org.alfresco.config.SystemPropertiesFactoryBean.java Source code

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Here is the source code for org.alfresco.config.SystemPropertiesFactoryBean.java

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/*
 * Copyright (C) 2005-2010 Alfresco Software Limited.
 *
 * This file is part of Alfresco
 *
 * Alfresco is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Alfresco 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with Alfresco. If not, see <http://www.gnu.org/licenses/>.
 */
package org.alfresco.config;

import java.io.IOException;
import java.util.Collections;
import java.util.HashSet;
import java.util.Map;
import java.util.Properties;
import java.util.Set;

import org.springframework.beans.factory.config.PropertiesFactoryBean;
import org.springframework.beans.factory.config.PropertyPlaceholderConfigurer;
import org.springframework.core.Constants;

/**
 * Like the parent <code>PropertiesFactoryBean</code>, but overrides or augments the resulting property set with values
 * from VM system properties. As with the Spring {@link PropertyPlaceholderConfigurer} the following modes are
 * supported:
 * <ul>
 * <li><b>SYSTEM_PROPERTIES_MODE_NEVER: </b>Don't use system properties at all.</li>
 * <li><b>SYSTEM_PROPERTIES_MODE_FALLBACK: </b>Fallback to a system property only for undefined properties.</li>
 * <li><b>SYSTEM_PROPERTIES_MODE_OVERRIDE: (DEFAULT)</b>Use a system property if it is available.</li>
 * </ul>
 * Note that system properties will only be included in the property set if defaults for the property have already been
 * defined using {@link #setProperties(Properties)} or {@link #setLocations(org.springframework.core.io.Resource[])} or
 * their names have been included explicitly in the set passed to {@link #setSystemProperties(Set)}.
 * 
 * @author Derek Hulley
 */
public class SystemPropertiesFactoryBean extends PropertiesFactoryBean {
    private static final Constants constants = new Constants(PropertyPlaceholderConfigurer.class);

    private int systemPropertiesMode = PropertyPlaceholderConfigurer.SYSTEM_PROPERTIES_MODE_OVERRIDE;
    private Set<String> systemProperties = Collections.emptySet();

    /**
     * Set the system property mode by the name of the corresponding constant, e.g. "SYSTEM_PROPERTIES_MODE_OVERRIDE".
     * 
     * @param constantName
     *            name of the constant
     * @throws java.lang.IllegalArgumentException
     *             if an invalid constant was specified
     * @see #setSystemPropertiesMode
     */
    public void setSystemPropertiesModeName(String constantName) throws IllegalArgumentException {
        this.systemPropertiesMode = SystemPropertiesFactoryBean.constants.asNumber(constantName).intValue();
    }

    /**
     * Set how to check system properties.
     * 
     * @see PropertyPlaceholderConfigurer#setSystemPropertiesMode(int)
     */
    public void setSystemPropertiesMode(int systemPropertiesMode) {
        this.systemPropertiesMode = systemPropertiesMode;
    }

    /**
     * Set the names of the properties that can be considered for overriding.
     * 
     * @param systemProperties
     *            a set of properties that can be fetched from the system properties
     */
    public void setSystemProperties(Set<String> systemProperties) {
        this.systemProperties = systemProperties;
    }

    @SuppressWarnings("unchecked")
    @Override
    protected Properties mergeProperties() throws IOException {
        // First do the default merge
        Properties props = super.mergeProperties();

        // Now resolve all the merged properties
        if (this.systemPropertiesMode == PropertyPlaceholderConfigurer.SYSTEM_PROPERTIES_MODE_NEVER) {
            // If we are in never mode, we don't refer to system properties at all
            for (String systemProperty : (Set<String>) (Set) props.keySet()) {
                resolveMergedProperty(systemProperty, props);
            }
        } else {
            // Otherwise, we allow unset properties to drift through from the systemProperties set and potentially set
            // ones to be overriden by system properties
            Set<String> propNames = new HashSet<String>((Set<String>) (Set) props.keySet());
            propNames.addAll(this.systemProperties);
            for (String systemProperty : propNames) {
                resolveMergedProperty(systemProperty, props);
                if (this.systemPropertiesMode == PropertyPlaceholderConfigurer.SYSTEM_PROPERTIES_MODE_FALLBACK
                        && props.containsKey(systemProperty)) {
                    // It's already there
                    continue;
                }
                // Get the system value and assign if present
                String systemPropertyValue = System.getProperty(systemProperty);
                if (systemPropertyValue != null) {
                    props.put(systemProperty, systemPropertyValue);
                }
            }
        }
        return props;
    }

    /**
     * Override hook. Allows subclasses to resolve a merged property from an alternative source, whilst still respecting
     * the chosen system property fallback path.
     * 
     * @param systemProperty String
     * @param props Properties
     */
    protected void resolveMergedProperty(String systemProperty, Properties props) {
    }
}