com.cedarsoft.configuration.xml.ConfigurationAccess.java Source code

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Here is the source code for com.cedarsoft.configuration.xml.ConfigurationAccess.java

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/**
 * Copyright (C) cedarsoft GmbH.
 *
 * Licensed under the GNU General Public License version 3 (the "License")
 * with Classpath Exception; you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at
 *
 *         http://www.cedarsoft.org/gpl3ce
 *         (GPL 3 with Classpath Exception)
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 3 only, as
 * published by the Free Software Foundation. cedarsoft GmbH designates this
 * particular file as subject to the "Classpath" exception as provided
 * by cedarsoft GmbH in the LICENSE file that accompanied this code.
 *
 * This code 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 General Public License
 * version 3 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 3 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact cedarsoft GmbH, 72810 Gomaringen, Germany,
 * or visit www.cedarsoft.com if you need additional information or
 * have any questions.
 */

package com.cedarsoft.configuration.xml;

import com.cedarsoft.configuration.DefaultValueProvider;
import org.apache.commons.configuration.Configuration;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;

import java.lang.Class;
import java.lang.IllegalArgumentException;
import java.lang.String;
import java.util.NoSuchElementException;

/**
 * Offers common access to configurations.
 * Implementations are independant of the type.
 *
 * @author Johannes Schneider (<a href=mailto:js@cedarsoft.com>js@cedarsoft.com</a>)
 */
public class ConfigurationAccess<T> {
    @Nonnull
    private final Class<? extends T> type;
    @Nonnull
    private final String key;
    @Nonnull
    private final ConfigurationResolver<T> resolver;
    @Nonnull
    private final DefaultValueProvider defaultValueProvider;
    @Nonnull
    private final Configuration configuration;

    /**
     * <p>Constructor for ConfigurationAccess.</p>
     *
     * @param configuration a Configuration object.
     * @param type          a Class object.
     * @param key           a String object.
     * @param defaultValue  a T object.
     */
    public ConfigurationAccess(@Nonnull Configuration configuration, @Nonnull Class<? extends T> type,
            @Nonnull String key, @Nonnull final T defaultValue) {
        this(configuration, type, key, new DefaultValueProvider() {
            @Override
            @Nonnull
            public <T> T getDefaultValue(@Nonnull String key, @Nonnull Class<T> type) {
                return type.cast(defaultValue);
            }
        });
    }

    /**
     * <p>Constructor for ConfigurationAccess.</p>
     *
     * @param configuration        a Configuration object.
     * @param type                 a Class object.
     * @param key                  a String object.
     * @param defaultValueProvider a DefaultValueProvider object.
     */
    public ConfigurationAccess(@Nonnull Configuration configuration, @Nonnull Class<? extends T> type,
            @Nonnull String key, @Nonnull DefaultValueProvider defaultValueProvider) {
        this(configuration, type, key, defaultValueProvider, ConfigurationResolver.getResolver(type));
    }

    /**
     * <p>Constructor for ConfigurationAccess.</p>
     *
     * @param configuration        a Configuration object.
     * @param type                 a Class object.
     * @param key                  a String object.
     * @param defaultValueProvider a DefaultValueProvider object.
     * @param resolver             a ConfigurationResolver object.
     */
    public ConfigurationAccess(@Nonnull Configuration configuration, @Nonnull Class<? extends T> type,
            @Nonnull String key, @Nonnull DefaultValueProvider defaultValueProvider,
            @Nonnull ConfigurationResolver<T> resolver) {
        this.configuration = configuration;
        this.type = type;
        this.key = key;
        this.defaultValueProvider = defaultValueProvider;
        this.resolver = resolver;
    }

    /**
     * <p>resolve</p>
     *
     * @return a T object.
     */
    @Nullable
    public T resolve() {
        try {
            T resolved = resolver.resolve(configuration, key);
            if (resolved != null) {
                return resolved;
            }
        } catch (NoSuchElementException ignore) {
        }
        T defaultValue = defaultValueProvider.getDefaultValue(key, type);
        if (defaultValue != null) {
            resolver.store(configuration, key, defaultValue);
        }
        return defaultValue;
    }

    /**
     * Resolves the value
     *
     * @return the resolved value
     *
     * @throws IllegalArgumentException
     *          if the key is invalid
     */
    @Nonnull
    public T resolveSafe() throws IllegalArgumentException {
        T resolved = resolve();
        if (resolved == null) {
            throw new IllegalArgumentException("No configured value found for " + key);
        }
        return resolved;
    }

    /**
     * <p>Getter for the field <code>type</code>.</p>
     *
     * @return a Class object.
     */
    @Nonnull
    public Class<? extends T> getType() {
        return type;
    }

    /**
     * <p>Getter for the field <code>key</code>.</p>
     *
     * @return a String object.
     */
    @Nonnull
    public String getKey() {
        return key;
    }

    /**
     * <p>store</p>
     *
     * @param value a T object.
     */
    public void store(@Nonnull T value) {
        resolver.store(configuration, key, value);
    }
}