以下是我正在使用的WinRegistry类来读取Key的StringSalues并获得NullPointerException：
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 Preferences userRoot = Preferences.userRoot();
private static Preferences systemRoot = Preferences.systemRoot();
private static Class<? extends Preferences> userClass = userRoot.getClass();
private static Method regOpenKey = null;
private static Method regCloseKey = null;
private static Method regQueryValueEx = null;
private static Method regEnumValue = null;
private static Method regQueryInfoKey = null;
private static Method regEnumKeyEx = null;
private static Method regCreateKeyEx = null;
private static Method regSetValueEx = null;
private static Method regDeleteKey = null;
private static Method regDeleteValue = null;
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) {
e.printStackTrace();
}
}
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;
}
}
I am using the winRegTest class to read Value Name and Value data under HKEY_LOCAL_MACHINE\\SOFTWARE\\ORACLE\\KEY_OraDb11g_home1
import java.util.*;
import java.util.Map.Entry;
public class winRegTest {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
try{
HashMap<String, String> h = WinRegistry.readStringValues(WinRegistry.HKEY_LOCAL_MACHINE,"SOFTWARE\\ORACLE\\KEY_OraDb11g_home1");
Collection<String> ke;
for(int i=0; i<h.size();i++){
ke = h.values();
System.out.println("TKey/Value:" + ke);
}
// iterate through the key set and display key and values
} catch(Exception e){
e.printStackTrace();
}
}
}
I get Error:
java.lang.NullPointerException
at java.lang.String.<init>(Unknown Source)
at com.isystem.jReg.WinRegistry.readStringValues(WinRegistry.java:325)
at com.isystem.jReg.WinRegistry.readStringValues(WinRegistry.java:120)
at com.isystem.jReg.winRegTest.main(winRegTest.java:35)
问题：
答案 0 :(得分：0)
看起来你的问题就在这里：
byte[] name = (byte[]) regEnumValue.invoke(root, new Object[] {
new Integer
(handles[0]), new Integer(index), new Integer(maxlen + 1)});
name可能保持为null，这使得对new String(name)的调用抛出NullPointerException。您应该使用调试器运行代码以验证这是问题所在。
答案 1 :(得分：0)
我有类似的问题。对我来说，事实证明＆＃34; maxlen＆＃34;信息并不总是在同一个位置，这取决于（我猜）Java版本。也就是说，＆＃34; regQueryInfoKey.invoke（...）＆＃34;返回一个整数数组，其中包含值的数量和最大值名称长度，它们在给定的源代码中位于0和3位置;在我的机器上它的位置2和4.我已经看到了2和3的例子。很容易混淆...
但是，可能有一个更清洁的解决方案：这些索引位于名为＆＃34; VALUES_NUMBER＆＃34;的私人字段中。和＆＃34; MAX_VALUE_NAME_LENGTH＆＃34;，您可以通过这种方式检索：
Field field=userClass.getDeclaredField("MAX_VALUE_NAME_LENGTH")
field.setAccessible(true);
int maxValueNameLengthINDEX=field.getInt(null);
您只需对＆＃34; VALUES_NUMBER＆＃34;。
执行相同的操作不确定是否是OP所遇到的问题，但这可以帮助其他人......
注意：使用Java 1.6.0_18-b07 64位进行测试。抱歉，我还没有尝试过其他版本，所以我不确定它是否依赖于Java版本，但您可以在网络上的Windows注册表中找到其他不同于索引值的示例...
答案 2 :(得分：0)
我有同样的问题。我花了整整两天时间来调试它。我挖得很深……（我几乎在此过程结束时就发现了这个StackOverflow问题，所以我牢记在心……）
我知道该方法有问题：private static Map<String, String> readStringValues(…)
首先，我认为这只是一行：int count = info[0];（在我的WinRegistry类版本中，有一条评论指出该行是由某人修复的，但是修复是在方法private static List<String> readStringSubKeys(…)中完全有效，但不在此readStringValues方法中。）
直到我分析了以下解决方案：http://alexradzin.blogspot.com/2011/01/access-windows-registry-with-pure-java.html（由AlexR撰写）后，我才知道还有第二个错误–在行上：int maxlen = info[3];（我是盲人，我自己没有注意到它…）
行：
int count = info[0];
int maxlen = info[3];
在readStringSubKeys方法中完全有效，但在方法readStringValues中它们应该听起来：
int count = info[2];
int maxlen = info[4];
（谢谢AlexR！您的代码帮助我们修复了其他代码...）