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  • What does the Spring framework do? Should I use it? Why or why not?

    - by sangfroid
    So, I'm starting a brand-new project in Java, and am considering using Spring. Why am I considering Spring? Because lots of people tell me I should use Spring! Seriously, any time I've tried to get people to explain what exactly Spring is or what it does, they can never give me a straight answer. I've checked the intros on the SpringSource site, and they're either really complicated or really tutorial-focused, and none of them give me a good idea of why I should be using it, or how it will make my life easier. Sometimes people throw around the term "dependency injection", which just confuses me even more, because I think I have a different understanding of what that term means. Anyway, here's a little about my background and my app : Been developing in Java for a while, doing back-end web development. Yes, I do a ton of unit testing. To facilitate this, I typically make (at least) two versions of a method : one that uses instance variables, and one that only uses variables that are passed in to the method. The one that uses instance variables calls the other one, supplying the instance variables. When it comes time to unit test, I use Mockito to mock up the objects and then make calls to the method that doesn't use instance variables. This is what I've always understood "dependency injection" to be. My app is pretty simple, from a CS perspective. Small project, 1-2 developers to start with. Mostly CRUD-type operations with a a bunch of search thrown in. Basically a bunch of RESTful web services, plus a web front-end and then eventually some mobile clients. I'm thinking of doing the front-end in straight HTML/CSS/JS/JQuery, so no real plans to use JSP. Using Hibernate as an ORM, and Jersey to implement the webservices. I've already started coding, and am really eager to get a demo out there that I can shop around and see if anyone wants to invest. So obviously time is of the essence. I understand Spring has quite the learning curve, plus it looks like it necessitates a whole bunch of XML configuration, which I typically try to avoid like the plague. But if it can make my life easier and (especially) if make it can make development and testing faster, I'm willing to bite the bullet and learn Spring. So please. Educate me. Should I use Spring? Why or why not?

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  • why use branches in svn?

    - by ajsie
    i know that you could organize your files according to this structure in svn: trunk branches tags that you copy the trunk to a folder in branches if you want to have a seperate development line. later on you merge this branch back to trunk. but i wonder why me and my group should do this. why should one copy the trunk to a branch and work with this copy just to merge it back to the trunk, and mean while the code is frequently updated/commited to stay in sync with the trunk. why not just work with the trunk then? what is the benefits with creating a branch? would be great if someone could shed a light on this topic. thanks in advance

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  • Why Do Browsers Leak Memory?

    - by Dane Balia
    A colleague and I were speaking about browsers (using browser control in a project), and it appears as plain as day that all browsers (Firefox, Chrome, IE, Opera) display the same characteristic or side-effect from their usage and that being 'Leaking Memory'. Can someone explain why that is the case? Surely as with any form of code, there should be proper garbage collection? PS. I've read about some defensive patterns on why this can happen from a developer's perspective. I am aware of an article Crockford wrote on IE; but why is the problem symptomatic of every browser? Thanks

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  • Why not standard Android emulators?

    - by Gerry
    I'm new to Android, but have published iphone and bberry apps. I see that I have to create an emulator using the SDK, before I can write and test an app. Why are there no default emulators? Why not at least a Nexus one, or HTC hero emulator shipped with the product? Sure its supposed to be flexible, but why not make it easy to create hello world and play around with a virtual Android phone? Both blackberry and iphone come with default simulators when you download the sdk. Thanks, Gerry

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  • Why is VB so popular? [closed]

    - by aaaidan
    To me, Visual Basic seems clumsy, ugly, error-prone, and difficult to read. I'll let others explain why. While VB.net has clearly been a huge leap forward for the language in terms of features, I still don't understand why anyone would choose to code in VB over, say, C#. However, I still see (what seems to be) the vast majority of commercial web apps from "MS shops" are built in VB. I could stand corrected on this, but VB still seems more popular than it deserves. Can anyone help answer any (or all) of these questions: Am I missing something with VB? Is it easier to learn, or "friendlier" than C#? Are there features I don't know about? Why is VB/VB.net so frequently used today, especially in web projects?

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  • Why don't stacks grow upwards (for security)?

    - by AshleysBrain
    This is related to the question 'Why do stacks typically grow downwards?', but more from a security point of view. I'm generally referring to x86. It strikes me as odd that the stack would grow downwards, when buffers are usually written to upwards in memory. For example a typical C++ string has its end at a higher memory address than the beginning. This means that if there's a buffer overflow you're overwriting further up the call stack, which I understand is a security risk, since it opens the possibility of changing return addresses and local variable contents. If the stack grew upwards in memory, wouldn't buffer overflows simply run in to dead memory? Would this improve security? If so, why hasn't it been done? What about x64, do those stacks grow upwards and if not why not?

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  • Java: why can't iterate over an iterator?

    - by noamtm
    I read http://stackoverflow.com/questions/839178/why-is-javas-iterator-not-an-iterable and http://stackoverflow.com/questions/27240/why-arent-enumerations-iterable, but I still don't understand why this: void foo(Iterator<X> it) { for (X x : it) { bar(x); baz(x); } } was not made possible. In other words, unless I'm missing something, the above could have been nice and valid syntactic sugar for: void foo(Iterator<X> it) { for (X x; it.hasNext();) { x = it.next(); bar(x); baz(x); } }

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  • Why my laptop sends ARP request to itself ?

    - by user58859
    I have just started to learn about protocols. While studying the packets in wireshark, I came across a ARP request sent by my machine to my own IP. Here is the details of the packet : No. Time Source Destination Protocol Info 15 1.463563 IntelCor_aa:aa:aa Broadcast ARP Who has 192.168.1.34? Tell 0.0.0.0 Frame 15: 42 bytes on wire (336 bits), 42 bytes captured (336 bits) Arrival Time: Jan 7, 2011 18:51:43.886089000 India Standard Time Epoch Time: 1294406503.886089000 seconds [Time delta from previous captured frame: 0.123389000 seconds] [Time delta from previous displayed frame: 0.123389000 seconds] [Time since reference or first frame: 1.463563000 seconds] Frame Number: 15 Frame Length: 42 bytes (336 bits) Capture Length: 42 bytes (336 bits) [Frame is marked: False] [Frame is ignored: False] [Protocols in frame: eth:arp] [Coloring Rule Name: ARP] [Coloring Rule String: arp] Ethernet II, Src: IntelCor_aa:aa:aa (aa:aa:aa:aa:aa:aa), Dst: Broadcast (ff:ff:ff:ff:ff:ff) Destination: Broadcast (ff:ff:ff:ff:ff:ff) Address: Broadcast (ff:ff:ff:ff:ff:ff) .... ...1 .... .... .... .... = IG bit: Group address (multicast/broadcast) .... ..1. .... .... .... .... = LG bit: Locally administered address (this is NOT the factory default) Source: IntelCor_aa:aa:aa (aa:aa:aa:aa:aa:aa) Address: IntelCor_aa:aa:aa (aa:aa:aa:aa:aa:aa) .... ...0 .... .... .... .... = IG bit: Individual address (unicast) .... ..0. .... .... .... .... = LG bit: Globally unique address (factory default) Type: ARP (0x0806) Address Resolution Protocol (request) Hardware type: Ethernet (0x0001) Protocol type: IP (0x0800) Hardware size: 6 Protocol size: 4 Opcode: request (0x0001) [Is gratuitous: False] Sender MAC address: IntelCor_aa:aa:aa (aa:aa:aa:aa:aa:aa) Sender IP address: 0.0.0.0 (0.0.0.0) Target MAC address: 00:00:00_00:00:00 (00:00:00:00:00:00) Target IP address: 192.168.1.34 (192.168.1.34) Here the sender's mac address is mine(Here I have hiden my mac address). target IP is mine. Why my machine is sending ARP request to itself? I found 3 packets of this type. There was no ARP reply for these packets. Can anybody explain me why it is? (My operating system is windows-7. I am directly connected to a wifi modem. I got these packets as soon as I started my connection.) I want one suggestion also. many places I read that RFC's are enough for study about protocols. I studied the RFC 826 on ARP. I personally feel that is not enough at all. Any suggestion regarding this? Is there more then 1 RFC for a protocol? I want to study about the protocols in very detail. Can anybody guide me for this? Thanks in advance.

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  • Why does it work

    - by A-ha
    Guys I've asked few days ago a question and didn't have really time to check it and think about it, but now I've tried one of the solutions and I can't understand why does it work? I mean why destructor is called at the end of line like this: #include "stdafx.h" #include "coutn.h" #define coutn coutn() int _tmain(int argc, _TCHAR* argv[]) { coutn << "Line one " << 1;//WHY DTOR IS CALLED HERE coutn << "Line two " << " and some text."; return 0; } I assume that it has something to do with lifetime of an object but I'm not sure what and how. As I think of it there are two unnamed objects created but they do not go out of scope so I can't understand for what reason is dtor called. Thank you.

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  • Why is sqrt() not a method on Float?

    - by KaptajnKold
    In Ruby everything is an object. That's why I don't understand why we have the Math module. It seems to me that most (all?) of the functions in the Math module should have been methods on the numeric types like Integer, Float and so on. E.g. instead of Math.sqrt(5) it would make more sense to have 5.sqrt The same goes for sin, cos, tan, log10 and so on. Does anyone know why all these functions ended up in the Math module?

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  • Why doesn't C++ have a garbage collector?

    - by Jason Baker
    I'm not asking this question because of the merits of garbage collection first of all. My main reason for asking this is that I do know that Bjarne Stroustrup has said that C++ will have a garbage collector at some point in time. With that said, why hasn't it been added? There are already some garbage collectors for C++. Is this just one of those "easier said than done" type things? Or are there other reasons it hasn't been added (and won't be added in C++0x)? Cross links: Garbage collectors for C++ EDIT: Just to clarify, I understand the reasons why C++ didn't have a garbage collector when it was first created. I'm wondering why the collector can't be added in.

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  • 1120: Why can't it access the variable?

    - by Oden
    I'm new at as3, maybe thats the reason why i don't understand, why the setInterval causes an error. <mx:Script> <![CDATA[ import flash.utils.setInterval; import mx.controls.Alert; [Bindable] public var MyInt:int = 500; setInterval(function():void{ ++MyInt; },1000); ]]> </mx:Script> I have a label where the value of MyInt gets visible, the bind works perfect, i've tested it several ways, and i i create a button it grows the number, but if i use the setInterval function i get an error: Access of undefined property myInt. Why? What does cause this? Please explain it, so I can avoid errors like this. Thanks

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  • Why do we need normalized coordinate system? Options

    - by jcyang
    Hi, I have problem understand following sentences in my textbook Computer Graphics with OpenGL. "To make viewing process independent of the requirements of any output device,graphic system convert object descriptions to normalized coordinates and apply the clipping routines." Why normalized coordinates could make viewing process independent of the requirements of any output devices? Isn't the projection coordinates already independent of output device?We only need to first scale and then translate the projection coordinate then we will get device coordinate. So why do we need first convert the projection coordinate to normalized coordinate first? "Clipping is usually performed in normlized coordinates.This allows us to reduce computations by first concatenating the various transformation matrices" Why clipping is usually performed in normlized coordinates? What kind of transformation concatenated? thanks. jcyang.

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  • Why is it called NoSQL?

    - by beef jerky
    I've recently worked with MongoDB and learned about its schemaless design. However, I'm confused with the term NoSQL? Why is it called that? Doesn't it use SQL or SQL-like queries? I've also read from an article that the main difference lies in how data is stored. In the case of MongoDB, it's stored like JSON documents. Is this true? Also, I'm confused why I always see 'NoSQL vs relational databases'. Aren't NoSQL databases relational? I believe documents in MongoDB are still related/linked through some keys (please correct me if I'm wrong). So why is it labeled as non-relational? Thanks in advance!

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  • Why can't I resize some virtual thick disks in VMWhare vSphere Client

    - by Paul-Jan
    Let me start off by mentioning I am really really new to this whole VMWare ESX/vSphere thing, so apologies if this is a FAQ or asked a million times before using better wording. Also, please correct me if I'm using the wrong terms all over the place. We just got this brand new VMWare EXS server, and we started importing virtual machines from around the office. Some of them were originally based on VMWare, others are converted from MS Virtual Server. One of these machines needs a bigger disk, but in the vSphere Client the disk size spinedit is disabled. Disk type is thick. However, for other machines, with the same disk type, the spinedit is enabled and I can happily resize their disks. So here is the question: why can't I resize this disk in particular? All machines are freshly converted, so I assume there are no snapshots yet, which I read would stop a resize from happening (again, correct me if I'm wrong).

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  • why does chkdsk always report errors on a bad shutdown

    - by rep_movsd
    Once in a while, Windows XP hangs on my laptop (usually when going into standby or hibernate and occasionally on startup) and I have to forcefully poweroff. Ususally chkdsk never runs automatically (I thought it should know that the partitions have nit been unmounted and do that). I religiously run chkdsk without /F after bad shutdowns like this, and invariably it reports that the drive has unfixed errors and must be checked with /F and I do that, and more often than not, the chdsk that runs on startup does not report fixing anything. I have had times in the past (and not only just on this system) when not running chkdsk leads to some strange errors like files not opening even though they exist and inability to save certain files, so I make it a point to always chkdsk after bad shutdown. I never understood why this is : Isnt the whole point of a journalling filesystem like NTFS to avoid file system corruption and endless chkdsks? I even tried once disabling write caching to see if it made any difference, but to no avail....

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  • Why aren't connections released by the tomcat AJP connector

    - by Chris
    I have here a jboss with a web application. The tomcat is configured to use the ajp connector. Incoming connections are tunneled via an apache reverse proxy to the connector. Now I recognized that under heavy load the connector keeps a bunch of connections in "keep alive" mode for eternity and doesn't release them any more. With the normal HTTP connector the app did well, but now with the ajp connector we have regular app stallments. Can someone give me some advice where to start to look to resolve this issue? Why does the connector not release the connection again after idling for 300 secs? thanks, chris

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  • What and why is my swap space used under linux

    - by Fabian
    on my linux system I get these stats from top: Tasks: 155 total, 1 running, 153 sleeping, 0 stopped, 1 zombie Cpu(s): 1.5%us, 0.3%sy, 0.0%ni, 97.4%id, 0.7%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 8177180k total, 2025504k used, 6151676k free, 44176k buffers Swap: 7999996k total, 495300k used, 7504696k free, 637612k cached There it shows me that my system is using 495Mb of swap. Why is this so? 6Gigs of ram are free. And if I would disable swap entirely the system would also work. Any explanation what the number really shows or who is swapping?

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  • Why do the IP addresses randomly change?

    - by GiddyUpHorsey
    I have a network with the following: Cable modem with static IP address Router Desktop - Win 7 VM Host - VMware ESXi 4.0 A couple of VM Guests - Windows Every now and then my Win 7 PC is unable to access some of the VMs. When I ping the VMs by their domain name their IP address shows up as the IP address of the cable modem. Sometimes I can fix it by running ipconfig /flushdns. The IP address will reset back to what it was supposed to be, but occasionally it wont work. Why does this happen and how can I fix it?

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  • Why is (free_space + used_space) != total_size in df? [migrated]

    - by Timothy Jones
    I have a ~2TB ext4 USB external disk which is about half full: $ df Filesystem 1K-blocks Used Available Use% Mounted on /dev/sdc 1922860848 927384456 897800668 51% /media/big I'm wondering why the total size (1922860848) isn't the same as Used+Available (1825185124)? From this answer I see that 5% of the disk might be reserved for root, but that would still only take the total used to 1921328166, which is still off. Is it related to some other filesystem overhead? In case it's relevant, lsof -n | grep deleted shows no deleted files on this disk, and there are no other filesystems mounted inside this one.

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  • FireFox/NoScript: why has the NoScript icon disappeared?

    - by Peter Mortensen
    Why has the appearence of NoScript changed? Using Noscript in FireFox (Microsoft Windows): Until now there has been an icon (the S icon) in the lower right of the screen. But now there is an button instead with the text "Options". Left clicking this button seems to bring up the menu as right clicking the old icon. Can I restore the previous state? Is there an auto-update function in NoScript and if so could it have caused the change? If it exists can the auto-update function be disabled? Platform: FireFox 3.0.6, NoScript 1.9.0.6, Windows XP 64 bit, 8 GB RAM.

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  • Why is port 444 open on this router?

    - by TJ Thind
    I have a Cisco RV110W. I ran nmap at it from the outside and nmap reports that the router has tcp port 444 open. Yet there are no port forwarding rules specifying this port. It should as far as I can tell, be closed. There's even a service listening to that port which I can connect to through telnet. I threw some SNPP commands at it but the service doesn't respond to any of them so I don't believe it's SNPP. Does anyone have any idea why this particular router has tcp port 444 open? I haven't been able to find anything in the manual or on Cisco's website.

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  • why use mixed-based replication for mysql

    - by Alistair Prestidge
    I am in the process of configuring MySQL replication and am intending to use row-based-replication but I was also reading up about mixed-based replication. This is where statement-based is the default and then for certain circumstances (http://dev.mysql.com/doc/refman/5.1/en/binary-log-mixed.html) MySQL will switch to row-based. The list is quit vast on when it will switch to row-based. My questions are: Does any one use mixed? If yes why did you chose this over just using one or the other? Thanks in advance

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  • Why does Windows run CHKDSK on every boot?

    - by khris
    Every time I turn on my PC, I get the following message: Checking file system on E: The type of the file systen is NTFS. One of your disks need to be checked for consistency. You may cancel the disk check, but it is strongly recommended that you continue. Windows will now check the disk. CHKDSK is verifying files (stage 1 of 3)... 0 percent completed I allow CHKDSK to to complete, but Windows does not load. This message appears every time I boot my computer. Could someone explain me why this message appears and what I should do to make it disappear?

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  • Why did my power supply fry itself?

    - by ULTRA_POROV
    I am in europe. There was a switch on my psu that could switch the voltage between 230v and 130v (not 100% sure). In europe we use 230. I switched the psu to 110 and turned it on. Several sparks and a power failiure resulted, the psu was fried. Can someone explain why this happened. I was assuming that because the system was using 230 and the psu only draws 130 it would be safe cause it's less. I guess i was wrong. Can someone explain me the physics behind this.

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