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• Lucene wildcard queries

  - by Javi

  Hello, I have this question relating to Lucene. I have a form and I get a text from it and I want to perform a full text search in several fields. Suppose I get from the input the text "textToLook". I have a Lucene Analyzer with several filters. One of them is lowerCaseFilter, so when I create the index, words will be lowercased. Imagine I want to search into two fields field1 and field2 so the lucene query would be something like this (note that 'textToLook' now is 'texttolook'): field1: texttolook* field2:texttolook* In my class I have something like this to create the query. I works when there is no wildcard. String text = "textToLook"; String[] fields = {"field1", "field2"}; //analyser is the same as the one used for indexing Analyzer analyzer = fullTextEntityManager.getSearchFactory().getAnalyzer("customAnalyzer"); MultiFieldQueryParser parser = new MultiFieldQueryParser(fields, analyzer); org.apache.lucene.search.Query queryTextoLibre = parser.parse(text); With this code the query would be: field1: texttolook field2:texttolook but If I set text to "textToLook*" I get field1: textToLook* field2:textToLook* which won't find correctly as the indexes are in lowercase. I have read in lucene website this: " Wildcard, Prefix, and Fuzzy queries are not passed through the Analyzer, which is the component that performs operations such as stemming and lowercasing" My problem cannot be solved by setting the behaviour case insensitive cause my analyzer has other fields which for examples remove some suffixes of words. I think I can solve the problem by getting how the text would be after going through the filters of my analyzer, then I could add the "*" and then I could build the Query with MultiFieldQueryParser. So in this example I woud get "textToLower" and after being passed to to these filters I could get "texttolower". After this I could make "textotolower*". But, is there any way to get the value of my text variable after going through all my analyzer's filters? How can I get all the filters of my analyzer? Is this possible? Thanks

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• Unboxing to unknown type

  - by Robert

  I'm trying to figure out syntax that supports unboxing an integral type (short/int/long) to its intrinsic type, when the type itself is unknown. Here is a completely contrived example that demonstrates the concept: // Just a simple container that returns values as objects struct DataStruct { public short ShortVale; public int IntValue; public long LongValue; public object GetBoxedShortValue() { return LongValue; } public object GetBoxedIntValue() { return LongValue; } public object GetBoxedLongValue() { return LongValue; } } static void Main( string[] args ) { DataStruct data; // Initialize data - any value will do data.LongValue = data.IntValue = data.ShortVale = 42; DataStruct newData; // This works if you know the type you are expecting! newData.ShortVale = (short)data.GetBoxedShortValue(); newData.IntValue = (int)data.GetBoxedIntValue(); newData.LongValue = (long)data.GetBoxedLongValue(); // But what about when you don't know? newData.ShortVale = data.GetBoxedShortValue(); // error newData.IntValue = data.GetBoxedIntValue(); // error newData.LongValue = data.GetBoxedLongValue(); // error } In each case, the integral types are consistent, so there should be some form of syntax that says "the object contains a simple type of X, return that as X (even though I don't know what X is)". Because the objects ultimately come from the same source, there really can't be a mismatch (short != long). I apologize for the contrived example, it seemed like the best way to demonstrate the syntax. Thanks.

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• Very weird C file-handling anomaly

  - by KáGé

  Hello, I got a very weird issue that I cant figure out in my school project, which is the simulation of a simple filesystem in a human-readable textfile. Unfortunately I don't yet have enough time to translate the comments in my code or make it less gibberish, so if you are bothered by that, you don't have to help, I understand. See the code HERE. Now in drive.h, at line 574 is this part: i = getline(); #ifdef DEBUG printf("Free space in all found at %d.\n\n", i); if(drive.disk != NULL){ printf("Disk OK\n\n"); } #endif //write in data state = seekline(i); Before this it finds place for the allocation database entry in the ALL sector (see the "image files" in the mounts folder, this issue was tested on mount_30.efs-dbf), then gets the line with i = getline() fine (getline is in lglobal.h, line 39), but after that any file manipulation (in this case seekline's fseek, but if I comment that out, then the first fprintf after that) crashes the program straight away. I think the file gets somehow corrupted (though the Disk OK message appears) but can't figure out how. I've tried putting i = getline(); into comment, but it didn't make any difference. I've also tried asking at local programming forums but they didn't really help either. The last few lines of the output before it crashes: Dir written. (drive.h line 562) Seekline entered: 268 (called at drive.h line 564) Getline entered. (called at drive.h line 574) Line got: 268. Free space in all found at 268. (drive.h line 576) Seekline entered: 268 (called at drive.h line 582, note that this exact call was run successfully less than 20 lines back. This one should set the pointer to the beginning of the line it is currently in) After this it crashes. Does anyone has any idea of what causes this and how could I fix it? Thank you.

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• general learning methodology

  - by momo

  just wanted to hear on the different general learning paths people embark on when learning a new language/framework. the one i currently use, which is how i learned bash and am currently learning python, is: instant hacking tutorial (very short tutorial introducing the basic syntax, variable declaration, loops, data types, etc. and how they are generally used) in depth tutorial with good programming style and slightly topic-specific (e.g. Mark Pilgrim's Dive into Python), important topics for me personally are regex methods, file IO, and ways the different data types are utilized best (i wrote a very primitive bayesian spam filter using python's dictionaries to keep track of word occurrences) spaced-repition of syntax or short recipes (i use anki, with questions like 'create dictionary with filename and filesize metadata, human-readable' or simpler ones like 'match 0 - 3 occurences of the letter M in a string', or 'return/create an iterator from two sequences') the use of spaced-repitition has been invaluable, and i credit it with the ease that i can recall/create python algorithms. however, i've recently started looking into django, and i've found that spaced-repitition, at least in my case, doesn't work very well for learning a framework, it works best with short code recipes (either that or i should start looking into more basic django framework tutorials). the problem i'm encountering is that since framework programming is not only algorithms, but actually learning the API, which can be quite complex since you have to learn all the methods, modules, the places where they are stored, and the sequence of which things have to be done. for ex. in django to start a project that deals with polls (from the django tutorial), one has to create the project, edit the settings.py file, create the polls app, edit the models.py file (which requires knowing the classes that are present in the module models), edit the urls.py file, etc. i found that my spaced-repition method didn't work very well for this type of learning, so i wanted to ask you guys what method(s) you use for learning the different frameworks/APIs.

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• Getting response status code 0 in SmartGWT webservice call using json

  - by Girish

  I have developed application using SmartGWT, now i need to call webservice using json to another application which is deployed in another server for submitting username and password. When i make a request with url and POST method, getting the response status code as 0 and response text as blank. Here is my code, public void sendRequest() throws Exception { // Get login json data to be sent to server. String strData = createLoginReqPacket(); String url = "some url"; RequestBuilder builder = new RequestBuilder(RequestBuilder.POST, url); builder.setHeader("Content-Type", "application/json"); builder.setHeader("Content-Length", strData.length() + ""); Request response = builder.sendRequest(strData, new RequestCallback() { @Override public void onResponseReceived(Request request, Response response) { int statusCode = response.getStatusCode(); System.out.println("Response code ----"+response.getStatusCode()+""); if (statusCode == Response.SC_OK) { String responseBody = response.getText(); System.out.println("Respose :" + responseBody); // do something with the response } else { GWT.log("Response error at server side ----",null); // do in case of server error } }// end of method. @Override public void onError(Request request, Throwable exception) { GWT.log("**** Error in service call ******",null); }// end of method. }); builder.send(); }// end of send request. Please anybody knows the solution?? Give some reference code or links for this. Thanks.

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• Are document-oriented databases any more suitable than relational ones for persisting objects?

  - by Owen Fraser-Green

  In terms of database usage, the last decade was the age of the ORM with hundreds competing to persist our object graphs in plain old-fashioned RMDBS. Now we seem to be witnessing the coming of age of document-oriented databases. These databases are highly optimized for schema-free documents but are also very attractive for their ability to scale out and query a cluster in parallel. Document-oriented databases also hold a couple of advantages over RDBMS's for persisting data models in object-oriented designs. As the tables are schema-free, one can store objects belonging to different classes in an inheritance hierarchy side-by-side. Also, as the domain model changes, so long as the code can cope with getting back objects from an old version of the domain classes, one can avoid having to migrate the whole database at every change. On the other hand, the performance benefits of document-oriented databases mainly appear to come about when storing deeper documents. In object-oriented terms, classes which are composed of other classes, for example, a blog post and its comments. In most of the examples of this I can come up with though, such as the blog one, the gain in read access would appear to be offset by the penalty in having to write the whole blog post "document" every time a new comment is added. It looks to me as though document-oriented databases can bring significant benefits to object-oriented systems if one takes extreme care to organize the objects in deep graphs optimized for the way the data will be read and written but this means knowing the use cases up front. In the real world, we often don't know until we actually have a live implementation we can profile. So is the case of relational vs. document-oriented databases one of swings and roundabouts? I'm interested in people's opinions and advice, in particular if anyone has built any significant applications on a document-oriented database.

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• With NHibernate and Transaction do I rollback on commit failure or does it auto rollback on single c

  - by mattcodes

  I've built the following Dispose method for my Unit Of Work which essentially wraps the active NH session & transaction (transaction set as variable after opening session as to not be replaced if NH session gets new transaction after error) public void Dispose() { Func<ITransaction,bool> transactionStateOkayFunc = trans => trans != null && trans.IsActive && !trans.WasRolledBack; try { if(transactionStateOkayFunc(this.transaction)) { if (HasErrored) { transaction.Rollback(); } else { try { transaction.Commit(); } catch (Exception) { if(transactionStateOkayFunc(transaction)) transaction.Rollback(); throw; } } } } finally { if(transaction != null) transaction.Dispose(); if(session.IsOpen) session.Close(); } I can't help feeling that code is a little bloated, will a transaction automatically rollback is a discrete Commit fails in the case of non-nested transactions? Will Commit or Rollback automatically Dipose the transaction? If not will Session.Close() automatically dispose the associated transaction?

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• Rails running multiple delayed_job - lock tables

  - by pepernik

  Hey. I use delayed_job for background processing. I have 8 CPU server, MySQL and I start 7 delayed_job processes RAILS_ENV=production script/delayed_job -n 7 start Q1: I'm wondering is it possible that 2 or more delayed_job processes start processing the same process (the same record-row in the database delayed_jobs). I checked the code of the delayed_job plugin but can not find the lock directive in a way it should be. I think each process should lock the database table before executing an UPDATE on lock_by column. They lock the record simply by updating the locked_by field (UPDATE delayed_jobs SET locked_by...). Is that really enough? No locking needed? Why? I know that UPDATE has higher priority than SELECT but I think this does not have the effect in this case. My understanding of the multy-threaded situation is: Process1: Get waiting job X. [OK] Process2: Get waiting jobs X. [OK] Process1: Update locked_by field. [OK] Process2: Update locked_by field. [OK] Process1: Get waiting job X. [Already processed] Process2: Get waiting jobs X. [Already processed] I think in some cases more jobs can get the same information and can start processing the same process. Q2: Is 7 delayed_jobs a good number for 8CPU server? Why yes/not. Thx 10x!

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• Tablet interface for the physically disabled?

  - by Glenn

  My sister has Cerebral Palsy, which in her case means she has only gross motor control and her speech is slurred. Implications should be obvious: traditional computer/phone/tablet interfaces won't work for her and she can't speak clearly enough for speech recognition software to help her at all. She enjoys reading but has difficulty holding the book and/or turning a page. There are a few options for helping her use a computer, but nothing for tablets or eReaders. That's where you come in. I would like to make (or buy, if such a thing exists) a better interface to an Android tablet that would work for someone with little to no physical dexterity or speech ability. I'd also be interested in work on the Kindle or iPad, but I'm most familiar with Android so I'm starting there. I know Android has Bluetooth capability. Is it possible to interface a joystick to control the Android device? By "control", I mean the entire operating system - selecting an app, launching it, controlling the menus, etc. I want to give her control over the whole thing, not just a specific app. On a PC this can be accomplished by creating a generic USB HID interface and an arcade joystick to move the mouse over the screen and click on thigns. Is it possible to do something like that in Android? Any help you can offer would be greatly appreciated. Thanks!

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• How do I get started designing and implementing a script interface for my .NET application?

  - by Peter Mortensen

  How do I get started designing and implementing a script interface for my .NET application? There is VSTA (the .NET equivalent of VBA for COM), but as far as I understand I would have to pay a license fee for every installation of my application. It is an open source application so this will not work. There is also e.g. the embedding of interpreters (IronPython?), but I don't understand how this would allow exposing an "object model" (see below) to external (or internal) scripts. What is the scripting interface story in .NET? Is it somehow trivial in .NET to do this? Background: I have once designed and implemented a fairly involved script interface for a Macintosh application for acquisition and analysis of data from a mass spectrometer (Mac OS, System 7) and later a COM interface for a Windows application. Both were designed with an "object model" and classes (that can have properties). These are overloaded words, but in a scripting interface context object model is essentially a containment hiarchy of objects of specific classes. Classes have properties and lists of contained objects. E.g. like in the COM interfaces exposed in Microsoft Office applications, where the application object can be used to add to its list of documents (with the side effect of creating the GUI representation of a document). External scripts can create new objects in a container and navigate through the content of the hiarchy at any given time. In the Macintosh case scripts could be written in e.g. AppleScript or Frontier. On the Macintosh the implementation of a scripting interface was very complicated. Support for it in Metroworks' C++ class library (the name escapes me right now) made it much simpler.

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• Constructor or Assignment Operator

  - by ju

  Can you help me is there definition in C++ standard that describes which one will be called constructor or assignment operator in this case: #include <iostream> using namespace std; class CTest { public: CTest() : m_nTest(0) { cout << "Default constructor" << endl; } CTest(int a) : m_nTest(a) { cout << "Int constructor" << endl; } CTest(const CTest& obj) { m_nTest = obj.m_nTest; cout << "Copy constructor" << endl; } CTest& operatorint rhs) { m_nTest = rhs; cout << "Assignment" << endl; return *this; } protected: int m_nTest; }; int _tmain(int argc, _TCHAR* argv[]) { CTest b = 5; return 0; } Or is it just a matter of compiler optimization?

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• How to extract block of XML from a log file on Linux

  - by dragonmantank

  I have a log file that looks like the following: 2010-05-12 12:23:45 Some sort of log entry 2010-05-12 01:45:12 Request XML: <RootTag> <Element>Value</Element> <Element>Another Value</Element> </RootTag> 2010-05-12 01:45:32 Response XML: <ResponseRoot> <Element>Value</Element> </ResponseRoot> 2010-05-12 01:45:49 Another log entry What I want to do is extract the Request and Response XML (and ultimately dump them into their own single files). I had a similar parser that used egrep but the XML was all on one line, not multiple ones like above. The log files are also somewhat large, hitting 500-600 megs a log. Smaller logs I would read in via a PHP script and use regex matching, but the amount of memory required for such a large file would more than likely kill the script. Is there an easy way using the built-in tools on a Linux box (CentOS in this case) to extract multiple lines or am I going to have to bite the bullet and use Perl or PHP to read in the entire file to extract it?

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• JPA joined column allow every value...

  - by Fabio Beoni

  I'm testing JPA, in a simple case File/FileVersions tables (Master/Details), with OneToMany relation, I have this problem: in FileVersions table, the field "file_id" (responsable for the relation with File table) accepts every values, not only values from File table. How can I use the JPA mapping to limit the input in FileVersion.file_id only for values existing in File.id? My class are File and FileVersion: FILE CLASS @Id @GeneratedValue(strategy = GenerationType.IDENTITY) @Column(name="FILE_ID") private Long id; @Column(name="NAME", nullable = false, length = 30) private String name; //RELATIONS ------------------------------------------- @OneToMany(mappedBy="file", fetch=FetchType.EAGER) private Collection <FileVersion> fileVersionsList; //----------------------------------------------------- FILEVERSION CLASS @Id @GeneratedValue(strategy = GenerationType.IDENTITY) @Column(name="VERSION_ID") private Long id; @Column(name="FILENAME", nullable = false, length = 255) private String fileName; @Column(name="NOTES", nullable = false, length = 200) private String notes; //RELATIONS ------------------------------------------- @ManyToOne(fetch=FetchType.EAGER) @JoinColumn(name="FILE_ID", referencedColumnName="FILE_ID", nullable=false) private File file; //----------------------------------------------------- and this is the FILEVERSION TABLE CREATE TABLE `JPA-Support`.`FILEVERSION` ( `VERSION_ID` bigint(20) NOT NULL AUTO_INCREMENT, `FILENAME` varchar(255) NOT NULL, `NOTES` varchar(200) NOT NULL, `FILE_ID` bigint(20) NOT NULL, PRIMARY KEY (`VERSION_ID`), KEY `FK_FILEVERSION_FILE_ID` (`FILE_ID`) ) ENGINE=MyISAM AUTO_INCREMENT=4 DEFAULT CHARSET=latin1

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• Passing IDisposable objects through constructor chains

  - by Matt Enright

  I've got a small hierarchy of objects that in general gets constructed from data in a Stream, but for some particular subclasses, can be synthesized from a simpler argument list. In chaining the constructors from the subclasses, I'm running into an issue with ensuring the disposal of the synthesized stream that the base class constructor needs. Its not escaped me that the use of IDisposable objects this way is possibly just dirty pool (plz advise?) for reasons I've not considered, but, this issue aside, it seems fairly straightforward (and good encapsulation). Codes: abstract class Node { protected Node (Stream raw) { // calculate/generate some base class properties } } class FilesystemNode : Node { public FilesystemNode (FileStream fs) : base (fs) { // all good here; disposing of fs not our responsibility } } class CompositeNode : Node { public CompositeNode (IEnumerable some_stuff) : base (GenerateRaw (some_stuff)) { // rogue stream from GenerateRaw now loose in the wild! } static Stream GenerateRaw (IEnumerable some_stuff) { var content = new MemoryStream (); // molest elements of some_stuff into proper format, write to stream content.Seek (0, SeekOrigin.Begin); return content; } } I realize that not disposing of a MemoryStream is not exactly a world-stopping case of bad CLR citizenship, but it still gives me the heebie-jeebies (not to mention that I may not always be using a MemoryStream for other subtypes). It's not in scope, so I can't explicitly Dispose () it later in the constructor, and adding a using statement in GenerateRaw () is self-defeating since I need the stream returned. Is there a better way to do this? Preemptive strikes: yes, the properties calculated in the Node constructor should be part of the base class, and should not be calculated by (or accessible in) the subclasses I won't require that a stream be passed into CompositeNode (its format should be irrelevant to the caller) The previous iteration had the value calculation in the base class as a separate protected method, which I then just called at the end of each subtype constructor, moved the body of GenerateRaw () into a using statement in the body of the CompositeNode constructor. But the repetition of requiring that call for each constructor and not being able to guarantee that it be run for every subtype ever (a Node is not a Node, semantically, without these properties initialized) gave me heebie-jeebies far worse than the (potential) resource leak here does.

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• Testing for interface implementation in WCF/SOA

  - by rabidpebble

  I have a reporting service that implements a number of reports. Each report requires certain parameters. Groups of logically related parameters are placed in an interface, which the report then implements: [ServiceContract] [ServiceKnownType(typeof(ExampleReport))] public interface IService1 { [OperationContract] void Process(IReport report); } public interface IReport { string PrintedBy { get; set; } } public interface IApplicableDateRangeParameter { DateTime StartDate { get; set; } DateTime EndDate { get; set; } } [DataContract] public abstract class Report : IReport { [DataMember] public string PrintedBy { get; set; } } [DataContract] public class ExampleReport : Report, IApplicableDateRangeParameter { [DataMember] public DateTime StartDate { get; set; } [DataMember] public DateTime EndDate { get; set; } } The problem is that the WCF DataContractSerializer does not expose these interfaces in my client library, thus I can't write the generic report generating front-end that I plan to. Can WCF expose these interfaces, or is this a limitation of the serializer? If the latter case, then what is the canonical approach to this OO pattern? I've looked into NetDataContractSerializer but it doesn't seem to be an officially supported implementation (which means it's not an option in my project). Currently I've resigned myself to including the interfaces in a library that is common between the service and the client application, but this seems like an unnecessary extra dependency to me. Surely there is a more straightforward way to do this? I was under the impression that WCF was supposed to replace .NET remoting; checking if an object implements an interface seems to be one of the most basic features required of a remoting interface?

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• django: control json serialization

  - by abolotnov

  Is there a way to control json serialization in django? Simple code below will return serialized object in json: co = Collection.objects.all() c = serializers.serialize('json',co) The json will look similar to this: [ { "pk": 1, "model": "picviewer.collection", "fields": { "urlName": "architecture", "name": "\u0413\u043e\u0440\u043e\u0434 \u0438 \u0430\u0440\u0445\u0438\u0442\u0435\u043a\u0442\u0443\u0440\u0430", "sortOrder": 0 } }, { "pk": 2, "model": "picviewer.collection", "fields": { "urlName": "nature", "name": "\u041f\u0440\u0438\u0440\u043e\u0434\u0430", "sortOrder": 1 } }, { "pk": 3, "model": "picviewer.collection", "fields": { "urlName": "objects", "name": "\u041e\u0431\u044a\u0435\u043a\u0442\u044b \u0438 \u043d\u0430\u0442\u044e\u0440\u043c\u043e\u0440\u0442", "sortOrder": 2 } } ] You can see it's serializing it in a way that you are able to re-create the whole model, shall you want to do this at some point - fair enough, but not very handy for simple JS ajax in my case: I want bring the traffic to minimum and make the whole thing little clearer. What I did is I created a view that passes the object to a .json template and the template will do something like this to generate "nicer" json output: [ {% if collections %} {% for c in collections %} {"id": {{c.id}},"sortOrder": {{c.sortOrder}},"name": "{{c.name}}","urlName": "{{c.urlName}}"}{% if not forloop.last %},{% endif %} {% endfor %} {% endif %} ] This does work and the output is much (?) nicer: [ { "id": 1, "sortOrder": 0, "name": "????? ? ???????????", "urlName": "architecture" }, { "id": 2, "sortOrder": 1, "name": "???????", "urlName": "nature" }, { "id": 3, "sortOrder": 2, "name": "??????? ? ?????????", "urlName": "objects" } ] However, I'm bothered by the fast that my solution uses templates (an extra step in processing and possible performance impact) and it will take manual work to maintain shall I update the model, for example. I'm thinking json generating should be part of the model (correct me if I'm wrong) and done with either native python-json and django implementation but can't figure how to make it strip the bits that I don't want. One more thing - even when I restrict it to a set of fields to serialize, it will keep the id always outside the element container and instead present it as "pk" outside of it.

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• C# Hiding, overriding and calling function from base class.

  - by Lukasz Lysik

  I'm learning C# and I encountered the following problem. I have two classes: base and derived: class MyBase { public void MyMethod() { Console.WriteLine("MyBase::MyMethod()"); } } class MyDerived: MyBase { public void MyMethod() { Console.WriteLine("MyDerived::MyMethod()"); } } For now, without virtual and override key words. When I compile this I get the warning (which is of course expected) that I try to hide MyMethod from MyBase class. What I want to do is to call the method from the base class having an instance of derived class. I do this like this: MyDerived myDerived = new MyDerived(); ((MyBase)myDerived).MyMethod(); It works fine when I do not specify any virtual, etc. keywords in the methods. I tried to put combination of the keywords and I got the following results: | MyBase::MyMethod | MyDerived::MyMethod | Result printed on the console | | -----------------|---------------------|-------------------------------| | - | - | MyBase::MyMethod() | | - | new | MyBase::MyMethod() | | virtual | new | MyBase::MyMethod() | | virtual | override | MyDerived::MyMethod() | I hope the table is clear to you. I have two questions: Is it the correct way to call the function from the base class (((MyBase)myDerived).MyMethod();)? I know about base keyword, but it can be called only from the inside of the derived class. Is it right? Why in the last case (with virtual and override modifiers) the method which was called came from the derived class? Would you please explain that?

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• Java Random Slowdowns on Mac OS cont'd

  - by javajustice

  I asked this question a few weeks ago, but I'm still having the problem and I have some new hints. The original question is here: http://stackoverflow.com/questions/1651887/java-random-slowdowns-on-mac-os Basically, I have a java application that splits a job into independent pieces and runs them in separate threads. The threads have no synchronization or shared memory items. The only resources they do share are data files on the hard disk, with each thread having an open file channel. Most of the time it runs very fast, but occasionally it will run very slow for no apparent reason. If I attach a CPU profiler to it, then it will start running quickly again. If I take a CPU snapshot, it says its spending most of its time in "self time" in a function that doesn't do anything except check a few (unshared unsynchronized) booleans. I don't know how this could be accurate because 1, it makes no sense, and 2, attaching the profiler seems to knock the threads out of whatever mode they're in and fix the problem. Also, regardless of whether it runs fast or slow, it always finishes and gives the same output, and it never dips in total cpu usage (in this case ~1500%), implying that the threads aren't getting blocked. I have tried different garbage collectors, different sizings the parts of the memory space, writing data output to non-raid drives, and putting all data output in threads separate the main worker threads. Does anyone have any idea what kind of problem this could be? Could it be the operating system (OS X 10.6.2) ? I have not been able to duplicate it on a windows machine, but I don't have one with a similar hardware configuration.

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• Using SiteMesh with RequestDispatcher's forward()

  - by Rob Hruska

  I'm attempting to integrate SiteMesh into a legacy application using Tomcat 5 as my a container. I have a main.jsp that I'm decorating with a simple decorator. In decorators.xml, I've just got one decorator defined: <decorators defaultdir="/decorators"> <decorator name="layout-main" page="layout-main.jsp"> <pattern>/jsp/main.jsp</pattern> </decorator> </decorators> This decorator works if I manually go to http://example.com/my-webapp/jsp/main.jsp. However, there are a few places where a servlet, instead of doing a redirect to a jsp, does a forward: getServletContext().getRequestDispatcher("/jsp/main.jsp").forward(request, response); This means that the URL remains at something like http://example.com/my-webapp/servlet/MyServlet instead of the jsp file and is therefore not being decorated, I presume since it doesn't match the pattern in decorators.xml. I can't do a <pattern>/*</pattern> because there are other jsps that do not need to be decorated by layout-main.jsp. I can't do a <pattern>/servlet/MyServlet*</pattern> because MyServlet may forward to main.jsp sometimes and perhaps error.jsp at other times. Is there a way to work around this without expansive changes to how the servlets work? Since it's a legacy app I don't have as much freedom to change things, so I'm hoping for something configuration-wise that will fix this. SiteMesh's documentation really isn't that great. I've been working mostly off the example application that comes with the distribution. I really like SiteMesh, and am hoping I can get it to work in this case.

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• Simple encryption - Sum of Hashes in C

  - by Dogbert

  I am attempting to demonstrate a simple proof of concept with respect to a vulnerability in a piece of code in a game written in C. Let's say that we want to validate a character login. The login is handled by the user choosing n items, (let's just assume n=5 for now) from a graphical menu. The items are all medieval themed: eg: _______________________________ | | | | | Bow | Sword | Staff | |-----------|-----------|-------| | Shield | Potion | Gold | |___________|___________|_______| The user must click on each item, then choose a number for each item. The validation algorithm then does the following: Determines which items were selected Drops each string to lowercase (ie: Bow becomes bow, etc) Calculates a simple string hash for each string (ie: `bow = b=2, o=15, w=23, sum = (2+15+23=40) Multiplies the hash by the value the user selected for the corresponding item; This new value is called the key Sums together the keys for each of the selected items; this is the final validation hash IMPORTANT: The validator will accept this hash, along with non-zero multiples of it (ie: if the final hash equals 1111, then 2222, 3333, 8888, etc are also valid). So, for example, let's say I select: Bow (1) Sword (2) Staff (10) Shield (1) Potion (6) The algorithm drops each of these strings to lowercase, calculates their string hashes, multiplies that hash by the number selected for each string, then sums these keys together. eg: Final_Validation_Hash = 1*HASH(Bow) + 2*HASH(Sword) + 10*HASH(Staff) + 1*HASH(Shield) + 6*HASH(Potion) By application of Euler's Method, I plan to demonstrate that these hashes are not unique, and want to devise a simple application to prove it. in my case, for 5 items, I would essentially be trying to calculate: (B)(y) = (A_1)(x_1) + (A_2)(x_2) + (A_3)(x_3) + (A_4)(x_4) + (A_5)(x_5) Where: B is arbitrary A_j are the selected coefficients/values for each string/category x_j are the hash values for each string/category y is the final validation hash (eg: 1111 above) B,y,A_j,x_j are all discrete-valued, positive, and non-zero (ie: natural numbers) Can someone either assist me in solving this problem or point me to a similar example (ie: code, worked out equations, etc)? I just need to solve the final step (ie: (B)(Y) = ...). Thank you all in advance.

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• Message queue proxy in Python + Twisted

  - by gasper_k

  Hi, I want to implement a lightweight Message Queue proxy. It's job is to receive messages from a web application (PHP) and send them to the Message Queue server asynchronously. The reason for this proxy is that the MQ isn't always avaliable and is sometimes lagging, or even down, but I want to make sure the messages are delivered, and the web application returns immediately. So, PHP would send the message to the MQ proxy running on the same host. That proxy would save the messages to SQLite for persistence, in case of crashes. At the same time it would send the messages from SQLite to the MQ in batches when the connection is available, and delete them from SQLite. Now, the way I understand, there are these components in this service: message listener (listens to the messages from PHP and writes them to a Incoming Queue) DB flusher (reads messages from the Incoming Queue and saves them to a database; due to SQLite single-threadedness) MQ connection handler (keeps the connection to the MQ server online by reconnecting) message sender (collects messages from SQlite db and sends them to the MQ server, then removes them from db) I was thinking of using Twisted for #1 (TCPServer), but I'm having problem with integrating it with other points, which aren't event-driven. Intuition tells me that each of these points should be running in a separate thread, because all are IO-bound and independent of each other, but I could easily put them in a single thread. Even though, I couldn't find any good and clear (to me) examples on how to implement this worker thread aside of Twisted's main loop. The example I've started with is the chatserver.py, which uses service.Application and internet.TCPServer objects. If I start my own thread prior to creating TCPServer service, it runs a few times, but the it stops and never runs again. I'm not sure, why this is happening, but it's probably because I don't use threads with Twisted correctly. Any suggestions on how to implement a separate worker thread and keep Twisted? Do you have any alternative architectures in mind?

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• How can I superimpose modified loess lines on a ggplot2 qplot?

  - by briandk

  Background Right now, I'm creating a multiple-predictor linear model and generating diagnostic plots to assess regression assumptions. (It's for a multiple regression analysis stats class that I'm loving at the moment :-) My textbook (Cohen, Cohen, West, and Aiken 2003) recommends plotting each predictor against the residuals to make sure that: The residuals don't systematically covary with the predictor The residuals are homoscedastic with respect to each predictor in the model On point (2), my textbook has this to say: Some statistical packages allow the analyst to plot lowess fit lines at the mean of the residuals (0-line), 1 standard deviation above the mean, and 1 standard deviation below the mean of the residuals....In the present case {their example}, the two lines {mean + 1sd and mean - 1sd} remain roughly parallel to the lowess {0} line, consistent with the interpretation that the variance of the residuals does not change as a function of X. (p. 131) How can I modify loess lines? I know how to generate a scatterplot with a "0-line,": # First, I'll make a simple linear model and get its diagnostic stats library(ggplot2) data(cars) mod <- fortify(lm(speed ~ dist, data = cars)) attach(mod) str(mod) # Now I want to make sure the residuals are homoscedastic qplot (x = dist, y = .resid, data = mod) + geom_smooth(se = FALSE) # "se = FALSE" Removes the standard error bands But does anyone know how I can use ggplot2 and qplot to generate plots where the 0-line, "mean + 1sd" AND "mean - 1sd" lines would be superimposed? Is that a weird/complex question to be asking?

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• Are finalizers ever allowed to call other managed classes' methods?

  - by romkyns

  I used to be pretty sure the answer is "no", as explained in Overriding the Finalize method and Object.Finalize documentation. However, while randomly browsing through FileStream in Reflector, I found that it can actually call just such a method from a finalizer: private SafeFileHandle _handle; ~FileStream() { if (this._handle != null) { this.Dispose(false); } } protected override void Dispose(bool disposing) { try { ... } finally { if ((this._handle != null) && !this._handle.IsClosed) // <=== HERE { this._handle.Dispose(); // <=== AND HERE } [...] } } I started wondering whether this will always work due to the exact way in which it's written, and hence whether the "do not touch managed classes from finalizers" is just a guideline that can be broken given a good reason and the necessary knowledge to do it right. I dug a bit deeper and found out that the worst that can happen when the "rule" is broken is that the managed object being accessed had already been finalized, or may be getting finalized in parallel on a separate thread. So if the SafeFileHandle's finalizer didn't do anything that would cause a subsequent call to Dispose fail then the above should be fine... right? Question: so there might after all be situations in which a method on another managed class may be called reliably from a finalizer? I've always believed this to be false, but this code suggests that it's possible and that there can be good enough reasons to do it. Bonus: Observe that the SafeFileHandle will not even know it's being called from a finalizer, since this is just a normal call to Dispose(). The base class, SafeHandle, actually has two private methods, InternalDispose and InternalFinalize, and in this case InternalDispose will be called. Isn't this a problem? Why not?...

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• m2eclipse: How to set Eclipse project settings when importing a maven project?

  - by Marius Andreiana

  Using m2eclipse Eclipse plugin, everybody on the dev team should be able to checkout source code, import Maven project in Eclipse and be good to go. I saw m2eclipse is being merged into Eclipse 3.7, and maven-eclipse-plugin won't be maintained any longer, so I'm looking for a m2eclipse-based solution (without running "mvn eclipse:clean eclipse:eclipse" before project import, which is what maven-eclipse-plugin does). maven-eclipse-plugin allows this in pom.xml <additionalConfig> <file> <name>.settings/com.google.gdt.eclipse.core.prefs</name> <content><![CDATA[ eclipse.preferences.version=2 jarsExcludedFromWebInfLib= warSrcDir=${project.build.directory}/${project.build.finalName} warSrcDirIsOutput=true ]]> </content> </file> The more general question is How would m2eclipse do something similar? For some cases, just saving the eclipse .settings/prefs file works (e.g. org.eclipse.jdt.ui.prefs), but in this case, com.google.gdt.eclipse.core.prefs is always overwritten on m2eclipse project import. A specific question is asked here, with no reply. Thanks! UPDATE: Not possible now, see request

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• Searching a column containing CSV data in a MySQL table for existence of input values

  - by Adarsh R

  Hi, I have a table say, ITEM, in MySQL that stores data as follows: ID FEATURES -------------------- 1 AB,CD,EF,XY 2 PQ,AC,A3,B3 3 AB,CDE 4 AB1,BC3 -------------------- As an input, I will get a CSV string, something like "AB,PQ". I want to get the records that contain AB or PQ. I realized that we've to write a MySQL function to achieve this. So, if we have this magical function MATCH_ANY defined in MySQL that does this, I would then simply execute an SQL as follows: select * from ITEM where MATCH_ANY(FEAURES, "AB,PQ") = 0 The above query would return the records 1, 2 and 3. But I'm running into all sorts of problems while implementing this function as I realized that MySQL doesn't support arrays and there's no simple way to split strings based on a delimiter. Remodeling the table is the last option for me as it involves lot of issues. I might also want to execute queries containing multiple MATCH_ANY functions such as: select * from ITEM where MATCH_ANY(FEATURES, "AB,PQ") = 0 and MATCH_ANY(FEATURES, "CDE") In the above case, we would get an intersection of records (1, 2, 3) and (3) which would be just 3. Any help is deeply appreciated. Thanks

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