In my Java 8 code,
public ChangePersonsName(String email, final String password, final String wantedUsername, final String uuid, final long time, int latency, int[] requests, int[] proxyRequests) throws IOException {
final AtomicReference<Object> token = new AtomicReference<Object>();
final AtomicReference<ArrayList<?>> newHeaders = new AtomicReference<ArrayList<?>>();
new Thread(() -> {
boolean lock = true;
while (lock) {
if (time - System.currentTimeMillis() > 60000) continue;
Map<Header[], String> loginResults = null;
try {
loginResults = this.login(email, password, uuid);
}
catch (IOException e) {
e.printStackTrace();
}
String token = loginResults.entrySet().iterator().next().getValue();
Header[] headers = loginResults.entrySet().iterator().next().getKey();
newHeaders.set(new ArrayList<Object>());
for (Header header : headers) {
if (!header.toString().startsWith("Set-Cookie:")) continue;
((List<BasicHeader>)newHeaders.get()).add(new BasicHeader("Cookie", header.toString().split("Set-Cookie: ")[1]));
}
lock = false;
}
}
).start();
new Timer().schedule(new TimerTask(){
You'll notice that
String token = loginResults.entrySet().iterator().next().getValue();
throws a compile error,
Lambda expression's local variable token cannot redeclare another local variable defined in an enclosing scope.
My question is, How would one go about fixing this? I'm pretty new to Java, I should probably know how to fix this, but i don't.
You already have variable with name token in this scope. You've declared it in 2nd row. To fix just rename 2nd variable:
String newToken = loginResults.entrySet().iterator().next().getValue();
Related
Here are my iterations, but one of them is nested:
objects.forEach(obj -> {
if (obj.getType() == Type.APPLICATION) {
clientApplicationPriorities.add(getClientApplicationPriority(obj.getApplicationShortInfo().getId(), clientId, priority, null));
} else if (obj.getType() == Type.FOLDER) {
final FoldersShortInfo folderInfo = obj.getFolderShortInfo();
final String folderName = folderInfo.getName();
final List<ApplicationShortInfo> appInfos = folderInfo.getApplications();
appInfos.forEach(appInfo -> clientApplicationPriorities.add(getClientApplicationPriority(appInfo.getId(), clientId, priority, folderName)));
} else {
throw new FolderRequestException();
}
});
How can I rewrite it using Stream API?
Please share some more logic related to the implementation of your code.
you should use switch case rather than if-elseif-else loop for more clean code.
List<Employee> objects = new ArrayList<Employee>();
for (Employee emp : objects) {
switch (emp.getType()) {
case Type.application: {
clientApplicationPriorities.add(
getClientApplicationPriority(obj.getApplicationShortInfo().getId(), clientId, priority, null));
}
case Type.folder: {
final FoldersShortInfo folderInfo = obj.getFolderShortInfo();
final String folderName = folderInfo.getName();
final List<ApplicationShortInfo> appInfos = folderInfo.getApplications();
appInfos.forEach(appInfo -> clientApplicationPriorities
.add(getClientApplicationPriority(appInfo.getId(), clientId, priority, folderName)));
}
default: {
throw new FolderRequestException();
}
}
};
I Have a multithreaded environment in android app. I use a singleton class to store data. This singleton class contains a arraylist that is accessed using a synchronized method.
The app uses this arraylist to render images in app.
Initial problem : Concurrent modification error use to come so I made the get arraylist function syncronized.
Current Problem:Concurrent modification error not coming but in between empty arraylist returned (maybe when there is concurrent access).
Objective : I want to detect when Concurrent modification so that Instead of empty arraylist being return I can return last state of the arraylist.
public synchronized List<FrameData> getCurrentDataToShow() {
List<FrameData> lisCurrDataToShow = new ArrayList<FrameData>();
//for (FrameData fd : listFrameData) {//concurrent modification exception
//todo iterator test
Iterator<FrameData> iterator = listFrameData.iterator();
while (iterator.hasNext()) {
FrameData fd = iterator.next();
long currentTimeInMillis = java.lang.System.currentTimeMillis();
if ((currentTimeInMillis > fd.getStartDate().getTime() && currentTimeInMillis < fd.getEndDate().getTime()) || (fd.isAllDay() && DateUtils.isToday(fd.getStartDate().getTime()))) {
if (new File(ImageFrameActivity.ROOT_FOLDER_FILES + fd.getFileName()).exists()) {
lisCurrDataToShow.add(fd);
}
}
}
if (lisCurrDataToShow.size() == 0) {
lisCurrDataToShow.add(new FrameData(defaultFileName, null, null, null, String.valueOf(120), false));
}
return lisCurrDataToShow;
}
Referred to Detecting concurrent modifications?
Please help!
EDIT1:
This problem occurs rarely not everytime.
If a threads is accessing getCurrentDataToShow() and another thread tries to access this function what will the function return?? I'm new to multithreading , please guide
Edit 2
in oncreate following methods of singleton are called periodically
DataModelManager.getInstance().getCurrentDataToShow();
DataModelManager.getInstance().parseData(responseString);
Complete singleton class
public class DataModelManager {
private static DataModelManager dataModelManager;
private ImageFrameActivity imageFrameAct;
private String defaultFileName;
public List<FrameData> listFrameData = new ArrayList<FrameData>();
// public CopyOnWriteArrayList<FrameData> listFrameData= new CopyOnWriteArrayList<FrameData>();
private String screensaverName;
private boolean isToDownloadDeafultFiles;
private String tickerMsg = null;
private boolean showTicker = false;
private boolean showHotspot = false;
private String hotspotFileName=null;
public String getDefaultFileName() {
return defaultFileName;
}
public boolean isToDownloadDeafultFiles() {
return isToDownloadDeafultFiles;
}
public void setToDownloadDeafultFiles(boolean isToDownloadDeafultFiles) {
this.isToDownloadDeafultFiles = isToDownloadDeafultFiles;
}
private String fileNames;
private DataModelManager() {
}
public static DataModelManager getInstance() {
if (dataModelManager == null) {
synchronized (DataModelManager.class) {
if (dataModelManager == null) {
dataModelManager = new DataModelManager();
}
}
}
return dataModelManager;
}
private synchronized void addImageData(FrameData frameData) {
//Log.d("Frame Data","Start date "+frameData.getStartDate()+ " " +"end date "+frameData.getEndDate());
listFrameData.add(frameData);
}
public synchronized void parseData(String jsonStr) throws JSONException {
listFrameData.clear();
if (jsonStr == null) {
return;
}
List<String> listFileNames = new ArrayList<String>();
JSONArray jsonArr = new JSONArray(jsonStr);
int length = jsonArr.length();
for (int i = 0; i < length; i++) {
JSONObject jsonObj = jsonArr.getJSONObject(i);
dataModelManager.addImageData(new FrameData(jsonObj.optString("filename", ""), jsonObj.optString("start", ""), jsonObj.optString("end", ""), jsonObj.optString("filetype", ""), jsonObj.optString("playTime", ""), jsonObj.optBoolean("allDay", false)));
listFileNames.add(jsonObj.optString("filename", ""));
}
fileNames = listFileNames.toString();
}
public void setDefaultFileData(String jsonStr) throws JSONException {
JSONObject jsonObj = new JSONObject(jsonStr);
defaultFileName = jsonObj.optString("default_image", "");
screensaverName = jsonObj.optString("default_screensaver ", "");
}
#Override
public String toString() {
return fileNames.replace("[", "").replace("]", "") + "," + defaultFileName + "," + screensaverName;
}
public FrameData getFrameData(int index) {
return listFrameData.get(index);
}
public synchronized List<FrameData> getCurrentDataToShow() {
List<FrameData> lisCurrDataToShow = new ArrayList<FrameData>();
// for (FrameData fd : listFrameData) {//concurrent modification exception
//todo iterator test
Iterator<FrameData> iterator = listFrameData.iterator();
while (iterator.hasNext()) {
FrameData fd = iterator.next();
long currentTimeInMillis = java.lang.System.currentTimeMillis();
if ((currentTimeInMillis > fd.getStartDate().getTime() && currentTimeInMillis < fd.getEndDate().getTime()) || (fd.isAllDay() && DateUtils.isToday(fd.getStartDate().getTime()))) {
if (new File(ImageFrameActivity.ROOT_FOLDER_FILES + fd.getFileName()).exists()) {
lisCurrDataToShow.add(fd);
}
}
}
if (lisCurrDataToShow.size() == 0) {
lisCurrDataToShow.add(new FrameData(defaultFileName, null, null, null, String.valueOf(120), false));
}
return lisCurrDataToShow;
}
public String getCurrentFileNames() {
String currFileNames = "";
List<FrameData> currFrameData = getCurrentDataToShow();
for (FrameData data : currFrameData) {
currFileNames += "," + data.getFileName();
}
return currFileNames;
}
public ImageFrameActivity getImageFrameAct() {
return imageFrameAct;
}
public void setImageFrameAct(ImageFrameActivity imageFrameAct) {
this.imageFrameAct = imageFrameAct;
}
}
This is the only part of your question that is currently answerable:
If a threads is accessing getCurrentDataToShow() and another thread tries to access this function what will the function return?
It depends on whether you are calling getCurrentDataToShow() on the same target object; i.e. what this is.
If this is the same for both calls, then the first call will complete before the second call starts.
If this is different, you will be locking on different objects, and the two calls could overlap. Two threads need to lock the same object to achieve mutual exclusion.
In either case, this method is not changing the listFrameData collection. Hence it doesn't matter whether the calls overlap! However, apparently something else is changing the contents of the collection. If that code is not synchronizing at all, or if it is synchronizing on a different lock, then that could be a source of problems.
Now you say that you are not seeing ConcurrentModificationException's at the moment. That suggests (but does not prove) that there isn't a synchronization problem at all. And that suggests (but does not prove) that your current problem is a logic error.
But (as I commented above) there are reasons to doubt that the code you have shown us is an true reflection of your real code. You need to supply an MVCE if you want a more definite diagnosis.
I am following the next tutorial to securized my Rest services.
But I have a problem with the step Verify Token Fields, first of all I don't known if my dependencies are the correct:
<dependency>
<groupId>com.google.api-client</groupId>
<artifactId>google-api-client</artifactId>
<version>1.13.1-beta</version>
</dependency>
<dependency>
<groupId>com.google.http-client</groupId>
<artifactId>google-http-client-gson</artifactId>
<version>1.13.1-beta</version>
</dependency>
Secondly when I used the class Checker like in the example, in the call Verifier.verify(token) it returns false, it happen because in the class GoogleIdTokenVerifier the Set clientIds is empty. I follow the tutorial step by step, I'm totally lost
Thanks for all.
EDIT: This is the code I'm using now, and it seems to be working:
public class Checker {
private final String mAudience;
private final Lock lock = new ReentrantLock();
private final GoogleIdTokenVerifier mVerifier;
private final JsonFactory mJFactory;
private String mProblem = "Verification failed. (Time-out?)";
private final List<String> mClientIDs;
private List<PublicKey> publicKeys;
private final Clock clock;
NetHttpTransport transport;
private long expirationTimeMilliseconds;
public Checker(String[] clientIDs, String audience) {
mClientIDs = Arrays.asList(clientIDs);
mAudience = audience;
transport = new NetHttpTransport();
mJFactory = new GsonFactory();
mVerifier = new GoogleIdTokenVerifier(transport, mJFactory);
clock = Clock.SYSTEM;
}
public GoogleIdToken.Payload check(String tokenString) {
GoogleIdToken.Payload payload = null;
try {
GoogleIdToken token = GoogleIdToken.parse(mJFactory, tokenString);
if (checkSignature(mClientIDs.get(0), token)) {
GoogleIdToken.Payload tempPayload = token.getPayload();
if (!tempPayload.getAudience().equals(mAudience))
mProblem = "Audience mismatch";
else if (!mClientIDs.contains(tempPayload.getIssuee()))
mProblem = "Client ID mismatch";
else
payload = tempPayload;
}
} catch (GeneralSecurityException e) {
mProblem = "Security issue: " + e.getLocalizedMessage();
} catch (IOException e) {
mProblem = "Network problem: " + e.getLocalizedMessage();
} catch (Exception e) {
mProblem = "Problem: " + e.getLocalizedMessage();
}
return payload;
}
public String problem() {
return mProblem;
}
boolean checkSignature(String clientIds, GoogleIdToken idToken)
throws GeneralSecurityException, IOException {
JsonWebSignature.Header header = idToken.getHeader();
String algorithm = header.getAlgorithm();
if (algorithm.equals("RS256")) {
lock.lock();
try {
if (publicKeys == null
|| clock.currentTimeMillis() + 300000 > expirationTimeMilliseconds) {
mVerifier.loadPublicCerts();
publicKeys = mVerifier.getPublicKeys();
expirationTimeMilliseconds = mVerifier
.getExpirationTimeMilliseconds();
}
Signature signer = Signature.getInstance("SHA256withRSA");
for (PublicKey publicKey : publicKeys) {
signer.initVerify(publicKey);
signer.update(idToken.getSignedContentBytes());
if (signer.verify(idToken.getSignatureBytes())) {
return true;
}
}
} finally {
lock.unlock();
}
}
return false;
}
}
Don't know about your dependencies; that’s Maven right? I’m a Maven moron.
As for your the clientIDs, the code assumes you're going to pass in a list of clientIDs, because you want to make sure you know what client you're going to talk to. If you don't want to do that, I can see two obvious options:
just remove the clientIds argument to the constructor, the mClientIDs member variable, and the "if (!mClientIDs.contains()" call in the check() method.
change the code to skip the check if mClientIDs is null
I'm using java.util.resourcebundle to format my JSTL messages and this works fine:
I use the class MessageFormat you can see here. Now I want to encapsulate this to a method that is just getParametrizedMessage(String key, String[]parameters) but I'm not sure how to do it. Now there is quite a lot of work to display just one or two messages with parameters:
UserMessage um = null;
ResourceBundle messages = ResourceBundle.getBundle("messages");
String str = messages.getString("PF1");
Object[] messageArguments = new String[]{nyreg.getNummer()};
MessageFormat formatter = new MessageFormat("");
formatter.applyPattern(messages.getString("PI14"));
String outputPI14 = formatter.format(messageArguments);
formatter.applyPattern(messages.getString("PI15"));
String outputPI15 = formatter.format(messageArguments)
if(ipeaSisFlag)
if(checkIfPCTExistInDB && nyreg.isExistInDB()) {
//um = new ExtendedUserMessage(MessageHandler.getParameterizedMessage("PI15", new String[]{nyreg.getNummer()}) , UserMessage.TYPE_INFORMATION, "Info");
um = new ExtendedUserMessage(outputPI15 , UserMessage.TYPE_INFORMATION, "Info");
…and so on. Now can I move this logic to a static class MessageHandler.getParameterizedMessage that now is not working and looking like this:
private final static String dictionaryFileName="messages.properties";
public static String getParameterizedMessage(String key, String [] params){
if (dictionary==null){
loadDictionary();
}
return getParameterizedMessage(dictionary,key,params);
}
private static void loadDictionary(){
String fileName = dictionaryFileName;
try {
dictionary=new Properties();
InputStream fileInput = MessageHandler.class.getClassLoader().getResourceAsStream(fileName);
dictionary.load(fileInput);
fileInput.close();
}
catch(Exception e) {
System.err.println("Exception reading propertiesfile in init "+e);
e.printStackTrace();
dictionary=null;
}
}
How can I make using my parametrized messages as easy as calling a method with key and parameter?
Thanks for any help
Update
The logic comes from an inherited method that in in the abstract class that this extends. The method looks like:
protected static String getParameterizedMessage(Properties dictionary,String key,String []params){
if (dictionary==null){
return "ERROR";
}
String msg = dictionary.getProperty(key);
if (msg==null){
return "?!Meddelande " +key + " saknas!?";
}
if (params==null){
return msg;
}
StringBuffer buff = new StringBuffer(msg);
for (int i=0;i<params.length;i++){
String placeHolder = "<<"+(i+1)+">>";
if (buff.indexOf(placeHolder)!=-1){
replace(buff,placeHolder,params[i]);
}
else {
remove(buff,placeHolder);
}
}
return buff.toString();
}
I think I must rewrite the above method in order to make it work like a resourcebundle rather than just a dictionary.
Update 2
The code that seems to work is here
public static String getParameterizedMessage(String key, Object [] params){
ResourceBundle messages = ResourceBundle.getBundle("messages");
MessageFormat formatter = new MessageFormat("");
formatter.applyPattern(messages.getString(key));
return formatter.format(params);
}
I'm not really sure what you're trying to achive, here's what I did in the past:
public static final String localize(final Locale locale, final String key, final Object... param) {
final String name = "message";
final ResourceBundle rb;
/* Resource bundles are cached internally,
never saw a need to implement another caching level
*/
try {
rb = ResourceBundle.getBundle(name, locale, Thread.currentThread()
.getContextClassLoader());
} catch (MissingResourceException e) {
throw new RuntimeException("Bundle not found:" + name);
}
String keyValue = null;
try {
keyValue = rb.getString(key);
} catch (MissingResourceException e) {
// LOG.severe("Key not found: " + key);
keyValue = "???" + key + "???";
}
/* Message formating is expensive, try to avoid it */
if (param != null && param.length > 0) {
return MessageFormat.format(keyValue, param);
} else {
return keyValue;
}
}
I'm probably doing something wrong, but this is what happens:
I register a listener, wait for it to be called and when it executes and calls "Vector.clear()" it locks. The problem happens in the "pipeMsgEvent" method, here it is the, not so friendly-looking, code (if you want, go directly to "this is important" lines):
public class JxtaCustomer implements PipeMsgListener {
public static final int ANSWER_OK = 0;
public static final int ANSWER_TIMEOUT =-1;
public static final int ANSWER_NOT_ASKED =-2;
public static final int ANSWER_WORKING =-3;
public static final int REQ_SENT = 0;
public static final int REQ_INV_PIPE_ID =-1;
public static final int REQ_INV_PIPE_IO =-2;
public static final int REQ_INV_GROUP_ID =-3;
protected int answer;
protected JxtaGenericAdvertisement serviceAdv = null;
protected JxtaNode ThePeer = null;
JxtaBiDiPipe myBiDiPipe = null;
protected Vector<Entry> output = null;
public JxtaCustomer(JxtaGenericAdvertisement adv, JxtaNode peer)
{
ThePeer = peer;
serviceAdv = new JxtaGenericAdvertisement((Element)adv.getDocument(new MimeMediaType("text/xml")));
answer = ANSWER_NOT_ASKED;
Vector<Entry> output = new Vector<Entry>();
}
public void pipeMsgEvent(PipeMsgEvent event)
{
System.out.println("It Works! Uhuuu");
// We received a message
Message message = event.getMessage();
System.out.println("Lets GO! Uhuuu");
Message.ElementIterator elIt = message.getMessageElementsOfNamespace( serviceAdv.getName() );
System.out.println("A little bit more");
answer = ANSWER_WORKING;
System.out.println("enter");
// This is important: Here I get stuck, "clear"
// never appears on the screen
output.clear();
System.out.println("clear");
while (elIt.hasNext()) {
MessageElement mElem = elIt.next();
System.out.println(mElem.getElementName() + " " + mElem.toString());
output.add( new Entry( mElem.getElementName(), mElem.toString() ) );
}
System.out.println("leave");
answer = ANSWER_OK;
}
public int sendRequest(Vector<Entry> params)
{
try {
// Creating Pipe Advertisement
String pipeAdvType = PipeAdvertisement.getAdvertisementType();
PipeAdvertisement pipeAd = (PipeAdvertisement)AdvertisementFactory.newAdvertisement(pipeAdvType);
URI pipeURI = new URI(serviceAdv.getPipeID());
pipeAd.setPipeID( IDFactory.fromURI(pipeURI) );
pipeAd.setType(PipeService.UnicastType);
pipeAd.setName(serviceAdv.getName() + " Service Pipe");
pipeAd.setDescription("Created by " + serviceAdv.getName());
// Creating Group
JxtaGroup jxgp = ThePeer.getGroupFromID( serviceAdv.getGroupID() );
if (null == jxgp)
return REQ_INV_GROUP_ID;
PeerGroup group = jxgp.getPeerGroup();
if (null == group)
return REQ_INV_GROUP_ID;
// This is important: In the JxtaBiDiPipe call I register
// the callback, while I have access to the code, I think
// the problem is in my code
myBiDiPipe = new JxtaBiDiPipe( group, pipeAd, 30000, this);
if (myBiDiPipe.isBound()) {
Thread.sleep(500);
Message myMessage = new Message();
if (0 == params.size())
params.add( new Entry("dummy", "null") );
for (int i=0; i<params.size(); i++) {
String Key = params.get(i).getKey();
String Value = params.get(i).getValue();
StringMessageElement strMsgElem = new StringMessageElement( Key, Value, null);
myMessage.addMessageElement( serviceAdv.getName(), strMsgElem);
}
myBiDiPipe.sendMessage(myMessage);
answer = ANSWER_TIMEOUT;
return REQ_SENT;
}
} catch (URISyntaxException e){
e.printStackTrace();
return REQ_INV_PIPE_ID;
} catch (IOException e) {
return REQ_INV_PIPE_IO;
} catch (Exception e) {
e.printStackTrace();
}
return REQ_INV_PIPE_IO;
}
public Vector<Entry> getResponse()
{
Vector<Entry> results = new Vector<Entry>();
if (ANSWER_OK != answer)
return results;
// This is important: I always call "getState()" and check its value
// before calling this method, so you can say it's guaranteed to be
// called after answer = ANSWER_OK, which never happens because of the
// lock
for (int i=0; i<output.size(); i++)
results.add( output.get(i) );
return results;
}
public int getState()
{
int count = 10;
return answer;
}
}
I always create JxtaCustomer like this:
JxtaCustomer customer = new JxtaCustomer(adv, ThePeer);
Vector<Entry> params = new Vector<Entry>();
params.add( new Entry("key1", "value1") );
params.add( new Entry("key2", "value2") );
customer.sendRequest(params);
while(JxtaCustomer.ANSWER_OK != customer.getState()) {
// I was actually using synchronized locks and timed waits
// but since I'm stuck there I'm using this nonsense instead
}
Vector<Entry> response = customer.getResponse();
Here is where in the code I call "sleep", "wait" or I create a "synchronized" (this last one is never)
$ grep synchronized $(find . -name "*.java")
$ grep sleep $(find . -name "*.java")
./Src/net/ubi/jxta/JxtaCustomer.java: Thread.sleep(500);
$ grep wait $(find . -name "*.java")
./App/ExampleServices/SimpleSigner.java: boolean waiting = false;
./App/ExampleServices/SimpleSigner.java: waiting = true;
./App/ExampleServices/SimpleSigner.java: return (waiting && JxtaCustomer.ANSWER_OK == customer.getState());
./App/ExampleServices/SimpleSigner.java: if (!waiting)
./App/ExampleServices/SimpleSigner.java: waiting = false;
./App/ExampleServices/SimpleSigner.java: return "Error: Response not ready, wait more time\n";
Your constructor sets a local variable called output,and not the member variable, you have
Vector<Entry> output = new Vector<Entry>();
when it should be
output = new Vector<Entry>();
So, later on when you call output.clear() you're getting an Null Pointer Exception thrown, which is why the following lines of code don't get executed.
compiler warnings like "unused local variables" can help spot these sorts of mistakes.