8. How to read and write windows registry with Java Java Debug Notes

8. How to read and write windows registry with Java Java Debug Notes

This article is participating in the "Java Theme Month-Java Debug Notes Activity", see < Activity Link > for details

Question: How to read and write windows registry with Java?

I know this question is old, but this is the first search result for "Read/Write Java to Registry" on Google. Recently, I discovered this amazing code snippet, which has the following characteristics:

1. You can read/write any part of the registry

2. Do not use JNI.

3. Do not use any third-party/external applications for work.

4. Do not use WINDOWS API directly, pure Java code.

It uses reflection to work by actually accessing private methods in the java.util.prefs.Preferences class.

The internal structure of this class is very complicated, but the class itself is very easy to use.

For example, the following code gets the exact Windows Distribution from the registry:

String value = WinRegistry.readString ( WinRegistry.HKEY_LOCAL_MACHINE, //HKEY "SOFTWARE/in the Microsoft Windows NT/CurrentVersion\\" , //Key "ProductName" ); //ValueName System.out.println ( "Distribution's Windows =" + value); Copy the code

This is the original class, just copy and paste, and it should work fine:

import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.util.HashMap; import java.util.Map; import java.util.ArrayList; import java.util.List; import java.util .prefs.Preferences; public class WinRegistry { public static final int HKEY_CURRENT_USER = 0x80000001 ; public static final int HKEY_LOCAL_MACHINE = 0x80000002 ; public static final int REG_SUCCESS = 0 ; public static final int REG_NOTFOUND = 2 ; public static final int REG_ACCESSDENIED = 5 ; private static final int KEY_ALL_ACCESS = 0xf003f ; private static final int KEY_READ = 0x20019 ; private static final Preferences userRoot = Preferences.userRoot(); private static final Preferences systemRoot = Preferences.systemRoot(); private static final Class<? extends Preferences> userClass = userRoot.getClass(); private static final Method regOpenKey; private static final Method regCloseKey; private static final Method regQueryValueEx; private static final Method regEnumValue; private static final Method regQueryInfoKey; private static final Method regEnumKeyEx; private static final Method regCreateKeyEx; private static final Method regSetValueEx; private static final Method regDeleteKey; private static final Method regDeleteValue; static { try { regOpenKey = userClass.getDeclaredMethod( "WindowsRegOpenKey" , new Class[] { int .class, byte [].class, int .class }); regOpenKey.setAccessible( true ); regCloseKey = userClass.getDeclaredMethod( "WindowsRegCloseKey" , new Class[] { int .class }); regCloseKey.setAccessible( true ); regQueryValueEx = userClass.getDeclaredMethod( "WindowsRegQueryValueEx" , new Class[] { int .class, byte [].class }); regQueryValueEx.setAccessible( true ); regEnumValue = userClass.getDeclaredMethod( "WindowsRegEnumValue" , new Class[] { int .class, int .class, int .class }); regEnumValue.setAccessible( true ); regQueryInfoKey = userClass.getDeclaredMethod( "WindowsRegQueryInfoKey1" , new Class[] { int .class }); regQueryInfoKey.setAccessible( true ); regEnumKeyEx = userClass.getDeclaredMethod( "WindowsRegEnumKeyEx" , new Class[] { int .class, int .class, int .class }); regEnumKeyEx.setAccessible( true ); regCreateKeyEx = userClass.getDeclaredMethod( "WindowsRegCreateKeyEx" , new Class[] { int .class, byte [].class }); regCreateKeyEx.setAccessible( true ); regSetValueEx = userClass.getDeclaredMethod( "WindowsRegSetValueEx" , new Class[] { int .class, byte [].class, byte [].class }); regSetValueEx.setAccessible( true ); regDeleteValue = userClass.getDeclaredMethod( "WindowsRegDeleteValue" , new Class[] { int .class, byte [].class }); regDeleteValue.setAccessible( true ); regDeleteKey = userClass.getDeclaredMethod( "WindowsRegDeleteKey" , new Class[] { int .class, byte [].class }); regDeleteKey.setAccessible( true ); } catch (Exception e) { throw new RuntimeException(e); } } private WinRegistry () {} /** * Read a value from key and value name * @param hkey HKEY_CURRENT_USER/HKEY_LOCAL_MACHINE * @param key * @param valueName * @return the value * @throws IllegalArgumentException * @throws IllegalAccessException * @throws InvocationTargetException */ public static String readString ( int hkey, String key, String valueName) throws IllegalArgumentException, IllegalAccessException, InvocationTargetException { if (hkey == HKEY_LOCAL_MACHINE) { return readString(systemRoot, hkey, key, valueName); } else if (hkey == HKEY_CURRENT_USER) { return readString(userRoot, hkey, key, valueName); } else { throw new IllegalArgumentException( "hkey=" + hkey); } } /** * Read value(s) and value name(s) form given key * @param hkey HKEY_CURRENT_USER/HKEY_LOCAL_MACHINE * @param key * @return the value name(s) plus the value(s) * @throws IllegalArgumentException * @throws IllegalAccessException * @throws InvocationTargetException */ public static Map<String, String> readStringValues ( int hkey, String key) throws IllegalArgumentException, IllegalAccessException, InvocationTargetException { if (hkey == HKEY_LOCAL_MACHINE) { return readStringValues(systemRoot, hkey, key); } else if (hkey == HKEY_CURRENT_USER) { return readStringValues(userRoot, hkey, key); } else { throw new IllegalArgumentException( "hkey=" + hkey); } } /** * Read the value name(s) from a given key * @param hkey HKEY_CURRENT_USER/HKEY_LOCAL_MACHINE * @param key * @return the value name(s) * @throws IllegalArgumentException * @throws IllegalAccessException * @throws InvocationTargetException */ public static List<String> readStringSubKeys ( int hkey, String key) throws IllegalArgumentException, IllegalAccessException, InvocationTargetException { if (hkey == HKEY_LOCAL_MACHINE) { return readStringSubKeys(systemRoot, hkey, key); } else if (hkey == HKEY_CURRENT_USER) { return readStringSubKeys(userRoot, hkey, key); } else { throw new IllegalArgumentException("hkey=" + hkey); } } /** * Create a key * @param hkey HKEY_CURRENT_USER/HKEY_LOCAL_MACHINE * @param key * @throws IllegalArgumentException * @throws IllegalAccessException * @throws InvocationTargetException */ public static void createKey ( int hkey, String key) throws IllegalArgumentException, IllegalAccessException, InvocationTargetException { int [] ret; if (hkey == HKEY_LOCAL_MACHINE) { ret = createKey(systemRoot, hkey, key); regCloseKey.invoke(systemRoot, new Object[] { new Integer(ret[ 0 ]) }); } else if (hkey == HKEY_CURRENT_USER) { ret = createKey(userRoot, hkey, key); regCloseKey.invoke(userRoot, new Object[] { new Integer(ret[ 0 ]) }); } else { throw new IllegalArgumentException( "hkey=" + hkey); } if (ret[ 1 ] != REG_SUCCESS) { throw new IllegalArgumentException( "rc=" + ret[ 1 ] + "key=" + key); } } /** * Write a value in a given key/value name * @param hkey * @param key * @param valueName * @param value * @throws IllegalArgumentException * @throws IllegalAccessException * @throws InvocationTargetException */ public static void writeStringValue ( int hkey, String key, String valueName, String value) throws IllegalArgumentException, IllegalAccessException, InvocationTargetException { if (hkey == HKEY_LOCAL_MACHINE) { writeStringValue(systemRoot, hkey, key, valueName, value); } else if (hkey == HKEY_CURRENT_USER) { writeStringValue(userRoot, hkey, key, valueName, value); } else { throw new IllegalArgumentException( "hkey=" + hkey); } } /** * Delete a given key * @param hkey * @param key * @throws IllegalArgumentException * @throws IllegalAccessException * @throws InvocationTargetException */ public static void deleteKey ( int hkey, String key) throws IllegalArgumentException, IllegalAccessException, InvocationTargetException { int rc = -1 ; if (hkey == HKEY_LOCAL_MACHINE) { rc = deleteKey(systemRoot, hkey, key); } else if (hkey == HKEY_CURRENT_USER) { rc = deleteKey(userRoot, hkey, key); } if (rc != REG_SUCCESS) { throw new IllegalArgumentException( "rc=" + rc + "key=" + key); } } /** * delete a value from a given key/value name * @param hkey * @param key * @param value * @throws IllegalArgumentException * @throws IllegalAccessException * @throws InvocationTargetException */ public static void deleteValue ( int hkey, String key, String value) throws IllegalArgumentException, IllegalAccessException, InvocationTargetException { int rc = -1 ; if (hkey == HKEY_LOCAL_MACHINE) { rc = deleteValue(systemRoot, hkey, key, value); } else if (hkey == HKEY_CURRENT_USER) { rc = deleteValue(userRoot, hkey, key, value); } if (rc != REG_SUCCESS) { throw new IllegalArgumentException( "rc=" + rc + "key=" + key + " value=" + value); } } //===================== private static int deleteValue (Preferences root, int hkey, String key, String value) throws IllegalArgumentException, IllegalAccessException, InvocationTargetException { int [] handles = ( int []) regOpenKey.invoke(root, new Object[] { new Integer(hkey), toCstr(key), new Integer(KEY_ALL_ACCESS) }); if (handles[ 1 ] != REG_SUCCESS ) { return handles[ 1 ]; //can be REG_NOTFOUND, REG_ACCESSDENIED } int rc =((Integer) regDeleteValue.invoke(root, new Object[] { new Integer(handles[ 0 ]), toCstr(value) })).intValue(); regCloseKey.invoke(root, new Object[] { new Integer(handles[ 0 ]) }); return rc; } private static int deleteKey (Preferences root, int hkey, String key) throws IllegalArgumentException, IllegalAccessException, InvocationTargetException { int rc =((Integer) regDeleteKey.invoke(root, new Object[] { new Integer(hkey), toCstr(key) })).intValue(); return rc; //can REG_NOTFOUND, REG_ACCESSDENIED, REG_SUCCESS } private static String readString (Preferences root, int hkey, String key, String value) throws IllegalArgumentException, IllegalAccessException, InvocationTargetException { int [] handles = ( int []) regOpenKey.invoke(root, new Object[] { new Integer(hkey), toCstr(key), new Integer(KEY_READ) }); if (handles[ 1 ] != REG_SUCCESS ) { return null ; } byte [] valb = ( byte []) regQueryValueEx.invoke(root, new Object[] { new Integer(handles[ 0 ]), toCstr(value) }); regCloseKey.invoke(root, new Object[] { new Integer(handles[ 0 ]) }); return (valb != null ? new String(valb).trim(): null ); } private static Map<String,String> readStringValues (Preferences root, int hkey, String key) throws IllegalArgumentException, IllegalAccessException, InvocationTargetException { HashMap<String, String> results = new HashMap<String,String>(); int [] handles = ( int []) regOpenKey.invoke(root, new Object[] { new Integer(hkey), toCstr(key), new Integer(KEY_READ) }); if (handles[ 1 ] != REG_SUCCESS) { return null ; } int [] info = ( int []) regQueryInfoKey.invoke(root, new Object[] { new Integer(handles[ 0 ]) }); int count = info[ 0 ]; //count int maxlen = info[ 3 ]; //value length max for ( int index = 0 ; index<count; index++) { byte [] name = ( byte []) regEnumValue. invoke(root, new Object[] { new Integer (handles[ 0 ]), new Integer(index), new Integer(maxlen + 1 )}); String value = readString(hkey, key, new String(name)); results.put( new String(name).trim(), value); } regCloseKey.invoke(root, new Object[] { new Integer(handles[ 0 ]) }); return results; } private static List<String> readStringSubKeys (Preferences root, int hkey, String key) throws IllegalArgumentException, IllegalAccessException, InvocationTargetException { List<String> results = new ArrayList<String>(); int [] handles = ( int []) regOpenKey.invoke(root, new Object[] { new Integer(hkey), toCstr(key), new Integer(KEY_READ ) }); if (handles[ 1 ] != REG_SUCCESS) { return null ; } int [] info = ( int []) regQueryInfoKey.invoke(root, new Object[] { new Integer(handles[ 0 ]) }); int count = info[ 0 ]; //Fix: info[2] was being used here with wrong results. Suggested by davenpcj, confirmed by Petrucio int maxlen = info[ 3 ]; //value length max for ( int index = 0 ; index<count; index++) { byte [] name = ( byte []) regEnumKeyEx.invoke(root, new Object[] { new Integer (handles[ 0 ]), new Integer(index), new Integer(maxlen + 1 ) }); results.add( new String(name).trim()); } regCloseKey.invoke(root, new Object[] { new Integer(handles[ 0 ]) }); return results; } private static int [] createKey(Preferences root, int hkey, String key) throws IllegalArgumentException, IllegalAccessException, InvocationTargetException { return ( int []) regCreateKeyEx.invoke(root, new Object[] { new Integer(hkey), toCstr(key) }); } private static void writeStringValue (Preferences root, int hkey, String key, String valueName, String value) throws IllegalArgumentException, IllegalAccessException, InvocationTargetException { int [] handles = ( int []) regOpenKey.invoke(root, new Object[] { new Integer(hkey), toCstr(key), new Integer(KEY_ALL_ACCESS) }); regSetValueEx.invoke(root, new Object[] { new Integer(handles[ 0 ]), toCstr(valueName), toCstr(value) }); regCloseKey.invoke(root, new Object[] { new Integer(handles[ 0 ]) }); } //utility private static byte [] toCstr(String str) { byte [] result = new byte [str.length() + 1 ]; for ( int i = 0 ; i <str.length(); i++) { result[i] = ( byte ) str.charAt(i); } result[str.length()] = 0 ; return result; } } Copy code