    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *     http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017
    018package org.apache.commons.configuration2;
    019
    020import java.io.IOException;
    021import java.io.InputStream;
    022import java.io.Reader;
    023import java.io.Writer;
    024import java.util.Map;
    025
    026import org.apache.commons.configuration2.ex.ConfigurationException;
    027import org.apache.commons.configuration2.ex.ConfigurationRuntimeException;
    028import org.apache.commons.configuration2.io.InputStreamSupport;
    029import org.apache.commons.configuration2.tree.ImmutableNode;
    030import org.yaml.snakeyaml.DumperOptions;
    031import org.yaml.snakeyaml.LoaderOptions;
    032import org.yaml.snakeyaml.Yaml;
    033import org.yaml.snakeyaml.constructor.Constructor;
    034import org.yaml.snakeyaml.representer.Representer;
    035
    036/**
    037 * <p>
    038 * A specialized hierarchical configuration class that is able to parse YAML documents.
    039 * </p>
    040 *
    041 * @since 2.2
    042 */
    043public class YAMLConfiguration extends AbstractYAMLBasedConfiguration implements FileBasedConfiguration, InputStreamSupport {
    044    /**
    045     * Creates a new instance of {@code YAMLConfiguration}.
    046     */
    047    public YAMLConfiguration() {
    048    }
    049
    050    /**
    051     * Creates a new instance of {@code YAMLConfiguration} as a copy of the specified configuration.
    052     *
    053     * @param c the configuration to be copied
    054     */
    055    public YAMLConfiguration(final HierarchicalConfiguration<ImmutableNode> c) {
    056        super(c);
    057    }
    058
    059    @Override
    060    public void read(final Reader in) throws ConfigurationException {
    061        try {
    062            final Yaml yaml = createYamlForReading(new LoaderOptions());
    063            final Map<String, Object> map = yaml.load(in);
    064            load(map);
    065        } catch (final Exception e) {
    066            rethrowException(e);
    067        }
    068    }
    069
    070    public void read(final Reader in, final LoaderOptions options) throws ConfigurationException {
    071        try {
    072            final Yaml yaml = createYamlForReading(options);
    073            final Map<String, Object> map = yaml.load(in);
    074            load(map);
    075        } catch (final Exception e) {
    076            rethrowException(e);
    077        }
    078    }
    079
    080    @Override
    081    public void write(final Writer out) throws ConfigurationException, IOException {
    082        final DumperOptions options = new DumperOptions();
    083        options.setDefaultFlowStyle(DumperOptions.FlowStyle.BLOCK);
    084        dump(out, options);
    085    }
    086
    087    public void dump(final Writer out, final DumperOptions options)
    088            throws ConfigurationException, IOException {
    089        final Yaml yaml = new Yaml(options);
    090        yaml.dump(constructMap(getNodeModel().getNodeHandler().getRootNode()), out);
    091    }
    092
    093    /**
    094     * Loads the configuration from the given input stream.
    095     *
    096     * @param in the input stream
    097     * @throws ConfigurationException if an error occurs
    098     */
    099    @Override
    100    public void read(final InputStream in) throws ConfigurationException {
    101        try {
    102            final Yaml yaml = createYamlForReading(new LoaderOptions());
    103            final Map<String, Object> map = yaml.load(in);
    104            load(map);
    105        } catch (final Exception e) {
    106            rethrowException(e);
    107        }
    108    }
    109
    110    public void read(final InputStream in, final LoaderOptions options) throws ConfigurationException {
    111        try {
    112            final Yaml yaml = createYamlForReading(options);
    113            final Map<String, Object> map = yaml.load(in);
    114            load(map);
    115        } catch (final Exception e) {
    116            rethrowException(e);
    117        }
    118    }
    119
    120    /**
    121     * Creates a {@code Yaml} object for reading a Yaml file. The object is configured with some default settings.
    122     *
    123     * @param options options for loading the file
    124     * @return the {@code Yaml} instance for loading a file
    125     */
    126    private static Yaml createYamlForReading(final LoaderOptions options) {
    127        return new Yaml(createClassLoadingDisablingConstructor(), new Representer(), new DumperOptions(), options);
    128    }
    129
    130    /**
    131     * Returns a {@code Constructor} object for the YAML parser that prevents all classes from being loaded. This
    132     * effectively disables the dynamic creation of Java objects that are declared in YAML files to be loaded.
    133     *
    134     * @return the {@code Constructor} preventing object creation
    135     */
    136    private static Constructor createClassLoadingDisablingConstructor() {
    137        return new Constructor() {
    138            @Override
    139            protected Class<?> getClassForName(final String name) {
    140                throw new ConfigurationRuntimeException("Class instantiation is disabled.");
    141            }
    142        };
    143    }
    144}