RMI :: Using RMI To Wrap A Process That Is Not Thread Safe
Apr 3, 2013
I have a multi-threaded application but one function (A) I need to call, that is provided by a third party, is not thread safe. I need to make parallel calls to function (A) so my only option is to start multiple process that I can call from each of my main applications threads.
To do this I created a RMI interface between a the client and the remote process. On the server side I start multiple processes each assigned a different port. On the client side I have a queue manager that connects to the processes I started and builds a queue of them. It passes the client to the threads as needed so they can function in parallel.
I am new to Java development and have the following questions:
1. Each of the server processes require an init function to be run before providing the service. How do I setup the server processes to continue to run in memory listening for a a service request after running the init processes.
2. Is there a better implementation of what I am trying to do?
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Jul 10, 2014
I have situation where a user can request java server to send a value to an embedded device, and if the device is asleep, that value needs to be stored in a queue until the device wakes up and sends a position to java server, at which point the server checks if there is a value in the queue and if there is, it then sends that value to the device. The maximum size of the queue is 1 for now. And if the user makes continuous requests to java server, the old value is removed and the new value is added.
Initially I was looking into BlockingQueue, but the problem with that is, well, it blocks. queue.put(value) will block if queue is full, and queue.take() will block if queue is empty. I can't have something that blocks. When the device responds to server, server checks if value is in queue, if it is not then the server carries on the rest of its responsibility. Thus, I then entertained ConcurrentLinkedQueue. While queue.offer(value) and queue.poll(); allow you to add and remove values respectively from the queue without blocking, it does not allow you to set a maximum size limit of the queue. My queue must have a maximum size limit and it has to always be the newest value the user submits to the queue (where old values are removed).So this is what I came up with:
Java Code: class Unit {
private List<Integer> cmdQueue;
public Unit(){
cmdQueue = Collections.synchronizedList(new LinkedList<Integer>());
[code]....
I use Collections.synchronizedList, as I do here, do I still need to use synchronize as I did above?
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Jul 10, 2014
Implementation that proves that instance variables are not thread safe ....
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Jan 22, 2015
Are the static variables in servlet thread-safe?
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May 8, 2014
I read JEE6 doc and confused with : Does container managed entity manager (injected by PersistenceContext annotation) is thread-safe in stateless session bean in multiple-thread env?
See code below, if there are 2 requests to stateless sesion bean in 2 concurrent threads , is it using same Entity Manager Instance or not?
@Stateless(name = "HRFacade", mappedName = "HR_FACES_EJB_JPA-HRFacade-HRFacade")
public class HRFacadeBean implements HRFacade, HRFacadeLocal {
@Resource
SessionContext sessionContext;
@PersistenceContext(unitName = "HRFacade")
private EntityManager em;
[Code] .....
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Nov 4, 2014
I created a main class called X and two Y and Z classes.
Y and Z implements Runnable classes.
class X contains a static array A that can be accessed in Y and Z.
The Run () method of the class Y reads an input file and populates the vector A.
The Run () method of the Z class uses data stored into the vector A to process some data.
The objective of using threads in this problem is: as the vector A is filled in the Run () method of class Y, the Run () method of the class Z will processing the received values in the vector A.
to do this I did the following calls in the main method of class X:
ObjectY y = new Y ();
Thready thread = new Thread (objectY);
threadY.start ();
ObjectZ new Z = Z ();
Threadz thread = new Thread (objectZ);
threadZ.start ();
is that correct? I'm getting the expected results, but dont know if the code is parallelized in fact.
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Sep 20, 2014
I'm currently learning about Swing but I can't get my head round this piece of the code. Here is a simplified gui (not interested in the gui part but the execution)
public class SwingDemo implements ActionListener {
SwingDemo(){
JFrame jfrm = new JFrame("Simple gui pro");
//rest of code
public static void main(String[] args) {
new SwingDemo();
}
I get the above, create a new instance of SwingDemo in the main thread which starts up the gui through the constructor. However, then the tutorial says that I should avoid doing the above but do this instead:
public class SwingDemo implements ActionListener {
SwingDemo(){
JFrame jfrm = new JFrame("Simple gui pro");
//rest of code
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() { //why do this instead?
public void run(){
new SwingDemo();
}
});
}
}
Reading, it talks about an event-dispatching thread which has completely lost me... Why not just instantiate the object directly instead of creating another thread?
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Oct 17, 2014
im having an issue with the 3rd thread that are supposed to merge the two sorted sub arrays , i pass the 2 subarrays to my runnable function sortlist and they are renamed IntSortList 1 and 2 and th1.start() and th1.join() are called and it works fine, but then i have another runnable constructor that takes IntSortList 1 and 2 but it does take a runnable. below is the code in my main,
Runnable InSortlist1 = new sortList(data2p1);
Runnable InSortlist1 = new sortList(data2p1);
Thread th1 = new Thread (IntSortlist1);
Thread th2 = new Thread (IntSortlist2);
try
{
th1.start();
th1.join();
[code]....
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Feb 14, 2015
I was wondering, if, for example I set font for my textarea like this:
area.setFont(new Font("Serif", Font.ITALIC, 18));
Is that last parameter, in this case 18, will be actually the same size for all users? Maybe I should avoid these absolute numbers?
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Jul 16, 2014
class A extends Thread
{
String str;
public void run( )
{
//random stuff
}
}
[Code]....
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Oct 8, 2014
How to access one thread from another thread?
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Aug 5, 2014
I didn't ask you to do my home work . tell me how to communicate two java program using named piped concept.
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Mar 15, 2014
I need a summary of the steps involve in building java application.I have my source code, already compiled but I don't know the next step to make it run on a particular device. I know of emulator but I need more information.
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Aug 22, 2014
I am using JAX-WS to develop web services.
I would like to know how i can find the process ID associated to a request.
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Apr 21, 2014
I'm Fresher and i'm new in ATG nd right now working on checkout module.Here I'm trying to take shipping information of user so it is fetching in the shipping information JSP bt when i'm trying to submit that JSP den it's not going to either in SuccessURL or in ErrorURL it's remaining in current JSP.
I'm doing any customization's i'm jst using al Out Of Box Components nd my code is almost same as Out Of Box Code and it is not giving any error also.
I'm attaching my JSP's
Attached File(s)
shipping_jsp.txt (4.17K)
Number of downloads: 293
shippingAddress_jsp.txt (1.9K)
Number of downloads: 135
shippingSingle_jsp.txt (70bytes)
Number of downloads: 19
shippingSingleForm_jsp.txt (2.05K)
Number of downloads: 102
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Apr 16, 2015
I am working on a management gui for a program. I have implemented the start server button. But now I need to get something working so that when I press stop server the javaw.exe process which is running the the other jar file is stopped and ended.
The gui is going to be using a javaw.exe as well and I don't want to end the entire thing.
I just want to end the javaw.exe process that is running the other jar file.
This is my code for starting it:
JButton btnNewButton_2 = new JButton("Start Server");
btnNewButton_2.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
Runtime rt = Runtime.getRuntime();
try {
Process pr = rt.exec("java -jar DEDServer_release.jar");
[Code] ....
I just need to figure out what to do to stop it now.
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Nov 3, 2014
I am looking for a way to have a Servlet (my container is Tomcat) calling a JSP file and processing it in order to retrieve the generated HTML. The compete scenario:
I have virtual shop and whenever a purchase is being carried out, the customer is redirected to a Servlet that post-processes the purchase (list of the items, etc.)
Among all these, the Servlet is also supposed to send me an email about the new purchase. I would like to have nice designed HTML mail and not just a simple plain text notification. I thought of having a designated JSP as a view, and it will only be available from the Servlet container, for this purpose. One way is having the Servlet create an HTTPClient (or any other method of network communication) to my own host and ask for the JSP.
I wonder if there is a simpler way to ask my own container to process a JSP, since I am not really making a request to an outside web application. Something like getServletContext.processAndReturnJsp("mail.jsp")
BTW, if you think my approach is too cumbersome to fill an email with HTML code, it would be great to know of a simpler way.
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Jul 28, 2014
I'm just starting out with learning how to process/parse XML data in Java, following online code/tutorials. I am currently only printing out "catalog."
XML File that I'm trying to read: URL...
import java.io.*;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
[code]...
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Jun 6, 2014
I want to do basic input/output using Process class. I basically wish that, I should ask user his name and when user provides his name then I would print "Hello '[name]'"
import java.io.*;
public class ReadAndPrintName
{
static Process p;
[Code]....
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Feb 23, 2014
I have an applet and start some process on Windows from applet. When I start this process just from another code(test), this code works fine and process runs from rt.exec() to proc.destroy(). When I use html call for applet - process runs only for 5 seconds every time (!!!) and then just alive, doesn't work, to proc.destroy(). This is really interesting for me (newbie in applets). I think, this issue caused by AccessController. I use Windows, medium Java security lever and applet is self-signed. It asks me to 'allow', applet works.Here's the code:
public String startRecording(final String filename) throws IOException {
try {
return (String) AccessController
.doPrivileged(new PrivilegedAction<String>() {
public String run() {
try {
proc = Runtime
.getRuntime()
[code]....
It's FFMPEG process, which records desktop video and writes it to file, maybe AccessController blocks access to file system.
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Jun 9, 2014
I've written an HTTPServlet that send an HTTP request to one HttpListener and receive POST requests from an Http Sender.This is the code:
package sspa.huvr.git;
import java.io.DataOutputStream;
import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.Date;
[code]...
but when is called from the doPost method it seems that the html content is not sent from the processRequest method.
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Aug 22, 2014
Is there a way to have global variable in Java associated to a process ?
I'm coming from PL/SQL world, I'm looking for something like package variables.
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Mar 3, 2014
I would like to use java se api names like, undo, redo, stylededitorkit, htmleditorkit in editorpane swing. So, I don't understand how to use these apis.
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Dec 1, 2014
We need to process (read and parse) big xml files (500 Mo to 1 or 2 Go). What's the best framework or Java library to use for this requirement ? Then what's a good OXM (in this case xml to object mapping) solution for this kind of file ?
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Oct 24, 2013
i want to create an application which detect an image which took from camera and to process it so that it can be verified ..for example number plate of the vehicle ..if i need to extract the numbers from the image ..
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Jun 15, 2014
I'm working on an assignment where the program has to process a file and read every line then print it out in all caps. I'm pretty sure I have most of it written out, however, I am having trouble with my main method. I am supposed to call my go method in my FileProcessor class and have it use the StringProcessor interface to call my Upper class. I'm using an interface because I will be adding other classes later, but for now I am having trouble with implementing it all in my Driver class.
How do I declare a StringProcessor object in my Driver class and how can I use it so that it would create the file in all caps?
Here's my code so far:
Driver.java
import java.util.Scanner;
import java.io.FileNotFoundException;
import javax.swing.JFileChooser;
import java.io.File;
[Code].....
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