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  • Hibernate Communications Link Failure in Hibernate Based Java Servlet application powered by MySQL

    - by Vatsala
    Let me describe my question - I have a Java application - Hibernate as the DB interfacing layer over MySQL. I get the communications link failure error in my application. The occurence of this error is a very specific case. I get this error , When I leave mysql server unattended for more than approximately 6 hours (i.e. when there are no queries issued to MySQL for more than approximately 6 hours). I am pasting a top 'exception' level description below, and adding a pastebin link for a detailed stacktrace description. javax.persistence.PersistenceException: org.hibernate.exception.JDBCConnectionException: Cannot open connection - Caused by: org.hibernate.exception.JDBCConnectionException: Cannot open connection - Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure - The last packet successfully received from the server was 1,274,868,181,212 milliseconds ago. The last packet sent successfully to the server was 0 milliseconds ago. - Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure - The last packet successfully received from the server was 1,274,868,181,212 milliseconds ago. The last packet sent successfully to the server was 0 milliseconds ago. - Caused by: java.net.ConnectException: Connection refused: connect the link to the pastebin for further investigation - http://pastebin.com/4KujAmgD What I understand from these exception statements is that MySQL is refusing to take in any connections after a period of idle/nil activity. I have been reading up a bit about this via google search, and came to know that one of the possible ways to overcome this is to set values for c3p0 properties as c3p0 comes bundled with Hibernate. Specifically, I read from here http://www.mchange.com/projects/c3p0/index.html that setting two properties idleConnectionTestPeriod and preferredTestQuery will solve this for me. But these values dont seem to have had an effect. Is this the correct approach to fixing this? If not, what is the right way to get over this? The following are related Communications Link Failure questions at stackoverflow.com, but I've not found a satisfactory answer in their answers. http://stackoverflow.com/questions/2121829/java-db-communications-link-failure http://stackoverflow.com/questions/298988/how-to-handle-communication-link-failure Note 1 - i dont get this error when I am using my application continuosly. Note 2 - I use JPA with Hibernate and hence my hibernate.dialect,etc hibernate properties reside within the persistence.xml in the META-INF folder (does that prevent the c3p0 properties from working?) edit - Here are the c3p0 parameters I tried out - select 1; 2

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  • Logic differences in C and Java

    - by paragjain16
    Compile and run this code in C #include <stdio.h> int main() { int a[] = {10, 20, 30, 40, 50}; int index = 2; int i; a[index++] = index = index + 2; for(i = 0; i <= 4; i++) printf("%d\n", a[i]); } Output : 10 20 4 40 50 Now for the same logic in Java class Check { public static void main(String[] ar) { int a[] = {10, 20, 30, 40, 50}; int index = 2; a[index++] = index = index + 2; for(int i = 0; i <= 4; i++) System.out.println(a[i]); } } Output : 10 20 5 40 50 Why is there output difference in both languages, output is understandable for Java but I cannot understand output in C One more thing, if we apply the prefix ++ operator, we get the same result in both languages, why?

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  • Java "compare cannot be resolved to a type" error

    - by King Triumph
    I'm getting a strange error when attempting to use a comparator with a binary search on an array. The error states that "compareArtist cannot be resolved to a type" and is thrown by Eclipse on this code: Comparator<Song> compare = new Song.compareArtist(); I've done some searching and found references to a possible bug with Eclipse, although I have tried the code on a different computer and the error persists. I've also found similar issues regarding the capitalization of the compare method, in this case compareArtist. I've seen examples where the first word in the method name is capitalized, although it was my understanding that method names are traditionally started with a lower case letter. I have experimented with changing the capitalization but nothing has changed. I have also found references to this error if the class doesn't import the correct package. I have imported java.util in both classes in question, which to my knowledge allows the use of the Comparator. I've experimented with writing the compareArtist method within the class that has the binary search call as well as in the "Song" class, which according to my homework assignment is where it should be. I've changed the constructor accordingly and the issue persists. Lastly, I've attempted to override the Comparator compare method by implementing Comparator in the Song class and creating my own method called "compare". This returns the same error. I've only moved to calling the comparator method something different than "compare" after finding several examples that do the same. Here is the relevant code for the class that calls the binary search that uses the comparator. This code also has a local version of the compareArtist method. While it is not being called currently, the code for this method is the same as the in the class Song, where I am trying to call it from. Thanks for any advice and insight. import java.io.*; import java.util.*; public class SearchByArtistPrefix { private Song[] songs; // keep a direct reference to the song array private Song[] searchResults; // holds the results of the search private ArrayList<Song> searchList = new ArrayList<Song>(); // hold results of search while being populated. Converted to searchResults array. public SearchByArtistPrefix(SongCollection sc) { songs = sc.getAllSongs(); } public int compareArtist (Song firstSong, Song secondSong) { return firstSong.getArtist().compareTo(secondSong.getArtist()); } public Song[] search(String artistPrefix) { String artistInput = artistPrefix; int searchLength = artistInput.length(); Song searchSong = new Song(artistInput, "", ""); Comparator<Song> compare = new Song.compareArtist(); int search = Arrays.binarySearch(songs, searchSong, compare);

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  • Invoke Java via Batch File with Filepath Arguments

    - by EricIdyll
    Hi there, I'm having an issue getting files loaded into an app called GCS, by dragging them onto the executable. GCS can be invoked on Windows with a bat file, which goes like this: @echo off start javaw -Xmx256M -jar "GURPS Character Sheet.app/Contents/Resources/Java/GCS.jar" %* If I hard code a filepath in place of the batch argument wildcard (with quotes), it works. If I run the debugger with a filepath argument it works. If I echo %, it gives me the correct filename with quotes around it. If I add quotes around % it still breaks. I have a disconnect here between DOS and Java, and I'm at a loss. Does anyone recognize this problem? Thanks in advance.

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  • a java applet question

    - by Robert
    Hello there. I have a question on the java applet.I've created a java applet,which is a board game,that can have a 2*2 array with row number and column number both set to 9 by default. Now I want to extend my applet a bit,that the user can specify the size they want on the command-line,then the applet class will create an applet with correspoding size. I try to add a constructor in the applet class,but the Eclipse complains,I also tried another class,which will create an instance of this applet with size as an instance variable,but it is not working. Could anyone help me a little bit on where to put a main() method that can take care of user-specified board sized,then create an array in my applet class accordingly? Thanks a lot. Rob

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  • Java WebStart: <property ...> ignored when using <extension>?

    - by Thorbjørn Ravn Andersen
    I have a problem modernizing a Java WebStart application under Java 6 u 13 (the latest at this moment) We desire to use the new mechanism to have several master configuration files each with their own configuration , which then "include" another jnlp file which is autogenerated to ensure that the jar list is accurate. After quite a bit of poking I have made it work, except for the fact that the properties defined in the master file is not available to the program when Main is invoked. The master JNLP looks like (anonymized): <jnlp> <information> <title>...</title> <vendor>...</vendor> <description>...</description> <description kind="short">...</description> <homepage href="http://....jnlp"/> <icon href="http://....gif"/> <!-- <offline-allowed/> --> </information> <security> <all-permissions/> </security> <resources> <j2se version="1.6+"/> <extension href="http://...extension.jnlp" /> <property name="server.name" value="SERVER"/> </resources> <application-desc main-class="Main"/> </jnlp> and the extension.jnlp looks like: <!-- Generated automatically. Do not edit! --> <jnlp> <information> <title>extension built 2009-04-22 12:39:58 CEST</title> <vendor>...</vendor> </information> <security><all-permissions/></security> <resources> <jar href="A.jar" /> <jar href="B.jar" /> <jar href="logback-classic-0.9.14.jar" /> <jar href="logback-core-0.9.14.jar" /> <jar href="slf4j-api-1.5.6.jar" /> </resources> <component-desc /> </jnlp> I have tried putting the proprty in the extension.jnlp too. Did not help. The JVM is reused and not relaunched according to the log in the Java Plugin Console. Any suggestions?

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  • Interop: HmacSHA1 in Java and dotNet

    - by wilth
    Hello, In an app we are calculating a SHA1Hmac in java using the following: SecretKey key = new SecretKeySpec(secret, "HmacSHA1"); Mac m = Mac.getInstance("HmacSHA1"); m.init(secret); byte[] hmac = m.doFinal(data); And later, the hmac is verified in C# - on a SmartCard - using: HMACSHA1 hmacSha = new HMACSHA1(secret); hmacSha.Initialize(); byte[] hmac = hmacSha.ComputeHash(data); However, the result is not the same. Did I overlook something important? The inputs seem to be the same. Here some sample inputs: Data: 546573746461746131323341fa3c35 Key: 6d795472616e73616374696f6e536563726574 Result Java: 37dbde318b5e88acbd846775e38b08fe4d15dac6 Result C#: dd626b0be6ae78b09352a0e39f4d0e30bb3f8eb9 I wouldn't mind to implement my own hmacsha1 on both platforms, but using what already exists.... Thanks!

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  • Problem with starting OpenOffice service (soffice) from Java (command working in commandline, but no

    - by Shervin
    I want to exceute a simple command which works from the shell but doesn't work from Java. This is the command I want to execute, which works fine: soffice -headless "-accept=socket,host=localhost,port=8100;urp;" This is the code I am excecuting from Java trying to run this command: String[] commands = new String[] {"soffice","-headless","\"-accept=socket,host=localhost,port=8100;urp;\""}; Process process = Runtime.getRuntime().exec(commands) int code = process.waitFor(); if(code == 0) System.out.println("Commands executed successfully"); When I run this program I get "Commands executed successfully". However the process is not running when the program finishes. Is it possible that the JVM kills the program after it has run? Why doesn't this work?

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  • Naming convention for utility classes in Java

    - by Zarjay
    When writing utility classes in Java, what are some good guidelines to follow? Should packges be "util" or "utils"? Is it ClassUtil or ClassUtils? When is a class a "Helper" or a "Utility"? Utility or Utilities? Or do you use a mixture of them? The standard Java library uses both Utils and Utilities: javax.swing.Utilities javax.print.attribute.AttributeSetUtilities javax.swing.plaf.basic.BasicGraphicsUtils Apache uses a variety of Util and Utils, although mostly Utils: org.apache.commons.modeler.util.DomUtil org.apache.commons.modeler.util.IntrospectionUtils org.apache.commons.io.FileSystemUtils org.apache.lucene.wordnet.AnalyzerUtil org.apache.lucene.util.ArrayUtil org.apache.lucene.xmlparser.DOMUtils Spring uses a lot of Helper and Utils classes: org.springframework.web.util.UrlPathHelper org.springframework.core.ReflectiveVisitorHelper org.springframework.core.NestedExceptionUtils org.springframework.util.NumberUtils So, how do you name your utility classes?

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  • java.util.BitSet -- set() doesn't work as expected

    - by dwhsix
    Am I missing something painfully obvious? Or does just nobody in the world actually use java.util.BitSet? The following test fails: @Test public void testBitSet() throws Exception { BitSet b = new BitSet(); b.set(0, true); b.set(1, false); assertEquals(2, b.length()); } It's really unclear to me why I don't end up with a BitSet of length 2 and the value 10. I peeked at the source for java.util.BitSet, and on casual inspection it seems to fail to make sufficient distinction between a bit that's been set false and a bit that has never been set to any value... (Note that explicitly setting the size of the BitSet in the constructor has no effect, e.g.: BitSet b = new BitSet(2);

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  • Error during maven build: "[java] Timestamp response not valid"

    - by fei
    My maven build started failing randomly, and it got the following error which I cannot make sense of, and googling it doesn't give me anything useful: [echo] Creating a full package... [java] Timestamp response not valid [INFO] ------------------------------------------------------------------------ [ERROR] BUILD ERROR [INFO] ------------------------------------------------------------------------ [INFO] Failed to execute: Executing Ant script: /airtest.build.xml [package-admin-air]: Failed to execute. Java returned: 10 This is a random error that pops up in various point during the build process, and sometimes the build will succeed and then the next one will fail again. This is really weird, does anyone seen this before? I'm using maven 2.2.1 BTW, the error return code 10 in windows mean "Environment is invalid.:

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  • include external jar when running java -jar

    - by prmatta
    From my readings, when you execute a command as follows: java -jar foo.jar Then the main classpath is ignored and the classpath is taken from the manifest file. Further, the classpath declared on the command line is also ignored. So in: java -classpath /usr/local/jar/foobar.jar -jar foo.jar /usr/local/jar/foobar.jar is ignored. Lastly, I have read that the manifest file can only only contain relative paths, within the jar file. So, how do you include absolute paths to external jars, that are present on the system, but not in the jar file being executed?

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  • Java - Creating a Compiler Help

    - by Brian
    So for my programming class we have had a project to create a virtual machine including a memory unit, cpu, Input, Output, Instruction Register, Program Counter, MAR, MDR and so on. Now we need to create a compiler using Java Code that will take a .exe file written in some txt editor and convert it to java byte code and run the code. The code we will be writing in the .exe file is machine code along the lines of: IN X IN Y ADD X STO Y OUT Y STOP DC X 0 DC Y 0 I am just a beginner and only have 2 days to write this and am very lost and have no idea where to start....Any Help will be much appreciated. Thanks

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  • Java Mail timeout & connectiontimeout handling

    - by Gnanam
    Hi, I'm using JavaMail to send email requests to an SMTP server. I would like to set both "mail.smtp.connectiontimeout" and "mail.smtp.timeout" properties within my code. Programmatically, I want to catch both when timeout and/or connectiontimeout operations are reached in Java and handle things accordingly. Handling in the sense, I need to retry the same email once again the next time. How do I handle this in Java/JavaMail? Is it possible to catch & handle this timeout operations?

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  • How to stop jucheck from running? Java won't remember "Check for Updates Automatically" setting.

    - by Ken
    I've installed Java on Windows Vista, and every day I get a Vista security warning asking me if I want to run "jucheck". Apparently this is the Java automatic updater. Well, I don't want it to run on its own, ever. I cancel it, and quit it. I right-click on the taskbar and unclick "Check for Updates Automatically", and then click "Never Check", and "Apply". And yet, it never remembers this setting. If I come back to the "Java Control Panel" right after clicking "OK", the very same box is checked again, all on its own. Is there some way to kill jucheck once and for all? If I simply delete jucheck.exe, will Java (other than the automatic check) still work, and will manual updates still work, and will it stop even trying to update every morning?

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  • Digital signature integration with software written in java

    - by Serkan Kasapbasi
    hi everyone, i'm extremely rookie on this security field, so please forgive if my questions are dumb. i am asked to convert and migrate couple "Lotus Forms" forms to our software that is written in java. One thing in forms that bother me is digital signatures. These forms can be signed by digital signatures, probably generated by "Silanis Approve-it". as i have said before, i dont have much knowledge about this technology. and strangely couldnt find any tutorial or example of integrating digital signature and java. So what are the possibilities here ? how my code read a digital signature, sign a document with this signature? There should be an API or something that is provided by vendors right :)

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  • UTF-8 to ISO-8859-1 mapping / lossless conversion libraries in Java

    - by Pawel Krupinski
    I need to perform a conversion of characters from UTF-8 to ISO-8859-1 in Java without losing for example all of the UTF-8 specific punctuation. Ideally would like these to be converted to equivalents in ISO (e.g. there are probably 5 different single quotes in UTF-8 and would like them all converted to ISO single quote character). String.getBytes("ISO-8859-1") just won't do the trick in this case as it will lose the UTF-8-specific chars. Do you know of any ready mappings or libraries in Java that would map UTF-8 specific characters to ISO?

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