RegistryEditor.java

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package org.feistymeow.system;
 
import java.io.*;
 
/*
 * this class supports reading and setting values in the Windows registry.
 * 
 * some example code came from http://www.rgagnon.com/javadetails/java-0480.html
 * @author Chris Koeritz
 */
public class RegistryEditor {
 
  // the values below can be used for the expected type in the registry calls.
  public static final String STRING_TYPE = "REG_SZ";
  public static final String DOUBLEWORD_TYPE = "REG_DWORD";  
 
  // looks up the key provided in the registry and returns true if the key seems to exist.
  // this is just a check for presence; it could have no subkeys or values under it, but it at
  // least seems to be there.
  public static boolean checkKey(String keyName) {
    try {
      // make a command to run in windows that will query the value.
      StringBuilder command = new StringBuilder(QUERY_COMMAND);
      command.append("\"");
      command.append(keyName);
      command.append("\"");
      // start the command running and trap its output.
      Process process = Runtime.getRuntime().exec(command.toString());
      StreamReader reader = new StreamReader(process.getInputStream());
      reader.start();
      process.waitFor();  // let the system call finish up.
      reader.join();  // let the stream reader finish also.
      return process.exitValue() == 0;
    } catch (Exception e) {
      return false;
    }
  }
 
  // retrieves the key provided from the registry and selects out the value requested.
  // it is necessary to know the expected type, such as REG_SZ or REG_DWORD.
  // the value is always returned as a string and needs to be cast to different types as appropriate.
  public static String getValue(String keyName, String valueName, String typeExpected) {
    try {
      // make a command to run in windows that will query the value.
      StringBuilder command = new StringBuilder(QUERY_COMMAND);
      command.append("\"");
      command.append(keyName);
      command.append("\"");
      command.append(VALUE_FLAG); 
      command.append(valueName);
      // start the command running and trap its output.
      Process process = Runtime.getRuntime().exec(command.toString());
      StreamReader reader = new StreamReader(process.getInputStream());
      reader.start();
      process.waitFor();  // let the system call finish up.
      reader.join();  // let the stream reader finish also.
      // now grab the results from running the command and extract the answer.
      String result = reader.getResult();
      int p = result.indexOf(typeExpected);
      if (p == -1) return null;
      // return the result with the stuff before the type chopped off.
      return result.substring(p + typeExpected.length()).trim();
    } catch (Exception e) {
      return null;
    }
  }
 
  // makes a change to the specified "keyName" value called "valueName".  the old value will be replaced
  // with the "newValue" provided.  the key and the value do not have to exist prior to the call, but if
  // they already did exist, they'll be updated.
  public static boolean setValue(String keyName, String valueName, String typeExpected, String newValue) {
    try {
      // make a command to run in windows that will set the value.
      StringBuilder command = new StringBuilder(SET_COMMAND);
      command.append("\"");
      command.append(keyName);
      command.append("\"");
      command.append(VALUE_FLAG); 
      command.append(valueName);
      command.append(TYPE_FLAG);
      command.append(typeExpected);
      command.append(FORCE_FLAG);
      command.append(DATA_FLAG);
      command.append(newValue);
      //System.out.println("command to run: " + command);
      // start the command running and trap its output.
      Process process = Runtime.getRuntime().exec(command.toString());
      StreamReader reader = new StreamReader(process.getInputStream());
      reader.start();
      process.waitFor();  // let the system call finish up.
      reader.join();  // let the stream reader finish also.
      return (process.exitValue() == 0);  // zero exit is a success.
    } catch (Exception e) {
      return false;
    }
  }
 
  // removes the "valueName" value from the key "keyName".  true is returned on success.
  public static boolean deleteValue(String keyName, String valueName) {
    try {
      // make a command to run in windows that will set the value.
      StringBuilder command = new StringBuilder(DELETE_COMMAND);
      command.append("\"");
      command.append(keyName);
      command.append("\"");
      command.append(VALUE_FLAG);
      command.append(valueName);
      command.append(FORCE_FLAG);
      //System.out.println("command to run: " + command);
      // start the command running and trap its output.
      Process process = Runtime.getRuntime().exec(command.toString());
      StreamReader reader = new StreamReader(process.getInputStream());
      reader.start();
      process.waitFor();  // let the system call finish up.
      reader.join();  // let the stream reader finish also.
      return (process.exitValue() == 0);  // zero exit is a success.
    } catch (Exception e) {
      return false;
    }
  } 
 
  // removes the entire key "keyName" from the registry.  true is returned on success.
  public static boolean deleteKey(String keyName) {
    try {
      // make a command to run in windows that will set the value.
      StringBuilder command = new StringBuilder(DELETE_COMMAND);
      command.append("\"");
      command.append(keyName);
      command.append("\"");
      command.append(FORCE_FLAG);
      //System.out.println("command to run: " + command);
      // start the command running and trap its output.
      Process process = Runtime.getRuntime().exec(command.toString());
      StreamReader reader = new StreamReader(process.getInputStream());
      reader.start();
      process.waitFor();  // let the system call finish up.
      reader.join();  // let the stream reader finish also.
      return (process.exitValue() == 0);  // zero exit is a success.
    } catch (Exception e) {
      return false;
    }
  }
 
  // constants used in the registry code for talking to windows' reg application.
  private static final String QUERY_COMMAND = "reg query ";
  private static final String VALUE_FLAG = " /v ";
 
  private static final String SET_COMMAND = "reg add ";
  private static final String TYPE_FLAG = " /t ";
  private static final String DATA_FLAG = " /d ";
  private static final String FORCE_FLAG = " /f ";
 
  private static final String DELETE_COMMAND = "reg delete ";
 
  // wrapper class for stream reading came from web example mentioned above. 
  static class StreamReader extends Thread {
    private InputStream is;
    private StringWriter sw;
 
    StreamReader(InputStream is) {
      this.is = is;
      sw = new StringWriter();
    }
 
    public void run() {
      int c;
      try {
        while ((c = is.read()) != -1) sw.write(c);
      } catch (IOException e) { /*nothing*/ }
    }
 
    String getResult() { return sw.toString(); }
  }
}