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On October 07 2017 09:05 Manit0u wrote:Show nested quote +On October 07 2017 06:10 berated- wrote:On October 07 2017 01:59 Manit0u wrote:On October 07 2017 01:00 spinesheath wrote:On October 06 2017 18:14 Manit0u wrote: I wanted to git gud at OOP. Now I have strategies built upon more abstract strategies which select factories built upon more abstract factories and it's all encompassed in even more abstractions with managers, providers, resolvers, handlers, services and such. All this to parse single JSON file...
Someone who is good with OOP would use an existing parser. I am using an existing parser. But I need to parse the contents of the JSON and then map them to our database structure creating/updating records as necessary. Every time I see stuff like this I always just want to post the image from the medium article showing java having the highest paid salaries. >_< Which parsing library are you using? You parsing into json objects and then doing the data transformations yourself or using something like Gson and going straight to objects? You even in java? Edit: I think you're in ruby, right? Design patterns never made much sense to me until I started testing. Once you starting writing code for testability they make a ton of sense. If you are just trying to break things down because you "want to git gud" (yeah I know you're joking), then it's really hard to see where you really need to make your seams. Yeah. Also, my original post was kind of a sitire (pointed at myself of course) about how you can sometimes go overboard and do simple stuff in most convoluted ways.
Understood , but I know how much everyone likes to make fun of us OOP fans too :D
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On October 06 2017 23:02 travis wrote: We are learning about, and implementing in our latest project, DFAs and NFAs. I think they are pretty interesting and I was surprised I had literally never heard of them.
The professor never really told us what their applications are, though. It seems to me that their role is basically to pattern match? They are probably used to implement regex, for example?
Have any of you used these in the real world?
Our log-in mechanism uses a Finite State Machine to determine what actions should be shown and displayed.
https://gist.github.com/andymatuschak/d5f0a8730ad601bcccae97e8398e25b2
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On October 06 2017 23:02 travis wrote: We are learning about, and implementing in our latest project, DFAs and NFAs. I think they are pretty interesting and I was surprised I had literally never heard of them.
The professor never really told us what their applications are, though. It seems to me that their role is basically to pattern match? They are probably used to implement regex, for example?
Have any of you used these in the real world? I use DFAs very extensively in a project of mine. It's an algorithm for calculating how far from winning a hand in riichi mahjong is. The straightforward implementation of that algorithm is recursive with a ridiculous amount of branching out, really slow. Other implementations use huge lookup tables (in the order of gigabytes) or medium sized lookup tables coupled with a small amount of recursion. My implementation basically takes a multi layered lookup table approach and instead of actually using lookup tables, I convert those into highly compressed DFAs. I got it down to a few of megabytes and no recursion at all.
In short: DFAs can be very useful when compressing data of the "words in a language" type.
There are plenty of other resonable applications though.
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On October 07 2017 17:27 spinesheath wrote:Show nested quote +On October 06 2017 23:02 travis wrote: We are learning about, and implementing in our latest project, DFAs and NFAs. I think they are pretty interesting and I was surprised I had literally never heard of them.
The professor never really told us what their applications are, though. It seems to me that their role is basically to pattern match? They are probably used to implement regex, for example?
Have any of you used these in the real world? I use DFAs very extensively in a project of mine. It's an algorithm for calculating how far from winning a hand in riichi mahjong is. The straightforward implementation of that algorithm is recursive with a ridiculous amount of branching out, really slow. Other implementations use huge lookup tables (in the order of gigabytes) or medium sized lookup tables coupled with a small amount of recursion. My implementation basically takes a multi layered lookup table approach and instead of actually using lookup tables, I convert those into highly compressed DFAs. I got it down to a few of megabytes and no recursion at all. In short: DFAs can be very useful when compressing data of the "words in a language" type. There are plenty of other resonable applications though. Working in AI there are about a billion uses for DFAs and NFAs. Not only that, but they are but a few of many graph-based formalisms for decision-making, and if you generalize these to Markov Decision Processes, you open a giant world of state-of-the-art research that is applied in all kinds of current applications from Siri to self-driving cars.
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Johto4893 Posts
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On October 06 2017 23:02 travis wrote: We are learning about, and implementing in our latest project, DFAs and NFAs. I think they are pretty interesting and I was surprised I had literally never heard of them.
The professor never really told us what their applications are, though. It seems to me that their role is basically to pattern match? They are probably used to implement regex, for example?
Have any of you used these in the real world?
*cough cough* compilers *cough cough*
In general there is Chomsky hierarchy, which you either already learned about or probably are going to learn about, which covers all of the classic compiler phases (and more). Your idea with regex for example was spot on. Regex is short for regular expressions, often used as a keyword for its function in programming languages, which is FSA in action. It is also an own category / set or subset in Chomsky’s hierarchy. There are 4 sets in Chomsky’s hierarchy (3 if you only count languages / grammars), whereby each set is including the previous set. Regular-expressions (not a language yet, which is why you will read about the 3 models for description of language) -> context-free grammar -> context-sensitive grammar -> recursively enumerable. Which means regular expressions are part of context-free grammar which is part of context-sensitive grammar…
Each of these sets get covered by an automata theory, and all but the last are usually featured in compiler theory: Regular expressions - this gets covered by FSA (DFAs and NFAs) as stated, in compiler theory this is used by the lexer (which basically matches pattern, so again: spot on). Context-free grammar - this gets covered by pushdown Automata and is used in compiler theory when building a parser. Context-sensitive grammar - this gets covered by linear bounded automata and basically covers a programming languages as a whole and in execution. Recursively enumerable - this gets covered by Turing machines, but doesn’t have to come up in compiler theory.
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Johto4893 Posts
Ah Elasticsearch is a beast, we use it on Liquipedia ^^
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On October 11 2017 17:53 FO-nTTaX wrote:Ah Elasticsearch is a beast, we use it on Liquipedia ^^
Yeah. Only got to work with it once though.
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Guys, I need help...
Can you think of possible reasons why triggers would stop working in the db (postgres)?
I've checked, they're there. Functions are there. Definitions are in place. They just don't fire.
Checked locally with same schema, triggers are fired. On the server, not at all.
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On October 12 2017 20:04 Manit0u wrote: Guys, I need help...
Can you think of possible reasons why triggers would stop working in the db (postgres)?
I've checked, they're there. Functions are there. Definitions are in place. They just don't fire.
Checked locally with same schema, triggers are fired. On the server, not at all.
Figure it out? I'm sure you checked all the easy stuff, looks like triggers can stop firing if one returns null, was a new one introduced?
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On October 13 2017 07:22 berated- wrote:Show nested quote +On October 12 2017 20:04 Manit0u wrote: Guys, I need help...
Can you think of possible reasons why triggers would stop working in the db (postgres)?
I've checked, they're there. Functions are there. Definitions are in place. They just don't fire.
Checked locally with same schema, triggers are fired. On the server, not at all. Figure it out? I'm sure you checked all the easy stuff, looks like triggers can stop firing if one returns null, was a new one introduced?
One was updated. Thankfully it wasn't in production yet so we could just drop and recreate the DB (it works fine now) because of lack of time to figure it out properly.
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Hi guys, I need a little help here,
I'm learning JavaEE (EJBs at the moment). I'm following this tutorial:https://www.tutorialspoint.com/ejb/ejb_create_application.htm
The tutorial uses JBoss 5.0.1. I used Wildfly 10 instead.
I'm having an issue with the JNDI.properties part:
java.naming.factory.initial=org.jnp.interfaces.NamingContextFactory java.naming.factory.url.pkgs=org.jboss.naming:org.jnp.interfaces java.naming.provider.url=localhost
When I try to run I get this:
javax.naming.NoInitialContextException: Cannot instantiate class: org.jnp.interfaces.NamingContextFactory [Root exception is java.lang.ClassNotFoundException: org.jnp.interfaces.NamingContextFactory] null at javax.naming.spi.NamingManager.getInitialContext(NamingManager.java:674) at javax.naming.InitialContext.getDefaultInitCtx(InitialContext.java:313) at javax.naming.InitialContext.init(InitialContext.java:244) at javax.naming.InitialContext.<init>(InitialContext.java:216) at com.tutorialspoint.test.EJBTester.<init>(EJBTester.java:38) at com.tutorialspoint.test.EJBTester.main(EJBTester.java:47) Caused by: java.lang.ClassNotFoundException: org.jnp.interfaces.NamingContextFactory at java.net.URLClassLoader.findClass(URLClassLoader.java:381) at java.lang.ClassLoader.loadClass(ClassLoader.java:424) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:335) at java.lang.ClassLoader.loadClass(ClassLoader.java:357) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:348) at com.sun.naming.internal.VersionHelper12.loadClass(VersionHelper12.java:72) at com.sun.naming.internal.VersionHelper12.loadClass(VersionHelper12.java:61) at javax.naming.spi.NamingManager.getInitialContext(NamingManager.java:672) ... 5 more java.lang.NullPointerException at com.tutorialspoint.test.EJBTester.testStatelessEjb(EJBTester.java:61) at com.tutorialspoint.test.EJBTester.main(EJBTester.java:49)
For some reason it is not able to find the org.jnp.interfaces.NamingContextFactory. I downloaded JFind to find it under wildfly installation but no luck. So I downloaded "jnp-client.jar" which contains org.jnp.interfaces.NamingContextFactory. Still, it can't find it. I added the path to the jnp-client.jar to the CLASSPATH, restarted wildfly and still it can't find it.
Any idea why this is happening?
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On October 14 2017 04:41 Wrath wrote:Hi guys, I need a little help here, I'm learning JavaEE (EJBs at the moment). I'm following this tutorial:https://www.tutorialspoint.com/ejb/ejb_create_application.htm The tutorial uses JBoss 5.0.1. I used Wildfly 10 instead. I'm having an issue with the JNDI.properties part: java.naming.factory.initial=org.jnp.interfaces.NamingContextFactory java.naming.factory.url.pkgs=org.jboss.naming:org.jnp.interfaces java.naming.provider.url=localhost
When I try to run I get this: javax.naming.NoInitialContextException: Cannot instantiate class: org.jnp.interfaces.NamingContextFactory [Root exception is java.lang.ClassNotFoundException: org.jnp.interfaces.NamingContextFactory] null at javax.naming.spi.NamingManager.getInitialContext(NamingManager.java:674) at javax.naming.InitialContext.getDefaultInitCtx(InitialContext.java:313) at javax.naming.InitialContext.init(InitialContext.java:244) at javax.naming.InitialContext.<init>(InitialContext.java:216) at com.tutorialspoint.test.EJBTester.<init>(EJBTester.java:38) at com.tutorialspoint.test.EJBTester.main(EJBTester.java:47) Caused by: java.lang.ClassNotFoundException: org.jnp.interfaces.NamingContextFactory at java.net.URLClassLoader.findClass(URLClassLoader.java:381) at java.lang.ClassLoader.loadClass(ClassLoader.java:424) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:335) at java.lang.ClassLoader.loadClass(ClassLoader.java:357) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:348) at com.sun.naming.internal.VersionHelper12.loadClass(VersionHelper12.java:72) at com.sun.naming.internal.VersionHelper12.loadClass(VersionHelper12.java:61) at javax.naming.spi.NamingManager.getInitialContext(NamingManager.java:672) ... 5 more java.lang.NullPointerException at com.tutorialspoint.test.EJBTester.testStatelessEjb(EJBTester.java:61) at com.tutorialspoint.test.EJBTester.main(EJBTester.java:49)
For some reason it is not able to find the org.jnp.interfaces.NamingContextFactory. I downloaded JFind to find it under wildfly installation but no luck. So I downloaded "jnp-client.jar" which contains org.jnp.interfaces.NamingContextFactory. Still, it can't find it. I added the path to the jnp-client.jar to the CLASSPATH, restarted wildfly and still it can't find it. Any idea why this is happening?
That tutorial looks like it was written for java ee 5 or so and you are trying to use a container that is meant for use with java ee 7. Is there any particular reason you are trying to use that exact tutorial?
Which version of Netbeans / java are you using?
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Using Java 1.8 / Netbeans 8.2
Edit: I'm using that tutorial because it is the one I find, and tutorialspoint has a lot of great tutorials for free. Except that most of them are outdated....
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On October 14 2017 15:28 Wrath wrote: Using Java 1.8 / Netbeans 8.2
Edit: I'm using that tutorial because it is the one I find, and tutorialspoint has a lot of great tutorials for free. Except that most of them are outdated....
Are you learning wildfly for a reason either? I haven't done EE tutorials in a long while, but, usually the java docs themselves are pretty good. If you're using netbeans and trying to learn base EE then sticking with glassfish might be easier too.
I'll try doing your combo real quick with wildfly that tutorial / netbeans and let you know what I find but, if you're using those other containers for no reason other than that's what suggested .. sticking with the reference implementation stack (netbeans / glassfish and their associated) could be quicker.
Edit : Certainly not trying to deter your learning, or avoid your question. It's just there are a lot of quirky things with using different versions of all the of different implementations. Java EE is just a spec, and there are multiple companies that become certified. Trying to swap out parts of the reference implementation (oracle/glassfish .. the stuff that comes with netbeans) with redhat's stuff (jboss/wildfly) is certainly doable, but, requires more tinkering.
I've been doing EEish dev (more spring and other frameworks than pure EE) and have made it to architect / director level and it would still take me some time to make sure that using some of each works correctly.
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I'm using wildfly as it is a more modern version of JBoss, the mentioned server in the tutorial. I just did not expect that things would be that off between Java 1.5 and 1.8. Also, as Netbeans is an IDE it should produce the same result, heck even if I replaced it by eclipse should be the same.
Do you have any more modern EJB tutorials? I'd like to be comfortable with basic JavaEE before moving to other frameworks like Spring and MVC.
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On October 14 2017 23:40 Wrath wrote: I'm using wildfly as it is a more modern version of JBoss, the mentioned server in the tutorial. I just did not expect that things would be that off between Java 1.5 and 1.8. Also, as Netbeans is an IDE it should produce the same result, heck even if I replaced it by eclipse should be the same.
Do you have any more modern EJB tutorials? I'd like to be comfortable with basic JavaEE before moving to other frameworks like Spring and MVC.
I'm looking and trying to get that tutorial point thing to work. It's mostly true what you're saying about the IDEs except that netbeans is doing a whole lot of work that you may or may not even be aware of when it starts the application server. It may take a bit cause honestly I'm not all that familiar with remote jndi so I'll let you know in a bit if I can get this thing working and what tutorials I used. It looks like in netbeans they had some samples (under new -> project), I'm not sure if any of those would help.
Spring/MVC is kind of a different world than Java EE. IMO and others can disagree but they are two different approaches to solving the same problem. EE depends heavily on the container providing you with a lot of the tools/configuration where as spring usually configures most things in the application itself.
I personally find the spring route much easier, but, I've also been doing it. But that's really tangental to the point at hand ... alright , trying to get this thing working.
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Alright, so I followed the first part of their tutorial almost exactly. Just picked glassfish as my application server. Didn't really detour too much from it. Built it, deployed it.
For the second part, I just did, new -> project, picked Enterprise Application Client.
And then I had to modify their file to this
package com.tutorialspoint.test; import com.tutorialspoint.stateless.LibrarySessionBeanRemote; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.util.List; import javax.naming.InitialContext; import javax.naming.NamingException; public class EJBTester { BufferedReader brConsoleReader = null; InitialContext ctx; { try { ctx = new InitialContext(); } catch (NamingException ex) { ex.printStackTrace(); } brConsoleReader = new BufferedReader(new InputStreamReader(System.in)); } public static void main(String[] args) { EJBTester ejbTester = new EJBTester(); ejbTester.testStatelessEjb(); } private void showGUI(){ System.out.println("**********************"); System.out.println("Welcome to Book Store"); System.out.println("**********************"); System.out.print("Options \n1. Add Book\n2. Exit \nEnter Choice: "); } private void testStatelessEjb(){ try { int choice = 1; LibrarySessionBeanRemote libraryBean = (LibrarySessionBeanRemote)ctx.lookup("com.tutorialspoint.stateless.LibrarySessionBeanRemote"); while (choice != 2) { String bookName; showGUI(); String strChoice = brConsoleReader.readLine(); choice = Integer.parseInt(strChoice); if (choice == 1) { System.out.print("Enter book name: "); bookName = brConsoleReader.readLine(); libraryBean.addBook(bookName); }else if (choice == 2) { break; } } List<String> booksList = libraryBean.getBooks(); System.out.println("Book(s) entered so far: " + booksList.size()); for (int i = 0; i < booksList.size(); ++i) { System.out.println((i+1)+". " + booksList.get(i)); } LibrarySessionBeanRemote libraryBean1 = (LibrarySessionBeanRemote)ctx.lookup("com.tutorialspoint.stateless.LibrarySessionBeanRemote"); List<String> booksList1 = libraryBean1.getBooks(); System.out.println( "***Using second lookup to get library stateless object***"); System.out.println( "Book(s) entered so far: " + booksList1.size()); for (int i = 0; i < booksList1.size(); ++i) { System.out.println((i+1)+". " + booksList1.get(i)); } } catch (Exception e) { System.out.println(e.getMessage()); e.printStackTrace(); }finally { try { if(brConsoleReader !=null){ brConsoleReader.close(); } } catch (IOException ex) { System.out.println(ex.getMessage()); } } } }
It's a bit of a shortcut, but , when I clicked run in the main file , it deployed it to the same application server that the EJB module was running in. Therefore, we didn't need to do a remote InitialContext, we could just construct a new one. I also had to change how I looked up the remote bean, as it didn't store it as the other tutorial did.
I was then able to get their output and add books.
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Not sure if I get it right... You made a enterprise application client and deployed to the server. Thus the client called the server from within the server? I'm still learning what is the InitialContext is so not sure what is the different between using here within the code or use it via jndi.properties. Sorry I'm still beginner
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