package org.apache.velocity.context;

/*
 * Copyright 2001,2004 The Apache Software Foundation.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 *  Interface describing the application data context.  This set of
 *  routines is used by the application to set and remove 'named' data
 *  object to pass them to the template engine to use when rendering
 *  a template.
 *
 *  This is the same set of methods supported by the original Context
 *  class
 *
 *  @see org.apache.velocity.context.AbstractContext
 *  @see org.apache.velocity.VelocityContext
 *
 *  @author <a href="mailto:jvanzyl@apache.org">Jason van Zyl</a>
 *  @author <a href="mailto:geirm@optonline.net">Geir Magnusson Jr.</a>
 *  @version $Id: Context.java,v 1.5.4.1 2004/03/03 23:22:54 geirm Exp $
 */
public interface Context
{
    /**
     * Adds a name/value pair to the context.
     *
     * @param key   The name to key the provided value with.
     * @param value The corresponding value.
     */
    Object put(String key, Object value);

    /**
     * Gets the value corresponding to the provided key from the context.
     *
     * @param key The name of the desired value.
     * @return    The value corresponding to the provided key.
     */
    Object get(String key);
 
    /**
     * Indicates whether the specified key is in the context.
     *
     * @param key The key to look for.
     * @return    Whether the key is in the context.
     */
    boolean containsKey(Object key);

    /**
     * Get all the keys for the values in the context
     */
    Object[] getKeys();

    /**
     * Removes the value associated with the specified key from the context.
     *
     * @param key The name of the value to remove.
     * @return    The value that the key was mapped to, or <code>null</code> 
     *            if unmapped.
     */
    Object remove(Object key);
}
