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• The Purpose of a Service Layer and ASP.NET MVC 2

  - by user332022

  In an effort to understand MVC 2 and attempt to get my company to adopt it as a viable platform for future development, I have been doing a lot of reading lately. Having worked with ASP.NET pretty exclusively for the past few years, I had some catching up to do. Currently, I understand the repository pattern, models, controllers, data annotations, etc. But there is one thing that is keeping me from completely understanding enough to start work on a reference application. The first is the Service Layer Pattern. I have read many blog posts and questions here on Stack Overflow, but I still don't completely understand the purpose of this pattern. I watched the entire video series at MVCCentral on the Golf Tracker Application and also looked at the demo code he posted and it looks to me like the service layer is just another wrapper around the repository pattern that doesn't perform any work at all. I also read this post: http://www.asp.net/Learn/mvc/tutorial-38-cs.aspx and it seemed to somewhat answer my question, however, if you are using data annotations to perform your validation, this seems unnecessary. I have looked for demonstrations, posts, etc. but I can't seem to find anything that simply explains the pattern and gives me compelling evidence to use it. Can someone please provide me with a 2nd grade (ok, maybe 5th grade) reason to use this pattern, what I would lose if I don't, and what I gain if I do?a

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• "date_part('epoch', now() at time zone 'UTC')" not the same time as "now() at time zone 'UTC'" in po

  - by sirlark

  I'm writing a web based front end to a database (PHP/Postgresql) in which I need to store various dates/times. The times are meant to be always be entered on the client side in the local time, and displayed in the local time too. For storage purposes, I store all dates/times as integers (UNIX timestamps) and normalised to UTC. One particular field has a restriction that the timestamp filled in is not allowed to be in the future, so I tried this with a database constraint... CONSTRAINT not_future CHECK (timestamp-300 <= date_part('epoch', now() at time zone 'UTC')) The -300 is to give 5 minutes leeway in case of slightly desynchronised times between browser and server. The problem is, this constraint always fails when submitting the current time. I've done testing, and found the following. In PostgreSQL client: SELECT now() -- returns correct local time SELECT date_part('epoch', now()) -- returns a unix timestamp at UTC (tested by feeding the value into the date function in PHP correcting for its compensation to my time zone) SELECT date_part('epoch', now() at time zone 'UTC') -- returns a unix timestamp at two time zone offsets west, e.g. I am at GMT+2, I get a GMT-2 timestamp. I've figured out obviously that dropping the "at time zone 'UTC'" will solve my problem, but my question is if 'epoch' is meant to return a unix timestamp which AFAIK is always meant to be in UTC, why would the 'epoch' of a time already in UTC be corrected? Is this a bug, or I am I missing something about the defined/normal behaviour here.

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• stop form during submission if it validates incorrectly

  - by muqman

  I am trying to use JavaScript to validate forms but if the form doesn't validate, I don't want the form to be sent to the "action" page. The validator: <script> function formSubmit() { document.getElementById("signup_form").submit(); var x=document.forms["signup_form"]["tname"].value; if (x==null || x=="") { alert("First name must be filled out"); return false; } } </script> The form itself: <form action="some_file.php" method="post" id="signup_form" name="signup_form" onsubmit="return formSubmit()"> But all this does is if the tname field empty, it will return an alert but as soon as the user hits ok, the form then redirects to some_file.php. What have I missed here? The submit button: <a href="" onclick="return formSubmit(); return false" class="purplebutton">Signup</a> So what have I missed? How do I avoid this in the future?

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• Can I create an activity for a particular task without that task coming to the foreground?

  - by Neil Traft

  Here's my use case: The app starts at a login screen. You enter your credentials and hit the "Login" button. Then a progress dialog appears and you wait for some stuff to download. Once the stuff has downloaded, you are taken to a new activity. Exactly which activity you are taken to depends on the server response. Here's my problem: If you go HOME during this login/download process, at some point in the near future your download will complete and will invoke startActivity(). So then the new activity will be pushed to the foreground, rudely interrupting the user. I can't start the activity before I start the download, because, as I mentioned earlier, the activity I start depends on the result of the download. I would obviously not like to interrupt the user like this. One way to solve this is to refrain from calling startActivity() until the user returns to the app. I can do this by keeping track of the LoginActivity's onStop() and onRestart(). But I'm wondering, is there any way to create the activity while it is in the background? That way the user returns to the app and he is ready to go... otherwise he would have to wait for the new activity to be created (which could take some time because the new activity also has to download and display some data). Update: Guess what? I LIED! I could have sworn that starting this activity was causing it to come to the foreground, but I went back to test it again and the problem has magically disappeared. I tested in both 1.6 and 2.0.1 and both OSes were smart enough not to bring a backgrounded task to the front.

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• What's the best practice for handling system-specific information under version control?

  - by Joe

  I'm new to version control, so I apologize if there is a well-known solution to this. For this problem in particular, I'm using git, but I'm curious about how to deal with this for all version control systems. I'm developing a web application on a development server. I have defined the absolute path name to the web application (not the document root) in two places. On the production server, this path is different. I'm confused about how to deal with this. I could either: Reconfigure the development server to share the same path as the production Edit the two occurrences each time production is updated. I don't like #1 because I'd rather keep the application flexible for any future changes. I don't like #2 because if I start developing on a second development server with a third path, I would have to change this for every commit and update. What is the best way to handle this? I thought of: Using custom keywords and variable expansion (such as setting the property $PATH$ in the version control properties and having it expanded in all the files). Git doesn't support this because it would be a huge performance hit. Using post-update and pre-commit hooks. Possibly the likely solution for git, but every time I looked at the status, it would report the two files as being changed. Not really clean. Pulling the path from a config file outside of version control. Then I would have to have the config file in the same location on all servers. Might as well just have the same path to begin with. Is there an easy way to deal with this? Am I over thinking it?

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• LINQ to SQL: NOTing a prebuilt expression

  - by ck

  I'm building a library of functions for one of my core L2S classes, all of which return a bool to allow checking for certain situations. Example: Expression<Func<Account, bool>> IsSomethingX = a => a.AccountSupplementary != null && a.AccountSupplementary.SomethingXFlag != null && a.AccountSupplementary.SomethingXFlag.Value; Now to query where this is not true, I CAN'T do this: var myAccounts= context.Accounts .Where(!IsSomethingX); // does not compile However, using the syntax from the PredicateBuilder class, I've come up with this: public static IQueryable<T> WhereNot<T>(this IQueryable<T> items, Expression<Func<T, bool>> expr1) { var invokedExpr = Expression.Invoke(expr1, expr1.Parameters.Cast<Expression>()); return items.Where(Expression.Lambda<Func<T, bool>> (Expression.Not(invokedExpr), expr1.Parameters)); } var myAccounts= context.Accounts .WhereNot(IsSomethingX); // does compile which actually produces the correct SQL. Does this look like a good solution, and is there anything I need to be aware of that might cause me problems in future?

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• Calculating collission for a moving circle, without overlapping the boundaries

  - by Robert Vella

  Let's say I have circle bouncing around inside a rectangular area. At some point this circle will collide with one of the surfaces of the rectangle and reflect back. The usual way I'd do this would be to let the circle overlap that boundary and then reflect the velocity vector. The fact that the circle actually overlaps the boundary isn't usually a problem, nor really noticeable at low velocity. At high velocity it becomes quite clear that the circle is doing something it shouldn't. What I'd like to do is to programmitically take reflection into account and place the circle at it's proper position before displaying it on the screen. This means that I have to calculate the point where it hits the boundary between it's current position and it's future position -- rather than calculating it's new position and then checking if it has hit the boundary. This is a little bit more complicated than the usual circle/rectangle collission problem. I have a vague idea of how I should do it -- basically create a bounding rectangle between the current position and the new position, which brings up a slew of problems of it's own (Since the rectangle is rotated according to the direction of the circle's velocity). However, I'm thinking that this is a common problem, and that a common solution already exists. Is there a common solution to this kind of problem? Perhaps some basic theories which I should look into?

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• Mixing stored procedures and ORM

  - by Jason

  The company I work for develops a large application which is almost entirely based on stored procedures. We use classic ASP and SQL Server and the major part of the business logic is contained inside those stored procedures. For example, (I know, this is bad...) a single stored procedure can be used for different purposes (insert, update, delete, make some calculations, ...). Most of the time, a stored procedure is used for operations on related tables, but this is not always the case. We are planning to move to ASP.NET in a near future. I have read a lot of posts on StackOverflow recommending that I move the business logic outside the database. The thing is, I have tried to convince the people who takes the decisions at our company and there is nothing I can do to change their mind. Since I want to be able to use the advantages of object-oriented programming, I want to map the tables to actual classes. So far, my solution is to use an ORM (Entity Framework 4 or nHibernate) to avoid mapping the objects manually (mostly to retrieve the data) and use some kind of Data Access Layer to call the existing stored procedures (for saving). I want your advice on this. Do you think it is a good solution? Any ideas?

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• Any techniques to interrupt, kill, or otherwise unwind (releasing synchronization locks) a single de

  - by gojomo

  I have a long-running process where, due to a bug, a trivial/expendable thread is deadlocked with a thread which I would like to continue, so that it can perform some final reporting that would be hard to reproduce in another way. Of course, fixing the bug for future runs is the proper ultimate resolution. Of course, any such forced interrupt/kill/stop of any thread is inherently unsafe and likely to cause other unpredictable inconsistencies. (I'm familiar with all the standard warnings and the reasons for them.) But still, since the only alternative is to kill the JVM process and go through a more lengthy procedure which would result in a less-complete final report, messy/deprecated/dangerous/risky/one-time techniques are exactly what I'd like to try. The JVM is Sun's 1.6.0_16 64-bit on Ubuntu, and the expendable thread is waiting-to-lock an object monitor. Can an OS signal directed to an exact thread create an InterruptedException in the expendable thread? Could attaching with gdb, and directly tampering with JVM data or calling JVM procedures allow a forced-release of the object monitor held by the expendable thread? Would a Thread.interrupt() from another thread generate a InterruptedException from the waiting-to-lock frame? (With some effort, I can inject an arbitrary beanshell script into the running system.) Can the deprecated Thread.stop() be sent via JMX or any other remote-injection method? Any ideas appreciated, the more 'dangerous', the better! And, if your suggestion has worked in personal experience in a similar situation, the best!

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• Is it theoretically possible to emulate a human brain on a computer?

  - by JoelK

  Our brain consists of billions of neurons which basically work with all the incoming data from our senses, handle our consciousness, emotions and creativity as well as our hormone system, etc. So I'm completely new to this topic but doesn't each neuron have a fixed function? E.g.: If a signal of strength x enters, if the last signal was x ms ago, redirect it. From what I've learned in biology about our nerves system which includes our brain because both consist of simple neurons, it seems to me as our brain is one big, complicated computer. Maybe so complicated that things such as intelligence and cognition become possible? As the most complicated things about a neuron pretty much are the chemical aspects on generating an electric singal, keeping itself alive, and eventually segmenting itself, it should be pretty easy emulating some on a computer, or? You won't have to worry about keeping your virtual neuron alive, or? If you can emulate a single neuron on a computer, which shouldn't be too hard, could you theoretically emulate more than 1000 billions of them, recreating intelligence, cognition and maybe even creativity? In my question I'm leaving out the following aspects: Speed of our current (super) computers Actually writing a program for emulating neurons I don't know much about this topic, please tell me if I got anything wrong :) (My secret goal: Make a copy of my brain and store it on some 10 million TB HDD and make someone start it up in the future)

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• Page URL and database organization.

  - by shurik2533

  I want that its name would be the page address. For example, if page has heading "Some Page", than its address should be http://somesite/some_page/. "some_page"-name generated by system automatically. "some_page" - is the unique identifier of page. The problem in that the user in the future can enter a name which already exists that will cause an error. It is necessary to find an optimum variant of the decision of a problem for great volumes of the data. I have solved a problem as follows: The page identifier in a database is the name of page and a suffix which is by default equal to zero. At page addition there is a check on existence. If such page does not exist, the suffix is equal 0 and its name is "some_page", if page is exist, than - search for the maximum number of a suffix and suffix=suffix+1 and page name become "some_page_1". For this I create in a database the compound key from fields "suffix" and "pageName": Table Pages suffix|pageName |pageTitle 0 |some_page |Some Page 1 |some_page |Some Page 0 |other_page|Other Page Addition of pages occurs through stored procedure: CREATE PROCEDURE addPage (pageNameVal VARCHAR(100), pageTitleVal VARCHAR(100)) BEGIN DECLARE v INT DEFAULT 0; SELECT MAX(suffix) FROM pages WHERE pageName=pageNameVal INTO v; IF v >= 0 THEN SET v = v + 1; ELSE SET v = 0; END IF; INSERT INTO pages (suffix, pageName) VALUES (pageNameVal, v, pageTitleVal); END; Whether there are more the best decisions?

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• strtotime not working with TIME?

  - by Prashant

  My mysql column has this datetime value, 2011-04-11 11:00:00 when I am applying strtotime then its returning date less than today,whereas it should be greater than today. also when I am trying this strtotime(date('d/m/Y h:i A')); code, its returning wrong values. Is there any problem with giving TIME in strtotime? Basically I want to do, is to compare my mysql column date with today's date, if its in future then show "Upcoming" else show nothing? Please help and advise, what should I do? Edited code $_startdatetime = $rs['startdatetime']; $_isUpcoming = false; if(!empty($_startdatetime)){ $TEMP_strtime = strtotime($_startdatetime); $TEMP_strtime_today = strtotime(date('d/m/Y h:i A')); if($TEMP_strtime_today < $TEMP_strtime){ $_isUpcoming = true; $_startdatetime = date('l, d F, Y h:i A' ,$TEMP_strtime); } } And the value in $rs['startdatetime'] is 2011-04-11 11:00:00. And with this value I am getting following output. $TEMP_strtime - 1302519600 $TEMP_strtime_today - 1314908160 $_startdatetime - 2011-04-11 11:00:00 $_startdatetime its value is not formatted as the upcoming condition is false, so returning as is mysql value.

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• Why do I get this exception? {An item with the same key has already been added."})

  - by Alan

  Aknittel NewSellerID is the result of a lookup on tblSellers. These tables (tblSellerListings and tblSellers) are not "officially" joined with a foreign key relationship, either in the model or in the database, but I want some referential integrity maintained for the future. So my issue remains. Why do I get the exception ({"An item with the same key has already been added."}) with this code, if I don't begin each iteration of the foreach loop with a new ObjectContext and end it with SaveChanges, which I think will affect performance. Also, could you tell me why ORCSolutionsDataService.tblSellerListings (An ADO.NET DataServices/WCF object is not IDisposable, like LINQ to Entities?? ============================================== // Add listings to previous seller int NewSellerID = 0; // Look up existing Seller key using SellerUniqueEBAYID var qryCurrentSeller = from s in service.tblSellers where s.SellerEBAYUserID == SellerUserID select s; foreach (var s in qryCurrentSeller) NewSellerID = s.SellerID; // Save the selected listings for this seller foreach (DataGridViewRow dgr in dgvRows) { ORCSolutionsDataService.tblSellerListings NewSellerListing = new ORCSolutionsDataService.tblSellerListings(); NewSellerListing.ItemID = dgr.Cells["txtSellerItemID"].Value.ToString(); NewSellerListing.Title = dgr.Cells["txtSellerItemTitle"].Value.ToString(); NewSellerListing.CurrentPrice = Convert.ToDecimal(dgr.Cells["txtSellerItemPrice"].Value); NewSellerListing.QuantitySold = Convert.ToInt32(dgr.Cells["txtSellerItemSold"].Value); NewSellerListing.EndTime = Convert.ToDateTime(dgr.Cells["txtSellerItemEnds"].Value); NewSellerListing.CategoryName = dgr.Cells["txtSellerItemCategory"].Value.ToString(); NewSellerListing.ExtendedPrice = Convert.ToDecimal(dgr.Cells["txtExtendedReceipts"].Value); NewSellerListing.RetrievedDtime = Convert.ToDateTime(dtSellerDataRetrieved.ToString()); NewSellerListing.SellerID = NewSellerID; service.AddTotblSellerListings(NewSellerListing); } service.SaveChanges(); } catch (Exception ex) { MessageBox.Show("Unable to add a new case. Exception: " + ex.Message); }

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• Ordering z-indexes in an array

  - by Tom Gullen

  I have an array which looks something along the lines of resourceData[0][0] = "pic1.jpg"; resourceData[0][1] = 5; resourceData[1][0] = "pic2.jpg"; resourceData[1][1] = 2; resourceData[2][0] = "pic3.jpg"; resourceData[2][1] = 900; resourceData[3][0] = "pic4.jpg"; resourceData[3][1] = 1; The numeric represents the z-index of the image. Minimum z-index value is 1. Maximum (not really important) is 2000. I have all the rendering and setting z-indexes done fine. My question is, I want to have four functions: // Brings image to z front function bringToFront(resourceIndex) { // Set z-index to max + 1 resourceData[resourceIndex][1] = getBiggestZindex() + 1; // Change CSS property of image to bring to front $('#imgD' + resourceIndex).css("z-index", resourceData[resourceIndex][1]); } function bringUpOne(resourceIndex) { } function bringDownOne(resourceIndex) { } // Send to back z function sendToBack(resourceIndex) { } So given then index [3] (900 z): If we send it to the back, it will take the value 1, and [3] will have to go to 2, but that conflicts with [1] who has a 2 z-index so they need to go to three etc. Is there an easy programatical way of doing this because as soon as I start doing this it's going to get messy. It's important that the indexes of the array don't change. We can't sort the array unfortunately due to design. Update Thanks for answers, I'll post the functions here once they are written incase anyone comes across this in the future (note this code has zindex listed in [6]) // Send to back z function sendToBack(resourceIndex) { resourceData[resourceIndex][6] = 1; $('#imgD' + resourceIndex).css("z-index", 1); for (i = 0; i < resourceData.length; i++) { if (i != resourceIndex) { resourceData[i][6]++; $('#imgD' + i).css("z-index", resourceData[i][6]); } } }

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• Entities used to serialize data have changed. How can the serialized data be upgraded for the new entities?

  - by i8abug

  Hi, I have a bunch of simple entity instances that I have serialized to a file. In the future, I know that the structure of these entities (ie, maybe I will rename Name to Header or something). The thing is, I don't want to lose the data that I have saved in all these old files. What is the proper way to either load the data from the old entities into new entities upgrade the old files so that they can be used with new entities Note: I think I am stuck with binary serialization, not xml serialization. Thanks in advance! Edit: So I have an answer for the case I have described. I can use a dataContractSerializer and do something like [DataMember("bar")] private string foo; and change the name in the code and keep the same name that was used for serialization. But what about the following additional cases: The original entity has new members which can be serialized Some serialized members that were in the original entity are removed Some members have actually changed in function (suppose that the original class had a FirstName and LastName member and it has been refactored to have only a FullName member which combines the two) To handle these, I need some sort of interpreter/translator deserialization class but I have no idea what I should use

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• Problem accessing private variables in jQuery like chainable design pattern

  - by novogeek

  Hi folks, I'm trying to create my custom toolbox which imitates jQuery's design pattern. Basically, the idea is somewhat derived from this post: http://stackoverflow.com/questions/2061501/jquery-plugin-design-pattern-common-practice-for-dealing-with-private-function (Check the answer given by "David"). So here is my toolbox function: (function(window){ var mySpace=function(){ return new PrivateSpace(); } var PrivateSpace=function(){ var testCache={}; }; PrivateSpace.prototype={ init:function(){ console.log('init this:', this); return this; }, ajax:function(){ console.log('make ajax calls here'); return this; }, cache:function(key,selector){ console.log('cache selectors here'); testCache[key]=selector; console.log('cached selector: ',testCache); return this; } } window.hmis=window.m$=mySpace(); })(window) Now, if I execute this function like: console.log(m$.cache('firstname','#FirstNameTextbox')); I get an error 'testCache' is not defined. I'm not able to access the variable "testCache" inside my cache function of the prototype. How should I access it? Basically, what I want to do is, I want to cache all my jQuery selectors into an object and use this object in the future.

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• Need help/guidance about creating a desktop application with gui

  - by Somebody still uses you MS-DOS

  I'm planning to do an Desktop application using Python, to learn some Desktop concepts. I'm going to use GTK or Qt, I still haven't decided which one. Fact is: I would like to create an application with the possibility to be called from command line, AND using a GUI. So it would be useful for cmd fans, and GUI users as well. It would be interesting to create a web interface too in the future, so it could be run in a server somewhere using an html interface created with a template language. I'm thinking about two approaches: - Creating a "model" with a simple interface which is called from a desktop/web implementation; - Creating a "model" with an html interface, and embeb a browser component so I could reuse all the code in both desktop/web scenarios. My question is: which exactly concepts are involved in this project? What advantages/disadvantages each approach has? Are they possible? By naming "interface", I'm planning to just do some interfaces.py files with def calls. Is this a bad approach? I would like to know some book recommendations, or resources to both options - or source code from projects which share the same GUI/cmd/web goals I'm after. Thanks in advance!

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• Using the XElement.Elements method, can I find elements with wildcard namespace but the same name?

  - by gav

  Hi All, Trying to do a simple parse of an XML document. What's the easiest way to pull out the two PropertyGroups below? <Project ToolsVersion="4.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003"> <PropertyGroup xmlns="http://schemas.microsoft.com/developer/msbuild/2003"> 1 </PropertyGroup> <PropertyGroup xmlns="http://schemas.microsoft.com/developer/msbuild/2003"> 2 </PropertyGroup> </Project> I have been trying to use XElement.Elements(XName) but to do so I need to prefix PropertyGroup with the xmlns. The issue is that I don't care about the name space and if it changes in future I would still like all PropertyGroups to be retrieved. var xml = XElement.Load(fileNameWithPath); var nameSpace = xml.GetDefaultNamespace(); var propertyGroups= xml.Elements(nameSpace + "PropertyGroup"); Can you improve on this code such that I don't need to prepend with nameSpace? I know I can essentially just reimplement the Elements method but I was hoping there was some way to pass a wildcard namespace? Thanks, Gavin

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• Why use Entity Framework over Linq2SQL if...

  - by Refracted Paladin

  To be clear, I am not asking for a side by side comparision which has already been asked Ad Nauseum here on SO. I am also Not asking if Linq2Sql is dead as I don't care. What I am asking is this.... I am building internal apps only for a non-profit organization. I am the only developer on staff. We ALWAYS use SQL Server as our Database backend. I design and build the Databases as well. I have used L2S successfully a couple of times already. Taking all this into consideration can someone offer me a compelling reason that I should use EF instead of L2S? I was at Code Camp this weekend and after an hour long demonstration on EF, all of which I could have done in L2S, I asked this same question. The speakers answer was, "L2S is dead..." Very well then! NOT! (see here) I understand EF is what MS WANTS us to use in the future(see here) and that it offers many more customization options. What I can't figure out is if any of that should, or does, matter for me in this environment. One particular issue we have here is that I inherited the Core App which was built on 4 different SQL Data bases. L2S has great difficulty with this but when I asked the aforementioned speaker if EF would help me in this regard he said "No!"

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• Google calendar query returns at most 25 entries

  - by Dean Hill

  I'm trying to delete all calendar entries from today forward. I run a query then call getEntries() on the query result. getEntries() always returns 25 entries (or less if there are fewer than 25 entries on the calendar). Why aren't all the entries returned? I'm expecting about 80 entries. As a test, I tried running the query, deleting the 25 entries returned, running the query again, deleting again, etc. This works, but there must be a better way. Below is the Java code that only runs the query once. CalendarQuery myQuery = new CalendarQuery(feedUrl); DateFormat dfGoogle = new SimpleDateFormat("yyyy-MM-dd'T00:00:00'"); Date dt = Calendar.getInstance().getTime(); myQuery.setMinimumStartTime(DateTime.parseDateTime(dfGoogle.format(dt))); // Make the end time far into the future so we delete everything myQuery.setMaximumStartTime(DateTime.parseDateTime("2099-12-31T23:59:59")); // Execute the query and get the response CalendarEventFeed resultFeed = service.query(myQuery, CalendarEventFeed.class); // !!! This returns 25 (or less if there are fewer than 25 entries on the calendar) !!! int test = resultFeed.getEntries().size(); // Delete all the entries returned by the query for (int j = 0; j < resultFeed.getEntries().size(); j++) { CalendarEventEntry entry = resultFeed.getEntries().get(j); entry.delete(); } PS: I've looked at the Data API Developer's Guide and the Google Data API Javadoc. These sites are okay, but not great. Does anyone know of additional Google API documentation?

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• What do I do about a Java program that spawned two instaces of itself?

  - by user288915

  I have a java JAR file that is triggered by a SQL server job. It's been running successfully for months. The process pulls in a structured flat file to a staging database then pushes that data into an XML file. However yesterday the process was triggered twice at the same time. I can tell from a log file that gets created, it looks like the process ran twice simultaneously. This caused a lot of issues and the XML file that it kicked out was malformed and contained duplicate nodes etc. My question is, is this a known issue with Java JVM's spawning multiple instances of itself? Or should I be looking at sql server as the culprit? I'm looking into 'socket locking' or file locking to prevent multiple instances in the future. This is the first instance of this issue that I've ever heard of. More info: The job is scheduled to run every minute. The job triggers a .bat file that contains the java.exe - jar filename.jar The java program runs, scans a directory for a file and then executes a loop to process if the file if it finds one. After it processes the file it runs another loop that kicks out XML messages. I can provide code samples if that would help. Thank you, Kevin

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• Should core application configuration be stored in the database, and if so what should be done to se

  - by Rl

  I'm writing an application around a lot of hierarchical data. Currently the hierarchy is fixed, but it's likely that new items will be added to the hierarchy in the future. (please let them be leaves) My current application and database design is fairly generic and nothing dealing with specific nodes in the hierarchy is hardcoded, with the exception of validation and lookup functions written to retrieve external data from each node's particular database. This pleases me from a design point of view, but I'm nervous at the realization that the entire application rests on a handful of records in the database. I'm also frustrated that I have to enforce certain aspects of data integrity with database triggers rather than by foreign key constraints (an example is where several different nodes in the hierarchy have their own proprietary IDs and I store them in a single column which, when coupled with the node ID can be used to locate the foreign data). I'm starting to wonder whether it may have been appropriate to simply hardcoded these known nodes into the system so that it would be more "type safe" and less generic. How does one know when something should be hardcoded, and when it should be a configuration item? Is it just a cost-benefit analysis of clarity/safety now vs less work later, or am I missing some metric I should be using to determine whether or not this is appropriate. The steps I'm taking to protect these valuable configurations are to add triggers that prevent updates/deletes. The database user that this application uses will only have the ability to manipulate data through stored procedures. What else can I do?

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• Fastest reliable way for Clojure (Java) and Ruby apps to communicate

  - by jkndrkn

  Hi There, We have cloud-hosted (RackSpace cloud) Ruby and Java apps that will interact as follows: Ruby app sends a request to Java app. Request consists of map structure containing strings, integers, other maps, and lists (analogous to JSON). Java app analyzes data and sends reply to Ruby App. We are interested in evaluating both messaging formats (JSON, Buffer Protocols, Thrift, etc.) as well as message transmission channels/techniques (sockets, message queues, RPC, REST, SOAP, etc.) Our criteria: Short round-trip time. Low round-trip-time standard deviation. (We understand that garbage collection pauses and network usage spikes can affect this value). High availability. Scalability (we may want to have multiple instances of Ruby and Java app exchanging point-to-point messages in the future). Ease of debugging and profiling. Good documentation and community support. Bonus points for Clojure support. What combination of message format and transmission method would you recommend? Why? I've gathered here some materials we have already collected for review: Comparison of various java serialization options Comparison of Thrift and Protocol Buffers (old) Comparison of various data interchange formats Comparison of Thrift and Protocol Buffers Fallacies of Protocol Buffers RPC features Discussion of RPC in the context of AMQP (Message-Queueing) Comparison of RPC and message-passing in distributed systems (pdf) Criticism of RPC from perspective of message-passing fan Overview of Avro from Ruby programmer perspective

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• Database (and ORM) choice for an small-medium size .NET Application

  - by jim

  I have a requirement to develop a .NET-based application whose data requirements are likely to exceed the 4 gig limit of SQL 2005 Express Edition. There may be other customers of the same application (in the future) with a requirement to use a specific DB platform (such as Oracle or SQL Server) due to in-house DBA expertise. Questions What RDBMS would you guys recommend? From the looks of it the major choices are PostGreSQL, MySQL or FireBird. I've only got experience of MYSQL from these. Which ORM tool (if any) would you recommend using - ideally one that can be swapped out between DB platforms with minimal effort? I like the look of the entity framework but unsure as to the degree to which platforms other than SQL Server are supported. If it helps, we'll be using the 3.5 version of the Framework. I'm open to the idea of using a tool such as NHibernate. On the other hand, if it's going to be easier, I'm happy to write my own stored procedures / DAL code - there won't be that many tables (perhaps 30-35).

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• Type-safe generic data structures in plain-old C?

  - by Bradford Larsen

  I have done far more C++ programming than "plain old C" programming. One thing I sorely miss when programming in plain C is type-safe generic data structures, which are provided in C++ via templates. For sake of concreteness, consider a generic singly linked list. In C++, it is a simple matter to define your own template class, and then instantiate it for the types you need. In C, I can think of a few ways of implementing a generic singly linked list: Write the linked list type(s) and supporting procedures once, using void pointers to go around the type system. Write preprocessor macros taking the necessary type names, etc, to generate a type-specific version of the data structure and supporting procedures. Use a more sophisticated, stand-alone tool to generate the code for the types you need. I don't like option 1, as it is subverts the type system, and would likely have worse performance than a specialized type-specific implementation. Using a uniform representation of the data structure for all types, and casting to/from void pointers, so far as I can see, necessitates an indirection that would be avoided by an implementation specialized for the element type. Option 2 doesn't require any extra tools, but it feels somewhat clunky, and could give bad compiler errors when used improperly. Option 3 could give better compiler error messages than option 2, as the specialized data structure code would reside in expanded form that could be opened in an editor and inspected by the programmer (as opposed to code generated by preprocessor macros). However, this option is the most heavyweight, a sort of "poor-man's templates". I have used this approach before, using a simple sed script to specialize a "templated" version of some C code. I would like to program my future "low-level" projects in C rather than C++, but have been frightened by the thought of rewriting common data structures for each specific type. What experience do people have with this issue? Are there good libraries of generic data structures and algorithms in C that do not go with Option 1 (i.e. casting to and from void pointers, which sacrifices type safety and adds a level of indirection)?

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