DefaultPropertiesProvider.java

/*
 * #%L
 * Gravia :: Runtime :: API
 * %%
 * Copyright (C) 2013 - 2014 JBoss by Red Hat
 * %%
 * Licensed 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.
 * #L%
 */
package org.jboss.gravia.runtime.spi;

import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Properties;

import org.jboss.gravia.utils.IllegalArgumentAssertion;

/**
 * The default properties provider.
 *
 * Discover the configuration properties as follows
 * <p>
 * <ol>
 * <li>Use the explicit 'gravia.properties' system property</li>
 * <li>Discover the 'gravia.properties' config file as resource</li>
 * </ol>
 *
 * @author thomas.diesler@jboss.com
 * @since 27-Sep-2013
 *
 * @ThreadSafe
 */
public class DefaultPropertiesProvider extends CompositePropertiesProvider {

    private final PropertiesProvider delegate;

    public DefaultPropertiesProvider() {
        this(new HashMap<String, Object>());
    }

    public DefaultPropertiesProvider(final Properties properties) {
        this(propsToMap(properties));
    }

    public DefaultPropertiesProvider(final Map<String, Object> properties) {
        this(properties, true);
    }

    public DefaultPropertiesProvider(final Properties properties, final boolean systemPropertyDelegation) {
        this(propsToMap(properties), systemPropertyDelegation, null);
    }

    public DefaultPropertiesProvider(final Map<String, Object> properties, final boolean systemPropertyDelegation) {
        this(properties, systemPropertyDelegation, null);
    }

    public DefaultPropertiesProvider(final Properties properties, final boolean systemPropertyDelegation, final String environmentVariablePrefix) {
        this(propsToMap(properties), systemPropertyDelegation, environmentVariablePrefix);
    }

    public DefaultPropertiesProvider(Map<String, Object> properties, final boolean systemPropertyDelegation, final String environmentVariablePrefix) {
        IllegalArgumentAssertion.assertNotNull(properties, "props");
        properties.putAll(propsToMap(getDefaultProperties()));
        PropertiesProvider system = systemPropertyDelegation ? new SystemPropertiesProvider() : new MapPropertiesProvider();
        PropertiesProvider env =  environmentVariablePrefix != null ? new EnvPropertiesProvider(environmentVariablePrefix) : new EnvPropertiesProvider(system);

                this.delegate = new SubstitutionPropertiesProvider(
                new CompositePropertiesProvider(
                        new MapPropertiesProvider(properties),
                        system,
                        env
                )
        );
    }

    @Override
    public Object getProperty(String key) {
        return delegate.getProperty(key, null);
    }

    @Override
    public Object getProperty(String key, Object defaultValue) {
       return delegate.getProperty(key, defaultValue);
    }

    private static Properties getDefaultProperties() {
        URL configURL = null;

        // #1 Use the explicit system property
        String sysprop = SecurityActions.getSystemProperty(org.jboss.gravia.Constants.GRAVIA_PROPERTIES, null);
        if (sysprop != null) {
            try {
                configURL = new URL(sysprop);
            } catch (MalformedURLException ex) {
                throw new IllegalStateException("Invalid configuration URL: " + sysprop);
            }
        }

        // #2 discover the config file as resource
        if (configURL == null) {
            ClassLoader classLoader = DefaultPropertiesProvider.class.getClassLoader();
            configURL = classLoader.getResource(org.jboss.gravia.Constants.GRAVIA_PROPERTIES);
        }

        Properties props = new Properties();
        if (configURL != null) {
            try {
                props.load(configURL.openStream());
            } catch (IOException ex) {
                throw new IllegalStateException("Cannot load configuration from: " + configURL, ex);
            }
        }
        return props;
    }

    private static Map<String, Object> propsToMap(Properties props) {
        Map<String, Object> result = new HashMap<String, Object>();
        synchronized (props) {
            for (Entry<Object, Object> entry : props.entrySet()) {
                String key = entry.getKey().toString();
                Object value = entry.getValue();
                result.put(key, value);
            }
        }
        return result;
    }
}