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• Good design of mapping Java Domain objects to Tables (using Hibernate)

  - by M. McKenzie

  Hey guys, I have a question that is more in the realm of design, than implementation. I'm also happy for anyone to point out resources for the answer and I'll gladly, research for myself. Highly simplified Java and SQL: Say I have a business domain POJO called 'Picture' with three attributes. class Picture int idPicture String fileName long size Say I have another business domain POJO called "Item" with 3 attributes Class Item int idItem String itemName ArrayList itemPictures These would be a normal simple relationship. You could say that 'Picture' object, will never exist outside an 'Item' object. Assume a picture belongs only to a specific item, but that an item can have multiple pictures Now - using good database design (3rd Normal Form), we know that we should put items and pictures in their own tables. Here is what I assume would be correct. table Item int idItem (primary key) String itemName table Picture int idPicture (primary key) varchar(45) fileName long size int idItem (foreign key) Here is my question: If you are making Hibernate mapping files for these objects. In the data design, your Picture table needs a column to refer to the Item, so that a foreign key relation can be maintained. However,in your business domain objects - your Picture does not hold a reference/attribute to the idItem - and does not need to know it. A java Picture instance is always instantiated inside an Item instance. If you want to know the Item that the Picture belongs to you are already in the correct scope. Call myItem.getIdItem() and myItem.getItemPictures(),and you have the two pieces of information you need. I know that Hibernate tools have a generator that can auto make your POJO's from looking at your database. My problem stems from the fact that I planned out the data design for this experiment/project first. Then when I went to make the domain java objects, I realized that good design dictated that the objects hold other objects in a nested way. This is obviously different from the way that a database schema is - where all objects(tables) are flat and hold no other complex types within them. What is a good way to reconcile this? Would you: (A) Make the hibernate mapping files so that Picture.hbm.xml has a mapping to the POJO parent's idItem Field (if it's even possible) (B) Add an int attribute in the Picture class to refer to the idItem and set it at instantiation, thus simplifying the hbm.xml mapping file by having all table fields as local attributes in the class (C) Fix the database design because it is wrong, dork. I'd truly appreciate any feedback

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• Moving 2d objects on a 3d plane - AS3

  - by Borkz

  I have a 2d plane rotated on its x axis, with 2d display objects I want to move around on the plane. Its pretty similar to a chess board: http://static.open.salon.com/files/chess011237853612.jpg The board is a rotated rectangle, and the pieces are just 2d display objects. Whats the easiest way to manipulate those objects so they appear to be moving on the board?

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• Struts:JSON:return multiple objects

  - by cp

  Hello Is it possible to return multiple JSON objects in the request header with Struts1? I am presently returning a single JSON objects, however the need now is to return a second data structure. All the client-side processing works perfectly for the single data structure in the single JSON objects, I really do not want to complicate it by putting two hetrogenous data structures in a single return JSON object. tia.

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• C++ program to calculate large factorials

  - by xbonez

  How can I write a c++ program to calculate large factorials. Example, if I want to calculate (100!) / (99!), we know the answer is 100, but if i calculate the factorials of the numerator and denominator individually, both the numbers are gigantically large.

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• Robust way to save/load objects with dependencies?

  - by mrteacup

  I'm writing an Android game in Java and I need a robust way to save and load application state quickly. The question seems to apply to most OO languages. To understand what I need to save: I'm using a Strategy pattern to control my game entities. The idea is I have a very general Entity class which e.g. stores the location of a bullet/player/enemy and I then attach a Behaviour class that tells the entity how to act: class Entiy { float x; float y; Behavior b; } abstract class Behavior { void update(Entity e); {} // Move about at a constant speed class MoveBehavior extends Behavior { float speed; void update ... } // Chase after another entity class ChaseBehavior extends Behavior { Entity target; void update ... } // Perform two behaviours in sequence class CombineBehavior extends Behavior { Behaviour a, b; void update ... } Essentially, Entity objects are easy to save but Behaviour objects can have a semi-complex graph of dependencies between other Entity objects and other Behaviour objects. I also have cases where a Behaviour object is shared between entities. I'm willing to change my design to make saving/loading state easier, but the above design works really well for structuring the game. Anyway, the options I've considered are: Use Java serialization. This is meant to be really slow in Android (I'll profile it sometime). I'm worried about robustness when changes are made between versions however. Use something like JSON or XML. I'm not sure how I would cope with storing the dependencies between objects however. Would I have to give each object a unique ID and then use these IDs on loading to link the right objects together? I thought I could e.g. change the ChaseBehaviour to store a ID to an entity, instead of a reference, that would be used to look up the Entity before performing the behaviour. I'd rather avoid having to write lots of loading/saving code myself as I find it really easy to make mistakes (e.g. forgetting to save something, reading things out in the wrong order). Can anyone give me any tips on good formats to save to or class designs that make saving state easier?

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• Passing objects across Appdomains

  - by MUSTAQ

  My issue is similar to the one posted in "http://stackoverflow.com/questions/981773/moving-objects-across-appdomains-in-net". In one of my application, I am creating a separate appdomain. I need to create an instance of a class (Note: this class is derived by MarshalByRefObject) in my parent domain and invoke a MethodA in that instance. This instance is created using "CreateInstanceAndUnwrap". The problem is that this MethodA takes objects of type class as an argument. These objects are not created in the MethodB where i created the appdomain. It was passed as an argument to the MethodB where i create the appdomain. So is it necessary to create a new instance of these objects using "CreateInstanceAndUnwrap" before passing it to the created domain. Not doing this gives me an error in the created domain mentioning that "MyClass object has no attribute foo" during some invocation. Please let me know how to pass the objects across appdomains and execute the method. My statements might be confusing, please let me know for any specific details required.

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• Finding the heaviest of N objects using M scales

  - by cpprulez

  We have N objects and M scales. It's up to us what the objects are, and we need to position the objects on the scales so that it is undoubtful which is the heaviest object. For example, if we have 3 objects: "a", "b", "c" and 2 scales, one possible solution is "a" "b", "b" = "c" (here "a" is the heaviest). I need an algorithm which generates such solutions given N and M. Also let's assume that "a" is always the heaviest object. I've lost a few hours figuring out how to do it, but no matter what I figure out, there's always cases which I miss. For example, another solution is: "a" + "c" = 2 * "b", "a" "c".

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• Interpreting type codes in sys.objects in SQL Server

  - by fatcat1111

  On SQL Server, the sys.objects table includes "Type" and "Type_Desc" attributes. For example: SELECT DISTINCT [Type], Type_Desc FROM Sys.Objects ORDER BY [Type] Returns: C CHECK_CONSTRAINT D DEFAULT_CONSTRAINT F FOREIGN_KEY_CONSTRAINT FN SQL_SCALAR_FUNCTION FS CLR_SCALAR_FUNCTION IT INTERNAL_TABLE P SQL_STORED_PROCEDURE PK PRIMARY_KEY_CONSTRAINT S SYSTEM_TABLE SQ SERVICE_QUEUE TR SQL_TRIGGER U USER_TABLE UQ UNIQUE_CONSTRAINT V VIEW Is there a comprehensive list of these types somewhere? There isn't a constraint on sys.objects that points me to table of these, and sys.types contains data types. I've searched SQL BOL but haven't found it. Any help would be appreciated. EDIT: Some DBs use only a subset of these types. For example, if I have a database with no views, when I query Sys.Objects as above, there are no "V" rows in the results. I am looking for a list of all possible types and descriptions used by SQL Server.

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• Using json_encode on objects in PHP

  - by Alan

  Hi, I'm trying to output lists of objects as json and would like to know if there's a way to make objects usable to json_encode? The code I've got looks something like $related = $user->getRelatedUsers(); echo json_encode($related); Right now, I'm just iterating through the array of users and individually exporting them into arrays for json_encode to turn into usable json for me. I've already tried making the objects iterable, but json_encode just seems to skip them anyway.

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• Automatically selecting and creating class objects

  - by Omin

  Lets say that we have a box class: class Box { private int width; private int height; //Box Constructor public Box( int height ) { this.height = height; width = 450; } } and a series of Box objects in our main: Box Box1 = new Box(147); Box Box2 = new Box(178); Box Box3 = new Box(784); Is there a way to use a "for" loop to go through these objects? Also, how would you make the computer create class objects for us? eg. create 10 objects using: for( int i=0; i>10; i++) { //method }

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• Defining relationship in value objects using Hibernate

  - by kate

  Hi, We have three tables .We need to get data from these tables based upon particular conditions. Like if TableA.columv=TableB.columc=tableC.column then get data. We are using value objects to map Objects to relations. Question is how to maintain these relation ships in value objects. And how to retrieve data from it. We have one value object per table.

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• Whats the best to way convert a set of Java objects to another set of objects?

  - by HDave

  Basic Java question here from a real newbie. I have a set of Java objects (of class "MyClass") that implement a certain interface (Interface "MyIfc"). I have a set of these objects stored in a private variable in my class that is declared as follows: protected Set<MyClass> stuff = new HashSet<MyClass>(); I need to provide a public method that returns this set as a collection of objects of type "MyIfc". public Collection<MyIfc> getMyStuff() {...} How do I do the conversion? The following line gives me an error that it can't do the conversion. I would have guessed the compiler knew that objects of class MyClass implemented MyIfc and therefore would have handled it. Collection<MyIfc> newstuff = stuff; Any enlightenment is appreciated.

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• Downsides to immutable objects in Java?

  - by parkr

  The advantages of immutable objects in Java seem clear: consistent state automatic thread safety simplicity You can favour immutability by using private final fields and constructor injection. But, what are the downsides to favouring immutable objects in Java? i.e. incompatibility with ORM or web presentation tools? Inflexible design? Implementation complexities? Is it possible to design a large-scale system (deep object graph) that predominately uses immutable objects?

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• c++ delete[] and array of objects

  - by osgx

  Hello I have allocated and array of Objects Objects *array = new Objects[N]; How should I delete this array? Just delete[] array; or with iterating over array's elements? for(int i=0;i<N;i++) delete array[i]; delete[]; Thanks

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• strategy to allocate/free lots of small objects

  - by aaa

  hello I am toying with certain caching algorithm, which is challenging somewhat. Basically, it needs to allocate lots of small objects (double arrays, < 256 elements), with objects accessible through mapped value, map[key] = array. time to initialized array may be quite large, generally more than 10 thousand cpu cycles. By lots I mean around gigabyte in total. objects may need to be popped/pushed as needed, generally in random places, one object at a time. lifetime of an object is generally long, minutes or more, however, object may be subject to allocation/deallocation several times during duration of program. What would be good strategy to avoid memory fragmentation, while still maintaining reasonable allocate deallocate speed? I am using C++, so I can use new and malloc. Thanks. I know there a similar questions on website, http://stackoverflow.com/questions/2156745/efficiently-allocating-many-short-lived-small-objects, are somewhat different, thread safety is not immediate issue for me.

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• Split Java ArrayList by properties of contained Objects

  - by tzippy

  I have an ArrayList containing Objects that have a date value. Now I want to manage to create a new ArrayList for each year that contains all the Objects from the main ArrayList that have the same year in their date Value. So all Objects from 2010 go in one List, all from 1999 in another.

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• Using IF LARGE when there is text in column

  - by Ray

  I have an excel column of numbers and texts. I tried to use "IF LARGE" to find top 3 numbers of the column (A1 to A7), and return "Yes" to the cells right next to the top 3 (in column B). But unfortunately, the cells next to the texts also returned "Yes". This is the data: 0.2 0.3 Yes 0.5 Yes 0.1 0.8 Yes asdf Yes jklm Yes This is the code for cell B7: =IF(A7>=LARGE($A$1:$A$7,3),"Yes","") Any suggestions to fix this? thanks in advance

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• Request Entity Too Large error while uploading files of more than 128KB over SSL

  - by tushar

  We have a web portal setup on Java spring framework. It running on tomcat app server. Portal is served through apache web server connected to tomcat through JK connector. Entire portal is HTTPS enabled using 443 port of apache. Apache version is : Apache/2.4.2 (Unix). it is the latest stable version of apache web server. Whenever we try to upload files more than 128 KB into the portal, We are facing 413 error: Request Entity Too Large The requested resource /teamleadchoachingtracking/doFileUpload does not allow request data with POST requests, or the amount of data provided in the request exceeds the capacity limit. In the apache error log we get the following errors: AH02018: request body exceeds maximum size (131072) for SSL buffer AH02257: could not buffer message body to allow SSL renegotiation to proceed We did search over google and there were suggestions to put SSLRenegBufferSize as some high value like 10MB. Based on these suggestions, we had put the following entry in virtualhost section of httpd config file: SSLRenegBufferSize 10486000 But still the error persists. Also we have specified SSLVerifyClient none, but still renegotiation is happening. This is a very inconsistent and frustrating error. Any help will be highly appreciated. Many thanks in advance.

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• Chunking large rsync transfers?

  - by Gabe Martin-Dempesy

  We use rsync to update a mirror of our primary file server to an off-site colocated backup server. One of the issues we currently have is that our file server has 1TB of mostly smaller files (in the 10-100kb range), and when we're transferring this much data, we often end up with the connection being dropped several hours into the transfer. Rsync doesn't have a resume/retry feature that simply reconnects to the server to pickup where it left off -- you need to go through the file comparison process, which ends up being very length with the amount of files we have. The solution that's recommended to get around is to split up your large rsync transfer into a series of smaller transfers. I've figured the best way to do this is by first letter of the top-level directory names, which doesn't give us a perfectly even distribution, but is good enough. I'd like to confirm if my methodology for doing this is sane, or if there's a more simple way to accomplish the goal. To do this, I iterate through A-Z, a-z, 0-9 to pick a one character $prefix. Initially I was thinking of just running rsync -av --delete --delete-excluded --exclude "*.mp3" "src/$prefix*" dest/ (--exclude "*.mp3" is just an example, as we have a more lengthy exclude list for removing things like temporary files) The problem with this is that any top-level directories in dest/ that are no longer present present on src will not get picked up by --delete. To get around this, I'm instead trying the following: rsync \ --filter 'S /$prefix*' \ --filter 'R /$prefix*' \ --filter 'H /*' \ --filter 'P /*' \ -av --delete --delete-excluded --exclude "*.mp3" src/ dest/ I'm using the show and hide over include and exclude, because otherwise the --delete-excluded will delete anything that doesn't match $prefix. Is this the most effective way of splitting the rsync into smaller chunks? Is there a more effective tool, or a flag that I've missed, that might make this more simple?

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• Viewing a large-resolution VNC server through a small-resolution viewer in Ubuntu

  - by Madiyaan Damha

  I have two Ubuntu computers, one with a large screen resolution (1920x1600) that is running default ubuntu vnc server. I have another computer that has a resolution of about 1200x1024 that I use to vnc into the server (I use the default ubuntu vnc viewer). Now everything works fine except there are annoying scrollbars in the viewer because the server's desktop resolution is so much higher than the viewer's. Is there a way to: 1) Scale the server's desktop down to the viewer's resolution. I know there will be a loss of image quality, but I am willing to try it out. This should be something like how windows media player or vlc scales down the window (and does some interpolation of pixels). 2) Automatically shrink the resolution of the server to the client's when I connect and scale the resolution back when I disconnect. This seems like a less attractive solution. 3) Any other solution that gurus out there use? I am sure someone has experienced this before (annoying scroll bars) so there must be a solution out there. Thanks,

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• Sharing large (multi-Gb) files with clients

  - by Tim Long

  I wasn't sure if this was the best place for this question, but I think it is squarely in the realm of the IT admin so that's the reason I put it here. We need to share large files (several Gigabytes) with external clients. We need a simple way of reliably and automatically publishing these files so that clients can then download them. Our organization has Windows desktops and a Windows SBS 2011 server. Sharing from our server is probably suboptimal from the client's perspective, because of the low upstream bandwidth of typical ADSL (around 1 Mbps) - it would take all day (9 hours for a 4Gb file) for the client to download the file. Uploading to a 3rd party sever is good for the client but painful for us, because we then have to deal with a multi-hour upload. Uploading to a third-part server would be less problematic if it could be made reliable and automatic, e.g. something like a Groove/SharePoint Workspace, simply drop the file in and wait for it to synchronize - but Groove has a 2Gb limit which is not big enough. So ideally I'd like a service with the following attributes: Must work for files of at least 5Gb, preferably 10Gb Once the transfer is started, it must be reliable (i.e. not sensitive to disconnections and service outages) and completely automatic Ideally, the sender would get a notification when the transfer completes. Has to work with Windows based systems. Any suggestions?

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• Viewing a large-resolution VNC server through a small-resolution viewer in Ubuntu

  - by Madiyaan Damha

  I have two Ubuntu computers, one with a large screen resolution (1920x1600) that is running the default Ubuntu VNC server. I have another computer that has a resolution of about 1200x1024 that I use to VNC into the server using the default Ubuntu VNC viewer). Now everything works fine except there are annoying scrollbars in the viewer because the server's desktop resolution is so much higher than the viewer's. Is there a way to: Scale the server's desktop down to the viewer's resolution. I know there will be a loss of image quality, but I am willing to try it out. This should be something like how Windows Media Player or VLC scales down the window (and does some interpolation of pixels). Automatically shrink the resolution of the server to the client's when I connect and scale the resolution back when I disconnect. This seems like a less attractive solution. Any other solution that gurus out there use? I am sure someone has experienced this before (annoying scroll bars) so there must be a solution out there.

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• Exim and receiving email with large recipient lists

  - by AceJordin

  I have Exim4 running on Debian configured to receive mail on multiple domains. Exim is set to forward all email that is received to one of the domains to another box. This box is configured with a catchall mailbox that everything goes in. My issue is that when an email is sent to the domain, which contains a large amount of addresses (all to the same domain, but different users), Exim will receive the single email over multiple connections. This means that the catchall mailbox receives multiple copies of the single email all containing the full recipient list. For example, I was able to reproduce it by sending an email from my gmail account that contained 500 recipients (eg [email protected]; [email protected]; [email protected]; etc. for a total of 500). Exim received the message as 20 messages (25 recipients per; appears to be a gmail server setting). So the catchall mailbox received 20 messages, each containing all 500 addresses. I'm pretty sure I understand why this is happening but is there any way I can configure Exim to only receive it once, or to combine it into one? Is there anything that can be done on my end, or am I at the mercy of the sending email server? This is causing havoc with a process that polls the catchall mailbox and parses each recipient in each email.

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• Two large, linked Excel files take 30 minutes to save, except in VMWare environment

  - by Gerald L

  I support some tax consultants who love to use Excel when they should probably be using Access. Anyway, they have created two Excel files, A and B. File B has cells linked to file A. File A is 27 MB and file B is 16 MB. One worksheet has roughly 1 million rows and there is another worksheet doing a whole bunch of SUMIF on the 1 million rows. Not the best idea, but whatever. Both Excel files open and recalculate within a reasonable amount of time (1-2 minutes). For a files that large, this is acceptable. Here is the problem: Once you change a cell, and save the file B, it takes a solid 30 minutes to save the file, and the processors are going full speed. I've tried this on 6 different machines, all running Windows XP SP3 with Office 2007 SP2 and all patches. The specs vary from one machine with 512 MB or RAM to a machine with 4 GB of RAM and quad processors. Same result every time. Here is the clincher: If I do this same save operation on a VMWare virtual machine, the file gets saved in 1 minute. I've tried this with my ESX servers at the office, my Mac Fusion at home, and VMWare workstation at the office. It does not matter how much RAM the virtual machine has... it saves in about 1 minute every time. Does anybody have any idea why this is happening and how to fix?

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• copy large LVM volume(14TB) from one server to another

  - by bruce

  recently,I have to copy a very large LVM volume()rom server A to server B. Below is the filesystem of server A and server B - server A [root@AVDVD-Filer ~]# df -h Filesystem Size Used Avail Use% Mounted on /dev/mapper/vg_avdvdfiler-lv_root 16T 14T 1.5T 91% / tmpfs 3.0G 0 3.0G 0% /dev/shm /dev/cciss/c0d0p1 194M 23M 162M 13% /boot /dev/mapper/vg_avdvdfiler-test 2.3T 201M 2.1T 1% /test /dev/sr0 3.3G 3.3G 0 100% /mnt server B [root@localhost ~]# df -h Filesystem Size Used Avail Use% Mounted on /dev/mapper/VolGroup-LogVol00 20G 2.5G 16G 14% / tmpfs 3.0G 0 3.0G 0% /dev/shm /dev/cciss/c0d0p1 194M 23M 162M 13% /boot /dev/mapper/VolGroup00-LogVol00 16T 133M 15T 1% /xiangao/lv1 /dev/mapper/VolGroup00-LogVol01 4.7T 190M 4.5T 1% /xiangao/lv2 I want to copy LVM volume /dev/mapper/vg_avdvdfiler-lv_root on server A to LVM volume /dev/mapper/VolGroup00-LogVol00 on server B . The server A and server B is in the same IP segment. IN the LVM volume on server A , there is all average 500M avi wmv mp4 etc. I tried mount /dev/mapper/vg_avdvdfiler-lv_root on server A to server B through NFS , then use cp command copy. It is clear I faild . Because the LVM volume is too big , I do not have good idea . I hope a good solution here. I'm a chinese, my english is very pool. sorry thanks everyone!

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