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  • Good JDBC pattern

    - by Java Developer
    What is the good practice for database operation in Java application? Do you construct the DML syntax in the Java code and send the statements to DB engine for execution, or you just collect the parameters and then make a call to stored procedure with the parameters via java code? or neither because that's just not how to do it? can anyone give an example of a full database utility classes to do database operations in Java app? also what about the transaction manager? My assignment is to make database operation that is modular in Java. Thanks

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  • how to use sed/awk to remove words with multiple pattern count

    - by user1461112
    I have a file of string records where one of the fields - delimited by "," - can contain one or more "-" inside it. The goal is to delete the field value if it contains more than two "-". i am trying to recoup my past knowledge of sed/awk but can't make much headway ========== info,whitepaper,Data-Centers,yes-the-6-top-problems-in-your-data-center-lane info,whitepaper,Data-Centers,the-evolution-center info,whitepaper,Data-Centers,the-evolution-of-lan-technology-lanner ========== expected outcome: info,whitepaper,Data-Centers info,whitepaper,Data-Centers,the-evolution-center info,whitepaper,Data-Centers thanks

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  • windows stdbool.h for python module

    - by swasheck
    I found this http://stackoverflow.com/questions/25461/stdbool-h-c as an answer to "where is stdbool.h on windows?" but now need to know what to do with it. I'm actually trying to install the lazyboy python extension on windows and this is the first error that I'm receiving. So, being completely unfamiliar with this, where do I put this header file so that it's seen?

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  • Code maintenance: keeping a bad pattern when extending new code for being consistent or not ?

    - by Guillaume
    I have to extend an existing module of a project. I don't like the way it has been done (lots of anti-pattern involved, like copy/pasted code). I don't want to perform a complete refactor. Should I: create new methods using existing convention, even if I feel it wrong, to avoid confusion for the next maintainer and being consistent with the code base? or try to use what I feel better even if it is introducing another pattern in the code ? Precison edited after first answers: The existing code is not a mess. It is easy to follow and understand. BUT it is introducing lots of boilerplate code that can be avoided with good design (resulting code might become harder to follow then). In my current case it's a good old JDBC (spring template inboard) DAO module, but I have already encounter this dilemma and I'm seeking for other dev feedback. I don't want to refactor because I don't have time. And even with time it will be hard to justify that a whole perfectly working module needs refactoring. Refactoring cost will be heavier than its benefits. Remember: code is not messy or over-complex. I can not extract few methods there and introduce an abstract class here. It is more a flaw in the design (result of extreme 'Keep It Stupid Simple' I think) So the question can also be asked like that: You, as developer, do you prefer to maintain easy stupid boring code OR to have some helpers that will do the stupid boring code at your place ? Downside of the last possibility being that you'll have to learn some stuff and maybe you will have to maintain the easy stupid boring code too until a full refactoring is done)

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  • How to resolve "dpkg: error processing /var/cache/apt/archives/python-apport_2.0.1-0ubuntu9_all.deb"?

    - by raz7588
    Update Manager will not update although I have over 100 updates to do I get a error message like this: installArchives() failed: Extracting templates from packages: 29%% Extracting templates from packages: 58%% Extracting templates from packages: 88%% Extracting templates from packages: 100%% Preconfiguring packages ... Extracting templates from packages: 29%% Extracting templates from packages: 58%% Extracting templates from packages: 88%% Extracting templates from packages: 100%% Preconfiguring packages ... Extracting templates from packages: 29%% Extracting templates from packages: 58%% Extracting templates from packages: 88%% Extracting templates from packages: 100%% Preconfiguring packages ... Extracting templates from packages: 29%% Extracting templates from packages: 58%% Extracting templates from packages: 88%% Extracting templates from packages: 100%% Preconfiguring packages ... (Reading database ... (Reading database ... 5%% (Reading database ... 10%% (Reading database ... 15%% (Reading database ... 20%% (Reading database ... 25%% (Reading database ... 30%% (Reading database ... 35%% (Reading database ... 40%% (Reading database ... 45%% (Reading database ... 50%% (Reading database ... 55%% (Reading database ... 60%% (Reading database ... 65%% (Reading database ... 70%% (Reading database ... 75%% (Reading database ... 80%% (Reading database ... 85%% (Reading database ... 90%% (Reading database ... 95%% (Reading database ... 100%% (Reading database ... 189751 files and directories currently installed.) Preparing to replace python-problem-report 2.0.1-0ubuntu7 (using .../python-problem-report_2.0.1-0ubuntu9_all.deb) ... Traceback (most recent call last): File "/usr/bin/pyclean", line 33, in <module> from debpython.namespace import add_namespace_files ValueError: bad marshal data (unknown type code) dpkg: warning: subprocess old pre-removal script returned error exit status 1 dpkg - trying script from the new package instead ... Traceback (most recent call last): File "/usr/bin/pyclean", line 33, in <module> from debpython.namespace import add_namespace_files ValueError: bad marshal data (unknown type code) dpkg: error processing /var/cache/apt/archives/python-problem-report_2.0.1-0ubuntu9_all.deb (--unpack): subprocess new pre-removal script returned error exit status 1 No apport report written because MaxReports is reached already Traceback (most recent call last): File "/usr/bin/pycompile", line 39, in <module> from debpython.namespace import add_namespace_files ValueError: bad marshal data (unknown type code) dpkg: error while cleaning up: subprocess installed post-installation script returned error exit status 1 Preparing to replace python-apport 2.0.1-0ubuntu7 (using .../python-apport_2.0.1-0ubuntu9_all.deb) ... Traceback (most recent call last): File "/usr/bin/pyclean", line 33, in <module> from debpython.namespace import add_namespace_files ValueError: bad marshal data (unknown type code) dpkg: warning: subprocess old pre-removal script returned error exit status 1 dpkg - trying script from the new package instead ... Traceback (most recent call last): File "/usr/bin/pyclean", line 33, in <module> from debpython.namespace import add_namespace_files ValueError: bad marshal data (unknown type code) dpkg: error processing /var/cache/apt/archives/python-apport_2.0.1-0ubuntu9_all.deb (--unpack): subprocess new pre-removal script returned error exit status 1 No apport report written because MaxReports is reached already Traceback (most recent call last): File "/usr/bin/pycompile", line 39, in <module> from debpython.namespace import add_namespace_files ValueError: bad marshal data (unknown type code) dpkg: error while cleaning up: subprocess installed post-installation script returned error exit status 1 Preparing to replace apport 2.0.1-0ubuntu7 (using .../apport_2.0.1-0ubuntu9_all.deb) ... apport stop/waiting Traceback (most recent call last): File "/usr/bin/pyclean", line 33, in <module> from debpython.namespace import add_namespace_files ValueError: bad marshal data (unknown type code) dpkg: warning: subprocess old pre-removal script returned error exit status 1 dpkg - trying script from the new package instead ... Traceback (most recent call last): File "/usr/bin/pyclean", line 33, in <module> from debpython.namespace import add_namespace_files ValueError: bad marshal data (unknown type code) dpkg: error processing /var/cache/apt/archives/apport_2.0.1-0ubuntu9_all.deb (--unpack): subprocess new pre-removal script returned error exit status 1 No apport report written because MaxReports is reached already apport start/running Traceback (most recent call last): File "/usr/bin/pycompile", line 39, in <module> from debpython.namespace import add_namespace_files ValueError: bad marshal data (unknown type code) dpkg: error while cleaning up: subprocess installed post-installation script returned error exit status 1 Preparing to replace gnome-orca 3.4.1-0ubuntu0.1 (using .../gnome-orca_3.4.2-0ubuntu0.1_all.deb) ... Traceback (most recent call last): File "/usr/bin/pyclean", line 33, in <module> from debpython.namespace import add_namespace_files ValueError: bad marshal data (unknown type code) dpkg: warning: subprocess old pre-removal script returned error exit status 1 dpkg - trying script from the new package instead ... Traceback (most recent call last): File "/usr/bin/pyclean", line 33, in <module> from debpython.namespace import add_namespace_files ValueError: bad marshal data (unknown type code) dpkg: error processing /var/cache/apt/archives/gnome-orca_3.4.2-0ubuntu0.1_all.deb (--unpack): subprocess new pre-removal script returned error exit status 1 No apport report written because MaxReports is reached already Traceback (most recent call last): File "/usr/bin/pycompile", line 39, in <module> from debpython.namespace import add_namespace_files ValueError: bad marshal data (unknown type code) dpkg: error while cleaning up: subprocess installed post-installation script returned error exit status 1 Preparing to replace python-piston-mini-client 0.7.2-0ubuntu1 (using .../python-piston-mini-client_0.7.2+bzr57-0ubuntu1_all.deb) ... Traceback (most recent call last): File "/usr/bin/pyclean", line 33, in <module> from debpython.namespace import add_namespace_files ValueError: bad marshal data (unknown type code) dpkg: warning: subprocess old pre-removal script returned error exit status 1 dpkg - trying script from the new package instead ... Traceback (most recent call last): File "/usr/bin/pyclean", line 33, in <module> from debpython.namespace import add_namespace_files ValueError: bad marshal data (unknown type code) dpkg: error processing /var/cache/apt/archives/python-piston-mini-client_0.7.2+bzr57-0ubuntu1_all.deb (--unpack): subprocess new pre-removal script returned error exit status 1 No apport report written because MaxReports is reached already Traceback (most recent call last): File "/usr/bin/pycompile", line 39, in <module> from debpython.namespace import add_namespace_files ValueError: bad marshal data (unknown type code) dpkg: error while cleaning up: subprocess installed post-installation script returned error exit status 1 Preparing to replace oneconf 0.2.8 (using .../oneconf_0.2.8.1_all.deb) ... Traceback (most recent call last): File "/usr/bin/pyclean", line 33, in <module> from debpython.namespace import add_namespace_files ValueError: bad marshal data (unknown type code) dpkg: warning: subprocess old pre-removal script returned error exit status 1 dpkg - trying script from the new package instead ... Traceback (most recent call last): File "/usr/bin/pyclean", line 33, in <module> from debpython.namespace import add_namespace_files ValueError: bad marshal data (unknown type code) dpkg: error processing /var/cache/apt/archives/oneconf_0.2.8.1_all.deb (--unpack): subprocess new pre-removal script returned error exit status 1 No apport report written because MaxReports is reached already Traceback (most recent call last): File "/usr/bin/pycompile", line 39, in <module> from debpython.namespace import add_namespace_files ValueError: bad marshal data (unknown type code) dpkg: error while cleaning up: subprocess installed post-installation script returned error exit status 1 Preparing to replace software-center 5.2.2 (using .../software-center_5.2.2.2_all.deb) ... Traceback (most recent call last): File "/usr/bin/pyclean", line 33, in <module> from debpython.namespace import add_namespace_files ValueError: bad marshal data (unknown type code) dpkg: warning: subprocess old pre-removal script returned error exit status 1 dpkg - trying script from the new package instead ... Traceback (most recent call last): File "/usr/bin/pyclean", line 33, in <module> from debpython.namespace import add_namespace_files ValueError: bad marshal data (unknown type code) dpkg: error processing /var/cache/apt/archives/software-center_5.2.2.2_all.deb (--unpack): subprocess new pre-removal script returned error exit status 1 No apport report written because MaxReports is reached already Traceback (most recent call last): File "/usr/bin/pycompile", line 39, in <module> from debpython.namespace import add_namespace_files ValueError: bad marshal data (unknown type code) dpkg: error while cleaning up: subprocess installed post-installation script returned error exit status 1 Preparing to replace libglade2-0 1:2.6.4-1ubuntu1 (using .../libglade2-0_1%%3a2.6.4-1ubuntu1.1_amd64.deb) ... Unpacking replacement libglade2-0 ... Preparing to replace libv4l-0 0.8.6-1ubuntu1 (using .../libv4l-0_0.8.6-1ubuntu2_amd64.deb) ... De-configuring libv4l-0:i386 ... Unpacking replacement libv4l-0 ... Preparing to replace libv4l-0:i386 0.8.6-1ubuntu1 (using .../libv4l-0_0.8.6-1ubuntu2_i386.deb) ... Unpacking replacement libv4l-0:i386 ... Preparing to replace libv4lconvert0:i386 0.8.6-1ubuntu1 (using .../libv4lconvert0_0.8.6-1ubuntu2_i386.deb) ... De-configuring libv4lconvert0 ... Unpacking replacement libv4lconvert0:i386 ... Preparing to replace libv4lconvert0 0.8.6-1ubuntu1 (using .../libv4lconvert0_0.8.6-1ubuntu2_amd64.deb) ... Unpacking replacement libv4lconvert0 ... Errors were encountered while processing: /var/cache/apt/archives/python-problem-report_2.0.1-0ubuntu9_all.deb /var/cache/apt/archives/python-apport_2.0.1-0ubuntu9_all.deb /var/cache/apt/archives/apport_2.0.1-0ubuntu9_all.deb /var/cache/apt/archives/gnome-orca_3.4.2-0ubuntu0.1_all.deb /var/cache/apt/archives/python-piston-mini-client_0.7.2+bzr57-0ubuntu1_all.deb /var/cache/apt/archives/oneconf_0.2.8.1_all.deb /var/cache/apt/archives/software-center_5.2.2.2_all.deb Error in function: SystemError: E:Sub-process /usr/bin/dpkg returned an error code (1) Setting up libglade2-0 (1:2.6.4-1ubuntu1.1) ... dpkg: error processing gnome-orca (--configure): Package is in a very bad inconsistent state - you should reinstall it before attempting configuration. dpkg: error processing python-problem-report (--configure): Package is in a very bad inconsistent state - you should reinstall it before attempting configuration. Setting up libv4lconvert0 (0.8.6-1ubuntu2) ... Setting up libv4lconvert0:i386 (0.8.6-1ubuntu2) ... dpkg: error processing python-piston-mini-client (--configure): Package is in a very bad inconsistent state - you should reinstall it before attempting configuration. Setting up libv4l-0 (0.8.6-1ubuntu2) ... Setting up libv4l-0:i386 (0.8.6-1ubuntu2) ... dpkg: dependency problems prevent configuration of python-apport: python-apport depends on python-problem-report (>= 0.94); however: Package python-problem-report is not configured yet. dpkg: error processing python-apport (--configure): dependency problems - leaving unconfigured dpkg: dependency problems prevent configuration of software-center: software-center depends on python-piston-mini-client (>= 0.1+bzr29); however: Package python-piston-mini-client is not configured yet. dpkg: error processing software-center (--configure): dependency problems - leaving unconfigured dpkg: dependency problems prevent configuration of oneconf: oneconf depends on python-piston-mini-client (>= 0.3+bzr32-0ubuntu1); however: Package python-piston-mini-client is not configured yet. dpkg: error processing oneconf (--configure): dependency problems - leaving unconfigured dpkg: dependency problems prevent configuration of apport: apport depends on python-apport (>= 2.0.1-0ubuntu7); however: Package python-apport is not configured yet. dpkg: error processing apport (--configure): dependency problems - leaving unconfigured Processing triggers for libc-bin ... ldconfig deferred processing now taking place This has been going on for two weeks now and I cannot get any updates. Any help would be great.

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  • Time to start returning IQueryable<T> instead of IList<T> to my Web UI / Web API Layer?

    - by JohnnyO
    I've got a multi-layer application that starts with the repository pattern for all data access and it returns IQueryable to the Services layer. The Services layer, which includes all of the business logic, returns IList to the Controllers (note: I'm using ASP.NET MVC for the UI layer). The benefit of returning IQueryable in the data access layer is that it allows my repositories to be extremely simple and the database queries to be deferred. However, I'm triggering the database queries in my services layer so that my unit tests is more reliable and I don't give flexibility to the Controllers to reshape my queries. However, I've recently encountered several situations where deferring the execution of queries down to the Controllers would have been significantly more performant because the Controllers had to do some projections on the data that was UI specific. Additionally, with the emergence of things like oData, I was starting to wonder if end points (e.g. web UI or web apis) should be working directly with IQueryable. What are your thoughts? Is it time to start returning IQueryable from the services layer to the UI layer? Or stick with IList? This thread here: http://stackoverflow.com/questions/718624/to-return-iqueryablet-or-not-return-iqueryablet seems to vouch for returning IList to the UI layers, but I was wondering if things are changing because of new emerging technologies and techniques.

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  • EntityFramework repository template- how to write GetByID lamba within a template class?

    - by FerretallicA
    I am trying to write a generic one-size-fits-most repository pattern template class for an Entity Framework-based project I'm currently working on. The (heavily simplified) interface is: internal interface IRepository<T> where T : class { T GetByID(int id); IEnumerable<T> GetAll(); IEnumerable<T> Query(Func<T, bool> filter); } GetByID is proving to be the killer. In the implementation: public class Repository<T> : IRepository<T>,IUnitOfWork<T> where T : class { // etc... public T GetByID(int id) { return this.ObjectSet.Single<T>(t=>t.ID == id); } t=t.ID == id is the particular bit I'm struggling with. Is it even possible to write lamba functions like that within template classes where no class-specific information is going to be available?

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  • Should a Perl constructor return an undef or a "invalid" object?

    - by DVK
    Question: What is considered to be "Best practice" - and why - of handling errors in a constructor?. "Best Practice" can be a quote from Schwartz, or 50% of CPAN modules use it, etc...; but I'm happy with well reasoned opinion from anyone even if it explains why the common best practice is not really the best approach. As far as my own view of the topic (informed by software development in Perl for many years), I have seen three main approaches to error handling in a perl module (listed from best to worst in my opinion): Construct an object, set an invalid flag (usually "is_valid" method). Often coupled with setting error message via your class's error handling. Pros: Allows for standard (compared to other method calls) error handling as it allows to use $obj->errors() type calls after a bad constructor just like after any other method call. Allows for additional info to be passed (e.g. 1 error, warnings, etc...) Allows for lightweight "redo"/"fixme" functionality, In other words, if the object that is constructed is very heavy, with many complex attributes that are 100% always OK, and the only reason it is not valid is because someone entered an incorrect date, you can simply do "$obj->setDate()" instead of the overhead of re-executing entire constructor again. This pattern is not always needed, but can be enormously useful in the right design. Cons: None that I'm aware of. Return "undef". Cons: Can not achieve any of the Pros of the first solution (per-object error messages outside of global variables and lightweight "fixme" capability for heavy objects). Die inside the constructor. Outside of some very narrow edge cases, I personally consider this an awful choice for too many reasons to list on the margins of this question. UPDATE: Just to be clear, I consider the (otherwise very worthy and a great design) solution of having very simple constructor that can't fail at all and a heavy initializer method where all the error checking occurs to be merely a subset of either case #1 (if initializer sets error flags) or case #3 (if initializer dies) for the purposes of this question. Obviously, choosing such a design, you automatically reject option #2.

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  • refactor LINQ TO SQL custom properties that instantiate datacontext

    - by Thiago Silva
    I am working on an existing ASP.NET MVC app that started small and has grown with time to require a good re-architecture and refactoring. One thing that I am struggling with is that we've got partial classes of the L2S entities so we could add some extra properties, but these props create a new data context and query the DB for a subset of data. This would be the equivalent to doing the following in SQL, which is not a very good way to write this query as oppsed to joins: SELECT tbl1.stuff, (SELECT nestedValue FROM tbl2 WHERE tbl2.Foo = tbl1.Bar), tbl1.moreStuff FROM tbl1 so in short here's what we've got in some of our partial entity classes: public partial class Ticket { public StatusUpdate LastStatusUpdate { get { //this static method call returns a new DataContext but needs to be refactored var ctx = OurDataContext.GetContext(); var su = Compiled_Query_GetLastUpdate(ctx, this.TicketId); return su; } } } We've got some functions that create a compiled query, but the issue is that we also have some DataLoadOptions defined in the DataContext, and because we instantiate a new datacontext for getting these nested property, we get an exception "Compiled Queries across DataContexts with different LoadOptions not supported" . The first DataContext is coming from a DataContextFactory that we implemented with the refactorings, but this second one is just hanging off the entity property getter. We're implementing the Repository pattern in the refactoring process, so we must stop doing stuff like the above. Does anyone know of a good way to address this issue?

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  • "User Friendly" .net compatible Regex/Text matching tools?

    - by Binary Worrier
    Currently in our software we provide a hook where we call a DLL built by our clients to parse information out of documents we are processing (the DLL takes in some text (or a file) and returns a list of name/value pairs). e.g. We're given a Word doc or Text file to Archive. We do various things to the file, and call a DLL that will return "pertinent" information about the file. Among other things we store that "pertinent" data for posterity. What is considered "pertinent" depends on the client and the type of the document, we don't care, we get it and store it. I've been asked to develop a user friendly "something" that will allow a non-programmer user to "configure" how to get this data from a plain text document (<humor>The user story ends with the helpful suggestion/query "We could use regex for this?"</humor>) It's safe to assume that a list of regex's isn't going to cut this, I've written some of these parsers for customers, the regex's to do these would be hedious and some of them can't be done by regex's. Also one of the requirements above is "user friendly" which negates anything that has users seeing or editing regex expressions. As you can guess, I don't have a fortune of time to do this, and am wondering is there anything out there that I can plug in to our app that has a nice front end and does exactly what I need? :) No? Whadda mean no! . . . sigh Ok then failing that, anything out there that "visually" builds regex's and/or other pattern matching expressions, and then allows one to run those expressions against some text? The MS BRE will do what I want, but I need something prettier that looks less like code. Thanks guys,

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  • Facade Design Patterns and Subclassing

    - by Code Sherpa
    Hi. I am using a facade design pattern for a C# program. The program basically looks like this... public class Api { #region Constants private const int version = 1; #endregion #region Private Data private XProfile _profile; private XMembership _membership; private XRoles _role; #endregion Private Data public Api() { _membership = new XMembership(); _profile = new XProfile(); _role = new XRoles(); } public int GetUserId(string name) { return _membership.GetIdByName(name); } } Now, as I would like subclass my methods into three categories: Role, Profile, and Member. This will be easier on the developers eye because both Profile and Membership expose a lot of methods that look similar (and a few by Role). For example, getting a user's ID would look like: int _id = Namespace.Api.Member.GetUserId("Henry222"); Can somebody "illustrate" how subclassing should work in this case to achieve the effect I am looking for? Thanks in advance.

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  • Factory Method Implementation

    - by cedar715
    I was going through the 'Factory method' pages in SO and had come across this link. And this comment. The example looked as a variant and thought to implement in its original way: to defer instantiation to subclasses... Here is my attempt. Does the following code implements the Factory pattern of the example specified in the link? Please validate and suggest if this has to undergo any re-factoring. public class ScheduleTypeFactoryImpl implements ScheduleTypeFactory { @Override public IScheduleItem createLinearScheduleItem() { return new LinearScheduleItem(); } @Override public IScheduleItem createVODScheduleItem() { return new VODScheduleItem(); } } public class UseScheduleTypeFactory { public enum ScheduleTypeEnum { CableOnDemandScheduleTypeID, BroadbandScheduleTypeID, LinearCableScheduleTypeID, MobileLinearScheduleTypeID } public static IScheduleItem getScheduleItem(ScheduleTypeEnum scheduleType) { IScheduleItem scheduleItem = null; ScheduleTypeFactory scheduleTypeFactory = new ScheduleTypeFactoryImpl(); switch (scheduleType) { case CableOnDemandScheduleTypeID: scheduleItem = scheduleTypeFactory.createVODScheduleItem(); break; case BroadbandScheduleTypeID: scheduleItem = scheduleTypeFactory.createVODScheduleItem(); break; case LinearCableScheduleTypeID: scheduleItem = scheduleTypeFactory.createLinearScheduleItem(); break; case MobileLinearScheduleTypeID: scheduleItem = scheduleTypeFactory.createLinearScheduleItem(); break; default: break; } return scheduleItem; } }

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  • Regular expression to match empty HTML tags that may contain embedded JSTL?

    - by Keith Bentrup
    I'm trying to construct a regular expression to look for empty html tags that may have embedded JSTL. I'm using Perl for my matching. So far I can match any empty html tag that does not contain JSTL with the following? /<\w+\b(?!:)[^<]*?>\s*<\/\w+/si The \b(?!:) will avoid matching an opening JTSL tag but that doesn't address the whether JSTL may be within the HTML tag itself (which is allowable). I only want to know if this HTML tag has no children (only whitespace or empty). So I'm looking for a pattern that would match both the following: <div id="my-id"> </div> <div class="<c:out var="${my.property}" />"></div> Currently the first div matches. The second does not. Is it doable? I tried several variations using lookahead assertions, and I'm starting to think it's not. However, I can't say for certain or articulate why it's not. Edit: I'm not writing something to interpret the code, and I'm not interested in using a parser. I'm writing a script to point out potential issues/oversights. And at this point, I'm curious, too, to see if there is something clever with lookaheads or lookbehinds that I may be missing. If it bothers you that I'm trying to "solve" a problem this way, don't think of it as looking for a solution. To me it's more of a challenge now, and an opportunity to learn more about regular expressions. Also, if it helps, you can assume that the html is xhtml strict.

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  • How should I handle this Optimistic Concurrency error in this Entity Framework code, I have?

    - by Pure.Krome
    Hi folks, I have the following pseduo code in some Repository Pattern project that uses EF4. public void Delete(int someId) { // 1. Load the entity for that Id. If there is none, then null. // 2. If entity != null, then DeleteObject(..); } Pretty simple but I'm getting a run-time error:- ConcurrencyException: Store, Update, Insert or Delete statement affected an unexpected number of rows (0). Now, this is what is happening :- Two instances of EF4 are running inthe app at the same time. Instance A calls delete. Instance B calls delete a nano second later. Instance A loads the entity. Instance B also loads the entity. Instance A now deletes that entity - cool bananas. Instance B tries to delete the entity, but it's already gone. As such, the no-count or what not is 0, when it expected 1 .. or something like that. Basically, it figured out that the item it is suppose to delete, didn't delete (because it happened a split sec ago). I'm not sure if this is like a race-condition or something. Anyways, is there any tricks I can do here so the 2nd call doesn't crash? I could make it into a stored procedure.. but I'm hoping to avoid that right now. Any ideas? I'm wondering If it's possible to lock that row (and that row only) when the select is called ... forcing Instance B to wait until the row lock has been relased. By that time, the row is deleted, so when Instance B does it's select, the data is not there .. so it will never delete.

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  • How to use the LINQ where expression?

    - by NullReference
    I'm implementing the service \ repository pattern in a new project. I've got a base interface that looks like this. Everything works great until I need to use the GetMany method. I'm just not sure how to pass a LINQ expression into the GetMany method. For example how would I simply sort a list of objects of type name? nameRepository.GetMany( ? ) public interface IRepository<T> where T : class { void Add(T entity); void Update(T entity); void Delete(T entity); void Delete(Expression<Func<T, bool>> where); T GetById(long Id); T GetById(string Id); T Get(Expression<Func<T, bool>> where); IEnumerable<T> GetAll(); IEnumerable<T> GetMany(Expression<Func<T, bool>> where); } public virtual IEnumerable<T> GetMany(Expression<Func<T, bool>> where) { return dbset.Where(where).ToList(); }

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  • Double hashing passwords - client & server

    - by J. Stoever
    Hey, first, let me say, I'm not asking about things like md5(md5(..., there are already topics about it. My question is this: We allow our clients to store their passwords locally. Naturally, we don't want them stored in plan text, so we hmac them locally, before storing and/or sending. Now, this is fine, but if this is all we did, then the server would have the stored hmac, and since the client only needs to send the hmac, not the plain text password, an attacker could use the stored hashes from the server to access anyone's account (in the catastrophic scenario where someone would get such an access to the database, of course). So, our idea was to encode the password on the client once via hmac, send it to the server, and there encode it a second time via hmac and match it against the stored, two times hmac'ed password. This would ensure that: The client can store the password locally without having to store it as plain text The client can send the password without having to worry (too much) about other network parties The server can store the password without having to worry about someone stealing it from the server and using it to log in. Naturally, all the other things (strong passwords, double salt, etc) apply as well, but aren't really relevant to the question. The actual question is: does this sound like a solid security design ? Did we overlook any flaws with doing things this way ? Is there maybe a security pattern for something like this ?

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  • F# How to tokenise user input: separating numbers, units, words?

    - by David White
    I am fairly new to F#, but have spent the last few weeks reading reference materials. I wish to process a user-supplied input string, identifying and separating the constituent elements. For example, for this input: XYZ Hotel: 6 nights at 220EUR / night plus 17.5% tax the output should resemble something like a list of tuples: [ ("XYZ", Word); ("Hotel:", Word); ("6", Number); ("nights", Word); ("at", Operator); ("220", Number); ("EUR", CurrencyCode); ("/", Operator); ("night", Word); ("plus", Operator); ("17.5", Number); ("%", PerCent); ("tax", Word) ] Since I'm dealing with user input, it could be anything. Thus, expecting users to comply with a grammar is out of the question. I want to identify the numbers (could be integers, floats, negative...), the units of measure (optional, but could include SI or Imperial physical units, currency codes, counts such as "night/s" in my example), mathematical operators (as math symbols or as words including "at" "per", "of", "discount", etc), and all other words. I have the impression that I should use active pattern matching -- is that correct? -- but I'm not exactly sure how to start. Any pointers to appropriate reference material or similar examples would be great.

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  • Project Naming Convention Feedback Please

    - by Sam Striano
    I am creating a ASP.NET MVC 3 application using Entity Framework 4. I am using the Repository/Service Pattern and was looking for feedback. I currently have the following: MVC Application (GTG.dll) GTG GTG.Controllers GTG.ViewModels Business POCO's (GTG.Business.dll) This contains all business objects (Customer, Order, Invoice, etc...) EF Model/Repositories (GTG.Data.dll) GTG.Business (GTG.Context.tt) I used the Entity POCO Generator Templates. GTG.Data.Repositories Service Layer (GTG.Data.Services.dll) GTG.Data.Services - Contains all of the service objects, one per aggregate root. The following is a little sample code: Controller Namespace Controllers Public Class HomeController Inherits System.Web.Mvc.Controller Function Index() As ActionResult Return View(New Models.HomeViewModel) End Function End Class End Namespace Model Namespace Models Public Class HomeViewModel Private _Service As CustomerService Public Property Customers As List(Of Customer) Public Sub New() _Service = New CustomerService _Customers = _Service.GetCustomersByBusinessName("Striano") End Sub End Class End Namespace Service Public Class CustomerService Private _Repository As ICustomerRepository Public Sub New() _Repository = New CustomerRepository End Sub Function GetCustomerByID(ByVal ID As Integer) As Customer Return _Repository.GetByID(ID) End Function Function GetCustomersByBusinessName(ByVal Name As String) As List(Of Customer) Return _Repository.Query(Function(x) x.CompanyName.StartsWith(Name)).ToList End Function End Class Repository Namespace Data.Repositories Public Class CustomerRepository Implements ICustomerRepository Public Sub Add(ByVal Entity As Business.Customer) Implements IRepository(Of Business.Customer).Add End Sub Public Sub Delete(ByVal Entity As Business.Customer) Implements IRepository(Of Business.Customer).Delete End Sub Public Function GetByID(ByVal ID As Integer) As Business.Customer Implements IRepository(Of Business.Customer).GetByID Using db As New GTGContainer Return db.Customers.FirstOrDefault(Function(x) x.ID = ID) End Using End Function Public Function Query(ByVal Predicate As System.Linq.Expressions.Expression(Of System.Func(Of Business.Customer, Boolean))) As System.Linq.IQueryable(Of Business.Customer) Implements IRepository(Of Business.Customer).Query Using db As New GTGContainer Return db.Customers.Where(Predicate) End Using End Function Public Sub Save(ByVal Entity As Business.Customer) Implements IRepository(Of Business.Customer).Save End Sub End Class End Namespace

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  • Store Business Rules in XML Document, Validate afterwards in Java, how?

    - by JavaPete
    Example XML Rules document: <user> <username> <not-null/> <capitals value="false"/> <max-length value="15"/> </username> <email> <not-null/> <isEmail/> <max-length value="40"/> </email> </user> How do I implement this? I'm starting from scratch, what I currently have is a User-class, and a UserController which saves the User object in de DB (through a Service-layer and Dao-layer), basic Spring MVC. I can't use Spring MVC Validation however in our Model-classes, I have to use an XML document so an Admin can change the rules I think I need a pattern which dynamically builds an algorithm based on what is provided by the XML Rules document, but I can't seem to think of anything other than a massive amount of if-statements. I also have nothing for the parsing yet and I'm not sure how I'm gonna (de)couple it from the actual implementation of the validation-process.

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  • Should Service Depend on Many Repositories, or Break Them Up?

    - by Josh Pollard
    I'm using a repository pattern for my data access. So I basically have a repository per table/class. My UI currently uses service classes to actually get things done, and these service classes wrap, and therefore depend on repositories. In many cases my services are only dependent upon one or two repositories, so things aren't too crazy. Unfortunately, one of my forms in the UI expects the user to enter data that will span five different tables. For this form I made a single service class that depends upon five repositories. Then the methods within the service for saving and loading the data call the appropriate methods on all of the corresponding repositories. As you can imagine, the save and load methods in this service are really big. Also, unit testing this service is getting really difficult because I have to setup so many fake repositories. Would it have been a better choice to break this single service apart into a few smaller services? It would put more code at the UI layer, but would make the services smaller and more testable.

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  • Given the presentation model pattern, is the view, presentation model, or model responsible for adding child views to an existing view at runtime?

    - by Ryan Taylor
    I am building a Flex 4 based application using the presentation model design pattern. This application will have several different components to it as shown in the image below. The MainView and DashboardView will always be visible and they each have corresponding presentation models and models as necessary. These views are easily created by declaring their MXML in the application root. <s:HGroup width="100%" height="100%"> <MainView width="75% height="100%"/> <DashboardView width="25%" height="100%"/> </s:HGroup> There will also be many WidgetViewN views that can be added to the DashboardView by the user at runtime through a simple drop down list. This will need to be accomplished via ActionScript. The drop down list should always show what WidgetViewN has already been added to the DashboardView. Therefore some state about which WidgetViewN's have been created needs to be stored. Since the list of available WidgetViewN and which ones are added to the DashboardView also need to be accessible from other components in the system I think this needs to be stored in a Model object. My understanding of the presentation model design pattern is that the view is very lean. It contains as close to zero logic as is practical. The view communicates/binds to the presentation model which contains all the necessary view logic. The presentation model is effectively an abstract representation of the view which supports low coupling and eases testability. The presentation model may have one or more models injected in in order to display the necessary information. The models themselves contain no view logic whatsoever. So I have a several questions around this design. Who should be responsible for creating the WidgetViewN components and adding these to the DashboardView? Is this the responsibility of the DashboardView, DashboardPresentationModel, DashboardModel or something else entirely? It seems like the DashboardPresentationModel would be responsible for creating/adding/removing any child views from it's display but how do you do this without passing in the DashboardView to the DashboardPresentationModel? The list of available and visible WidgetViewN components needs to be accessible to a few other components as well. Is it okay for a reference to a WidgetViewN to be stored/referenced in a model? Are there any good examples of the presentation model pattern online in Flex that also include creating child views at runtime?

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  • Is there a Design Pattern for preventing dangling references?

    - by iFreilicht
    I was thinking about a design for custom handles. The thought is to prevent clients from copying around large objects. Now a regular handle class would probably suffice for that, but it doesn't solve the "dangling reference problem"; If a client has multiple handles of the same object and deletes the object via one of them, all the others would be invalid, but not know it, so the client could write or read parts of the memory he shouldn't have access to. Is there a design pattern to prevent this from happening? Two ideas: An observer-like pattern where the destructor of an object would notify all handles. "Handle handles" (does such a thing even exist?). All the handles don't really point to the object, but to another handle. When the object gets destroyed, this "master-handle" invalidates itself and therefore all that point to it.

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  • Is there a good design pattern for this messaging class?

    - by salonMonsters
    Is there a good design pattern for this? I want to create a messaging class. The class will be passed: the type of message (eg. signup, signup confirmation, password reminder etc) the client's id The class needs to then look up the client's messaging preferences in the db (whether they want communication by email, sms or both) Then depending on the client's preference it will format the message for the medium (short version for sms, long form for email) and send it through our mail or sms provider's API. Because the fact that we want to be able to change out email and sms providers if need be I wondered if the Command Pattern would be a good choice.

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  • Is there a name for this functional programming construct/pattern?

    - by dietbuddha
    I wrote a function and I'd like to find out if it is an implementation of some functional programming pattern or construct. I'd like to find out the name of this pattern or construct (if it exists)? I have a function which takes a list of functions and does this to them: wrap(fn1, fn2, fn3, fn4) # returns partial(fn4, partial(fn3, partial(fn2, fn1))) There are strong similarities to compose, reduce, and other fp metaprogramming constructs, since the functions are being arranged together and returned as one function. It also has strong similarities to decorators and Python context managers since it provides a way to encapsulate pre and post execution behaviors in one function. Which was the impetus for writing this function. I wanted the ability that context managers provide, but I wanted to be able to have it defined in one function, and to be able to layer function after function on top.

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