function.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

		    ps[i] = exp;

		} else {

		    // Eval this expression.
		    try
		    {

			ps[i] = exp.getValue (o,
					      q);

		    } catch (Exception e) {
			
			throw new QueryExecutionException ("Unable to get parameter: " + 
							   i + 
							   " (\"" +
							   exp.toString () + 
							   "\") for function: " +
							   this.name,
							   e);
			
		    }

		}

	    }

	}

	Object v = null;

	try
	{

	    v = this.function.invoke (this.handler,
				      ps);

	} catch (Exception e) {

	    throw new QueryExecutionException ("Unable to execute function: " + 
					       this.name + 
					       " (\"" +
					       this.toString () + 
					       "\") with values: " +
					       Arrays.asList (ps),
					       e);

	}

	if (v != null)
	{

	    // See if we have an accessor.
	    if (this.acc != null)
	    {

		// See if we have a Getter.
		if (this.get == null)
		{

		    // No getter, so now try and init it.  This assumes that the return
		    // type won't ever change!
		    try
		    {

			this.get = new Getter (this.acc,
					       v.getClass ());
			
		    } catch (Exception e) {
			
			throw new QueryExecutionException ("Unable to create accessor for: " +
							   this.acc +
							   " from return type: " +
							   v.getClass ().getName () + 
							   " after execution of function: " +
							   this,
							   e);

		    }

		}

		try
		{

		    v = this.get.getValue (v);
		    
		} catch (Exception e) {
		    
		    throw new QueryExecutionException ("Unable to get value for accessor: " +
						       this.acc +
						       " from return type: " +
						       v.getClass ().getName () + 
						       " after execution of function: " +
						       this,
						       e);
		    
		}

	    }

	}

	if (this.fixedResult)
	{

	    this.fixedValue = v;

	}

	return v;

    }

    /**
     * Return whether the evaluation of this function (see: {@link #evaluate(Object,Query)})
     * will result in a <code>true</code> value.
     * See: {@link ArithmeticExpression#isTrue(Object,Query)} for details of how this is 
     * determined.
     *
     * @param o The current object.
     * @param q The Query object.
     * @return <code>true</code> if the function return value evaluates to <code>true</code>.
     * @throws QueryExecutionException If something goes wrong with evaluating the function.
     */
    public boolean isTrue (Object o,
			   Query  q)
	                   throws QueryExecutionException
    {

	o = this.evaluate (o,
			   q);

	if (o == null)
	{
	    
	    return false;

	}

	if (Utilities.isNumber (o))
	{

	    return Utilities.getDouble (o) > 0;

	}

	if (o instanceof Boolean)
	{

	    return ((Boolean) o).booleanValue ();

	}

	// Not null so return true...
	return true;	

    }

    /**
     * Return a string representation of the function.
     * In the form: Name ( {@link Expression} [ , {@link Expression} ] )
     * 
     * @return A string representation of the function.
     */
    public String toString ()
    {

	StringBuffer buf = new StringBuffer ();

	buf.append (this.name);
	buf.append ("(");

	if (this.params != null)
	{

	    for (int i = 0; i < this.params.size (); i++)
	    {

		Expression p = (Expression) this.params.get (i);

		buf.append (p);

		if (i < (this.params.size () - 1))
		{

		    buf.append (",");

		}

	    }

	}

	buf.append (")");

	if (this.acc != null)
	{

	    buf.append (".");
	    buf.append (this.acc);

	}

	if (this.isBracketed ())
	{

	    buf.insert (0,
			"(");

	    buf.append (")");

	}

	return buf.toString ();

    }

    /**
     * Return whether the function will return a fixed result, this only
     * occurs iff all the arguments to the function also return a fixed result.
     *
     * @param q The Query object.
     */
    public boolean hasFixedResult (Query q)
    {

	return this.fixedResult;

    }

    private int matchMethodArgs (Class[] methArgs,
				 Query   q)
                                 throws  QueryParseException
    {

	// The score here helps in argument resolution, a more specific argument
	// match (that is NOT expression in the method args) will score higher and
	// thus is a better match.
	int score = 0;

	for (int i = 0; i < methArgs.length; i++)
	{

	    Class c = methArgs[i];
	    
	    Expression exp = (Expression) this.params.get (i);

	    // See if the arg is object, which means "I can accept any type".
	    if (c.getClass ().getName ().equals (Object.class.getName ()))
	    {

		score += 1;

		continue;

	    }

	    // Now try and get the expected return type...
	    Class expC = exp.getExpectedReturnType (q);

	    if (expC == null)
	    {

		// Can't match this arg.
		continue;

	    } else {

		if (c.isAssignableFrom (expC))
		{

		    score += 2;

		    continue;

		}

	    }

	    if (Expression.class.isAssignableFrom (c))
	    {

		score += 1;

		// This is a match... i.e. the arg is an expression and thus supported
		// in a "special" way.
		continue;

	    }

	    if ((Utilities.isNumber (expC))
		&&
		((Utilities.isNumber (c))
		 ||
		 (c.getName ().equals (Object.class.getName ()))
		)
	       )
	    {

		score += 1;

		// This matches...
		continue;

	    }

	    if ((Utilities.isPrimitiveClass (c))
		&&
		(Utilities.isPrimitiveClass (expC))
	       )
	    {

		// It is a primitive class as well, so now see if they are compatible.
		if (Utilities.getPrimitiveClass (c).isAssignableFrom (Utilities.getPrimitiveClass (expC)))
		{

		    score += 1;

		    // They are assignable...
		    continue;

		}

	    }

	    // See if the expression return type is an object... this "may" mean
	    // that we can match and it may not, it will be determined at runtime.
	    if (expC.getName ().equals (Object.class.getName ()))
	    {

		score += 1;

		continue;

	    }

	    // If we are here then we can't match this arg type...
	    // No point checking any further...
	    return 0;

	}

	// All args can be matched.
	return score;

    } 

    private void getMethods (Class  c,
			     Query  q,
			     Map    matches)
                             throws QueryParseException
    {

	Method[] meths = c.getMethods ();

	for (int i = 0; i < meths.length; i++)
	{

	    Method m = meths[i];

	    if (!m.getName ().equals (this.name))
	    {

		continue;

	    }

	    // Make sure it's public...
	    if (!Modifier.isPublic (m.getModifiers ()))
	    {

		continue;

	    }

	    // Now check the args... sigh...
	    Class[] mpt = m.getParameterTypes ();

	    int ps = 0;
	    int fps = 0;

	    if (mpt != null)
	    {

		ps = mpt.length;

	    }

	    if (this.params != null)
	    {

		fps = this.params.size ();

	    }

	    if (ps != fps)
	    {

		continue;

	    }

	    int score = this.matchMethodArgs (mpt,
					      q);

	    if (score > 0)
	    {

		matches.put (new Integer (score),
			     m);

	    }

	}

    }

}