Assertion.java

/*
 * JBoss, Home of Professional Open Source.
 * See the COPYRIGHT.txt file distributed with this work for information
 * regarding copyright ownership.  Some portions may be licensed
 * to Red Hat, Inc. under one or more contributor license agreements.
 * 
 * This library 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 library 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 library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301 USA.
 */

package org.teiid.core.util;

import org.teiid.core.CorePlugin;


/**
 * <p>
 * This class contains a set of static utility methods for assertion checking. 
 * Assertions are used to document the assumptions a programmer is making about the
 * code they are writing.  Assertions should not be used in cases where the user of 
 * a class can affect whether the assertion is true or false, such as argument 
 * checking.  Rather, assertions should be considered a much stronger statement by
 * the programmer that such a condition is NEVER true.  In fact, this statement is 
 * so strong that assertions should be considered optional as they should never occur.
 * However, these assertions may be violated during development and that is primarily
 * where these assertions are useful.
 * </p><p>
 * In JDK 1.4, Sun introduces the "assert" keyword and builds assertion support directly
 * into the language.  When MetaMatrix begins using JDK 1.4 across the board, this
 * class should no longer be needed and all usage of assertions should be replaced with 
 * use of the built-in JDK assertion facility.
 * </p>
 */
public final class Assertion {
    //============================================================================================================================
	// Constructors
    
	// Can't construct - just utility methods
	private Assertion() {
	}

    //============================================================================================================================
	// Methods
	
	// ########################## BASIC METHODS ###################################

    public static final void assertTrue(boolean condition) {
        assertTrue(condition,null);
    }
    
    public static final void assertTrue(boolean condition, String msgKey) {
        if(! condition) {
            final String msg = msgKey != null ?
                               msgKey :
                               CorePlugin.Util.getString("Assertion.Assertion_failed"); //$NON-NLS-1$ 
            failed(msg);
        }   
    }
		
	public static final void failed(String msg) {
		throw new AssertionError(msg);
	}

	// ########################## OBJECT METHODS ###################################
	
	public static final void isNull(Object value) {
        isNull(value,null);
	}

	public static final void isNull(Object value, String message) {
        if ( value != null ) {
            final String msg = message != null ?
                               message :
                               CorePlugin.Util.getString("Assertion.isNull"); //$NON-NLS-1$
            failed(msg);
        }
	}

	public static final void isNotNull(Object value) {
        isNotNull(value,null);
	}

	public static final void isNotNull(Object value, String message) {
        if ( value == null ) {
            final String msg = message != null ?
                               message :
                               CorePlugin.Util.getString("Assertion.isNotNull"); //$NON-NLS-1$
            failed(msg);
        }
	}

    /**
     * Verifies that the specified value is an instance of the specified class.
     * @param value            The value to verify
     * @param exprectedClass   The class of which the value must be an instance
     * @param name             The text identifying the name or type of value
     * @throws ClassCastException If the value is not an instance of the specified class.
     * @since 2.1
     */
    public static final <T> T isInstanceOf(final Object object, final Class<T> expectedClass, final String name) {
        if (object == null) {
            return null;
        }
        final Class<?> objClass = object.getClass();
        if (!expectedClass.isAssignableFrom(objClass)) {
            final Object[] params = new Object[]{name, expectedClass, objClass.getName()};
            final String msg = CorePlugin.Util.getString("Assertion.invalidClassMessage",params); //$NON-NLS-1$
            throw new ClassCastException(msg);
        }
        return expectedClass.cast(object);
    }

}