这是奥列格解决方案的修改版本。我注意到在我的系统(Windows server 2003)上,“reg query”的输出不是由制表符('\t')分隔,而是由4个空格分隔。
我还简化了解决方案,因为线程是不需要的。
public static final String readRegistry(String location, String key)
{
try
{
// Run reg query, then read output with StreamReader (internal class)
Process process = Runtime.getRuntime().exec("reg query " +
'"'+ location + "\" /v " + key);
InputStream is = process.getInputStream();
StringBuilder sw = new StringBuilder();
try
{
int c;
while ((c = is.read()) != -1)
sw.append((char)c);
}
catch (IOException e)
{
}
String output = sw.toString();
// Output has the following format:
// \n<Version information>\n\n<key> <registry type> <value>\r\n\r\n
int i = output.indexOf("REG_SZ");
if (i == -1)
{
return null;
}
sw = new StringBuilder();
i += 6; // skip REG_SZ
// skip spaces or tabs
for (;;)
{
if (i > output.length())
break;
char c = output.charAt(i);
if (c != ' ' && c != '\t')
break;
++i;
}
// take everything until end of line
for (;;)
{
if (i > output.length())
break;
char c = output.charAt(i);
if (c == '\r' || c == '\n')
break;
sw.append(c);
++i;
}
return sw.toString();
}
catch (Exception e)
{
return null;
}
// Write Operation
Preferences p = Preferences.userRoot();
p.put("key","value");
// also there are various other methods such as putByteArray(), putDouble() etc.
p.flush();
//Read Operation
Preferences p = Preferences.userRoot();
String value = p.get("key");
import java.util.*;
import java.lang.reflect.Method;
/**
* Simple registry access class implemented using some private APIs
* in java.util.prefs. It has no other prerequisites.
*/
public final class WindowsRegistry {
/**
* Tells if the Windows registry functions are available.
* (They will not be available when not running on Windows, for example.)
*/
public static boolean isAvailable() {
return initError == null;
}
/** Reads a string value from the given key and value name. */
public static String readValue(String keyName, String valueName) {
try (Key key = Key.open(keyName, KEY_READ)) {
return fromByteArray(invoke(regQueryValueEx, key.handle, toByteArray(valueName)));
}
}
/** Returns a map of all the name-value pairs in the given key. */
public static Map<String,String> readValues(String keyName) {
try (Key key = Key.open(keyName, KEY_READ)) {
int[] info = invoke(regQueryInfoKey, key.handle);
checkError(info[INFO_ERROR_CODE]);
int count = info[INFO_COUNT_VALUES];
int maxlen = info[INFO_MAX_VALUE_LENGTH] + 1;
Map<String,String> values = new HashMap<>();
for (int i = 0; i < count; i++) {
String valueName = fromByteArray(invoke(regEnumValue, key.handle, i, maxlen));
values.put(valueName, readValue(keyName, valueName));
}
return values;
}
}
/** Returns a list of the names of all the subkeys of a key. */
public static List<String> readSubkeys(String keyName) {
try (Key key = Key.open(keyName, KEY_READ)) {
int[] info = invoke(regQueryInfoKey, key.handle);
checkError(info[INFO_ERROR_CODE]);
int count = info[INFO_COUNT_KEYS];
int maxlen = info[INFO_MAX_KEY_LENGTH] + 1;
List<String> subkeys = new ArrayList<>(count);
for (int i = 0; i < count; i++) {
subkeys.add(fromByteArray(invoke(regEnumKeyEx, key.handle, i, maxlen)));
}
return subkeys;
}
}
/** Writes a string value with a given key and value name. */
public static void writeValue(String keyName, String valueName, String value) {
try (Key key = Key.open(keyName, KEY_WRITE)) {
checkError(invoke(regSetValueEx, key.handle, toByteArray(valueName), toByteArray(value)));
}
}
/** Deletes a value within a key. */
public static void deleteValue(String keyName, String valueName) {
try (Key key = Key.open(keyName, KEY_WRITE)) {
checkError(invoke(regDeleteValue, key.handle, toByteArray(valueName)));
}
}
/**
* Deletes a key and all values within it. If the key has subkeys, an
* "Access denied" error will be thrown. Subkeys must be deleted separately.
*/
public static void deleteKey(String keyName) {
checkError(invoke(regDeleteKey, keyParts(keyName)));
}
/**
* Creates a key. Parent keys in the path will also be created if necessary.
* This method returns without error if the key already exists.
*/
public static void createKey(String keyName) {
int[] info = invoke(regCreateKeyEx, keyParts(keyName));
checkError(info[INFO_ERROR_CODE]);
invoke(regCloseKey, info[INFO_HANDLE]);
}
/**
* The exception type that will be thrown if a registry operation fails.
*/
public static class RegError extends RuntimeException {
public RegError(String message, Throwable cause) {
super(message, cause);
}
}
// *************
// PRIVATE STUFF
// *************
private WindowsRegistry() {}
// Map of registry hive names to constants from winreg.h
private static final Map<String,Integer> hives = new HashMap<>();
static {
hives.put("HKEY_CLASSES_ROOT", 0x80000000); hives.put("HKCR", 0x80000000);
hives.put("HKEY_CURRENT_USER", 0x80000001); hives.put("HKCU", 0x80000001);
hives.put("HKEY_LOCAL_MACHINE", 0x80000002); hives.put("HKLM", 0x80000002);
hives.put("HKEY_USERS", 0x80000003); hives.put("HKU", 0x80000003);
hives.put("HKEY_CURRENT_CONFIG", 0x80000005); hives.put("HKCC", 0x80000005);
}
// Splits a path such as HKEY_LOCAL_MACHINE\Software\Microsoft into a pair of
// values used by the underlying API: An integer hive constant and a byte array
// of the key path within that hive.
private static Object[] keyParts(String fullKeyName) {
int x = fullKeyName.indexOf('\\');
String hiveName = x >= 0 ? fullKeyName.substring(0, x) : fullKeyName;
String keyName = x >= 0 ? fullKeyName.substring(x + 1) : "";
Integer hkey = hives.get(hiveName);
if (hkey == null) throw new RegError("Unknown registry hive: " + hiveName, null);
return new Object[] { hkey, toByteArray(keyName) };
}
// Type encapsulating a native handle to a registry key
private static class Key implements AutoCloseable {
final int handle;
private Key(int handle) {
this.handle = handle;
}
static Key open(String keyName, int accessMode) {
Object[] keyParts = keyParts(keyName);
int[] ret = invoke(regOpenKey, keyParts[0], keyParts[1], accessMode);
checkError(ret[INFO_ERROR_CODE]);
return new Key(ret[INFO_HANDLE]);
}
@Override
public void close() {
invoke(regCloseKey, handle);
}
}
// Array index constants for results of regOpenKey, regCreateKeyEx, and regQueryInfoKey
private static final int
INFO_HANDLE = 0,
INFO_COUNT_KEYS = 0,
INFO_ERROR_CODE = 1,
INFO_COUNT_VALUES = 2,
INFO_MAX_KEY_LENGTH = 3,
INFO_MAX_VALUE_LENGTH = 4;
// Registry access mode constants from winnt.h
private static final int
KEY_READ = 0x20019,
KEY_WRITE = 0x20006;
// Error constants from winerror.h
private static final int
ERROR_SUCCESS = 0,
ERROR_FILE_NOT_FOUND = 2,
ERROR_ACCESS_DENIED = 5;
private static void checkError(int e) {
if (e == ERROR_SUCCESS) return;
throw new RegError(
e == ERROR_FILE_NOT_FOUND ? "Key not found" :
e == ERROR_ACCESS_DENIED ? "Access denied" :
("Error number " + e), null);
}
// Registry access methods in java.util.prefs.WindowsPreferences
private static final Method
regOpenKey = getMethod("WindowsRegOpenKey", int.class, byte[].class, int.class),
regCloseKey = getMethod("WindowsRegCloseKey", int.class),
regQueryValueEx = getMethod("WindowsRegQueryValueEx", int.class, byte[].class),
regQueryInfoKey = getMethod("WindowsRegQueryInfoKey", int.class),
regEnumValue = getMethod("WindowsRegEnumValue", int.class, int.class, int.class),
regEnumKeyEx = getMethod("WindowsRegEnumKeyEx", int.class, int.class, int.class),
regSetValueEx = getMethod("WindowsRegSetValueEx", int.class, byte[].class, byte[].class),
regDeleteValue = getMethod("WindowsRegDeleteValue", int.class, byte[].class),
regDeleteKey = getMethod("WindowsRegDeleteKey", int.class, byte[].class),
regCreateKeyEx = getMethod("WindowsRegCreateKeyEx", int.class, byte[].class);
private static Throwable initError;
private static Method getMethod(String methodName, Class<?>... parameterTypes) {
try {
Method m = java.util.prefs.Preferences.systemRoot().getClass()
.getDeclaredMethod(methodName, parameterTypes);
m.setAccessible(true);
return m;
} catch (Throwable t) {
initError = t;
return null;
}
}
@SuppressWarnings("unchecked")
private static <T> T invoke(Method method, Object... args) {
if (initError != null)
throw new RegError("Registry methods are not available", initError);
try {
return (T)method.invoke(null, args);
} catch (Exception e) {
throw new RegError(null, e);
}
}
// Conversion of strings to/from null-terminated byte arrays.
// There is no support for Unicode; sorry, this is a limitation
// of the underlying methods that Java makes available.
private static byte[] toByteArray(String str) {
byte[] bytes = new byte[str.length() + 1];
for (int i = 0; i < str.length(); i++)
bytes[i] = (byte)str.charAt(i);
return bytes;
}
private static String fromByteArray(byte[] bytes) {
if (bytes == null) return null;
char[] chars = new char[bytes.length - 1];
for (int i = 0; i < chars.length; i++)
chars[i] = (char)((int)bytes[i] & 0xFF);
return new String(chars);
}
}
import java.util.prefs.Preferences;
public class RegistryDemo {
public static final String PREF_KEY = "org.username";
public static void main(String[] args) {
//
// Write Preferences information to HKCU (HKEY_CURRENT_USER),
// HKCU\Software\JavaSoft\Prefs\org.username
//
Preferences userPref = Preferences.userRoot();
userPref.put(PREF_KEY, "xyz");
//
// Below we read back the value we've written in the code above.
//
System.out.println("Preferences = "
+ userPref.get(PREF_KEY, PREF_KEY + " was not found."));
//
// Write Preferences information to HKLM (HKEY_LOCAL_MACHINE),
// HKLM\Software\JavaSoft\Prefs\org.username
//
Preferences systemPref = Preferences.systemRoot();
systemPref.put(PREF_KEY, "xyz");
//
// Read back the value we've written in the code above.
//
System.out.println("Preferences = "
+ systemPref.get(PREF_KEY, PREF_KEY + " was not found."));
}
}