SecurityActions.java

package io.vertx.resourceadapter.impl;

import java.security.AccessController;
import java.security.PrivilegedAction;

/**
 * 
 * @author Lin Gao <lgao@redhat.com>
 * 
 */
class SecurityActions {

  private SecurityActions() {
  }

  /**
   * Gets current context class loader
   * 
   * @return the current context class loader
   */
  static ClassLoader getContextClassLoader() {
    if (System.getSecurityManager() == null) {
      return Thread.currentThread().getContextClassLoader();
    }
    return AccessController.doPrivileged(new PrivilegedAction<ClassLoader>() {
      @Override
      public ClassLoader run() {
        return Thread.currentThread().getContextClassLoader();
      }
    });
  }

  /**
   * Sets current context classloader
   * 
   * @param classLoader
   */
  static void setCurrentContextClassLoader(final ClassLoader classLoader) {
    if (System.getSecurityManager() == null) {
      Thread.currentThread().setContextClassLoader(classLoader);
    } else {
      AccessController.doPrivileged(new PrivilegedAction<Void>() {
        @Override
        public Void run() {
          Thread.currentThread().setContextClassLoader(classLoader);
          return null;
        }
      });
    }
  }

  /**
   * Gets the system property.
   * 
   * @param propName
   *          the property name
   * @return the property value
   */
  static String getSystemProperty(final String propName) {
    if (System.getSecurityManager() == null) {
      return System.getProperty(propName);
    }
    return AccessController.doPrivileged(new PrivilegedAction<String>() {
      @Override
      public String run() {
        return System.getProperty(propName);
      }
    });
  }

  // =========================================================
  // Some Util Methods Below
  // =========================================================

  /**
   * Whether the string is a valid expression.
   * 
   * @param string
   *          the string
   * @return true if the string starts with '${' and ends with '}', false
   *         otherwise
   */
  static boolean isExpression(final String string) {
    if (string == null) {
      return false;
    }
    return string.startsWith("${") && string.endsWith("}");
  }

  /**
   * Gets the express value by the key.
   * 
   * @param key
   *          the key where the system property is set.
   * @return the expression value or the key itself if the system property is
   *         not set.
   */
  static String getExpressValue(final String key) {
    if (isExpression(key)) {
      String keyValue = getSystemProperty(key.substring(2, key.length() - 1));
      return keyValue == null ? key : keyValue;
    } else {
      return key;
    }
  }

}