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• Suggestions for connecting .NET WPF GUI with Java SE Server aoo

  - by Sam Goldberg

  BACKGROUND We are building a Java (SE) trading application which will be monitoring market data and sending trade messages based on the market data, and also on user defined configuration parameters. We are planning to provide the user with a thin client, built in .NET (WPF) for managing the parameters, controlling the server behavior, and viewing the current state of the trading. The client doesn't need real-time updates; it will instead update the view once every few seconds (or whatever interval is configured by the user). The client has about 6 different operations it needs to perform with the server, for example: CRUD with configuration parameters query subset of the data receive updates of current positions from server It is possible that most of the different operations (except for receiving data) are just different flavors of managing the configuration parameters, but it's too early in our analysis for us to be sure. To connect the client with the server, we have been considering using: SOAP Web Service RESTful service building a custom TCP/IP based API (text or xml) (least preferred - but we use this approach with other applications we have) As best as I understand, pros and cons of the different web service flavors are: SOAP pro: totally automated in .NET (and Java), modifying server side interface require no code changes in communication layer, just running refresh on Web Service reference to regenerate the classes. con: more overhead in the communication layer sending more text, etc. We're not using J2EE container so maybe doesn't work so well with J2SE REST pro: lighter weight, less data. Has good .NET and Java support. (I don't have any real experience with this, so don't know what other benefits it has.) con: client will not be automatically aware if there are any new operations or properties added (?), so communication layer needs to be updated by developer if server interface changes. con: (both approaches) Server cannot really push updates to the client at regular intervals (?) (However, we won't mind if client polls the server to get updates.) QUESTION What are your opinions on the above options or suggestions for other ways to connect the 2 parts? (Ideally, we don't want to put much work into the communication layer, because it's not the significant part of the application so the more off-the-shelf and automated the better.)

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• Quantifying the value of refactoring in commercial terms

  - by Myles McDonnell

  Here is the classic scenario; Dev team build a prototype. Business mgmt like it and put it into production. Dev team now have to continue to deliver new features whilst at the same time pay the technical debt accrued when the code base was a prototype. My question is this (forgive me, it's rather open ended); how can the value of the refactoring work be quantified in commercial terms? As developers we can clearly understand and communicate the value in technical terms, such a the removal of code duplication, the simplification of an object model and so on. But this means little to an executive focussed on the commercial elements. What will mean something to this executive is the dev. team being able to deliver requirements at faster velocity. Just making this statement without any metrics that clearly quantify return on investment (increased velocity in return for resource allocated to refactoring) carries little weight. I'm interested to hear from anyone who has had experience, positive or negative, in relation to the above. ----------------- EDIT ---------------- Thanks for the responses so far, all of which I think are good. What I want to develop is a metric that proves (or disproves!) all of these statements. A report that ties velocity to refactoring and shows a positive effect.

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• How to "translate" interdependent object states in code?

  - by Earl Grey

  I have the following problem. My UI interace contains several buttons, labels, and other visual information. I am able to describe every possible workflow scenario that should be be allowed on that UI. That means I can describe it like this - when button A is pressed, the following should follow - In the case of that A button, there are three independent factors that influence the possible result when pushing the A button. The state of the session (blank, single, multi, multi special), the actual work that is being done by the system at the moment of pressing the A button (nothing was happening, work was being done, work was paused) and a separate UI element that has two states (on , off)..This gives me a 3 dimensional cube with 24 possible outcomes. I could write code for this using if cycles, switch cycles etc....but the problem is, I have another 7 buttons on that ui, I can enter this UI from different states..some buttons change the state, some change parameters... To sum up, the combinations are mindbogling and I am not able come up with a methodology that scales and is systematically reliable. I am able to describe EVERY workflow with words, I am sure my description is complete and without logical errors. But I am not able to translate that into code. I was trying to draw flowcharts but it soon became visually too complicated due to too many if "emafors". Can you advice how to proceeed?

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• SQL query. An unusual join. DB implemented in sqlite-3

  - by user02814

  This is essentially a question about constructing an SQL query. The db is implemented with sqlite3. I am a relatively new user of SQL. I have two tables and want to join them in an unusual way. The following is an example to explain the problem. Table 1 (t1): id year name ------------------------- 297 2010 Charles 298 2011 David 300 2010 Peter 301 2011 Richard Table 2 (t2) id year food --------------------------- 296 2009 Bananas 296 2011 Bananas 297 2009 Melon 297 2010 Coffee 297 2012 Cheese 298 2007 Sugar 298 2008 Cereal 298 2012 Chocolate 299 2000 Peas 300 2007 Barley 300 2011 Beans 300 2012 Chickpeas 301 2010 Watermelon I want to join the tables on id and year. The catch is that (1) id must match exactly, but if there is no exact match in Table 2 for the year in Table 1, then I want to choose the year that is the next (lower) available. A selection of the kind that I want to produce would give the following result id year matchyr name food ------------------------------------------------- 297 2010 2010 Charles Coffee 298 2011 2008 David Cereal 300 2010 2007 Peter Barley 301 2011 2010 Richard Watermelon To summarise, id=297 had an exact match for year=2010 given in Table 1, so the corresponding line for id=297, year=2010 is chosen from Table 2. id=298, year=2011 did not have a matching year in Table 2, so the next available year (less than 2011) is chosen. As you can see, I would also like to know what that matched year (whether exactly , or inexactly) actually was. I would very much appreciate (1) an indication (yes/no answer) of whether this is possible to do in SQL alone, or whether I need to look outside SQL, and (2) a solution, if that is not too onerous.

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• REST - Tradeoffs between content negotiation via Accept header versus extensions

  - by Brandon Linton

  I'm working through designing a RESTful API. We know we want to return JSON and XML for any given resource. I had been thinking we would do something like this: GET /api/something?param1=value1 Accept: application/xml (or application/json) However, someone tossed out using extensions for this, like so: GET /api/something.xml?parm1=value1 (or /api/something.json?param1=value1) What are the tradeoffs with these approaches? Is it best to rely on the accept header when an extension isn't specified, but honor extensions when specified? Is there a drawback to that approach?

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• Getting started with ClojureScript and Google Closure

  - by Andrea

  I would like to investigate whether ClojureScript, with the associated Google Closure library is a reasonable tool to build modern, in-browser, Javascript applications. My current Javascript stack consists of jQuery, Backbone and RequireJS with the possible additions of some widgets libraries like jQueryUI or KendoUI. So it will be quite a big leap (I already know how to work in Clojure, although I have little experience). What is a good roadmap to do so? Should I learn the Google Closure library first, or can I grasp it together with ClojureScript? One thing I am concerned about is the overall application structure. Backbone is rather opinionated on how to organize your application. I am not sure whether Google Closure also includes some components to help with the design of the application. And, if this is the case, I do not know how to tell whether this structure will port to ClojureScript or a ClojureScript application will require a different organization anyway, and only use - say - the widgets and DOM manipulation features of Closure.

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• Exclusive use of a Jini server during long-running call

  - by Matthew Flint

  I'm trying to use Jini, in a "Masters/Workers" arrangement, but the Worker jobs may be long running. In addition, each worker needs to have exclusive access to a singleton resource on that machine. As it stands, if a Worker receives another request while a previous request is running, then the new request is accepted and executed in a second thread. Are there any best-practices to ensure that a Worker accepts no further jobs until the current job is complete? Things I've considered: synchronize the job on the server, with a lock on the singleton resource. This would work, but is far from ideal. A call from a Master would block until the current Worker thread completes, even if other Workers become free in the meantime unregister the Worker from the registry while the job is running, then re-register when it completes. Might work OK, but something doesn't smell right with this idea... Of course, I'm quite happy to be told that there are more appropriate technologies than Jini... but I wouldn't want anything too heavyweight, like rolling out EJB containers all over the place.

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• Microkernel architectural pattern and applicability for business applications

  - by Pangea

  We are in the business of building customizable web applications. We have the core team that provides what we call as the core platform (provides services like security, billing etc.) on top of which core products are built. These core products are industry specific solutions like telecom, utility etc. These core products are later used by other teams to build customer specific solutions in a particular industry. Until now we have a loose separation between platform and core product. The customer specific solutions are build by customizing 20-40% of the core offering and re-packaging. The core-platform and core products are released together as monolithic apps (ear). I am looking to improvise the current situation so that there is a cleaner separation on these 3. This allows us to have evolve each of these 3 separately etc. I've read through the Mircokernel architecture and kind of felt that I can take apply the principles in my context. But most of my reading about this pattern is always in the context of operating systems or application servers etc. I am wondering if there are any examples on how that pattern was used for architecting business applications. Or you could provide some insight on how to apply that pattern to my problem.

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• Fast set indexing data structure for superset retrieval

  - by Asterios

  I am given a set of sets: {{a,b}, {a,b,c}, {a,c}, {a,c,f}} I would like to have a data structure to index those sets such that the following "lookup" is executed fast: find all supersets of a given set. For example, given the set {a,c} the structure would return {{a,b,c}, {a,c,f}, {a,c}} but not {a,b}. Any suggestions? Could this be done with a smart trie-like data structure storing sets after a proper sorting? This data structures is going to be queried a lot. Thus, I'm searching for a structure that might be expensive in build but rather fast to query.

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• What are basic programming directions? [closed]

  - by Goward Gerald

  What are basic programming directions? Can you please list them and give a brief review of each? Would be nice to have a list for each direction (web-development/*enterprise*/standalone/*mobile*/etc, correct me if I skipped something) like this: 1). Most popular languages of this direction (php for web, objective C for iOS mobile development etc) 2). It's demand on market (from 0 to 5, subjective) 3). How much tasks differ (do you always create same-of-a-kind programs which are like clones of each oother or projects change and you often get to create something interesting, new and fresh?) 4). Freelance demand (from 0 to 5) 5). Fun factor (from 0 to 5, totally subjective but still write it please) Thanks!

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• Why do large IT projects tend to fail or have big cost/schedule overruns?

  - by Pratik

  I always read about large scale transformation or integration project that are total or almost total disaster. Even if they somehow manage to succeed the cost and schedule blow out is enormous. What is the real reason behind large projects being more prone to failure. Can agile be used in these sort of projects or traditional approach is still the best. One example from Australia is the Queensland Payroll project where they changed test success criteria to deliver the project. See some more failed projects in this SO question Have you got any personal experience to share?

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• Is it typical for a provider of a web services to also provide client libraries?

  - by HDave

  My company is building a corporate Java web-app and we are leaning towards using GWT-RPC as the client-server protocol for performance reasons. However, in the future, we will need to provide an API for other enterprise systems to access our data as well. For this, we were thinking of a SOAP based web service. In my experience it is common for commercial providers of enterprise web applications to provide client libraries (Java, .NET, C#, etc.). Is this generally the case? I ask because if so, then why bother using SOAP or REST or any standard web services protocol at all? Why not just create a client libraries that communicate via GWT-RPC?

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• UML Diagrams of Multi-Threaded Applications

  - by PersonalNexus

  For single-threaded applications I like to use class diagrams to get an overview of the architecture of that application. This type of diagram, however, hasn’t been very helpful when trying to understand heavily multi-threaded/concurrent applications, for instance because different instances of a class "live" on different threads (meaning accessing an instance is save only from the one thread it lives on). Consequently, associations between classes don’t necessarily mean that I can call methods on those objects, but instead I have to make that call on the target object's thread. Most literature I have dug up on the topic such as Designing Concurrent, Distributed, and Real-Time Applications with UML by Hassan Gomaa had some nice ideas, such as drawing thread boundaries into object diagrams, but overall seemed a bit too academic and wordy to be really useful. I don’t want to use these diagrams as a high-level view of the problem domain, but rather as a detailed description of my classes/objects, their interactions and the limitations due to thread-boundaries I mentioned above. I would therefore like to know: What types of diagrams have you found to be most helpful in understanding multi-threaded applications? Are there any extensions to classic UML that take into account the peculiarities of multi-threaded applications, e.g. through annotations illustrating that some objects might live in a certain thread while others have no thread-affinity; some fields of an object may be read from any thread, but written to only from one; some methods are synchronous and return a result while others are asynchronous that get requests queued up and return results for instance via a callback on a different thread.

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• How to achieve a loosely coupled REST API but with a defined and well understood contract?

  - by BestPractices

  I am new to REST and am struggling to understand how one would properly design a REST system to both allow for loose coupling but at the same time allow a consumer of a REST API to understand the API. If, in my client code, I issue a GET request for a resource and get back XML, how do I know what to do with that xml? e.g. if it contains <fname>John</fname><lname>Smith</lname> how do I know that these refer to the concept of "first name", "last name"? Is it up to the person writing the REST API to define in documentation some place what each of the XML fields mean? What if producer of the API wants to change the implementation to be <firstname> instead of <fname>? How do they do this and notify their consumers that this change occurred? Or do the consumers just encounter the error and then look at the payload and figure out on their own that it changed? I've read in REST in Practice that using a WADL tool to create a client implementation based on the WADL (and hide the fact that you're doing a distributed call) is an "anti-pattern". But I was planning to do this-- at least then I would have a statically typed API call that, if it changed, I would know at compile time and not at run time. Why is this a bad thing to generate client code based on a WADL? And how do I know what to do with the links that returned in the response of a POST to a REST API? What defines this contract and gives true meaning to what each link will do? Please help! I dont understand how to go from statically-typed or even SOAP/RPC to REST!

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• Class instance clustering in object reference graph for multi-entries serialization

  - by Juh_

  My question is on the best way to cluster a graph of class instances (i.e. objects, the graph nodes) linked by object references (the -directed- edges of the graph) around specifically marked objects. To explain better my question, let me explain my motivation: I currently use a moderately complex system to serialize the data used in my projects: "marked" objects have a specific attributes which stores a "saving entry": the path to an associated file on disc (but it could be done for any storage type providing the suitable interface) Those object can then be serialized automatically (eg: obj.save()) The serialization of a marked object 'a' contains implicitly all objects 'b' for which 'a' has a reference to, directly s.t: a.b = b, or indirectly s.t.: a.c.b = b for some object 'c' This is very simple and basically define specific storage entries to specific objects. I have then "container" type objects that: can be serialized similarly (in fact their are or can-be "marked") they don't serialize in their storage entries the "marked" objects (with direct reference): if a and a.b are both marked, a.save() calls b.save() and stores a.b = storage_entry(b) So, if I serialize 'a', it will serialize automatically all objects that can be reached from 'a' through the object reference graph, possibly in multiples entries. That is what I want, and is usually provides the functionalities I need. However, it is very ad-hoc and there are some structural limitations to this approach: the multi-entry saving can only works through direct connections in "container" objects, and there are situations with undefined behavior such as if two "marked" objects 'a'and 'b' both have a reference to an unmarked object 'c'. In this case my system will stores 'c' in both 'a' and 'b' making an implicit copy which not only double the storage size, but also change the object reference graph after re-loading. I am thinking of generalizing the process. Apart for the practical questions on implementation (I am coding in python, and use Pickle to serialize my objects), there is a general question on the way to attach (cluster) unmarked objects to marked ones. So, my questions are: What are the important issues that should be considered? Basically why not just use any graph parsing algorithm with the "attach to last marked node" behavior. Is there any work done on this problem, practical or theoretical, that I should be aware of? Note: I added the tag graph-database because I think the answer might come from that fields, even if the question is not.

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• Pros and cons of hosted scripts

  - by P.Brian.Mackey

  I have seen some developers use hosted scripts to link their libraries. cdn.jquerytools.org is one example. I have also seen people complain that a hosted script link has been hijacked. How safe is using hosted scripts in reality? Are the scripts automatically updated? For example, if jQuery 5 goes to 6 do I automatically get version 6 or do I need to update my link? I also see that Google has a large set of these scripts setup for hosting. What are the pros and cons?

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• Why maven so slow compared to automake?

  - by ???'Lenik

  I have a Maven project consists of around 100 modules. I have reason to decompose the project to so many modules, and I don't think I should merge them in order to speed up the build process. I have read a lot of projects by other people, e.g., the Maven project itself, and Apache Archiva, and Hudson project, they all consists of a lot of modules, nearly 100 maybe, more or less. The problem is, to build them all need so much time, 3 hours for the first time build (this is acceptable because a lot of artifacts to download), and 15 minutes for the second build (this is not acceptable). For automake, things are similarly, the first time you need to configure the project, to prepare the magical config.h file, it's far more complex then what maven does. But it's still fast, maybe 10 seconds on my Debian box. After then, make install requires maybe 10 minutes for the first time build. However, when everything get prepared, the .o object files are generated, they don't have to be rebuild at all for the second time build. (In Maven, everything rebuild at everytime.) I'm very wondering, how guys working for Maven projects can bare this long time for each build, I'm just can't sit down calmly during each time Maven build, it took too long time, really.

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• Library to fake intermittent failures according to tester-defined policy?

  - by crosstalk

  I'm looking for a library that I can use to help mock a program component that works only intermittently - usually, it works fine, but sometimes it fails. For example, suppose I need to read data from a file, and my program has to avoid crashing or hanging when a read fails due to a disk head crash. I'd like to model that by having a mock data reader function that returns mock data 90% of the time, but hangs or returns garbage otherwise. Or, if I'm stress-testing my full program, I could turn on debugging code in my real data reader module to make it return real data 90% of the time and hang otherwise. Now, obviously, in this particular example I could just code up my mock manually to test against a random() routine. However, I was looking for a system that allows implementing any failure policy I want, including: Fail randomly 10% of the time Succeed 10 times, fail 4 times, repeat Fail semi-randomly, such that one failure tends to be followed by a burst of more failures Any policy the tester wants to define Furthermore, I'd like to be able to change the failure policy at runtime, using either code internal to the program under test, or external knobs or switches (though the latter can be implemented with the former). In pig-Java, I'd envision a FailureFaker interface like so: interface FailureFaker { /** Return true if and only if the mocked operation succeeded. Implementors should override this method with versions consistent with their failure policy. */ public boolean attempt(); } And each failure policy would be a class implementing FailureFaker; for example there would be a PatternFailureFaker that would succeed N times, then fail M times, then repeat, and a AlwaysFailFailureFaker that I'd use temporarily when I need to simulate, say, someone removing the external hard drive my data was on. The policy could then be used (and changed) in my mock object code like so: class MyMockComponent { FailureFaker faker; public void doSomething() { if (faker.attempt()) { // ... } else { throw new RuntimeException(); } } void setFailurePolicy (FailureFaker policy) { this.faker = policy; } } Now, this seems like something that would be part of a mocking library, so I wouldn't be surprised if it's been done before. (In fact, I got the idea from Steve Maguire's Writing Solid Code, where he discusses this exact idea on pages 228-231, saying that such facilities were common in Microsoft code of that early-90's era.) However, I'm only familiar with EasyMock and jMockit for Java, and neither AFAIK have this function, or something similar with different syntax. Hence, the question: Do such libraries as I've described above exist? If they do, where have you found them useful? If you haven't found them useful, why not?

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• Is the output of Eclipse's incremental java compiler used in production? Or is it simply to support Eclipse's features?

  - by Doug T.

  I'm new to Java and Eclipse. One of my most recent discoveries was how Eclipse comes shipped with its own java compiler (ejc) for doing incremental builds. Eclipse seems to by default output incrementally built class files to the projRoot/bin folder. I've noticed too that many projects come with ant files to build the project that uses the java compiler built into the system for doing the production builds. Coming from a Windows/Visual Studio world where Visual Studio is invoking the compiler for both production and debugging, I'm used to the IDE having a more intimate relationship with the command-line compiler. I'm used to the project being the make file. So my mental model is a little off. Is whats produced by Eclipse ever used in production? Or is it typically only used to support Eclipse's features (ie its intellisense/incremental building/etc)? Is it typical that for the final "release" build of a project, that ant, maven, or another tool is used to do the full build from the command line? Mostly I'm looking for the general convention in the Eclipse/Java community. I realize that there may be some outliers out there who DO use ecj in production, but is this generally frowned upon? Or is this normal/accepted practice?

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• Importance of a 1st Class Degree

  - by Nipuna Silva

  I'm currently at the 3rd year following a degree in Software Engineering. I'm thinking of moving into a research field in the future (programming language design, AI etc.) My problems are, What is the advantage/importance of carrying a 1st Class Degree (Honors for Americans) in to the industry rather than with just simple pass. Is it really important to have a 1st Class? Is it the practical knowledge i have to give priority or the theoretical knowledge, or both?

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• Does Microsoft really offer "support"?

  - by SpashHit

  One of the arguments against using Open Source is that there is no "support". However, do big vendors (e.g. Microsoft) really offer "support" of any kind? I'm sure there is some sort of 4-figure-per-hour "paid support" option out there, but is that really an "option" for any problem short of one that is going to bankrupt your business? To put it more concretely... I buy a Microsoft product... it has a bug... now what? And how is that better than what I get from Open Source?

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• How should I determine my rates for writing custom software?

  - by Carson Myers

  For a custom software that will likely take a year or more to develop, how would I go about determining what to charge as a consultant? I'm having a hard time coming up with a number, and searches online are providing vastly different numbers (between $55/hr and $300/hr). I don't want to shoot too low because it's going to take me so much time (and I'm deferring my education for this project). I also don't want to shoot too high and get unpleasant looks and demand for justification. FWIW I live in Canada, and have approx. 10 years of development experience. I've read the "take your salary and divide it by 1000" rule of thumb, but the thing is I don't have a salary. Currently I'm just doing fairly small programming tasks for a friend who is starting a marketing company, pricing each task fairly arbitrarily. I don't know what I would make over the course of a year doing it, but it would be incredibly low. My responsibilities for the project would be the architecture, programming, database, server, and UX to some degree. It's going to be a public facing web service so I will also need to put a lot of effort into security and scalability. Any advice or experience?

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• What are the steps to grouping related classes into packages

  - by user2368481

  I've been googling this for some time, but what I haven't found are the clear steps needed to be taken to group related classes into packages in Java. In my case, I have about a number of .java files that I'd like to group into 3 packages according to the MVC pattern. One package for Model classes, one package for View classes and one package for Controller classes. I've identified which belong in what package, but not sure of the next step.

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• Looking software for making an animated cartoon to present a new application/scenario idea

  - by Skarab

  I have an idea for an application (+usage scenario) and I would like to create an animated cartoon that shows a use case for this application and its novelty. My company is a rather big so I am looking for an interesting way to get people know my idea to get feedback/get a green light to further develop it. Therefore I am looking for an application (free or commercial) that I could use to realize such an animated cartoon. I have posted this quesion before on stackoverflow, but I think this might be a better community to ask such a question.

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• Web services, Java EE, Spring, DB integration project ideas - maybe data mining related?

  - by saral jain

  I am a graduate Computer Science student (Data Mining and Machine Learning) and have good exposure to core Java (3 years). I have read up on a bunch of stuff on the following topics: Design patterns, Java EE Web services (SOAP and REST), Spring, and Hibernate Java Concurrency - advanced features like Task and Executors. I would now like to do a project combining this stuff -- over my free time of course -- to get a better understanding of these things and to kind of make an end to end software (to learn the best design principles etc + SVN, maven). Any good project ideas would be really appreciated. I just want to build this stuff to learn, so I don't really mind re-inventing the wheel. Also, anything related to data mining would be an added bonus as it fits with my research but is absolutely not necessary since this project is more to learn to do large scale software development.

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