DefaultIconRepository.java

/*******************************************************************************
 * Copyright (c) 1998, 2015 Oracle and/or its affiliates. All rights reserved.
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
 * which accompanies this distribution.
 * The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * Contributors:
 *     Oracle - initial API and implementation from Oracle TopLink
******************************************************************************/
package org.eclipse.persistence.tools.workbench.framework.resources;

import java.net.URL;
import java.util.HashMap;
import java.util.Map;

import javax.swing.Icon;
import javax.swing.ImageIcon;

import org.eclipse.persistence.tools.workbench.utility.string.StringTools;


/**
 * DefaultIconRepository uses a IconResourceFileNameMap to associate
 * an icon key with the resource file containing the icon (typically a .gif).
 * Icons are loaded and cached the first time they are requested; all
 * subsequent requests for loaded icons are fulfilled by the cache.
 */
public class DefaultIconRepository implements IconRepository {

    /**
     * The the names of the resource files containing
     * the actual icons. Keyed by icon key.
     */
    private IconResourceFileNameMap resourceFileNames;

    /**
     * Cache the icons as they are requested, so we don't have
     * to fetch them from the files every time. Keyed by icon key.
     */
    private final Map cache;


    // ********** constructors **********

    /**
     * Use this constructor when constructing an instance of a
     * subclass that overrides #getResourceFileNames()
     */
    public DefaultIconRepository() {
        this(IconResourceFileNameMap.NULL_INSTANCE);
    }

    public DefaultIconRepository(IconResourceFileNameMap resourceFileNames) {
        super();
        if (resourceFileNames == null) {
            throw new NullPointerException();
        }
        this.resourceFileNames = resourceFileNames;
        this.cache = new HashMap();
    }


    // ********** IconRepository implementation **********

     /**
     * @see IconRepository#hasIcon(String)
     */
    public boolean hasIcon(String key) {
        return (key == null) ||
                this.cache.containsKey(key) ||
                this.canLoadIcon(key);
    }

    /**
     * @see IconRepository#getIcon(String)
     */
    public synchronized Icon getIcon(String key) {
        // allow clients to request a "non-icon"
        if (key == null) {
            return null;
        }
        // first check the cache
        Icon icon = (Icon) this.cache.get(key);
        if (icon != null) {
            return icon;
        }
        // load the icon from a file and cache it
        icon = this.loadIcon(key);
        this.cache.put(key, icon);
        return icon;
    }


    // ********** internal methods **********

    /**
     * Load and return the icon corresponding to the specified key.
     * This method will be called, on demand, once for each key.
     */
    protected Icon loadIcon(String key) {
        String resourceFileName = this.getResourceFileNames().getResourceFileName(key);

        URL url = this.getClass().getClassLoader().getResource(resourceFileName);
        if (url == null) {
            throw new MissingIconException("Missing icon file: " + key + " => " + resourceFileName, key);
        }

        return new ImageIcon(url);
    }

    /**
     * Return whether the icon corresponding to the specified key
     * can be loaded.
     */
    protected boolean canLoadIcon(String key) {
        String resourceFileName;
        if (this.getResourceFileNames().hasResourceFileName(key)) {
            resourceFileName = this.getResourceFileNames().getResourceFileName(key);
        } else {
            return false;
        }

        return this.getClass().getClassLoader().getResource(resourceFileName) != null;
    }

    protected IconResourceFileNameMap getResourceFileNames() {
        return this.resourceFileNames;
    }

    public String toString() {
        return StringTools.buildToStringFor(this);
    }

}