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  • Using Hibernate with MS ACCESS 2007 Database (Free JDBC Driver)

    - by Quentin T.
    1. I want to do a reverse engineering action with the Hibernate plugin of Eclipse on a MS Access 2007 Database. I'm forced to use a existing MS Access 2007 db. A easy solution is to buy the HXTT. But I want to use a free driver to do my work. So I tried to apply this post : http://www.programmingforfuture.com/2011/06/how-to-use-ms-access-with-hibernate.html (That uses the SQL Server dialect and the driver sun.jdbc.odbc.JdbcOdbcDriver) Unfortunately I have an error that nobody seems to have been on the internet: Exception while generating code Reason : org.hibernate.exception.GenericJDBCException: Error while reading primary key meta data for `c:/myaccessdb.mdb`.TableTest1 I have try to change the primary key on my MS Access DB (deleting all primary key) or to try the reverse engineering on a MS ACCESS with only one table without primary key, but I got all times the problems. 2. The purpose of my job is to transfer daily (weekly) an Oracle 11g database with data from an existing database MS ACCESS 2007. And I thought to use a procedure (Hibernate EJB) Java to be launched automatically every week to do the data transfer. Is this is the best solution ? Configuration : sun.jdbc.odbc.JdbcOdbcDriver v??? Hibernate v3.4 Eclipse ps: If you are a HXTT developer or seller please be indulgent with my post ;). Making money by making people believe that you help, it's bad ! A solution is to use Derby Client driver, as the solution in the post: Does anyone know if Hibernate and java will work effectively with Access? But a clarification of the answer of Rich Seller is required. Could you explain your answer and explain your configuration (hibernate.cfg.xml, persistence.xml and what URL you use in the property name="hibernate.connection.url") without using paying HXTT driver but with the free Derby driver.

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  • From where to send mails in a MVC framework, so that there is no duplication of code?

    - by Sabya
    It's a MVC question. Here is the situation: I am writing an application where I have "groups". You can invite other persons to your groups by typing their email and clicking "invite". There are two ways this functionality can be called: a) web interface and b) API After the mail sending is over I want to report to the user which mails were sent successfully (i.e., if the SMTP send succeeded. Currently, I am not interested in reporting mail bounces). So, I am thinking how should I design so that there is no code duplication. That is, API and web-interface should share the bulk of the code. To do this, I can create the method "invite" inside the model "group". So, the API and and the Web-interface can just call: group-invite($emailList); This method can send the emails. But the, problem is, then I have to access the mail templates, create the views for the mails, and then send the mails. Which should actually be in the "View" part or at least in the "Controller" part. What is the most elegant design in this situation? Note: I am really thinking to write this in the Model. My only doubt is: previously I thought sending mails also as "presentation". Since it is may be considered as a different form of generating output.

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  • Howto create dynamic named folders with Maven2 Archetype?

    - by chrsk
    Hey, i try to build a structure like this +---src +---main +---webapp +---WEB-INF +---cfg ¦ +---log4j ¦ +---resources ¦ +---extensions ¦ +---${artifactIdKey}-business ¦ +---${artifactIdKey}-layout +---lib I added a required property to my archetype-metadata.xml to have an short-name for the project, which is used among other things for generating unique folders. <requiredProperties> <requiredProperty key="artifactIdKey" /> </requiredProperties> The property artifactIdKey i use in a fileSet: <fileSet> <directory>[..]/resources/extensions/${artifactIdKey}-business</directory> </fileSet> <fileSet> <directory>[..]/resources/extensions/${artifactIdKey}-layout</directory> </fileSet> The command to generate the archetype: mvn archetype:generate -B \ -DgroupId=com.stackoverflow \ -DartifactId=stackoverflow-question -DarchetypeGroupId=com.stackoverflow \ -DarchetypeArtifactId=stackoverflow-archetype -DarchetypeVersion=1.0 \ -DartifactIdKey=soq I assume to get the following folder structure, but i get the ${artifactIdKey} property as folder. Without beeing replaces. ..\ +---soq-business +---soq-layout ..\ +---${artifactIdKey}-business +---${artifactIdKey}-layout How can i achieve this? And how can i place files below soq-business? Without knowing the folder name at this time?

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  • Where is the taglib definition of PrimeFaces 4?

    - by Michael Wölm
    I am looking around how to define custom components in JSF. According to the Java EE tutorial, any custom component needs to be described in a taglib. When I take a look into the PrimeFaces source, I cannot find any taglib file or any hint where the namespace is bound and the available components are defined. I am adding primefaces jar to my dependencies, adding xmlns:p="http://primefaces.org/ui to the xml namespace, defining some primfaces components on my page and it works... Ok, but neither I can find the related taglib in the source or binary package nor my IDE (IntelliJ) is able to find where "xmlns:p="http://primefaces.org/ui" is pointing to. Therefore, code completion is also not possible. (all other mojarra taglibs are found.) Is it possible that PrimeFaces is defining the taglib via annotations directly in Java classes or is it generating it during runtime? I can easily find the UIComponents, primefaces defines in its source, but the configuration of the taglib seems to be missing. I am sure I just don't know how PrimeFaces is doing it, but the javaeetutorial is not describing any other opportunity than defining a ...-taglib.xml

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  • Change Powerpoint chart data with .NET

    - by mc6688
    I have a Powerpoint template that contains 1 slide and on that slide is a chart. I'd like to be able to manipulate that charts data using .NET. So far I have code that... unzips the Powerpoint file. unzips the embedded excel file (ppt\embeddings\Microsoft_Office_Excel_Worksheet1.xlsx) It successfully manipulates the data in the excel sheet and zips it back up. Opens and manipulates ppt\charts\chart1.xml Powerpoint is then zipped up and delivered to the user The result of this is a Powerpoint file that shows a blank chart. But when I click on the chart and go to edit data it updates the data and shows the correct chart. I believe my problem is with the chart1.xml that I am generating. I have compared my generated version with a version created by Powerpoint and they are almost identical. The only differences are in the values for <c:crossAx> and <c:axId>. There are also some rounding difference in the data. But I do not feel like that would result in an blank chart. Is there another file that I need to edit? Does anyone have any ideas as to what else I should try to get this working?

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  • Controller changes format on variables when publishing

    - by Christoffer
    I am a newbie to ROR but catching on quickly. I have been working on this problem for a couple of hours now and it seems like a bug. I does not make any sense. I have a database with the following migration: class CreateWebsites < ActiveRecord::Migration def self.up create_table :websites do |t| t.string :name t.integer :estimated_value t.string :webhost t.string :purpose t.string :description t.string :tagline t.string :url t.integer :adsense t.integer :tradedoubler t.integer :affiliator t.integer :adsense_cpm t.boolean :released t.string :empire_type t.string :oldid t.string :old_outlink_policy t.string :old_inlink_policy t.string :old_priority t.string :old_profitability t.integer :priority_id t.integer :project_id t.integer :outlink_policy_id t.integer :inlink_policy_id t.timestamps end end def self.down drop_table :websites end end I have verified that what is created in the database also is integers, strings etc according to this migration. I have not touched the controller after generating it through scaffold, i.e. it is the standard controller with show, index etc. Now. When I enter data into the database, either through the web form, in rails console or directly in the database - such as www.domain.com for url or 500 for adsense - it will be created in the db without problem. However, when it is being published on the website the variables go completely nuts. Adsense (integer) turns into date, url (string) turns into a float, and so on. This only happens to a few of the variables. This will also create a problem with "argument out of range" since I input 500 and Rails will try to output it as date = crash and "argument out of range". So, how do I fix/trouble shoot this? Why do the formats change? Could it be because of the respond_to in the controller? Cheers, Christoffer

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  • How to generate lots of redundant ajax elements like checkboxes and pulldowns in Django?

    - by iJames
    Hello folks. I've been getting lots of answers from stackoverflow now that I'm in Django just be searching. Now I hope my question will also create some value for everybody. In choosing Django, I was hoping there was some similar mechanism to the way you can do partials in ROR. This was going to help me in two ways. One was in generating repeating indexed forms or form elements, and also in rendering only a piece of the page on the round trip. I've done a little bit of that by using taconite with a simple URL click but now I'm trying to get more advanced. This will focus on the form issue which boils down to how to iterate over a secondary object. If I have a list of photo instances, each of which has a couple of parameters, let's say a size and a quantity. I want to generate form elements for each photo instance separately. But then I have two lists I want to iterate on at the same time. Context: photos : Photo.objects.all() and forms = {} for photo in photos: forms[photo.id] = PhotoForm() In other words we've got a list of photo objects and a dict of forms based on the photo.id. Here's an abstraction of the template: {% for photo in photos %} {% include "photoview.html" %} {% comment %} So here I want to use the photo.id as an index to get the correct form. So that each photo has its own form. I would want to have a different action and each form field would be unique. Is that possible? How can I iterate on that? Thanks! {% endcomment %} Quantity: {{ oi.quantity }} {{ form.quantity }} Dimensions: {{ oi.size }} {{ form.size }} {% endfor %} What can I do about this simple case. And how can I make it where every control is automatically updating the server instead of using a form at all? Thanks! James

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  • IIS 6+ASP.NET - many temp files generated

    - by moshe_ravid
    I have a ASP.NET + some .NET web-services running on IIS 6 (win 2003 server). The issue is that IIS is generating a lot (!) of files in "c:\WINDOWS\Temp" directory. a lot of files means thousands of files, which get to more than 3G of size so far. The files are generated by this command: C:\WINDOWS\SysWOW64\inetsrv "C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\csc.exe" /t:library /utf8output /R:"C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET Files\vfagt\113819dd\db0d5802\assembly\dl3\fedc6ef1\006e24d8_3bc9ca01\VfAgentWService.DLL" /R:"C:\WINDOWS\assembly\GAC_MSIL\System.Web.Services\2.0.0.0__b03f5f7f11d50a3a\System.Web.Services.dll" /R:"C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\mscorlib.dll" /R:"C:\WINDOWS\assembly\GAC_MSIL\System.Xml\2.0.0.0__b77a5c561934e089\System.Xml.dll" /R:"C:\WINDOWS\assembly\GAC_MSIL\System\2.0.0.0__b77a5c561934e089\System.dll" /out:"C:\WINDOWS\TEMP\9i_i2bmg.dll" /debug- /optimize+ /nostdlib /D:_DYNAMIC_XMLSERIALIZER_COMPILATION "C:\WINDOWS\TEMP\9i_i2bmg.0.cs" The files in the temp directory are pairs of *.out & *.err, where the *.err file is zero size, and the *.out file contains the compilation output messages. What is causing IIS to generate so many files? How can I prevent it? UPDATE: The problem is that the command i described above (csc.exe) is being executed many (many) times, causing the .out & .err to be generated so many times, until it consumes the disk space. So - my question is: what is causing this command to run so many times? (i don't have that many .aspx & .asmx files in my web app). Thanks, Moe

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  • new Stateful session bean instance without calling lookup

    - by kislo_metal
    Scenario: I have @Singleton UserFactory (@Stateless could be) , its method createSession() generating @Stateful UserSession bean by manual lookup. If I am injecting by DI @EJB - i will get same instance during calling fromFactory() method(as it should be) What I want - is to get new instance of UserSession without preforming lookup. Q1: how could I call new instance of @Stateful session bean? Code: @Singleton @Startup @LocalBean public class UserFactory { @EJB private UserSession session; public UserFactory() { } @Schedule(second = "*/1", minute = "*", hour = "*") public void creatingInstances(){ try { InitialContext ctx = new InitialContext(); UserSession session2 = (UserSession) ctx.lookup("java:global/inferno/lic/UserSession"); System.out.println("in singleton UUID " +session2.getSessionUUID()); } catch (NamingException e) { e.printStackTrace(); } } @Schedule(second = "*/1", minute = "*", hour = "*") public void fromFactory(){ System.out.println("in singleton UUID " +session.getSessionUUID()); } public UserSession creatSession(){ UserSession session2 = null; try { InitialContext ctx = new InitialContext(); session2 = (UserSession) ctx.lookup("java:global/inferno/lic/UserSession"); System.out.println("in singleton UUID " +session2.getSessionUUID()); } catch (NamingException e) { e.printStackTrace(); } return session2; } } As I understand, calling of session.getClass().newInstance(); is not a best idea Q2 : is it true? I am using glassfish v3, ejb 3.1.

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  • PHP Notice: Undefined property: stdClass:

    - by 4D
    I've got an array coming back from a Flash app created in Flash Builder 4. I have a service setup that queries and brings data back from the DB successfully, however the Update script is generating the Undefined Property errors. I'm still learning both PHP and Flash Builder, and don't fully understand what the $this- commands do. If anyone can suggest where this script is going wrong, it is basically just generated by Flash Builder and is not something I've developed myself, I would appreciate it? Also if someone can explain $this- to me that would be awesome too? I've seen them before, but then I've seen scripts doing the same thing that do not use them, so is this an old way of doing things? Really appreciate any input anyone can give. public function updateItem($item) { // TODO Auto-generated method stub // Update an existing record in the database and return the item // Sample code \' $this->connect(); $sql = "UPDATE tbltrust SET inst_code = '$item->inst_code', trust_name = '$item->trust_name', trust_code = '$item->trust_code' WHERE trust_key = '$item->trust_key'"; mysqli_query($this->connection, $sql) or die('Query failed: ' . mysqli_error($this->connection)); mysqli_close($this->connection); }

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  • Best way to dynamically get column names from oracle tables

    - by MNC
    Hi, We are using an extractor application that will export data from the database to csv files. Based on some condition variable it extracts data from different tables, and for some conditions we have to use UNION ALL as the data has to be extracted from more than one table. So to satisfy the UNION ALL condition we are using nulls to match the number of columns. Right now all the queries in the system are pre-built based on the condition variable. The problem is whenever there is change in the table projection (i.e new column added, existing column modified, column dropped) we have to manually change the code in the application. Can you please give some suggestions how to extract the column names dynamically so that any changes in the table structure do not require change in the code? My concern is the condition that decides which table to query. The variable condition is like if the condition is A, then load from TableX if the condition is B then load from TableA and TableY. We must know from which table we need to get data. Once we know the table it is straightforward to query the column names from the data dictionary. But there is one more condition, which is that some columns need to be excluded, and these columns are different for each table. I am trying to solve the problem only for dynamically generating the list columns. But my manager told me to make solution on the conceptual level rather than just fixing. This is a very big system with providers and consumers constantly loading and consuming data. So he wanted solution that can be general. So what is the best way for storing condition, tablename, excluded columns? One way is storing in database. Are there any other ways? If yes what is the best? As I have to give at least a couple of ideas before finalizing. Thanks,

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  • Insert data in an object to a database.

    - by paul
    I am facing the following design/implementation dilemma. I have a class Customer which is below with getters and setters. I would like to insert the value of the Customer into a "Customer" table of a database. But Customer has an address which is of type "Address". How do I go about inserting this field into the database?(I am using sqlite3). I thought of writing a separate table "Address(customerId,doorNo,city,state,country,pinCode)". But I am having second thoughts about generating the primary key(customerId) which should be same for both the "customer" and "Address" table. Sqlite3 faq states that I can do "Integer Primary Key" to use the field to generate an auto number. But if I do that in customer table, I would have to retrieve the same Id to be used in Address table. This kinda looks wrong to me :-?. There should be an elegant method to solve this. Any ideas would be much appreciated. Thanks in advance. import java.io.*; import java.sql.*; class Customer { private String id; private String name; private Address address; private Connection connection; private ResultSet resultSet; private PreparedStatement preparedStatement; public void insertToDatabase(){ } } class Address{ private String doorNumber; private String streetName; private String cityName; private String districtName; private String stateName; private String countryName; private long pinCode; }

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  • Export to csv in jQuery

    - by Rahul Joshi
    I am dynamically generating a div which is like : <div id='PrintDiv'> <table id="mainTable"> <tr> <td> Col1 </td> <td> Col2 </td> <td> Col3 </td> </tr> <tr> <td> Val1 </td> <td> Val2 </td> <td> Val3 </td> </tr> <tr> <td> Val11 </td> <td> Val22 </td> <td> Val33 </td> </tr> <tr> <td> Val111 </td> <td> Val222 </td> <td> Val333 </td> </tr> </table> </div> And there are lot more elements on the page as well. Now, how can i get a csv file like this : Col1,Col2,Col3 Val1,Val2,Val3 Val11,Val22,Val33 Val111,Val222,Val333 using jQuery ? need a file save dailog box too,like this : Thanks.

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  • Unit test project doesn't recognize the classes it was generated from

    - by DougLeary
    I have a fairly simple file-system website consisting of one aspx page and several classes in separate .cs files. Everything is on my own HD. The web app itself builds and runs fine. Out of curiosity I decided to try out Visual Studio's nifty, easy-to-use unit test feature. So I opened each class file and clicked Create Unit Tests. VS generated a test project containing a set of test classes and some other files. Easy! But when I try to build or run the test project it throws a series of build errors, one for every class: The type or namespace name 'class-name' could not be found (are you missing a using directive or an assembly reference?). Somebody asked if my test project has a reference to the original project. Well no, because the original project is a file-system website. It has no bin folder and no DLL, so there's nothing to reference as far as I can tell. I would think that since VS generated these unit tests it would generate whatever references it needs, but apparently not. Is generating unit tests for file-system web apps an undocumented no-no, or is there a magic trick to getting it to work?

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  • Editing a remote file on-the-fly with PHP

    - by user275074
    Hi, I have a requirement to edit a remote text file on-the-fly, the content of which currently stands at ~1Mb. I have tried a couple of approaches and both seem to be clunky or hog memory which I can't rely on. Thinking out logically what I'm trying to achieve is: FTP to a remote server. Download a copy of the file for backup purposes and store it somewhere locally. Open the remote file and add the necessary lines required. Remove lines from the remote file as per an array of un-required data generated from the local server. Is this possible? I've managed to code steps 1 and 2 but I'm having difficult with 3 and 4. The way I'm doing it now is to use fgets and return the whole string. Really, I don't want to do this as it involves manipulating and re-generating the whole string (and it's large) and then re-inserting it in between two markers in the remote file. Is there no way of manipulating the lines of text in the file on-the-fly?

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  • 2D Histogram in R: Converting from Count to Frequency within a Column

    - by Jac
    Would appreciate help with generating a 2D histogram of frequencies, where frequencies are calculated within a column. My main issue: converting from counts to column based frequency. Here's my starting code: # expected packages library(ggplot2) library(plyr) # generate example data corresponding to expected data input x_data = sample(101:200,10000, replace = TRUE) y_data = sample(1:100,10000, replace = TRUE) my_set = data.frame(x_data,y_data) # define x and y interval cut points x_seq = seq(100,200,10) y_seq = seq(0,100,10) # label samples as belonging within x and y intervals my_set$x_interval = cut(my_set$x_data,x_seq) my_set$y_interval = cut(my_set$y_data,y_seq) # determine count for each x,y block xy_df = ddply(my_set, c("x_interval","y_interval"),"nrow") # still need to convert for use with dplyr # convert from count to frequency based on formula: freq = count/sum(count in given x interval) ################ TRYING TO FIGURE OUT ################# # plot results fig_count <- ggplot(xy_df, aes(x = x_interval, y = y_interval)) + geom_tile(aes(fill = nrow)) # count fig_freq <- ggplot(xy_df, aes(x = x_interval, y = y_interval)) + geom_tile(aes(fill = freq)) # frequency I would appreciate any help in how to calculate the frequency within a column. Thanks! jac EDIT: I think the solution will require the following steps 1) Calculate and store overall counts for each x-interval factor 2) Divide the individual bin count by its corresponding x-interval factor count to obtain frequency. Not sure how to carry this out though. .

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  • Binding KeyUp event to Input Field

    - by user306686
    I am dynamically generating textboxes in ruby using <%0.upto(4) do |i| % <%= text_field_tag('relative_factor[]', @prefill_values[:relative_factor][i],:size = 6,:maxlength = 5) % <%end% it generates following HTML markup Another set of textboxes: <%0.upto(4) do |i| % <%= text_field_tag('rating_factor[]', @prefill_values[:relative_factor][i],:size = 6,:maxlength = 5) % <%end% it generates following HTML markup I have one more textbox: ..... I want to update id="rating_factor_" textboxes as the value in either id="multiple" textbox changes or id="relative_factor_" textboxes changes. E.g. id="multiple" textbox = 5 id="relative_factor_" value= 0.0 textbox = 1 id="relative_factor_" value= 1.0 textbox = 2 id="relative_factor_" value= 2.0 textbox = 3 id="relative_factor_" value= 3.0 textbox = 4 id="relative_factor_" value= 4.0 textbox = 5 I want to show (multiple multiple and relative_factor_ and show) id="rating_factor_" value= 0.0 textbox = 5 id="rating_factor_" value= 1.0 textbox = 10 id="rating_factor_" value= 2.0 textbox = 15 id="rating_factor_" value= 3.0 textbox = 20 id="rating_factor_" value= 4.0 textbox = 25 Now if user changes, id="relative_factor_" value= 1.0 textbox as 1.5 then id="rating_factor_" value= 1.0 textbox should be updated as 7.5 To achieve above goal, I tried binding #relative_factor_ to keyup event but as id is same for all i.e.#relative_factor_, it returns value for first textbox i.e. id="relative_factor_" value= 0.0. Please guide me to crack this problem. Thanks in Advance.

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  • How to generate XML from an Excel VBA macro?

    - by SuperNES
    So, I've got a bunch of content that was delivered to us in the form of Excel spreadsheets. I need to take that content and push it into another system. The other system takes its input from an XML file. I could do all of this by hand (and trust me, management has no problem making me do that!), but I'm hoping there's an easy way to write an Excel macro that would generate the XML I need instead. This seems like a better solution to me, as this is a job that will need to be repeated regularly (we'll be getting a LOT of content in Excel sheets) and it just makes sense to have a batch tool that does it for us. However, I've never experimented with generating XML from Excel spreadsheets before. I have a little VBA knowledge but I'm a newbie to XML. I guess my problem in Googling this is that I don't even know what to Google for. Can anyone give me a little direction to get me started? Does my idea sound like the right way to approach this problem, or am I overlooking something obvious? Thanks StackOverflow!

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  • Disable validation in an object in Ruby on Rails

    - by J. Pablo Fernández
    I have an object which whether validation happens or not should depend on a boolean, or in another way, validation is optional. I haven't found a clean way to do it. What I'm currently doing is this (disclaimer: you cannot unsee, leave this page if you are too sensitive): def valid? if perform_validation super else super # Call valid? so that callbacks get called and things like encrypting passwords and generating salt in before_validation actually happen errors.clear # but then clear the errors true # and claim ourselves to be valid. This is super hacky! end end Any better ways? Before you point to the :if argument of many validations, this is for a user model which is using authlogic so it has a lot of validation rules. You can stop reading here if you belive me. If you don't, authlogic already sets some :ifs like: :if => :email_changed? which I have to turn into :if => Proc.new {|user| user.email_changed? and user.perform_validation} and in some other cases, since I'm also using authlogic-oid (OpenID) I just don't have control over the :if, authlogic-oid sets it in a way I cannot change it (in time) without further monkey patching. So I have to override seemingly unrelated functions, catch exceptions if a method doesn't exist, etc. The previous hacky solution if the best of my two attempts.

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  • Using maven to distribute a swing application that can have each dependency individually tracked

    - by tms
    I'm moving my project to Maven and eventually OSGi. I currently distribute the project is a large Zip file with all the dependencies. Although my projects code is only 20% of the total package I have to redistribute all the dependency. With smaller independent modules this may be even less. Looking here on stack overflow it seems that to keep my current plan the maven-assembly-plugin should do the trick. I was considering having a base installer that would look at a XML manifest, then collect all the libraries that needed to be updated. This would mean that libraries that change occasionally would be downloaded less often. This also makes since for something like OSGi plugins (which could have independent release schedules). In essence I want my software to look and manage individual libraries, and download on demand (based on the manifest). I was wondering if there is a "maven way" of generating this Manifest and publishing all the libraries to a website? I believe the deploy life-cycle would do the second step. As an alternative, is there a OpenSource Java library that does this type of deployment? I don't want to embed Maven or something larger with the distributed code. The application is not for coders, the simpler the better, and the smaller the installer the better.

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  • What is an efficient strategy for multiple threads posting jobs and waiting for response from a single thread?

    - by jakewins
    In java, what is an efficient solution to the following problem: I have multiple threads (10-20 or so) generating jobs ("Job Creators"), and a single thread capable of performing them ("The worker"). Once a job creator has posted a job, it should wait for the job to finish, yielding no result other than "it's done", before it keeps going. For sending the jobs to the worker thread, I think a ring buffer or similar standard fan-in setup would perhaps be a good approach? But for a Job Creator to find out that her job has been done, I'm not so sure.. The job creators could sleep, and the worker interrupt them when done.. Or each job creator could have an atomic boolean that it checks, and that the worker sets. I dunno, neither of those feel very nice. I'd like to do it with as few (none, if possible) locks as absolutely possible. So to be clear: What I'm looking for is speed, not necessarily simplicity. Does anyone have any suggestions? Links to reading about concurrency strategies would also be very welcome!

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  • LINQ-SQL Updating Multiple Rows in a single transaction

    - by RPM1984
    Hi guys, I need help re-factoring this legacy LINQ-SQL code which is generating around 100 update statements. I'll keep playing around with the best solution, but would appreciate some ideas/past experience with this issue. Here's my code: List<Foo> foos; int userId = 123; using (DataClassesDataContext db = new FooDatabase()) { foos = (from f in db.FooBars where f.UserId = userId select f).ToList(); foreach (FooBar fooBar in foos) { fooBar.IsFoo = false; } db.SubmitChanges() } Essentially i want to update the IsFoo field to false for all records that have a particular UserId value. Whats happening is the .ToList() is firing off a query to get all the FooBars for a particular user, then for each Foo object, its executing an UPDATE statement updating the IsFoo property. Can the above code be re-factored to one single UPDATE statement? Ideally, the only SQL i want fired is the below: UPDATE FooBars SET IsFoo = FALSE WHERE UserId = 123 EDIT Ok so looks like it cant be done without using db.ExecuteCommand. Grr...! What i'll probably end up doing is creating another extension method for the DLINQ namespace. Still require some hardcoding (ie writing "WHERE" and "UPDATE"), but at least it hides most of the implementation details away from the actual LINQ query syntax.

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  • How would I code a complex formula parser manually?

    - by StormianRootSolver
    Hm, this is language - agnostic, I would prefer doing it in C# or F#, but I'm more interested this time in the question "how would that work anyway". What I want to accomplish ist: a) I want to LEARN it - it's about my ego this time, it's for a fun project where I want to show myself that I'm a really good at this stuff b) I know a tiny little bit about EBNF (although I don't know yet, how operator precedence works in EBNF - Irony.NET does it right, I checked the examples, but this is a bit ominous to me) c) My parser should be able to take this: 5 * (3 + (2 - 9 * (5 / 7)) + 9) for example and give me the right results d) To be quite frankly, this seems to be the biggest problem in writing a compiler or even an interpreter for me. I would have no problem generating even 64 bit assembler code (I CAN write assembler manually), but the formula parser... e) Another thought: even simple computers (like my old Sharp 1246S with only about 2kB of RAM) can do that... it can't be THAT hard, right? And even very, very old programming languages have formula evaluation... BASIC is from 1964 and they already could calculate the kind of formula I presented as an example f) A few ideas, a few inspirations would be really enough - I just have no clue how to do operator precedence and the parentheses - I DO, however, know that it involves an AST and that many people use a stack So, what do you think?

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  • Handling user interface in a multi-threaded application (or being forced to have a UI-only main thre

    - by Patrick
    In my application, I have a 'logging' window, which shows all the logging, warnings, errors of the application. Last year my application was still single-threaded so this worked [quite] good. Now I am introducing multithreading. I quickly noticed that it's not a good idea to update the logging window from different threads. Reading some articles on keeping the UI in the main thread, I made a communication buffer, in which the other threads are adding their logging messages, and from which the main thread takes the messages and shows them in the logging window (this is done in the message loop). Now, in a part of my application, the memory usage increases dramatically, because the separate threads are generating lots of logging messages, and the main thread cannot empty the communication buffer quickly enough. After the while the memory decreases again (if the other threads have finished their work and the main thread gradually empties the communication buffer). I solved this problem by having a maximum size on the communication buffer, but then I run into a problem in the following situation: the main thread has to perform a complex action the main thread takes some parts of the action and let's separate threads execute this while the seperate threads are executing their logic, the main thread processes the results from the other threads and continues with its work if the other threads are finished Problem is that in this situation, if the other threads perform logging, there is no UI-message loop, and so the communication buffer is filled, but not emptied. I see two solutions in solving this problem: require the main thread to do regular polling of the communication buffer only performing user interface logic in the main thread (no other logic) I think the second solution seems the best, but this may not that easy to introduce in a big application (in my case it performs mathematical simulations). Are there any other solutions or tips? Or is one of the two proposed the best, easiest, most-pragmatic solution? Thanks, Patrick

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  • Synchronizing one or more databases with a master database - Foreign keys

    - by Ikke
    I'm using Google Gears to be able to use an application offline (I know Gears is deprecated). The problem I am facing is the synchronization with the database on the server. The specific problem is the primary keys or more exactly, the foreign keys. When sending the information to the server, I could easily ignore the primary keys, and generate new ones. But then how would I know what the relations are. I had one sollution in mind, bet the I would need to save all the pk for every client. What is the best way to synchronize multiple client with one server db. Edit: I've been thinking about it, and I guess seqential primary keys are not the best solution, but what other possibilities are there? Time based doesn't seem right because of collisions which could happen. A GUID comes to mind, is that an option? It looks like generating a GUID in javascript is not that easy. I can do something with natural keys or composite keys. As I'm thinking about it, that looks like the best solution. Can I expect any problems with that?

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