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  • Performance tuning of a Hibernate+Spring+MySQL project operation that stores images uploaded by user

    - by Umar
    Hi I am working on a web project that is Spring+Hibernate+MySQL based. I am stuck at a point where I have to store images uploaded by a user into the database. Although I have written some code that works well for now, but I believe that things will mess up when the project would go live. Here's my domain class that carries the image bytes: @Entity public class Picture implements java.io.Serializable{ long id; byte[] data; ... // getters and setters } And here's my controller that saves the file on submit: public class PictureUploadFormController extends AbstractBaseFormController{ ... protected ModelAndView onSubmit(HttpServletRequest request, HttpServletResponse response, Object command, BindException errors) throws Exception{ MutlipartFile file; // getting MultipartFile from the command object ... // beginning hibernate transaction ... Picture p=new Picture(); p.setData(file.getBytes()); pictureDAO.makePersistent(p); // this method simply calls getSession().saveOrUpdate(p) // committing hiernate transaction ... } ... } Obviously a bad piece of code. Is there anyway I could use InputStream or Blob to save the data, instead of first loading all the bytes from the user into the memory and then pushing them into the database? I did some research on hibernate's support for Blob, and found this in Hibernate In Action book: java.sql.Blob and java.sql.Clob are the most efficient way to handle large objects in Java. Unfortunately, an instance of Blob or Clob is only useable until the JDBC transaction completes. So if your persistent class defines a property of java.sql.Clob or java.sql.Blob (not a good idea anyway), you’ll be restricted in how instances of the class may be used. In particular, you won’t be able to use instances of that class as detached objects. Furthermore, many JDBC drivers don’t feature working support for java.sql.Blob and java.sql.Clob. Therefore, it makes more sense to map large objects using the binary or text mapping type, assuming retrieval of the entire large object into memory isn’t a performance killer. Note you can find up-to-date design patterns and tips for large object usage on the Hibernate website, with tricks for particular platforms. Now apparently the Blob cannot be used, as it is not a good idea anyway, what else could be used to improve the performance? I couldn't find any up-to-date design pattern or any useful information on Hibernate website. So any help/recommendations from stackoverflowers will be much appreciated. Thanks

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  • Event sourcing: Write event before or after updating the model

    - by Magnus
    I'm reasoning about event sourcing and often I arrive at a chicken and egg problem. Would be grateful for some hints on how to reason around this. If I execute all I/O-bound processing async (ie writing to the event log) then how do I handle, or sometimes even detect, failures? I'm using Akka Actors so processing is sequential for each event/message. I do not have any database at this time, instead I would persist all the events in an event log and then keep an aggregated state of all the events in a model stored in memory. Queries are all against this model, you can consider it to be a cache. Example Creating a new user: Validate that the user does not exist in model Persist event to journal Update model (in memory) If step 3 breaks I still have persisted my event so I can replay it at a later date. If step 2 breaks I can handle that as well gracefully. This is fine, but since step 2 is I/O-bound I figured that I should do I/O in a separate actor to free up the first actor for queries: Updating a user while allowing queries (A0 = Front end/GUI actor, A1 = Processor Actor, A2 = IO-actor, E = event bus). (A0-E-A1) Event is published to update user 'U1'. Validate that the user 'U1' exists in model (A1-A2) Persist event to journal (separate actor) (A0-E-A1-A0) Query for user 'U1' profile (A2-A1) Event is now persisted continue to update model (A0-E-A1-A0) Query for user 'U1' profile (now returns fresh data) This is appealing since queries can be processed while I/O-is churning along at it's own pace. But now I can cause myself all kinds of problems where I could have two incompatible commands (delete and then update) be persisted to the event log and crash on me when replayed up at a later date, since I do the validation before persisting the event and then update the model. My aim is to have a simple reasoning around my model (since Actor processes messages sequentially single threaded) but not be waiting for I/O-bound updates when Querying. I get the feeling I'm modeling a database which in itself is might be a problem. If things are unclear please write a comment.

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  • Is It Possible to get a (rough) Mobile Phone Location from a HTTP Request

    - by Tim Lytle
    If memory serves me correctly, google does this for the maps site. I know google's mobile maps app can determine the rough location (I assume using some kind of cell tower lookup), yet I seem to remember the site getting somewhat close to the current location when viewing on a mobile browser. Anyone know how/if that's possible? Does the IP address change based on the tower or area (seems like they'd be using some kind of gateway common to the carrier)?

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  • Can managed and unmanaged C++/MFC be mixed in one dll?

    - by Walter Williams
    Previously we had software in MFC (VC6), VB6 and C# applications that needed to call the same engine written in C++ (and MFC). The engine required C++ for speed. At the time we decided to use COM as the interface because all three could use it with the least issues in marshalling, etc. Our MFC application is now deprecated and we have recently decided to dump VB6, so what we've got left is C#. We can just leave the COM engine as-is, but it would be nice to get away from COM registration, etc., and have a managed interface to work with. COM registration occasionally causes support issues if there is something wrong with the person's machine. Is it possible to have a dll with the existing unmanaged C++/MFC, and a .NET front end interface?

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  • T-SQL query with date range

    - by Moo
    Hi, I have a fairly weird 'bug' with a simple query, and I vaguely remember reading the reason for it somewhere a long time ago but would love someone to refresh my memory. The table is a basic ID, Datetime table. The query is: select ID, Datetime from Table where Datetime <= '2010-03-31 23:59:59' The problem is that the query results include results where the Datetime is '2010-04-01 00:00:00'. The next day. Which it shouldn't. Anyone? Cheers Moo

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  • Is it allowed to load Swing classes in non-EDT thread?

    - by ddimitrov
    After the introduction of Java Memory Model, the Swing guidelines were changed to state that any Swing components need to be instantiated on the EDT in order to avoid non-published instance state. What I could not find anywhere is whether the classloading is also mandated to be on the EDT or can we pre-load key Swing classes in a background thread? Is there any official statement from Sun/Oracle on this? Are there any classes that are known to hold non-threadsafe static state, hence need to be loaded on EDT?

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  • Flex maps howto examples

    - by alessandro ferrucci
    Hello, I've stumbled upon this flash map http://www.washingtonpost.com/wp-srv/special/nation/unemployment-by-county/ it looks like they used this map to construct the website. http://commons.wikimedia.org/wiki/File:USA_Counties_with_FIPS_and_names.svg I am curious as to what people have done or any blogs that describe what can be done with flex and simple maps like this (not google maps style maps) but simple all-in-memory maps like this one. It would be cool to see what/ and how flex can do in terms of maps. thanks!

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  • Synchronising local and remote DB

    - by nico
    Hi everyone, I have a general question about DB synchronisation. So, I'm developing a website locally (PHP + MySQL) and I would like to be able to synchronise at least the structure (and maybe the contents) of the two DB when one of the two is changed (normally I would change the local copy). Right now what I'm doing is to use mysqldump to dump the modified tables and then import them in the remote DB or do it by hand if the changes are minimal. However I find this tedious and error-prone. For the PHP I'm currently using Quanta+ which has the handy feature of finding files that have changed and just upload those. Is there something similar for MySQL? Otherwise how do you keep your DBs synchronised? Thanks nico PS: I'm sorry if this was already asked, I saw other questions that deal with similar topics, but couldn't really find an answer.

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  • Why should i use EJB?

    - by Nitesh Panchal
    Hello, As we all know that EJB's in 3.1 or 3.0 are simple POJOs. You just need to give annotations here and there and it gets converted to EJB from simple class. So, now my question is why should i use EJBs at all? Can i not do without them? In .Net i created class library and got things done. I never felt the need for anything like EJB. Simple classes were enough. Then, why in Java people stress on EJB? What is difference between a simple POJO and EJB in terms of execution and memory? Further which function should i write in EJB and which should i write in simple class? Should i dump every function in EJB only? or there is some kind of strategy? Does EJB provide anything special?

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  • flash game lags every 20 seg

    - by ZoserLock
    My game has delta time for frame independent movement, at 250 fps run perfectly smooth, but if i limit the fps to 60, the game slow down for a 2-4 seg every 20 seg aprox, even in small programs i have this same problem. no memory is created or released i comment everything i can and the problem persist thanks and sorry for my english

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  • Rails CSV import, adding to a related table

    - by Jack
    Hi, I have a csv importing system on my app (used locally only) which parses the csv file line by line and adds the data to the database table. This is based on a tutorial here. require 'csv' def csv_import @parsed_file=CSV::Reader.parse(params[:dump][:file]) n = 0 @parsed_file.each_with_index do |row, i| next if i == 0 #ignore the first row course = Course.new course.title = row[0] course.unit_code = row[1] course.course_type = row[2] course.value = row[3] course.pass_mark = row[4] if course.save n = n+1 GC.start if n%50==0 end flash.now[:message] = "CSV Import Successful, #{n} new courses added to the database." end redirect_to(courses_url) end This is all in the courses controller and works fine. There is a relationship that courses HABTM years and years HABTM courses. In the csv file (effectively in row[5] to row[8]) are the year_id s. Is there a way that I can add this within the method above. I am confused as to how to loop over the 4 items and add them to the courses_years table. Thank you Jack

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  • Dropping PendingIntents

    - by Jeremy Edwards
    Is it ok to drop PendingIntents in android if they are never used. Such as in an AppWidgetProvider where a PendingIntent that was never used be overwritten by a new PendingIntent. Or should we call cancel on all unused PendingIntents to clean up memory appropriately?

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  • Summary of the last decade of garbage collection?

    - by Ben Karel
    I've been reading through the Jones & Lin book on garbage collection, which was published in 1996. Obviously, the computing world has changed dramatically since then: multicore, out-of-order chips with large caches, and even larger main memory in desktops. The world has also more-or-less settled on the x86 and ARM microarchitectures for most consumer-facing systems. How has the field of garbage collection changed since the seminal book was published?

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  • Good Postgres graphical client for Windows

    - by alex
    The name pretty much says it all. Right now I'm using Squirrel - it crashes frequently and suffers from memory problems (I've tried increasing the heap size). I don't need anything particularly fancy or full-featured - just something that won't take up 2.4 GB of RAM to store a 1.5 million line, 8 column result set.

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  • Filtering Attributes with Weka

    - by hrzafer
    Hi eveyone! I have a simple question about filtering attributes in WEKA. Let's say I have 500 attributes 30 classes and 100 samples for each class which equals 3000 rows and 500 columns. This causes time and memory problems a you can guess. How do I filter attributes that occur only once or twice (or n times) in 3000 rows. And is it a good idea? Thank you

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  • lightweight publish/subscribe framework in java

    - by mdma
    Is there a good lightweight framework for java that provides the publish/subscribe pattern? Some ideal features Support for generics Registration of multiple subscribers to a publisher API primarily interfaces and some useful implementations purely in-memory, persistence and transaction guarantees not required. I know about JMS but that is overkill for my need. The publish/subscribed data are the result of scans of a file system, with scan results being fed to another component for processing, which are then processed before being fed to another and so on.

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  • Is marshaling/ serialization in PHP as simple as serialize($var) ?

    - by Ygam
    here's a definition of marshaling from Wikipedia: In computer science, marshalling (similar to serialization) is the process of transforming the memory representation of an object to a data format suitable for storage or transmission. It is typically used when data must be moved between different parts of a computer program or from one program to another. I have always done data serialization in php via its serialize function, usually on objects or arrays. But how is wikipedia's definition of marshaling/serialization takes place in this serizalize() function?

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  • How do you drop in substitute JRE classes?

    - by evilfred
    Hi, java.util.zip has well-known problems with native memory usage, so i'm trying to use a drop-in replacement called "jazzlib". unfortunately as is typical for sourceforge projects there is no documentation. If I add the jar to my classpath then Java freaks out and gives me "prohibited package name" errors because it replaced java.util.zip. How do I tell Java that this is what I want it to do?

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  • Is the first persistance of an Entity Data Model in EF 4.0 slower due to the connection cost ?

    - by Scott Davies
    Hi, I've got a console app written that persists an object graph via Entity Framework 4.0. I loop through this to dump the execution times for each persistance. The first persistance is always the largest. Is this due to EF making the initial connection to the database and/or JIT'ing ? Here's a sample of the output: Persisted graph in **3318** millseconds. Persisted graph in 25 millseconds. Persisted graph in 26 millseconds. Persisted graph in 22 millseconds. Thanks, Scott

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  • What's holding up my PHP script?

    - by gAMBOOKa
    We've got a PHP crawler running on our web server. When the crawler is running, there are no cpu, memory or network bandwidth spikes. Everything is normal. But our website (also PHP), hosted on the same server, stops responding. Basically the crawler blocks any other php script from running. What could be the problem? EDIT: ** fsockopen is being used to download files to crawler! **

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  • Programmaticaly grabbing text from a web page that is dynamically generated.

    - by bstullkid
    There is a website I am trying to pull information from in perl, however the section of the page I need is being generated using javascript so all you see in the source is <div id="results"></div> I need to somehow pull out the contents of that div and save it to a file using perl/proxies/whatever. e.g. the information I want to save would be document.getElementById('results').innerHTML; I am not sure if this is possible or if anyone had any ideas or a way to do this. I was using a lynx source dump for other pages but since I cant straight forward screen scrape this page I came here to ask about it! If anyone is interested, the page is http://downloadcenter.trendmicro.com/index.php?clk=left_nav&clkval=pattern_file&regs=NABU and the info I am trying to get is the row about the ConsumerOPR

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  • How can user change the jre parameter values after the exe is generated in Launch4j?

    - by Wing C. Chen
    Is it possible to change the jre parameter values after the exe file is generated through Launch4j? The ideal scenario is like this: The default parameter values are applied when the program is started. However, when the user wants to change some jre parameter values, he goes to a .ini file, MyProgram.ini for example, changes the values there, and the new values will be applied next time the program is started. I think eclipse uses the same way for its memory and some other parameter settings.

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