SystemPropertiesProxy.java

/**
 * Logback: the reliable, generic, fast and flexible logging framework.
 * Copyright (C) 1999-2013, QOS.ch. All rights reserved.
 *
 * This program and the accompanying materials are dual-licensed under
 * either the terms of the Eclipse Public License v1.0 as published by
 * the Eclipse Foundation
 *
 *   or (per the licensee's choosing)
 *
 * under the terms of the GNU Lesser General Public License version 2.1
 * as published by the Free Software Foundation.
 */
package ch.qos.logback.core.android;

import java.lang.reflect.Method;

/**
 * A proxy to get Android's global system properties (as opposed
 * to the default process-level system properties). Settings from
 * `adb setprop` can be accessed from this class.
 */
public class SystemPropertiesProxy {

  private static final SystemPropertiesProxy SINGLETON = new SystemPropertiesProxy(null);
  private Class<?> SystemProperties;
  private Method getString, getBoolean;

  private SystemPropertiesProxy(ClassLoader cl) {
    try {
      setClassLoader(cl);
    } catch (Exception e) {
    }
  }

  /**
   * Gets the singleton instance for this class
   *
   * @return the singleton
   */
  public static SystemPropertiesProxy getInstance() {
    return SINGLETON;
  }

  /**
   * Sets the classloader to lookup the class for android.os.SystemProperties
   *
   * @param cl desired classloader
   * @throws ClassNotFoundException android.os.SystemProperties class not found
   * @throws SecurityException security manager does not allow class loading
   * @throws NoSuchMethodException get/getBoolean method does not exist
   */
  public void setClassLoader(ClassLoader cl)
      throws ClassNotFoundException, SecurityException, NoSuchMethodException {
    if (cl == null) cl = this.getClass().getClassLoader();
    SystemProperties = cl.loadClass("android.os.SystemProperties");
    getString = SystemProperties.getMethod("get", new Class[]{ String.class, String.class });
    getBoolean = SystemProperties.getMethod("getBoolean", new Class[]{ String.class, boolean.class });
  }

  /**
   * Get the value for the given key in the Android system properties
   *
   * @param key
   *          the key to lookup
   * @param def
   *          a default value to return
   * @return an empty string if the key isn't found
   * @throws IllegalArgumentException
   *           if the key exceeds 32 characters
   */
  public String get(String key, String def)
      throws IllegalArgumentException {

    if (SystemProperties == null || getString == null) return null;

    String ret = null;
    try {
      ret = (String) getString.invoke(SystemProperties, new Object[]{ key, def });
    } catch (IllegalArgumentException e) {
      throw e;
    } catch (Exception e) {
    }
    // if return value is null or empty, use the default
    // since neither of those are valid values
    if (ret == null || ret.length() == 0) {
      ret = def;
    }
    return ret;
  }

  /**
   * Get the value for the given key in the Android system properties, returned
   * as a boolean.
   *
   * Values 'n', 'no', '0', 'false' or 'off' are considered false. Values 'y',
   * 'yes', '1', 'true' or 'on' are considered true. (case insensitive). If the
   * key does not exist, or has any other value, then the default result is
   * returned.
   *
   * @param key
   *          the key to lookup
   * @param def
   *          a default value to return
   * @return the key parsed as a boolean, or def if the key isn't found or is
   *         not able to be parsed as a boolean.
   * @throws IllegalArgumentException
   *           if the key exceeds 32 characters
   */
  public Boolean getBoolean(String key, boolean def)
      throws IllegalArgumentException {

    if (SystemProperties == null || getBoolean == null) return def;

    Boolean ret = def;
    try {
      ret = (Boolean) getBoolean.invoke(SystemProperties, new Object[]{ key, def });
    } catch (IllegalArgumentException e) {
      throw e;
    } catch (Exception e) {
    }
    return ret;
  }
}