I'm trying to create pull-based source of items. For some reason after pushing one item nothing arrives to the consumer. Whole pipeline is stuck. What am I missing ?
private static Flux<ByteBuffer> testRun(String path) {
return Flux.using(() -> {
FileInputStream in = new FileInputStream(path);
FileChannel channel = in.getChannel();
return Tuple.of(in, channel);
}, t -> s -> {
ByteBuffer bb = ByteBuffer.allocate(1000);
try {
if (t._2.read(bb) > 0)
s.onNext(bb.rewind());
else
s.onComplete();
} catch (IOException ex) {
s.onError(ex);
}
}, t -> {
try {
t._1.close();
t._2.close();
} catch (IOException ex) {
throw new RuntimeException(ex);
}
});
}
I got it. sourceSupplier of using is called only once.
private static Flux<ByteBuffer> testRun(String path) {
return Flux.using(() -> {
final FileInputStream in = new FileInputStream(path);
final FileChannel channel = in.getChannel();
return Tuple.of(in, channel);
}, t -> {
return Flux.generate(s -> {
ByteBuffer bb = ByteBuffer.allocate(1000);
try {
if (t._2.read(bb) > 0)
s.next(bb.rewind());
else
s.complete();
} catch (IOException ex) {
s.error(ex);
}
});
}, t -> {
try {
t._1.close();
t._2.close();
} catch (IOException ex) {
throw new RuntimeException(ex);
}
});
}
Related
In my veracode scan, I have very low vulnerability: Improper Resource Shutdown or Release CWE ID 404
And here is my code:
public static boolean nioCopy(File source, File destination) {
boolean retval = false;
FileChannel inChannel = null, outChannel = null;
try {
inChannel = (new FileInputStream(source)).getChannel();
outChannel = (new FileOutputStream(destination)).getChannel();
long size = inChannel.size();
long position = 0;
while ( position < size )
{
position += inChannel.transferTo( position, WINDOWS_MAGIC_BUFFER_SIZE, outChannel );
}
retval = true;
} catch (FileNotFoundException e) {
e.printStackTrace();
retval = false;
} catch (IOException e) {
e.printStackTrace();
retval = false;
} finally {
try {
if (inChannel != null) {
inChannel.close();
}
if (outChannel != null) {
outChannel.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
return retval;
}
Veracode is specifically pointing to this line:
outChannel = (new FileOutputStream(destination)).getChannel();
However, I believe I am releasing the resource in finally block. I was referring to this link: http://javaelegance.blogspot.com/2015/10/improper-resource-shutdown-or-release.html
What am I doing wrong here?
Assuming Java 8 or higher, use try with resources statements. See https://docs.oracle.com/javase/tutorial/essential/exceptions/tryResourceClose.html. It basically will handle automatically closing closable objects for you.
try (inChannel = (new FileInputStream(source)).getChannel()) {
//Use inChannel
}
catch(IOException ex) {
//Handle exception
}
I was wondering, when exception occurs how try with resource statement manages to close resources before entering catch block.
When exception occurs execution immediately jumps to catch block. So where actually try-with-resource closes the resources.
To get better understanding of how it works I decided to see how compiler implements it. I wrote following code and and compiled it.
public class Test
{
public static void main(final String[] args) {
//I used same JDK for compilation and execution.
System.out.println("Java version: " + System.getProperty("java.version") + "\n");
try(CloseMe me = new CloseMe();
CloseMeToo meToo = new CloseMeToo()){
System.out.println("trying");
throw new Exception("try failed");
} catch(Exception e) {
System.out.println("failed");
System.out.println("\n");
System.out.println(e.getMessage());
System.out.println(e.getSuppressed()[0].getMessage());
System.out.println(e.getSuppressed()[1].getMessage());
}
}
}
class CloseMe implements AutoCloseable {
#Override
public void close() throws Exception {
System.out.println("me closing!");
throw new Exception("don't close me :o");
}
}
class CloseMeToo implements AutoCloseable {
#Override
public void close() throws Exception {
System.out.println("meToo closing!");
throw new Exception("don't close me too :O");
}
}
Output
Java version: 15.0.1
trying
meToo closing!
me closing!
failed
try failed
don't close me too :O
don't close me :o
Then I went to www.javadecompilers.com and tried the decompilers there. Two decompilers gave decent results: CFR 0.150 and Fernflower.
CFR is most readable and complete so posting it here.
public class Test
{
public static void main(final String[] args) throws Throwable{
System.out.println("Java version: " + System.getProperty("java.version") + "\n");
try {
Throwable throwable = null;
Object var2_4 = null; //<-- where this variable is used?
try {
CloseMe me = new CloseMe();
try {
CloseMeToo meToo = new CloseMeToo();
try {
System.out.println("trying");
throw new Exception("try failed");
}
catch (Throwable throwable2) {
throwable = throwable2; //<-- I put this line to make it work
if (meToo != null) {
meToo.close();
}
throw throwable2;
}
}
catch (Throwable throwable3) {
if (throwable == null) {
throwable = throwable3;
} else if (throwable != throwable3) {
throwable.addSuppressed(throwable3);
}
if (me != null) {
me.close();
}
throw throwable;
}
}
catch (Throwable throwable4) {
if (throwable == null) {
throwable = throwable4;
} else if (throwable != throwable4) {
throwable.addSuppressed(throwable4);
}
throw throwable;
}
}
catch (Exception e) {
System.out.println("failed");
System.out.println("\n");
System.out.println(e.getMessage());
System.out.println(e.getSuppressed()[0].getMessage());
System.out.println(e.getSuppressed()[1].getMessage());
}
}
}
I understand decompilers have limitations. Ideal decompiler would've given me same try-with-resource back and I wouldn't have seen these details. So it is ok.
My questions are:
In above decompiled code, variable var2_4 is unused. Also, I had to add a line to make it work like try-with-resource. I think the code is not complete. If there are any, can you add/explain missing parts?
If anyone, who understands bytecode, translate class file to exact java code would be great. Or give me pointers about where can I get the tools to do the job.
Thank you!
The behavior of try-with-resources is fully documented in the Java Language Specification, section 14.20.3. try-with-resources.
It specifically shows that the following abbreviated version of the question code:
try (CloseMe me = new CloseMe(); CloseMeToo meToo = new CloseMeToo()) {
System.out.println("trying");
} catch (Exception e) {
System.out.println("failed");
}
first gets converted to:
try {
try (CloseMe me = new CloseMe(); CloseMeToo meToo = new CloseMeToo()) {
System.out.println("trying");
}
} catch (Exception e) {
System.out.println("failed");
}
then to:
try {
final CloseMe me = new CloseMe();
Throwable #primaryExc1 = null;
try (CloseMeToo meToo = new CloseMeToo()) {
System.out.println("trying");
} catch (Throwable #t) {
#primaryExc1 = #t;
throw #t;
} finally {
if (me != null) {
if (#primaryExc1 != null) {
try {
me.close();
} catch (Throwable #suppressedExc) {
#primaryExc1.addSuppressed(#suppressedExc);
}
} else {
me.close();
}
}
}
} catch (Exception e) {
System.out.println("failed");
}
then to:
try {
final CloseMe me = new CloseMe();
Throwable #primaryExc1 = null;
try {
final CloseMeToo meToo = new CloseMeToo()
Throwable #primaryExc2 = null;
try {
System.out.println("trying");
catch (Throwable #t) {
#primaryExc2 = #t;
throw #t;
} finally {
if (meToo != null) {
if (#primaryExc2 != null) {
try {
meToo.close();
} catch (Throwable #suppressedExc) {
#primaryExc2.addSuppressed(#suppressedExc);
}
} else {
meToo.close();
}
}
}
} catch (Throwable #t) {
#primaryExc1 = #t;
throw #t;
} finally {
if (me != null) {
if (#primaryExc1 != null) {
try {
me.close();
} catch (Throwable #suppressedExc) {
#primaryExc1.addSuppressed(#suppressedExc);
}
} else {
me.close();
}
}
}
} catch (Exception e) {
System.out.println("failed");
}
I am working on my first server project for school and I am receiving a NoSuchElementException when reaching the code below in my client. From my understanding, the way I have written it, the scanner should be waiting for the server to send back a string. Instead it seems to be jumping right to the exception. In the server code (second below) I have the output that is supposed to return all strings in an array. My goal is to have the client print all of the strings in the text area (status).
static void runClient() {
Socket client = null;
PrintWriter output = null;
Scanner input = null;
try {
client = new Socket("localhost", 5007);
input = new Scanner(client.getInputStream());
output = new PrintWriter(client.getOutputStream());
output.println(game);
output.println(numberOfPicks);
output.flush();
pStr("Data Sent");
while (true) {
pStr("Waiting for Server");
status.appendText(input.nextLine());
if (!input.hasNext())
break;
}
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
input.close();
} catch (Exception e) {
}
try {
output.close();
} catch (Exception e) {
}
try {
client.close();
} catch (Exception e) {
}
}
}
private static void pStr(String string) {
System.out.println(string);
}
}
PARTIAL SERVER CODE BELOW
public void run() {
PrintWriter output = null;
Scanner input = null;
try {
// Get input and output streams.]
input = new Scanner(connection.getInputStream());
output = new PrintWriter(connection.getOutputStream());
String game;
int quickPicks;
try {
game = input.nextLine();
quickPicks = Integer.parseInt(input.nextLine());
switch (game) {
case "PowerBall":
ansStr = new pickNumbers(game, quickPicks, 69, 26).getQuickPicks();
break;
case "MegaMillions":
ansStr = new pickNumbers(game, quickPicks, 70, 25).getQuickPicks();
break;
case "Lucky4Life":
ansStr = new pickNumbers(game, quickPicks, 48, 18).getQuickPicks();
break;
default:
throw new RuntimeException("Incorrect Game");
}
} catch (Exception e) {
output.println(e.getMessage());
}
for (int i = 0; i < ansStr.length; i++) {
output.println(ansStr[i]);
//output.flush();
}
} catch (Exception e) {
pStr(e.getMessage());
} finally {
try {
input.close();
} catch (Exception e) {
}
try {
output.close();
} catch (Exception e) {
}
try {
connection.close();
} catch (Exception e) {
}
}
}
}
How about nesting status.appendText(input.nextLine()); in a test for hasNextLine e.g:
if(input.hasNextLine()){
status.appendText(input.nextLine());
}
I really don't know what to look for and if this is even possible. I am trying to code a dynamic Fileloader.
This is the code:
public static Serializable loadSerializable(Context context,
String filename, Object object) {
final String DEBUGTAG = "Loading data" ;
Serializable serializable = null;
ObjectInputStream oin = null;
try {
File file = new File(context.getFilesDir(), filename);
FileInputStream in = new FileInputStream(file);
oin = new ObjectInputStream(in);
Object readElement = oin.readObject();
serializable = (Serializable) readElement; // here I want dynamic casting
Log.d(DEBUGTAG, "Success : " + filename);
} catch (FileNotFoundException e) {
Log.d(DEBUGTAG, "File not found");
} catch (StreamCorruptedException e) {
Log.d(DEBUGTAG, "Stream Corrupted");
} catch (IOException e) {
Log.d(DEBUGTAG, "IOException");
} catch (ClassNotFoundException e) {
Log.d(DEBUGTAG, "Class not Found");
} catch (NullPointerException e) {
Log.d(DEBUGTAG, "NullPointer - File does not exist yet");
} finally {
if (oin != null)
try {
oin.close();
} catch (IOException e) {
Log.d(DEBUGTAG, "IOException - Stream not closed");
}
}
return serializable;
}
What I want to do now is instead of creating a new method for every single object I want to use the 3rd argument (object or whatever) for the type casting.
So I could write
String myString = loadSerializable(this, test.dat, String) or
ArrayList<Fragment> = loadSerializable(this, test.dat, ArrayList<Fragment>) and so on....
Help appreciated
Something like
public static <T> T loadSerializable(Context context, String filename) {
// ...
T t = (T) readElement;
// ...
return t;
}
hello dear colleagues,
I have a Garden class in which I serialize and deserialize multiple Plant class objects. The serializing is working but the deserializing is not working if a want to assign it to calling variable in the mein static method.
public void searilizePlant(ArrayList<Plant> _plants) {
try {
FileOutputStream fileOut = new FileOutputStream(fileName);
ObjectOutputStream out = new ObjectOutputStream(fileOut);
for (int i = 0; i < _plants.size(); i++) {
out.writeObject(_plants.get(i));
}
out.close();
fileOut.close();
} catch (IOException ex) {
}
}
deserializing code:
public ArrayList<Plant> desearilizePlant() {
ArrayList<Plant> plants = new ArrayList<Plant>();
Plant _plant = null;
try {
ObjectInputStream in = new ObjectInputStream(new FileInputStream(fileName));
Object object = in.readObject();
// _plant = (Plant) object;
// TODO: ITERATE OVER THE WHOLE STREAM
while (object != null) {
plants.add((Plant) object);
object = in.readObject();
}
in.close();
} catch (IOException i) {
return null;
} catch (ClassNotFoundException c) {
System.out.println("Employee class not found");
return null;
}
return plants;
}
My invoking code:
ArrayList<Plant> plants = new ArrayList<Plant>();
plants.add(plant1);
Garden garden = new Garden();
garden.searilizePlant(plants);
// THIS IS THE PROBLEM HERE
ArrayList<Plant> dp = new ArrayList<Plant>();
dp = garden.desearilizePlant();
edit
I got a null Pointer exception
The solution of #NilsH is working fine, thanks!
How about serializing the entire list instead? There's no need to serialize each individual object in a list.
public void searilizePlant(ArrayList<Plant> _plants) {
try {
FileOutputStream fileOut = new FileOutputStream(fileName);
ObjectOutputStream out = new ObjectOutputStream(fileOut);
out.writeObject(_plants);
out.close();
fileOut.close();
} catch (IOException ex) {
}
}
public List<Plant> deserializePlant() {
List<Plants> plants = null;
try {
ObjectInputStream in = new ObjectInputStream(new FileInputStream(fileName));
plants = in.readObject();
in.close();
}
catch(Exception e) {}
return plants;
}
If that does not solve your problem, please post more details about your error.
It may not always be feasible to deserialize a whole list of objects (e.g., due to memory issues). In that case try:
ObjectInputStream in = new ObjectInputStream(new FileInputStream(
filename));
while (true) {
try {
MyObject o = (MyObject) in.readObject();
// Do something with the object
} catch (EOFException e) {
break;
}
}
in.close();
Or using the Java SE 7 try-with-resources statement:
try (ObjectInputStream in = new ObjectInputStream(new FileInputStream(
filename))) {
while (true) {
MyObject o = (MyObject) in.readObject();
// Do something with the object
}
} catch (EOFException e) {
return;
}
If you serialize it to an array linear list, you can cast it back to an array linear list when deserializing it -- all other methods failed for me:
import java.io.*;
import java.util.ArrayList;
import java.util.Arrays;
public class Program
{
public static void writeToFile(String fileName, Object obj, Boolean appendToFile) throws Exception
{
FileOutputStream fs = null;
ObjectOutputStream os = null;
try
{
fs = new FileOutputStream(fileName);
os = new ObjectOutputStream(fs);
//ObjectOutputStream.writeObject(object) inherently writes binary
os.writeObject(obj); //this does not use .toString() & if you did, the read in would fail
}
catch (FileNotFoundException e)
{
e.printStackTrace();
}
catch (IOException e)
{
e.printStackTrace();
}
catch(Exception e)
{
e.printStackTrace();
}
finally
{
try
{
os.close();
fs.close();
}
catch(Exception e)
{
//if this fails, it's probably open, so just do nothing
}
}
}
#SuppressWarnings("unchecked")
public static ArrayList<Person> readFromFile(String fileName)
{
FileInputStream fi = null;
ObjectInputStream os = null;
ArrayList<Person> peopleList = null;
try
{
fi = new FileInputStream(fileName);
os = new ObjectInputStream(fi);
peopleList = ((ArrayList<Person>)os.readObject());
}
catch (FileNotFoundException e)
{
e.printStackTrace();
}
catch(EOFException e)
{
e.printStackTrace();
}
catch(ClassNotFoundException e)
{
e.printStackTrace();
}
catch (IOException e)
{
e.printStackTrace();
}
catch(Exception e)
{
e.printStackTrace();
}
finally
{
try
{
os.close();
fi.close();
}
catch(Exception e)
{
//if this fails, it's probably open, so just do nothing
}
}
return peopleList;
}
public static void main(String[] args)
{
Person[] people = { new Person(1, 39, "Coleson"), new Person(2, 37, "May") };
ArrayList<Person> peopleList = new ArrayList<Person>(Arrays.asList(people));
System.out.println("Trying to write serializable object array: ");
for(Person p : people)
{
System.out.println(p);
}
System.out.println(" to binary file");
try
{
//writeToFile("output.bin", people, false); //serializes to file either way
writeToFile("output.bin", peopleList, false); //but only successfully read back in using single cast
} // peopleList = (ArrayList<Person>)os.readObject();
// Person[] people = (Person[])os.readObject(); did not work
// trying to read one at a time did not work either (not even the 1st object)
catch (Exception e)
{
e.printStackTrace();
}
System.out.println("\r\n");
System.out.println("Trying to read object from file. ");
ArrayList<Person> foundPeople = null;
try
{
foundPeople = readFromFile("input.bin");
}
catch (Exception e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
if (foundPeople == null)
{
System.out.println("got null, hummm...");
}
else
{
System.out.println("found: ");
for(int i = 0; i < foundPeople.size(); i++)
{
System.out.println(foundPeople.get(i));
}
//System.out.println(foundPeople); //implicitly calls .toString()
}
}
}