actionmessages.java.svn-base

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/*
 * $Id$
 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 */
package org.apache.struts.action;

import java.io.Serializable;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;

/**
 * <p>A class that encapsulates messages. Messages can be either global or
 * they are specific to a particular bean property.</p>
 *
 * <p>Each individual message is described by an <code>ActionMessage</code>
 * object, which contains a message key (to be looked up in an appropriate
 * message resources database), and up to four placeholder arguments used for
 * parametric substitution in the resulting message.</p>
 *
 * <p><strong>IMPLEMENTATION NOTE</strong> - It is assumed that these objects
 * are created and manipulated only within the context of a single thread.
 * Therefore, no synchronization is required for access to internal
 * collections.</p>
 *
 * @version $Rev$ $Date: 2005-08-26 21:58:39 -0400 (Fri, 26 Aug 2005)
 *          $
 * @since Struts 1.1
 */
public class ActionMessages implements Serializable {
    /**
     * <p>Compares ActionMessageItem objects.</p>
     */
    private static final Comparator ACTION_ITEM_COMPARATOR =
        new Comparator() {
            public int compare(Object o1, Object o2) {
                return ((ActionMessageItem) o1).getOrder()
                - ((ActionMessageItem) o2).getOrder();
            }
        };

    // ----------------------------------------------------- Manifest Constants

    /**
     * <p>The "property name" marker to use for global messages, as opposed to
     * those related to a specific property.</p>
     */
    public static final String GLOBAL_MESSAGE =
        "org.apache.struts.action.GLOBAL_MESSAGE";

    // ----------------------------------------------------- Instance Variables

    /**
     * <p>Have the messages been retrieved from this object?</p>
     *
     * <p>The controller uses this property to determine if session-scoped
     * messages can be removed.</p>
     *
     * @since Struts 1.2
     */
    protected boolean accessed = false;

    /**
     * <p>The accumulated set of <code>ActionMessage</code> objects
     * (represented as an ArrayList) for each property, keyed by property
     * name.</p>
     */
    protected HashMap messages = new HashMap();

    /**
     * <p>The current number of the property/key being added. This is used to
     * maintain the order messages are added.</p>
     */
    protected int iCount = 0;

    // --------------------------------------------------------- Public Methods

    /**
     * <p>Create an empty <code>ActionMessages</code> object.</p>
     */
    public ActionMessages() {
        super();
    }

    /**
     * <p>Create an <code>ActionMessages</code> object initialized with the
     * given messages.</p>
     *
     * @param messages The messages to be initially added to this object. This
     *                 parameter can be <code>null</code>.
     * @since Struts 1.1
     */
    public ActionMessages(ActionMessages messages) {
        super();
        this.add(messages);
    }

    /**
     * <p>Add a message to the set of messages for the specified property. An
     * order of the property/key is maintained based on the initial addition
     * of the property/key.</p>
     *
     * @param property Property name (or ActionMessages.GLOBAL_MESSAGE)
     * @param message  The message to be added
     */
    public void add(String property, ActionMessage message) {
        ActionMessageItem item = (ActionMessageItem) messages.get(property);
        List list;

        if (item == null) {
            list = new ArrayList();
            item = new ActionMessageItem(list, iCount++, property);

            messages.put(property, item);
        } else {
            list = item.getList();
        }

        list.add(message);
    }

    /**
     * <p>Adds the messages from the given <code>ActionMessages</code> object
     * to this set of messages. The messages are added in the order they are
     * returned from the <code>properties</code> method. If a message's
     * property is already in the current <code>ActionMessages</code> object,
     * it is added to the end of the list for that property. If a message's
     * property is not in the current list it is added to the end of the
     * properties.</p>
     *
     * @param actionMessages The <code>ActionMessages</code> object to be
     *                       added. This parameter can be <code>null</code>.
     * @since Struts 1.1
     */
    public void add(ActionMessages actionMessages) {
        if (actionMessages == null) {
            return;
        }

        // loop over properties
        Iterator props = actionMessages.properties();

        while (props.hasNext()) {
            String property = (String) props.next();

            // loop over messages for each property
            Iterator msgs = actionMessages.get(property);

            while (msgs.hasNext()) {
                ActionMessage msg = (ActionMessage) msgs.next();

                this.add(property, msg);
            }
        }
    }

    /**
     * <p>Clear all messages recorded by this object.</p>
     */
    public void clear() {
        messages.clear();
    }

    /**
     * <p>Return <code>true</code> if there are no messages recorded in this
     * collection, or <code>false</code> otherwise.</p>
     *
     * @return <code>true</code> if there are no messages recorded in this
     *         collection; <code>false</code> otherwise.
     * @since Struts 1.1
     */
    public boolean isEmpty() {
        return (messages.isEmpty());
    }

    /**
     * <p>Return the set of all recorded messages, without distinction by
     * which property the messages are associated with. If there are no
     * messages recorded, an empty enumeration is returned.</p>
     *
     * @return An iterator over the messages for all properties.
     */
    public Iterator get() {
        this.accessed = true;

        if (messages.isEmpty()) {
            return Collections.EMPTY_LIST.iterator();
        }

        ArrayList results = new ArrayList();
        ArrayList actionItems = new ArrayList();

        for (Iterator i = messages.values().iterator(); i.hasNext();) {
            actionItems.add(i.next());
        }

        // Sort ActionMessageItems based on the initial order the
        // property/key was added to ActionMessages.
        Collections.sort(actionItems, ACTION_ITEM_COMPARATOR);

        for (Iterator i = actionItems.iterator(); i.hasNext();) {
            ActionMessageItem ami = (ActionMessageItem) i.next();

            for (Iterator msgsIter = ami.getList().iterator();
                msgsIter.hasNext();) {
                results.add(msgsIter.next());
            }
        }

        return results.iterator();
    }

    /**
     * <p>Return the set of messages related to a specific property. If there
     * are no such messages, an empty enumeration is returned.</p>
     *
     * @param property Property name (or ActionMessages.GLOBAL_MESSAGE)
     * @return An iterator over the messages for the specified property.
     */
    public Iterator get(String property) {
        this.accessed = true;

        ActionMessageItem item = (ActionMessageItem) messages.get(property);

        if (item == null) {
            return (Collections.EMPTY_LIST.iterator());
        } else {
            return (item.getList().iterator());
        }
    }

    /**
     * <p>Returns <code>true</code> if the <code>get()</code> or
     * <code>get(String)</code> methods are called.</p>
     *
     * @return <code>true</code> if the messages have been accessed one or
     *         more times.
     * @since Struts 1.2
     */
    public boolean isAccessed() {
        return this.accessed;
    }

    /**
     * <p>Return the set of property names for which at least one message has
     * been recorded. If there are no messages, an empty <code>Iterator</code>
     * is returned. If you have recorded global messages, the
     * <code>String</code> value of <code>ActionMessages.GLOBAL_MESSAGE</code>
     * will be one of the returned property names.</p>
     *
     * @return An iterator over the property names for which messages exist.
     */
    public Iterator properties() {
        if (messages.isEmpty()) {
            return Collections.EMPTY_LIST.iterator();
        }

        ArrayList results = new ArrayList();
        ArrayList actionItems = new ArrayList();

        for (Iterator i = messages.values().iterator(); i.hasNext();) {
            actionItems.add(i.next());
        }

        // Sort ActionMessageItems based on the initial order the
        // property/key was added to ActionMessages.
        Collections.sort(actionItems, ACTION_ITEM_COMPARATOR);

        for (Iterator i = actionItems.iterator(); i.hasNext();) {
            ActionMessageItem ami = (ActionMessageItem) i.next();

            results.add(ami.getProperty());
        }

        return results.iterator();
    }

    /**
     * <p>Return the number of messages recorded for all properties (including
     * global messages). <strong>NOTE</strong> - it is more efficient to call
     * <code>isEmpty</code> if all you care about is whether or not there are
     * any messages at all.</p>
     *
     * @return The number of messages associated with all properties.
     */
    public int size() {
        int total = 0;

        for (Iterator i = messages.values().iterator(); i.hasNext();) {
            ActionMessageItem ami = (ActionMessageItem) i.next();

            total += ami.getList().size();
        }

        return (total);
    }

    /**
     * <p>Return the number of messages associated with the specified
     * property. </p>
     *
     * @param property Property name (or ActionMessages.GLOBAL_MESSAGE)
     * @return The number of messages associated with the property.
     */
    public int size(String property) {
        ActionMessageItem item = (ActionMessageItem) messages.get(property);

        return (item == null) ? 0 : item.getList().size();
    }

    /**
     * <p>Returns a String representation of this ActionMessages' property
     * name=message list mapping.</p>
     *
     * @return String representation of the messages
     * @see Object#toString()
     */
    public String toString() {
        return this.messages.toString();
    }

    /**
     * <p>This class is used to store a set of messages associated with a
     * property/key and the position it was initially added to list.</p>
     */
    protected class ActionMessageItem implements Serializable {
        /**
         * <p>The list of <code>ActionMessage</code>s.</p>
         */
        protected List list = null;

        /**
         * <p>The position in the list of messages.</p>
         */
        protected int iOrder = 0;

        /**
         * <p>The property associated with <code>ActionMessage</code>.</p>
         */
        protected String property = null;

        /**
         * <p>Construct an instance of this class.</p>
         *
         * @param list     The list of ActionMessages.
         * @param iOrder   The position in the list of messages.
         * @param property The property associated with ActionMessage.
         */
        public ActionMessageItem(List list, int iOrder, String property) {
            this.list = list;
            this.iOrder = iOrder;
            this.property = property;
        }

        /**
         * <p>Retrieve the list of messages associated with this item.</p>
         *
         * @return The list of messages associated with this item.
         */
        public List getList() {
            return list;
        }

        /**
         * <p>Set the list of messages associated with this item.</p>
         *
         * @param list The list of messages associated with this item.
         */
        public void setList(List list) {
            this.list = list;
        }

        /**
         * <p>Retrieve the position in the message list.</p>
         *
         * @return The position in the message list.
         */
        public int getOrder() {
            return iOrder;
        }

        /**
         * <p>Set the position in the message list.</p>
         *
         * @param iOrder The position in the message list.
         */
        public void setOrder(int iOrder) {
            this.iOrder = iOrder;
        }

        /**
         * <p>Retrieve the property associated with this item.</p>
         *
         * @return The property associated with this item.
         */
        public String getProperty() {
            return property;
        }

        /**
         * <p>Set the property associated with this item.</p>
         *
         * @param property The property associated with this item.
         */
        public void setProperty(String property) {
            this.property = property;
        }

        /**
         * <p>Construct a string representation of this object.</p>
         *
         * @return A string representation of this object.
         */
        public String toString() {
            return this.list.toString();
        }
    }
}