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  • (outofmemoryerror: java heap space) when iterating through oracle records...

    - by rockit
    hello fellow java developers. I'm having a bit of an issue here. I have code that gets a resultset from an oracle database, prints each row to a file, then gets the next row - and continues till the end of the resultset. Only this isn't what happens. What happens is that it gets the resultset, starts iterating through the rows, printing to file as it goes, until it runs out of memory - claiming it needs more space on the java heap. The app is currently running with 2g of memory on the heap and the code breaks at about the 150000th row. I'm using jodbc6.jar and java 6 Here is an idea of what my code is doing: Connection conn = DriverManager.getConnection(url,"name","pwd"); conn.setAutoCommit(false); Statement stmt = conn.createStatement(); ResultSet rset = stmt.executeQuery(strSql); String strVar_1 = null; long lCount = 0; while(rset.next()){ lCount++; if (lCount % 100000 == 0){ System.out.println(lCount + " rows completed"); } strVar_1 = rset.getString("StringID"); /// breaks here!!!!!!!!! if (strVar_1 == null){ strVar_1 = ""; } if (!strQuery_1.equals("")){ out.write(strVar_1 + "\n"); } } out.close();

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  • PHP: What is an efficient way to parse a text file containing very long lines?

    - by Shaun
    I'm working on a parser in php which is designed to extract MySQL records out of a text file. A particular line might begin with a string corresponding to which table the records (rows) need to be inserted into, followed by the records themselves. The records are delimited by a backslash and the fields (columns) are separated by commas. For the sake of simplicity, let's assume that we have a table representing people in our database, with fields being First Name, Last Name, and Occupation. Thus, one line of the file might be as follows [People] = "\Han,Solo,Smuggler\Luke,Skywalker,Jedi..." Where the ellipses (...) could be additional people. One straightforward approach might be to use fgets() to extract a line from the file, and use preg_match() to extract the table name, records, and fields from that line. However, let's suppose that we have an awful lot of Star Wars characters to track. So many, in fact, that this line ends up being 200,000+ characters/bytes long. In such a case, taking the above approach to extract the database information seems a bit inefficient. You have to first read hundreds of thousands of characters into memory, then read back over those same characters to find regex matches. Is there a way, similar to the Java String next(String pattern) method of the Scanner class constructed using a file, that allows you to match patterns in-line while scanning through the file? The idea is that you don't have to scan through the same text twice (to read it from the file into a string, and then to match patterns) or store the text redundantly in memory (in both the file line string and the matched patterns). Would this even yield a significant increase in performance? It's hard to tell exactly what PHP or Java are doing behind the scenes.

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  • CM and Agile validation process of merging to the Trunk?

    - by LoneCM
    Hello All, We are a new Agile shop and we are encountering an issue that I hope others have seen. In our process, the Trunk is considered an integration branch; it does not have to be releasable, but it does have to be stable and functional for others to branch off of. We create Feature branches of the Trunk for new development. All work and testing occurs in these branches. An individual branch pulls up as needed to stay integrated with the Trunk as other features that are accepted and are committed. But now we have numerous feature branches. Each are focused, have a short life cycle, and are pushed to the trunk as they are completed, so we not debating the need for the branches and trying very much to be Agile. My issue comes in here: I require that the branches pull up from the Trunk at the end of their life cycle and complete the validation, regression testing and handle all configuration issues before pushing to the trunk. Once reintegrated into the Trunk, I ask for at least a build and an automated smoke test. However, I am now getting push back on the Trunk validation. The argument is that the developers can merge the code and not need the QA validation steps because they already complete the work in the feature branch. Therefore, the extra testing is not needed. I have attempted to remind management of the numerous times "brainless" merges have failed. Thier solution is to instead of build and regression testing to have the developer diff the Feature branch and the newly merged Trunk. That process in thier mind would replace the regression testing I asked for. So what do you require when you reintegrate back to the Trunk? What are the issues that we will encounter if we remove this step and replace with the diff? Is the cost of staying Agile the additional work of the intergration of the branches? Thanks for any input. LoneCM

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  • Reverse search in Hibernate Search

    - by Javi
    Hello, I'm using Hibernate Search (which uses Lucene) for searching some Data I have indexed in a directory. It works fine but I need to do a reverse search. By reverse search I mean that I have a list of queries stored in my database I need to check which one of these queries match with a Data object each time Data Object is created. I need it to alert the user when a Data Object matches with a Query he has created. So I need to index this single Data Object which has just been created and see which queries of my list has this object as a result. I've seen Lucene MemoryIndex Class to create an index in memory so I can do something like this example for every query in a list (though iterating in a Java list of queries would not be very efficient): //Iterating over my list<Query> MemoryIndex index = new MemoryIndex(); //Add all fields index.addField("myField", "myFieldData", analyzer); ... QueryParser parser = new QueryParser("myField", analyzer); float score = index.search(query); if (score > 0.0f) { System.out.println("it's a match"); } else { System.out.println("no match found"); } The problem here is that this Data Class has several Hibernate Search Annotations @Field,@IndexedEmbedded,... which indicated how fields should be indexed, so when I invoke index() method on the FullTextEntityManager instance it uses this information to index the object in the directory. Is there a similar way to index it in memory using this information? Is there a more efficient way of doing this reverse search? Thanks

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  • Dynamic stack allocation in C++

    - by Poni
    I want to allocate memory on the stack. Heard of _alloca / alloca and I understand that these are compiler-specific stuff, which I don't like. So, I came-up with my own solution (which might have it's own flaws) and I want you to review/improve it so for once and for all we'll have this code working: /*#define allocate_on_stack(pointer, size) \ __asm \ { \ mov [pointer], esp; \ sub esp, [size]; \ }*/ /*#define deallocate_from_stack(size) \ __asm \ { \ add esp, [size]; \ }*/ void test() { int buff_size = 4 * 2; char *buff = 0; __asm { // allocate mov [buff], esp; sub esp, [buff_size]; } // playing with the stack-allocated memory for(int i = 0; i < buff_size; i++) buff[i] = 0x11; __asm { // deallocate add esp, [buff_size]; } } void main() { __asm int 3h; test(); } Compiled with VC9. What flaws do you see in it? Me for example, not sure that subtracting from ESP is the solution for "any kind of CPU". Also, I'd like to make the commented-out macros work but for some reason I can't.

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  • How can I declare and initialize an array of pointers to a structure in C?

    - by worlds-apart89
    I have a small assignment in C. I am trying to create an array of pointers to a structure. My question is how can I initialize each pointer to NULL? Also, after I allocate memory for a member of the array, I can not assign values to the structure to which the array element points. #include <stdio.h> #include <stdlib.h> typedef struct list_node list_node_t; struct list_node { char *key; int value; list_node_t *next; }; int main() { list_node_t *ptr = (list_node_t*) malloc(sizeof(list_node_t)); ptr->key = "Hello There"; ptr->value = 1; ptr->next = NULL; // Above works fine // Below is erroneous list_node_t **array[10] = {NULL}; *array[0] = (list_node_t*) malloc(sizeof(list_node_t)); array[0]->key = "Hello world!"; //request for member ‘key’ in something not a structure or union array[0]->value = 22; //request for member ‘value’ in something not a structure or union array[0]->next = NULL; //request for member ‘next’ in something not a structure or union // Do something with the data at hand // Deallocate memory using function free return 0; }

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  • Exposed onsite vs IFD deployments for MS Dynamics CRM

    - by Greg McGuffey
    I'm working for the first time on a MS Dyanmics CRM 4.0 project. Our company has a high number of remote employees and even more remote consultants. As such it will be necessary to make the CRM solution available over the internet. As near as I can tell, I have three options: Have everyone use a VPN to access an intranet site (typical onsite deployment). However, we have found that VPNs are far from trouble free and cause many support issues. We avoid them like the plague. Use IFD to expose the CRM on the internet. I don't know much about this except that the URL will be different than the onsite URL, which could cause some headaches (see below). Expose the CRM site by opening the site to the internet, using SSL to encrypt traffic. We currently do this with our MS sharepoint sites. I'm not sure how secure this would be (one of the reasons for this question). I'd like to avoid using both the onsite intranet deployment and the IFD together for a couple of reasons. One of the requests for the solution is use email to notify users that they've been assigned a task, and include the URL to the task within the email. For this reason. If both deployments are used, then I'll need to include two URLs and the user would need to know which to use. Which leads to the second reason, the main users of the solution split time between being in the office and being remote. Thus they would need to access the solution two different ways, and know when to use which. Bad. So, what are the advantages/disadvantages of any of these methods? Any other options? Is there any issue using IFD from within the intranet? Security issues? Thanks!

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  • Stale connection with Pheanstalk

    - by token47
    I'm using beanstalkd to offload some work to other machines. The setup is a bit unusual, the server is on the internet (public ip) but the consumers are behind adsl lines on some peoples homes. So there is a linux server as client going out through a dynamic ip and connecting to the server to get a job. It's all PHP and I'm using pheanstalk library. Everything runs smoothly for some time, but then the adsl changes the IP (every 24h hours the provider forces a disconnect-reconnect) the client just hangs, never to go out of "reserve". I thought that putting a timeout on the reserve would help it, but it didn't. As it seems, the client issues a command and blocks, it never checks the timeout. It just issues a reserve-with-timeout (instead of a simple reserve) and it is the servers responsibility to return a TIME_OUT as the timeout occurs. The problem is, the connection is broken (but the TCP/IP doesn't know about that yet until any of the sides try to talk to the other side) and if the client blocked reading, it will never return. The library seems to have support for some kind of timeouts locally (for example when trying to connect to server), but it does not seem to contemplate this scenario. How could I detect the stale connection and force a reconnect? Is there some kind of keepalive on the protocol (and on the pheanstalk itself)? Thanks!

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  • zend session exception on zend_session::start with forms

    - by Grant Collins
    Hi I'm having issues with trying to use Zend_Form_SubForm and sessions. My controller is in essance acting a wizard showing different subforms depending on the stage of the wizard. Using the example I am planning on storing the forms in a session namespace. My controller looks like this. include 'mylib/Form/addTaskWizardForm.php'; class AddtaskController extends Zend_Controller_Action{ private $config = null; private $log = null; private $subFormSession = null; /** * This function is called and initialises the global variables to this object * which is the configuration details and the logger to write to the log file. */ public function init(){ $this->config = Zend_Registry::getInstance()->get('config'); $this->log = Zend_Registry::getInstance()->get('log'); //set layout $this->_helper->layout->setLayout('no-sidemenus'); //we need to get the subforms and $wizardForms = new addTaskWizardForm(); $this->subFormSession = new Zend_Session_Namespace('addTaskWizardForms'); if(!isset($this->subFormSession->subforms)){ $this->subFormSession->subforms = $wizardForms; } } /** * The Landing page controller for the site. */ public function indexAction(){ $form = $this->subFormSession->subforms->getSubForm('start'); $this->view->form = $form; } However this is causing the application session to crash out with Uncaught exception 'Zend_Session_Exception' with message 'Zend_Session::start() Any idea why this is having issues with the Zend Session?? thanks.

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  • Visual Studio crashes consistently on web-related projects

    - by Traveling Tech Guy
    Hi, I have a brand new VS2010 installed on a Win2008R2 machine. I started getting this error when debugging a WCF service project: "Attempted to read or write protected memory. This is often an indication that other memory is corrupt." When I started developing a web site a week later, this became consistent - I can't debug it. The stack dump reads: at Microsoft.VisualStudio.WebHost.Host.ProcessRequest(Connection conn) at Microsoft.VisualStudio.WebHost.Server.OnSocketAccept(Object acceptedSocket) at System.Threading.QueueUserWorkItemCallback.WaitCallback_Context(Object state) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx) at System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem() at System.Threading.ThreadPoolWorkQueue.Dispatch() at System.Threading._ThreadPoolWaitCallback.PerformWaitCallback() I tried searching online, and some recommend turning off the "Suppress JIT Optimizations" in the Debugging options - this dos not seem to make a difference. Clearly the problem is with the built in web server. But am I doing something wrong? Is there something I can do? Or is this a known bug? Thanks for your time, Guy Update 12/31: Today I tried using CassiniDev as a replacement to the original VS2010 WebServer - exact same result. My suspicion is that there's some internal conflict between VS2010, Windows Server 2008R2 and maybe the fact that it's a 64 bit OS. I switched to using IIS as my debug server - and that seems to work, with some annoying side effects. My conclusion: do not use a 64 bit server system as your dev machine. Develop on 32bit - deploy to 64bit. Side conclusion: there are some scenarios Microsoft's QA doesn't test.

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  • Problems with display of UTF-8 encoded content from a DB

    - by LookUp Webmaster
    Dear members of the Stackoverflow community, We are developing a web application using the Zend Framework, and we are facing some encoding issues that we hope you might help us solve. The situation goes something like this: There are certain tables on a MySQL database that need to be displayed as html. Because the site is designed using the Spanish language, the database contains some characters like "á" or "ñ". Our internal policy is to set all the encodings as UTF-8, including all the databases and the tables. The problem is, that when we retrieve the content from the DB, some characters are displayed as question marks. We are out of ideas. These are all the things that we have already tried and double-checked: 1. The SQL file from which we load all the data is properly UTF-8 encoded. 2. The SQL is loaded through phpmyadmin (which is configured as UTF-8), and the resulting tables are displayed properly. 3. The netbeans environment used for coding is also set as UTF-8. The weird thing is that all the content that is hard-coded either as php or html is displayed properly. Only the values that are extracted from the database have issues. Any ideas? Thank you very much.

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  • Should we deploy a Webkit browser for our intranet applications?

    - by Jeff Meatball Yang
    At my place of employment, we are increasingly finding it difficult to develop for IE, which was historically the easiest browser to target, from an intranet-app point of view. It was already deployed. It already understood NTLM authentication, thus well integrated with our domain-level security. It had neat, albeit non-standard features such as XMLDOM and XmlHTTP. Now, we are increasingly irritated by issues presented by IE: There are several versions: IE 7, 8, and soon 9 beta, which all have slightly different issues related to performance, functionality (especially re:security and zones), and aesthetics. IE 7 and 8 are slower than Webkit-based browsers. Period. There are technology limitations such as missing canvas element, CSS bugs, etc. that make it hard to use 3rd party packages or even consistently write code across IE versions. Users are increasingly using Firefox or Chrome, even for intranet use. Does anyone have experience with making a transition? Any advice would be welcome.

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  • How to create an instance of object with RTTI in Delphi 2010?

    - by Paul
    As we all known, when we call a constructor of a class like this: instance := TSomeClass.Create; The Delphi compiler actually do the following things: Call the static NewInstance method to allocate memory and initialize the memory layout. Call the constructor method to perform the initialization of the class Call the AfterConstruction method It's simple and easy to understand. but I'm not very sure how the compiler handle exceptions in the second and the third step. It seems there are no explicit way to create an instance using a RTTI constructor method in D2010. so I wrote a simple function in the Spring Framework for Delphi to reproduce the process of the creation. class function TActivator.CreateInstance(instanceType: TRttiInstanceType; constructorMethod: TRttiMethod; const arguments: array of TValue): TObject; var classType: TClass; begin TArgument.CheckNotNull(instanceType, 'instanceType'); TArgument.CheckNotNull(constructorMethod, 'constructorMethod'); classType := instanceType.MetaclassType; Result := classType.NewInstance; try constructorMethod.Invoke(Result, arguments); except on Exception do begin if Result is TInterfacedObject then begin Dec(TInterfacedObjectHack(Result).FRefCount); end; Result.Free; raise; end; end; try Result.AfterConstruction; except on Exception do begin Result.Free; raise; end; end; end; I feel it maybe not 100% right. so please show me the way. Thanks!

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  • Alignment in assembly

    - by jena
    Hi, I'm spending some time on assembly programming (Gas, in particular) and recently I learned about the align directive. I think I've understood the very basics, but I would like to gain a deeper understanding of its nature and when to use alignment. For instance, I wondered about the assembly code of a simple C++ switch statement. I know that under certain circumstances switch statements are based on jump tables, as in the following few lines of code: .section .rodata .align 4 .align 4 .L8: .long .L2 .long .L3 .long .L4 .long .L5 ... .align 4 aligns the following data on the next 4-byte boundary which ensures that fetching these memory locations is efficient, right? I think this is done because there might be things happening before the switch statement which caused misalignment. But why are there actually two calls to .align? Are there any rules of thumb when to call .align or should it simply be done whenever a new block of data is stored in memory and something prior to this could have caused misalignment? In case of arrays, it seems that alignment is done on 32-byte boundaries as soon as the array occupies at least 32 byte. Is it more efficient to do it this way or is there another reason for the 32-byte boundary? I'd appreciate any explanation or hint on literature.

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  • What happens when value types are created?

    - by Bob
    I'm developing a game using XNA and C# and was attempting to avoid calling new struct() type code each frame as I thought it would freak the GC out. "But wait," I said to myself, "struct is a value type. The GC shouldn't get called then, right?" Well, that's why I'm asking here. I only have a very vague idea of what happens to value types. If I create a new struct within a function call, is the struct being created on the stack? Will it simply get pushed and popped and performance not take a hit? Further, would there be some memory limit or performance implications if, say, I need to create many instances in a single call? Take, for instance, this code: spriteBatch.Draw(tex, new Rectangle(x, y, width, height), Color.White); Rectangle in this case is a struct. What happens when that new Rectangle is created? What are the implications of having to repeat that line many times (say, thousands of times)? Is this Rectangle created, a copy sent to the Draw method, and then discarded (meaning no memory getting eaten up the more Draw is called in that manner in the same function)? P.S. I know this may be pre-mature optimization, but I'm mostly curious and wish to have a better understanding of what is happening.

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  • App hosting Report Viewer crashes on exit after export

    - by Paul Sasik
    We have a .NET Winforms application that hosts the Crystal Reports Viewer control (Version XI). It works well for the most part but when an export of data from the viewer is performed the application will crash on exit and in unmanaged code. The error message is not very useful and just says that an incorrect memory location was accessed. No other info such a specific DLL etc. is provided. This only happens after the viewer is used to export a report to CSV, XML etc. My guess is that at some point in the export process Crystal creates a resource that attempts an action on shut down to a parent window (perhaps) that no longer exists. I've seen a number of memory leak and shut down issues with Crystal but this one's new. Has anyone seen it and come up with a workaround or has ideas for workarounds? So far we've tried explicitly disposing of all crystal-related objects, setting to null and even setting a Thread.Sleep cycle on shut down to "give Crystal time to clean up." Update: The crash happens only on shut down (so not immediate) All export formats work All export files are created properly CR is installed on the same machine as the hosting .NET app not sure about exporting from the IDE... is that even possible?

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  • Atomic swap in GNU C++

    - by Steve
    I want to verify that my understanding is correct. This kind of thing is tricky so I'm almost sure I am missing something. I have a program consisting of a real-time thread and a non-real-time thread. I want the non-RT thread to be able to swap a pointer to memory that is used by the RT thread. From the docs, my understanding is that this can be accomplished in g++ with: // global Data *rt_data; Data *swap_data(Data *new_data) { #ifdef __GNUC__ // Atomic pointer swap. Data *old_d = __sync_lock_test_and_set(&rt_data, new_data); #else // Non-atomic, cross your fingers. Data *old_d = rt_data; rt_data = new_data; #endif return old_d; } This is the only place in the program (other than initial setup) where rt_data is modified. When rt_data is used in the real-time context, it is copied to a local pointer. For old_d, later on when it is sure that the old memory is not used, it will be freed in the non-RT thread. Is this correct? Do I need volatile anywhere? Are there other synchronization primitives I should be calling? By the way I am doing this in C++, although I'm interested in whether the answer differs for C. Thanks ahead of time.

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  • Why is Core Data not persisting these changes to disk?

    - by scott
    I added a new entity to my model and it loads fine but no changes made in memory get persisted to disk. My values set on the car object work fine in memory but aren't getting persisted to disk on hitting the home button (in simulator). I am using almost exactly the same code on another entity in my application and its values persist to disk fine (core data - sqlite3); Does anyone have a clue what I'm overlooking here? Car is the managed object, cars in an NSMutableArray of car objects and Car is the entity and Visible is the attribute on the entity which I am trying to set. Thanks for you assistance. Scott - (void)viewDidLoad { myAppDelegate* appDelegate = (myAppDelegate*)[[UIApplication sharedApplication] delegate]; NSManagedObjectContext* managedObjectContex = appDelegate.managedObjectContext; NSFetchRequest* request = [[NSFetchRequest alloc] init]; NSEntityDescription* entity = [NSEntityDescription entityForName:@"Car" inManagedObjectContext:managedObjectContex]; [request setEntity:entity]; NSSortDescriptor* sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"Name" ascending:YES]; NSArray* sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil]; [request setSortDescriptors:sortDescriptors]; [sortDescriptors release]; [sortDescriptor release]; NSError* error = nil; cars = [[managedObjectContex executeFetchRequest:request error:&error] mutableCopy]; if (cars == nil) { NSLog(@"Can't load the Cars data! Error: %@, %@", error, [error userInfo]); } [request release]; } - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath*)indexPath { Car* car = [cars objectAtIndex:indexPath.row]; if (car.Visible == [NSNumber numberWithBool:YES]) { car.Visible = [NSNumber numberWithBool:NO]; [tableView cellForRowAtIndexPath:indexPath].accessoryType = UITableViewCellAccessoryNone; } else { car.Visible = [NSNumber numberWithBool:YES]; [tableView cellForRowAtIndexPath:indexPath].accessoryType = UITableViewCellAccessoryCheckmark; } }

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  • Simplest distributed persistent key/value store that supports primary key range queries

    - by StaxMan
    I am looking for a properly distributed (i.e. not just sharded) and persisted (not bounded by available memory on single node, or cluster of nodes) key/value ("nosql") store that does support range queries by primary key. So far closest such system is Cassandra, which does above. However, it adds support for other features that are not essential for me. So while I like it (and will consider using it of course), I am trying to figure out if there might be other mature projects that implement what I need. Specifically, for me the only aspect of value I need is to access it as a blob. For key, however, I need range queries (as in, access values ordered, limited by start and/or end values). While values can have structures, there is no need to use that structure for anything on server side (can do client-side data binding, flexible value/content types etc). For added bonus, Cassandra style storage (journaled, all sequential writes) seems quite optimal for my use case. To help filter out answers, I have investigated some alternatives within general domain like: Voldemort (key/value, but no ordering) and CouchDB (just sharded, more batch-oriented); and am aware of systems that are not quite distributed while otherwise qualifying (bdb variants, tokyo cabinet itself (not sure if Tyrant might qualify), redis (in-memory store only)).

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  • C++ Beginner Delete Question

    - by Pooch
    Hi all, This is my first year learning C++ so bear with me. I am attempting to dynamically allocate memory to the heap and then delete the allocated memory. Below is the code that is giving me a hard time: // String.cpp #include "String.h" String::String() {} String::String(char* source) { this->Size = this->GetSize(source); this->CharArray = new char[this->Size + 1]; int i = 0; for (; i < this->Size; i++) this->CharArray[i] = source[i]; this->CharArray[i] = '\0'; } int String::GetSize(const char * source) { int i = 0; for (; source[i] != '\0'; i++); return i; } String::~String() { delete[] this->CharArray; } Here is the error I get when the compiler tries to delete the CharArray: 0xC0000005: Access violation reading location 0xccccccc0. And here is the last call on the stack: msvcr100d.dll!operator delete(void * pUserData) Line 52 + 0x3 bytes C++ I am fairly certain the error exists within this piece of code but will provide you with any other information needed. Oh yeah, using VS 2010 for XP. Thanks for any and all help!

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  • Question about cloning in Java

    - by devoured elysium
    In Effective Java, the author states that: If a class implements Cloneable, Object's clone method returns a field-by-field copy of the object; otherwise it throws CloneNotSupportedException. What I'd like to know is what he means with field-by-field copy. Does it mean that if the class has X bytes in memory, it will just copy that piece of memory? If yes, then can I assume all value types of the original class will be copied to the new object? class Point { private int x; private int y; @Override public Point clone() { return (Point)super.clone(); } } If what Object.clone() does is a field by field copy of the Point class, I'd say that I wouldn't need to explicitly copy fields x and y, being that the code shown above will be more than enough to make a clone of the Point class. That is, the following bit of code is redundant: @Override public Point clone() { Point newObj = (Point)super.clone(); newObj.x = this.x; //redundant newObj.y = this.y; //redundant } Am I right? I know references of the cloned object will point automatically to where the original object's references pointed to, I'm just not sure what happens specifically with value types. If anyone could state clearly what Object.clone()'s algorithm specification is (in easy language) that'd be great. Thanks

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  • JDBC transaction dead-lock solution required?

    - by user49767
    It's a scenario described my friend and challenged to find solution. He is using Oracle database and JDBC connection with read committed as transaction isolation level. In one of the transaction, he updates a record and executes selects statement and commits the transaction. when everything happening within single thread, things are fine. But when multiple requests are handled, dead-lock happens. Thread-A updates a record. Thread B updates another record. Thread-A issues select statement and waits for Thread-B's transaction to complete the commit operation. Thread-B issues select statement and waits for Thread-A's transaction to complete the commit operation. Now above causes dead-lock. Since they use command pattern, the base framework allows to issue commit only once (at the end of all the db operation), so they are unable to issue commit immediately after select statement. My argument was Thread-A supposed to select all the records which are committed and hence should not be issue. But he said that Thread-A will surely wait till Thread-B commits the record. is that true? What are all the ways, to avoid the above issue? is it possible to change isolation-level? (without changing underlying java framework) Little information about base framework, it is something similar to Struts action, their each and every request handled by one action, transaction begins before execution and commits after execution.

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  • Using Javascript to generate and save a file

    - by Toji
    I've been fiddling with WebGL lately, and have gotten a Collada reader working. Problem is it's pretty slow (Collada is a very verbose format), so I'm going to start converting files to a easier to use format (probably JSON). Thing is, I already have the code to parse the file in Javascript, so I may as well use it as my exporter too! The problem is saving. Now, I know that I can parse the file, send the result to the server, and have the browser request the file back from the server as a download. But in reality the server has nothing to do with this particular process, so why get it involved? I already have the contents of the desired file in memory. Is there any way that I could present the user with a download using pure javascript? (I doubt it, but might as well ask...) And to be clear: I am not trying to access the filesystem without the users knowledge! The user will provide a file (probably via drag and drop), the script will transform the file in memory, and the user will be prompted to download the result. All of which should be "safe" activities as far as the browser is concerned.

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  • Unable to persist objects in GAE JDO

    - by Basil Dsouza
    Hello Guys, I am completely fresh to both JDO and GAE, and have been struggling to get my data layer to persist any code at all! The issues I am facing may be very simple, but I just cant seem to find any a way no matter what solution I try. Firstly the problem: (Slightly simplified, but still contains all the info necessary) My data model is as such: User: (primary key) String emailID String firstName Car: (primary key) User user (primary key) String registration String model This was the initial datamodel. I implemented a CarPK object to get a composite primary key of the User and the registration. However that ran into a variety of issues. (Which i will save for another time/question) I then changed the design as such: User: (Unchanged) Car: (primary key) String fauxPK (here fauxPK = user.getEmailID() + SEP + registration) User user String registration String model This works fine for the user, and it can insert and retrieve user objects. However when i try to insert a Car Object, i get the following error: "Cannot have a java.lang.String primary key and be a child object" Found the following helpful link about it: http://stackoverflow.com/questions/2063467/persist-list-of-objects Went to the link suggested there, that explains how to create Keys, however they keep talking about "Entity Groups" and "Entity Group Parents". But I cant seem to find any articles or sites that explain what are "Entity Group"s or an "Entity Group Parents" I could try fiddling around some more to figure out if i can store an object somehow, But I am running sort on patience and also would rather understand and implement than vice versa. So i would appreciate any docs (even if its huge) that covers all these points, and preferably has some examples that go beyond the very basic data modeling. And thanks for reading such a long post :)

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  • What is a NULL value

    - by Adi
    I am wondering , what exactly is stored in the memory when we say a particular variable pointer to be NULL. suppose I have a structure, say typdef struct MEM_LIST MEM_INSTANCE; struct MEM_LIST { char *start_addr; int size; MEM_INSTANCE *next; }; MEM_INSTANCE *front; front = (MEM_INSTANCE*)malloc(sizeof(MEM_INSTANCE*)); -1) If I make front=NULL. What will be the value which actually gets stored in the different fields of the front, say front-size ,front-start_addr. Is it 0 or something else. I have limited knowledge in this NULL thing. -2) If I do a free(front); It frees the memory which is pointed out by front. So what exactly free means here, does it make it NULL or make it all 0. -3) What can be a good strategy to deal with initialization of pointers and freeing them . Thanks in advance

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