					       listFunction + 
					       " to return instance of: " +
					       List.class.getName () + 
					       " but returned instance of: " +
					       o.getClass ().getName ());

	}

	List l = (List) o;

	return this.foreach (l,
			     exp);

    }    

    /**
     * Find objects from the List based upon the expression passed in.  If
     * the expression evaluates to <code>true</code> then the object will
     * be returned.
     * Note: in accordance with the general operating methodology for the Query
     *       object, the ":_allobjs" special bind variable will be set to the 
     *       the List passed in and the "_currobj" will be set to the relevant
     *       object in the List.
     *
     * @param objs The List of objects to search.
     * @param exp The expression to evaulate against each object in the List.
     * @return The List of matching objects, if none match then an empty list is returned.
     * @throws QueryExecutionException If the expression cannot be evaulated against each
     *                                 object.
     */
    public List find (List       objs,
		      Expression exp)
	              throws     QueryExecutionException
    {

	// Get the current object, it's important that we leave the Query in the
	// same state at the end of this function as when we started!
	Object currobj = this.q.getCurrentObject ();
	List allobjs = (List) this.q.getVariable (Query.ALL_OBJS_VAR_NAME);

	this.q.setAllObjects (objs);

	List r = new ArrayList ();

	int s = objs.size ();

	for (int i = 0; i < s; i++)
	{

	    Object o = objs.get (i);

	    this.q.setCurrentObject (o);

	    try
	    {

		if (exp.isTrue (o,
				this.q))
		{

		    r.add (o);

		}

	    } catch (Exception e) {

		throw new QueryExecutionException ("Unable to evaulate expression: " + 
						   exp + 
						   " against object: " +
						   i + 
						   " (class: " + 
						   o.getClass ().getName () + 
						   ")",
						   e);

	    }

	}

	// Restore the currobj and allobjs.
	this.q.setCurrentObject (currobj);
	this.q.setAllObjects (allobjs);

	return r;

    }

    /**
     * Group objects from the List based upon the expression passed in.  The expression
     * is evaulated for each object, by calling: {@link Expression#getValue(Object,Query)}
     * and the return value used as the key to the Map.  All objects with that value are
     * added to a List held against the key.  To maintain the ordering of the keys (if
     * desirable) a {@link LinkedHashMap} is used as the return Map.
     *
     * Note: in accordance with the general operating methodology for the Query
     *       object, the ":_allobjs" special bind variable will be set to the 
     *       the List passed in and the "_currobj" will be set to the relevant
     *       object in the List.
     *
     * @param objs The List of objects to search.
     * @param exp The expression to evaulate against each object in the List.
     * @return The LinkedHashMap of matching objects, grouped according to the return value
     *         of executing the expression against each object in the input List.
     * @throws QueryExecutionException If the expression cannot be evaulated against each
     *                                 object.
     */
    public Map grp (List       objs,
		    Expression exp)
	            throws     QueryExecutionException
    {
    
	// Get the current object, it's important that we leave the Query in the
	// same state at the end of this function as when we started!
	Object currobj = this.q.getCurrentObject ();
	List allobjs = (List) this.q.getVariable (Query.ALL_OBJS_VAR_NAME);

	this.q.setAllObjects (objs);

	Map r = new LinkedHashMap ();

	int s = objs.size ();

	for (int i = 0; i < s; i++)
	{

	    Object o = objs.get (i);

	    this.q.setCurrentObject (o);

	    try
	    {

		Object v = exp.getValue (o,
					 this.q);

		List vs = (List) r.get (v);

		if (vs == null)
		{

		    vs = new ArrayList ();

		    r.put (v,
			   vs);

		}

		vs.add (v);

	    } catch (Exception e) {

		throw new QueryExecutionException ("Unable to evaulate expression: " + 
						   exp + 
						   " against object: " +
						   i + 
						   " (class: " + 
						   o.getClass ().getName () + 
						   ")",
						   e);

	    }

	}

	// Restore the currobj and allobjs.
	this.q.setCurrentObject (currobj);
	this.q.setAllObjects (allobjs);

	return r;	

    }

}