org.ops4j.pax.runner.AuditedProperties.java Source code

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Here is the source code for org.ops4j.pax.runner.AuditedProperties.java

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/*
 * Copyright 2007 Alin Dreghiciu.
 *
 * 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. 
 */
package org.ops4j.pax.runner;

import java.util.*;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * Java Properties that audits changes of properties from the moment that was created.
 *
 * @author Alin Dreghiciu
 * @since 0.5.0
 */
public class AuditedProperties extends Properties {

    /**
     * Logger.
     */
    private static final Log LOGGER = LogFactory.getLog(AuditedProperties.class);
    /**
     * Pattern used for replacing placeholders.
     */
    private static final Pattern PLACEHOLDER_PATTERN = Pattern.compile("(.*?\\$\\{)([.[^\\$]]+?)(\\}.*)");

    /**
     * Default properties to be used.
     */
    final Properties m_defaults;

    /**
     * Creates an empty property list with the specified defaults.
     *
     * @param defaults the defaults.
     */
    public AuditedProperties(Properties defaults) {
        super();
        m_defaults = defaults != null ? defaults : new Properties();
    }

    /**
     * Delegate to defaults if not found.
     *
     * @see java.util.Properties#getProperty(String)
     */
    @Override
    public String getProperty(String key) {
        return getProperty(key, null);
    }

    /**
     * Delegate to defaults if not found.
     *
     * @see java.util.Properties#getProperty(String,String)
     */
    @Override
    public String getProperty(String key, String defaultValue) {
        String value = super.getProperty(key);
        if (value == null) {
            value = m_defaults.getProperty(key, defaultValue);
        }
        return value;
    }

    @Override
    public synchronized Object setProperty(String key, String value) {
        final String replaced = replacePlaceholders(value);
        LOGGER.trace("Setting system property [" + key + "=" + replaced + "]");
        return super.setProperty(key, replaced);
    }

    /**
     * Replaces placeholders = ${*}.
     *
     * @param value the string where the place holders should be replaced
     *
     * @return replaced place holders or the original if there are no place holders or a value for place holder could
     *         not be found
     */
    private String replacePlaceholders(final String value) {
        String replaced = value;
        String rest = value;
        while (rest != null && rest.length() != 0) {
            final Matcher matcher = PLACEHOLDER_PATTERN.matcher(rest);
            if (matcher.matches() && matcher.groupCount() == 3) {
                // groups 2 contains the placeholder name
                final String placeholderName = matcher.group(2);
                final String placeholderValue = getProperty(placeholderName);
                if (placeholderValue != null) {
                    replaced = replaced.replace("${" + placeholderName + "}", placeholderValue);
                }
                rest = matcher.group(3);
            } else {
                rest = null;
            }
        }
        if (replaced != null && !replaced.equals(value)) {
            replaced = replacePlaceholders(replaced);
        }
        return replaced;
    }

}