src/main/java/org/apache/commons/configuration2/PatternSubtreeConfigurationWrapper.java

/*
 * 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.commons.configuration2;

import java.io.IOException;
import java.io.Reader;
import java.io.Writer;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Objects;
import java.util.Properties;

import org.apache.commons.configuration2.event.Event;
import org.apache.commons.configuration2.event.EventListener;
import org.apache.commons.configuration2.event.EventType;
import org.apache.commons.configuration2.ex.ConfigurationException;
import org.apache.commons.configuration2.io.FileBased;
import org.apache.commons.configuration2.tree.ExpressionEngine;
import org.apache.commons.configuration2.tree.ImmutableNode;

/**
 * Wraps a BaseHierarchicalConfiguration and allows subtrees to be accessed via a configured path with replaceable
 * tokens derived from the ConfigurationInterpolator. When used with injection frameworks such as Spring it allows
 * components to be injected with subtrees of the configuration.
 *
 * @since 1.6
 */
public class PatternSubtreeConfigurationWrapper extends BaseHierarchicalConfiguration implements FileBasedConfiguration {
    /** The wrapped configuration */
    private final HierarchicalConfiguration<ImmutableNode> config;

    /** The path to the subtree */
    private final String path;

    /** True if the path ends with '/', false otherwise */
    private final boolean trailing;

    /** True if the constructor has finished */
    private final boolean init;

    /**
     * Constructor
     *
     * @param config The Configuration to be wrapped.
     * @param path The base path pattern.
     */
    public PatternSubtreeConfigurationWrapper(final HierarchicalConfiguration<ImmutableNode> config, final String path) {
        this.config = Objects.requireNonNull(config, "config");
        this.path = path;
        this.trailing = path.endsWith("/");
        this.init = true;
    }

    @Override
    public <T extends Event> void addEventListener(final EventType<T> eventType, final EventListener<? super T> listener) {
        getConfig().addEventListener(eventType, listener);
    }

    @Override
    protected void addNodesInternal(final String key, final Collection<? extends ImmutableNode> nodes) {
        getConfig().addNodes(key, nodes);
    }

    @Override
    protected void addPropertyInternal(final String key, final Object value) {
        config.addProperty(makePath(key), value);
    }

    @Override
    public void clearErrorListeners() {
        getConfig().clearErrorListeners();
    }

    @Override
    public void clearEventListeners() {
        getConfig().clearEventListeners();
    }

    @Override
    protected void clearInternal() {
        getConfig().clear();
    }

    @Override
    protected void clearPropertyDirect(final String key) {
        config.clearProperty(makePath(key));
    }

    @Override
    protected Object clearTreeInternal(final String key) {
        config.clearTree(makePath(key));
        return Collections.emptyList();
    }

    @Override
    public HierarchicalConfiguration<ImmutableNode> configurationAt(final String key) {
        return config.configurationAt(makePath(key));
    }

    @Override
    public HierarchicalConfiguration<ImmutableNode> configurationAt(final String key, final boolean supportUpdates) {
        return config.configurationAt(makePath(key), supportUpdates);
    }

    @Override
    public List<HierarchicalConfiguration<ImmutableNode>> configurationsAt(final String key) {
        return config.configurationsAt(makePath(key));
    }

    @Override
    protected boolean containsKeyInternal(final String key) {
        return config.containsKey(makePath(key));
    }

    /**
     * Returns the wrapped configuration as a {@code FileBased} object. If this cast is not possible, an exception is
     * thrown.
     *
     * @return the wrapped configuration as {@code FileBased}
     * @throws ConfigurationException if the wrapped configuration does not implement {@code FileBased}
     */
    private FileBased fetchFileBased() throws ConfigurationException {
        if (!(config instanceof FileBased)) {
            throw new ConfigurationException("Wrapped configuration does not implement FileBased!" + " No I/O operations are supported.");
        }
        return (FileBased) config;
    }

    @Override
    public BigDecimal getBigDecimal(final String key) {
        return config.getBigDecimal(makePath(key));
    }

    @Override
    public BigDecimal getBigDecimal(final String key, final BigDecimal defaultValue) {
        return config.getBigDecimal(makePath(key), defaultValue);
    }

    @Override
    public BigInteger getBigInteger(final String key) {
        return config.getBigInteger(makePath(key));
    }

    @Override
    public BigInteger getBigInteger(final String key, final BigInteger defaultValue) {
        return config.getBigInteger(makePath(key), defaultValue);
    }

    @Override
    public boolean getBoolean(final String key) {
        return config.getBoolean(makePath(key));
    }

    @Override
    public boolean getBoolean(final String key, final boolean defaultValue) {
        return config.getBoolean(makePath(key), defaultValue);
    }

    @Override
    public Boolean getBoolean(final String key, final Boolean defaultValue) {
        return config.getBoolean(makePath(key), defaultValue);
    }

    @Override
    public byte getByte(final String key) {
        return config.getByte(makePath(key));
    }

    @Override
    public byte getByte(final String key, final byte defaultValue) {
        return config.getByte(makePath(key), defaultValue);
    }

    @Override
    public Byte getByte(final String key, final Byte defaultValue) {
        return config.getByte(makePath(key), defaultValue);
    }

    private BaseHierarchicalConfiguration getConfig() {
        return (BaseHierarchicalConfiguration) config.configurationAt(makePath());
    }

    @Override
    public double getDouble(final String key) {
        return config.getDouble(makePath(key));
    }

    @Override
    public double getDouble(final String key, final double defaultValue) {
        return config.getDouble(makePath(key), defaultValue);
    }

    @Override
    public Double getDouble(final String key, final Double defaultValue) {
        return config.getDouble(makePath(key), defaultValue);
    }

    @Override
    public <T extends Event> Collection<EventListener<? super T>> getEventListeners(final EventType<T> eventType) {
        return getConfig().getEventListeners(eventType);
    }

    @Override
    public ExpressionEngine getExpressionEngine() {
        return config.getExpressionEngine();
    }

    @Override
    public float getFloat(final String key) {
        return config.getFloat(makePath(key));
    }

    @Override
    public float getFloat(final String key, final float defaultValue) {
        return config.getFloat(makePath(key), defaultValue);
    }

    @Override
    public Float getFloat(final String key, final Float defaultValue) {
        return config.getFloat(makePath(key), defaultValue);
    }

    @Override
    public int getInt(final String key) {
        return config.getInt(makePath(key));
    }

    @Override
    public int getInt(final String key, final int defaultValue) {
        return config.getInt(makePath(key), defaultValue);
    }

    @Override
    public Integer getInteger(final String key, final Integer defaultValue) {
        return config.getInteger(makePath(key), defaultValue);
    }

    @Override
    protected Iterator<String> getKeysInternal() {
        return config.getKeys(makePath());
    }

    @Override
    protected Iterator<String> getKeysInternal(final String prefix) {
        return config.getKeys(makePath(prefix));
    }

    @Override
    public List<Object> getList(final String key) {
        return config.getList(makePath(key));
    }

    @Override
    public List<Object> getList(final String key, final List<?> defaultValue) {
        return config.getList(makePath(key), defaultValue);
    }

    @Override
    public long getLong(final String key) {
        return config.getLong(makePath(key));
    }

    @Override
    public long getLong(final String key, final long defaultValue) {
        return config.getLong(makePath(key), defaultValue);
    }

    @Override
    public Long getLong(final String key, final Long defaultValue) {
        return config.getLong(makePath(key), defaultValue);
    }

    @Override
    protected int getMaxIndexInternal(final String key) {
        return config.getMaxIndex(makePath(key));
    }

    @Override
    public Properties getProperties(final String key) {
        return config.getProperties(makePath(key));
    }

    @Override
    protected Object getPropertyInternal(final String key) {
        return config.getProperty(makePath(key));
    }

    @Override
    public short getShort(final String key) {
        return config.getShort(makePath(key));
    }

    @Override
    public short getShort(final String key, final short defaultValue) {
        return config.getShort(makePath(key), defaultValue);
    }

    @Override
    public Short getShort(final String key, final Short defaultValue) {
        return config.getShort(makePath(key), defaultValue);
    }

    @Override
    public String getString(final String key) {
        return config.getString(makePath(key));
    }

    @Override
    public String getString(final String key, final String defaultValue) {
        return config.getString(makePath(key), defaultValue);
    }

    @Override
    public String[] getStringArray(final String key) {
        return config.getStringArray(makePath(key));
    }

    @Override
    public Configuration interpolatedConfiguration() {
        return getConfig().interpolatedConfiguration();
    }

    @Override
    protected boolean isEmptyInternal() {
        return getConfig().isEmpty();
    }

    private String makePath() {
        final String pathPattern = trailing ? path.substring(0, path.length() - 1) : path;
        return substitute(pathPattern);
    }

    /*
     * Resolve the root expression and then add the item being retrieved. Insert a separator character as required.
     */
    private String makePath(final String item) {
        final String pathPattern;
        if ((item.isEmpty() || item.startsWith("/")) && trailing) {
            pathPattern = path.substring(0, path.length() - 1);
        } else if (!item.startsWith("/") || !trailing) {
            pathPattern = path + "/";
        } else {
            pathPattern = path;
        }
        return substitute(pathPattern) + item;
    }

    @Override
    public void read(final Reader reader) throws ConfigurationException, IOException {
        fetchFileBased().read(reader);
    }

    @Override
    public <T extends Event> boolean removeEventListener(final EventType<T> eventType, final EventListener<? super T> listener) {
        return getConfig().removeEventListener(eventType, listener);
    }

    @Override
    public void setExpressionEngine(final ExpressionEngine expressionEngine) {
        if (init) {
            config.setExpressionEngine(expressionEngine);
        } else {
            super.setExpressionEngine(expressionEngine);
        }
    }

    @Override
    protected void setPropertyInternal(final String key, final Object value) {
        getConfig().setProperty(key, value);
    }

    @Override
    public Configuration subset(final String prefix) {
        return getConfig().subset(prefix);
    }

    /**
     * Uses this configuration's {@code ConfigurationInterpolator} to perform variable substitution on the given pattern
     * string.
     *
     * @param pattern the pattern string
     * @return the string with variables replaced
     */
    private String substitute(final String pattern) {
        return Objects.toString(getInterpolator().interpolate(pattern), null);
    }

    @Override
    public void write(final Writer writer) throws ConfigurationException, IOException {
        fetchFileBased().write(writer);
    }
}