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• Correct permissions for /var/www and wordpress

  - by dpbklyn

  Hello and thank you in advance! I am relatively new to ubuntu, so please excuse the newbie-ness of this question... I have set up a LAMP server (ubuntu server 11.10) and I have access via SSH and to the "it works" page from a web browser from inside my network (via ip address) and from outside using dyndns. I have a couple of projects in development with some outside developers and I want to use this server as a development server for testing and for client approvals. We have some Wordpress projects that sit in subdirectories in /var/www/wordpress1 /var/www/wordpress2, etc. I cannot access these sub directories from a browser in order to set up WP--or (I assume) to see the content on a browser. I get a 403 Forbidden error on my browser. I assume that this is a permissions problem. Can you please tell me the proper settings for the permissions to: 1) Allow the developers and me to read/write. 2) to allow WP set up and do its thing 3) Allow visitors to access the site(s) via the web. I should also mention that the subfolder are actually simlinks to folder on another internal hdd--I don't think this will make a difference, but I thought I should disclose. Since I am a newbie to ubuntu, step-by-step directions are greatly appreciated! Thank you for taking the time! dp total 12 drwxr-xr-x 2 root root 4096 2012-07-12 10:55 . drwxr-xr-x 13 root root 4096 2012-07-11 20:02 .. lrwxrwxrwx 1 root root 43 2012-07-11 20:45 admin_media -> /root/django_src/django/contrib/admin/media -rw-r--r-- 1 root root 177 2012-07-11 17:50 index.html lrwxrwxrwx 1 root root 14 2012-07-11 20:42 media -> /hdd/web/media lrwxrwxrwx 1 root root 18 2012-07-12 10:55 wordpress -> /hdd/web/wordpress Here is the result of using chown -R www-data:www-data /var/www total 12 drwxr-xr-x 2 www-data www-data 4096 2012-07-12 10:55 . drwxr-xr-x 13 root root 4096 2012-07-11 20:02 .. lrwxrwxrwx 1 www-data www-data 43 2012-07-11 20:45 admin_media -> /root/django_src/django/contrib/admin/media -rw-r--r-- 1 www-data www-data 177 2012-07-11 17:50 index.html lrwxrwxrwx 1 www-data www-data 14 2012-07-11 20:42 media -> /hdd/web/media lrwxrwxrwx 1 www-data www-data 18 2012-07-12 10:55 wordpress -> /hdd/web/wordpress I am still unable to access via browser...

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• What do you do when working with multiple languages with different capitalization schemes?

  - by dvcolgan

  I'm making a webapp using Django. The Python convention for naming variables is lowercase_with_underscores, but the Javascript convention is camelCase. In addition, I've seen many people use lowercase-with-hyphens for CSS identifiers. Would you suggest using all three naming conventions where appropriate, or picking one and using it, even if the other two recommend something else? Switching back and forth isn't a huge problem, but it can still be mental overhead.

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• What is the best language to learn for WEB Development? [closed]

  - by Spoon Yukina

  I'm an IT student in my second year, and I want to learn a web development language, but I'm confused to choose between these languages: Django-J2EE-PHP-ASP.NET-Ruby & Rails, So what is the best language to learn of these, And which management database can be work perfectly with it? note that I learned these languages: C# - C - Assembly language - Python, for web development : HTML-CSS-JavaScript and for management database : SQL SERVER - ACCESS and for the moment I'm learning Java and C++

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• What’s the use of code reuse?

  - by Tony Davis

  All great developers write reusable code, don’t they? Well, maybe, but as with all statements regarding what “great” developers do or don’t do, it’s probably an over-simplification. A novice programmer, in particular, will encounter in the literature a general assumption of the importance of code reusability. They spend time worrying about DRY (don’t repeat yourself), moving logic into specific “helper” modules that they can then reuse, agonizing about the minutiae of the class structure, inheritance and interface design that will promote easy reuse. Unfortunately, writing code specifically for reuse often leads to complicated object hierarchies and inheritance models that are anything but reusable. If, instead, one strives to write simple code units that are highly maintainable and perform a single function, in a concise, isolated fashion then the potential for reuse simply “drops out” as a natural by-product. Programmers, of course, care about these principles, about encapsulation and clean interfaces that don’t expose inner workings and allow easy pluggability. This is great when it helps with the maintenance and development of code but how often, in practice, do we actually reuse our code? Most DBAs and database developers are familiar with the practical reasons for the limited opportunities to reuse database code and its potential downsides. However, surely elsewhere in our code base, reuse happens often. After all, we can all name examples, such as date/time handling modules, which if we write with enough care we can plug in to many places. I spoke to a developer just yesterday who looked me in the eye and told me that in 30+ years as a developer (a successful one, I’d add), he’d never once reused his own code. As I sat blinking in disbelief, he explained that, of course, he always thought he would reuse it. He’d often agonized over its design, certain that he was creating code of great significance that he and other generations would reuse, with grateful tears misting their eyes. In fact, it never happened. He had in his head, most of the algorithms he needed and would simply write the code from scratch each time, refining the algorithms and tailoring the code to meet the specific requirements. It was, he said, simply quicker to do that than dig out the old code, check it, correct the mistakes, and adapt it. Is this a common experience, or just a strange anomaly? Viewed in a certain light, building code with a focus on reusability seems to hark to a past age where people built cars and music systems with the idea that someone else could and would replace and reuse the parts. Technology advances so rapidly that the next time you need the “same” code, it’s likely a new technique, or a whole new language, has emerged in the meantime, better equipped to tackle the task. Maybe we should be less fearful of the idea that we could write code well suited to the system requirements, but with little regard for reuse potential, and then rewrite a better version from scratch the next time.

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• Measuring Code Quality

  - by DotNetBlues

  Several months back, I was tasked with measuring the quality of code in my organization. Foolishly, I said, "No problem." I figured that Visual Studio has a built-in code metrics tool (Analyze -> Calculate Code Metrics) and that would be a fine place to start with. I was right, but also very wrong. The Visual Studio calculates five primary metrics: Maintainability Index, Cyclomatic Complexity, Depth of Inheritance, Class Coupling, and Lines of Code. The first two are figured at the method level, the second at (primarily) the class level, and the last is a simple count. The first question any reasonable person should ask is "Which one do I look at first?" The first question any manager is going to ask is, "What one number tells me about the whole application?" My answer to both, in a way, was "Maintainability Index." Why? Because each of the other numbers represent one element of quality while MI is a composite number that includes Cyclomatic Complexity. I'd be lying if I said no consideration was given to the fact that it was abstract enough that it's harder for some surly developer (I've been known to resemble that remark) to start arguing why a high coupling or inheritance is no big deal or how complex requirements are to blame for complex code. I should also note that I don't think there is one magic bullet metric that will tell you objectively how good a code base is. There are a ton of different metrics out there, and each one was created for a specific purpose in mind and has a pet theory behind it. When you've got a group of developers who aren't accustomed to measuring code quality, picking a 0-100 scale, non-controversial metric that can be easily generated by tools you already own really isn't a bad place to start. That sort of answers the question a developer would ask, but what about the management question; how do you dashboard this stuff when Visual Studio doesn't roll up the numbers to the solution level? Since VS does roll up the MI to the project level, I thought I could just figure out what sort of weighting Microsoft used to roll method scores up to the class level and then to the namespace and project levels. I was a bit surprised by the answer: there is no weighting. That means that a class with one 1300 line method (which will score a 0 MI) and one empty constructor (which will score a 100 MI) will have an overall MI of a respectable 50. Throw in a couple of DTOs that are nothing more than getters and setters (which tend to score 95 or better) and the project ends up looking really, really healthy. The next poor bastard who has to work on the application is probably not going to be singing the praises of its maintainability, though. For the record, that 1300 line method isn't a hypothetical, either. So, what does one do with that? Well, I decided to weight the average by the Lines of Code per method. For our above example, the formula for the class's MI becomes ((1300 * 0) + (1 * 100))/1301 = .077, rounded to 0. Sounds about right. Continue the pattern for namespace, project, solution, and even multi-solution application MI scores. This can be done relatively easily by using the "export to Excel" button and running a quick formula against the data. On the short list of follow-up questions would be, "How do I improve my application's score?" That's an answer for another time, though.

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• Why is there no service-oriented language?

  - by Wolfgang

  Edit: To avoid further confusion: I am not talking about web services and such. I am talking about structuring applications internally, it's not about how computers communicate. It's about programming languages, compilers and how the imperative programming paradigm is extended. Original: In the imperative programming field, we saw two paradigms in the past 20 years (or more): object-oriented (OO), and service-oriented (SO) aka. component-based (CB). Both paradigms extend the imperative programming paradigm by introducing their own notion of modules. OO calls them objects (and classes) and lets them encapsulates both data (fields) and procedures (methods) together. SO, in contrast, separates data (records, beans, ...) from code (components, services). However, only OO has programming languages which natively support its paradigm: Smalltalk, C++, Java and all other JVM-compatibles, C# and all other .NET-compatibles, Python etc. SO has no such native language. It only comes into existence on top of procedural languages or OO languages: COM/DCOM (binary, C, C++), CORBA, EJB, Spring, Guice (all Java), ... These SO frameworks clearly suffer from the missing native language support of their concepts. They start using OO classes to represent services and records. This leads to designs where there is a clear distinction between classes that have methods only (services) and those that have fields only (records). Inheritance between services or records is then simulated by inheritance of classes. Technically, its not kept so strictly but in general programmers are adviced to make classes to play only one of the two roles. They use additional, external languages to represent the missing parts: IDL's, XML configurations, Annotations in Java code, or even embedded DSL like in Guice. This is especially needed, but not limited to, since the composition of services is not part of the service code itself. In OO, objects create other objects so there is no need for such facilities but for SO there is because services don't instantiate or configure other services. They establish an inner-platform effect on top of OO (early EJB, CORBA) where the programmer has to write all the code that is needed to "drive" SO. Classes represent only a part of the nature of a service and lots of classes have to be written to form a service together. All that boiler plate is necessary because there is no SO compiler which would do it for the programmer. This is just like some people did it in C for OO when there was no C++. You just pass the record which holds the data of the object as a first parameter to the procedure which is the method. In a OO language this parameter is implicit and the compiler produces all the code that we need for virtual functions etc. For SO, this is clearly missing. Especially the newer frameworks extensively use AOP or introspection to add the missing parts to a OO language. This doesn't bring the necessary language expressiveness but avoids the boiler platform code described in the previous point. Some frameworks use code generation to produce the boiler plate code. Configuration files in XML or annotations in OO code is the source of information for this. Not all of the phenomena that I mentioned above can be attributed to SO but I hope it clearly shows that there is a need for a SO language. Since this paradigm is so popular: why isn't there one? Or maybe there are some academic ones but at least the industry doesn't use one.

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• Getting client denied when accessing a wsgi graphite script

  - by Dr BDO Adams

  I'm trying to set up graphite on my Mac OS X 10.7 lion, i've set up apache to call the python graphite script via WSGI, but when i try to access it, i get a forbiden from apache and in the error log. "client denied by server configuration: /opt/graphite/webapp/graphite.wsgi" I've checked that the scripts location is allowed in httpd.conf, and the permissions of the file, but they seem correct. What do i have to do to get access. Below is the httpd.conf, which is nearly the graphite example. <IfModule !wsgi_module.c> LoadModule wsgi_module modules/mod_wsgi.so </IfModule> WSGISocketPrefix /usr/local/apache/run/wigs <VirtualHost _default_:*> ServerName graphite DocumentRoot "/opt/graphite/webapp" ErrorLog /opt/graphite/storage/log/webapp/error.log CustomLog /opt/graphite/storage/log/webapp/access.log common WSGIDaemonProcess graphite processes=5 threads=5 display-name='%{GROUP}' inactivity-timeout=120 WSGIProcessGroup graphite WSGIApplicationGroup %{GLOBAL} WSGIImportScript /opt/graphite/conf/graphite.wsgi process-group=graphite application-group=%{GLOBAL} # XXX You will need to create this file! There is a graphite.wsgi.example # file in this directory that you can safely use, just copy it to graphite.wgsi WSGIScriptAlias / /opt/graphite/webapp/graphite.wsgi Alias /content/ /opt/graphite/webapp/content/ <Location "/content/"> SetHandler None </Location> # XXX In order for the django admin site media to work you Alias /media/ "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site- packages/django/contrib/admin/media/" <Location "/media/"> SetHandler None </Location> # The graphite.wsgi file has to be accessible by apache. <Directory "/opt/graphite/webapp/"> Options +ExecCGI Order deny,allow Allow from all </Directory> </VirtualHost> Can you help?

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• Apache error: could not make child process 25105 exit, attempting to continue anyway

  - by Temnovit

  Hello! I have a web server based on Ubuntu Server 9.10 with this software: apache 2 PHP 5.3 MySQL 5 Python 2.5 Few of my websites are PHP based, few use python/django through mod_wsgi. For month or so, every day my apache server stops responding until I manually restart it. Error logs show: [Fri Mar 05 17:06:47 2010] [error] could not make child process 25059 exit, attempting to continue anyway [Fri Mar 05 17:06:47 2010] [error] could not make child process 25061 exit, attempting to continue anyway [Fri Mar 05 17:06:47 2010] [error] could not make child process 24930 exit, attempting to continue anyway [Fri Mar 05 17:06:47 2010] [error] could not make child process 25084 exit, attempting to continue anyway [Fri Mar 05 17:06:47 2010] [error] could not make child process 25105 exit, attempting to continue anyway and so on. I tried to google this problem but it seems, that I can't find a solution there. How can I determine the cause of this error and how do I fix it? Thank you for your help. UPDATE Updating mod-wsgi to version 3.1 didn't solve the problem Updating PHP to 5.3 also didn't solve it Here is a list of all installed modules: core mod_log_config mod_logio prefork http_core mod_so mod_alias mod_auth_basic mod_authn_file mod_authz_default mod_authz_groupfile mod_authz_host mod_authz_user mod_autoindex mod_cgi mod_deflate mod_dir mod_env mod_mime mod_negotiation mod_php5 mod_rewrite mod_setenvif mod_status mod_wsgi Here's how my virtual host with wsgi looks: <VirtualHost *:80> ServerName example.net DocumentRoot /var/www/example.net #wcgi script that serves all the thing WSGIScriptAlias / /var/www/example.net/index.wsgi WSGIDaemonProcess example user=wsgideamonuser group=root processes=1 threads=10 WSGIProcessGroup example Alias /static /var/www/example.net/static #serving admin files Alias /media/ /usr/local/lib/python2.6/dist-packages/django/contrib/admin/media/ <Location "/static"> SetHandler None </Location> <Location "/media"> SetHandler None </Location> ErrorLog /var/www/example.net/error.log </VirtualHost> Error log now contains two types of errors fallowed one by another: [error] child process 9486 still did not exit, sending a SIGKILL [error] could not make child process 9106 exit, attempting to continue anyway

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• mod_wsgi, .htaccess and rewriterule

  - by hadaraz

  I'm using several django projects running on the same apache instance through mod_wsgi, configured with virtualhost for each site, see the httpd.conf here. For one of the sites I want to use static-cache (staticgenerator), so I set up a directory with .htaccess file which contains: RequestHeader unset X-Forwarded-Host RewriteEngine on RewriteBase / RewriteCond %{REQUEST_FILENAME} !-d RewriteCond %{REQUEST_FILENAME}/index.html !-f RewriteRule ^(.*) http://127.0.0.1:3456/$1 [P] where 3456 is the django port on the server. Using this rewrite rule, the request is always forwarded to the mod_wsgi handler, even if the file or directory exists, and if the file index.html exists the request shows as request-path/index.html. I tried another setup: RequestHeader unset X-Forwarded-Host RewriteEngine on RewriteBase / RewriteCond $1 !-d RewriteCond $1index.html !-f RewriteRule ^(.*) http://127.0.0.1:3456/$1 [P] but got almost the same results. All requests are transferred to the mod_wsgi handler, but the request path is now the original one. To sum it up: What is the correct RewriteCond to use here? How do you transfer a request to the mod_wsgi handler? Is it the right way? If that's not the way to do it, then how do you serve static files from a directory when they exist, and when they don't you serve from apache/mode_wsgi? Thanks for your help.

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• sharing a folder between linux and windows over the internet

  - by valya

  Hello Currently my job is to make websites with Django. I use many things like virtualenv, PIL, etc. The problem is, I can't stand Linux on my desktop. I like it on servers, It's greate to use it over the SSH. But for desktop? No way. But for the development Linux is quite essential. Of course almost everything is ported to Windows, but it's not as simple to use as in Linux. For example, Windows shell is awful in comparison with Linux. So I've tried Cygwin, but it's too damn slow. Every time django dev server reloads, it tooks almost 20-30 seconds. In comparison, then using "native" python on Windows or Linux, it reloads instantly. Even worse, Cygwin makes all my system very slow. I've been thinking about it and have thought up a way to go. I can share a folder with my application with some Linux box. The devserver and everything will run on that box, while I'll be happy editing files and running the browser on my Windows 7. SSH shell is much quickier and handy than Cygwin. Currently there are no Linux boxes in my home network (except for my android phone :) but I have several VDS boxes with Debian. So, how do I share a Windows folder with VDS box? I can't rely on my desktop IP but I can rely on the VDS's one. I need sharing to be as quick as possible (well, 2-3 seconds ping is OK) and "native" for both systems, so I could use a folder like a normal folder in both Windows and Linux.

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• How to get nginx to pass HTTP_AUTHORIZATION header to Apache

  - by codeinthehole

  Am using Nginx as a reverse proxy to an Apache server that uses HTTP Auth. For some reason, I can't get the HTTP_AUTHORIZATION header through to Apache, it seems to get filtered out by Nginx. Hence, no requests can authenticate. Note that the Basic auth is dynamic so I don't want to hard-code it in my nginx config. My nginx config is: server { listen 80; server_name example.co.uk ; access_log /var/log/nginx/access.cdk-dev.tangentlabs.co.uk.log; gzip on; proxy_set_header Host $host; proxy_set_header X-Real-IP $remote_addr; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; proxy_read_timeout 120; location / { proxy_pass http://localhost:81/; } location ~* \.(jpg|png|gif|jpeg|js|css|mp3|wav|swf|mov|doc|xls|ppt|docx|pptx|xlsx|swf)$ { if (!-f $request_filename) { break; proxy_pass http://localhost:81; } root /var/www/example; } } Anyone know why this is happening? Update - turns out the problem was something I had overlooked in my original question: mod_wsgi. The site in question here is a Django site, and it turns out that Apache does get the auth variables passed through, however mod_wsgi filters them out. The resolution is to use: WSGIPassAuthorization On See http://www.arnebrodowski.de/blog/508-Django,-mod_wsgi-and-HTTP-Authentication.html for more details

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• In solaris, how monitor & auto-respond to critical events

  - by mamcx

  I have a website that randomly fail. Is running in open solaris on joyent. I have a monitoring service that alert me when the site is down, but, I want a way to put a "insider" tool that tell me why that happened. Is because the cpu is too high? Not memory? Which process fail? Is possible to have a backtrace of that? Everything is running on the Solaris Service Management Facility. The webserver is cherokee, the database is mysql and the language is python/django. I want the most simple setup to monitor that & auto-respond , ie: restart the webserver or the django process in case of failure. I prefer a low-overhead tool. I don't need the fancy monitoring that some tools have, no ned graphs or sms alert. Only know what fail, restart it if possible (maybe up to n times), and have a log somewhere when I will check it.

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• System Slow After Uprading Ubuntu

  - by Aragon N

  I have an Ubuntu network machine which has release of 10.04.1 LTS Lucid. On this system I have Apache, PostgreSQL and django. For some app. development I have to install PGP and php-curl. Due to being on network, I have exported a VMware machine to the Internet and firstly I have upgraded the system and then installed php5 packages on it. I don't know is it all about django or apache configuration. Maybe some Apache settings had changed. In this case in apache where I have to look at ? After all replacing it with its old place, I see that the new system query is slow according to another. Old system query time : 140 ms New system query time : 9.11 s I have checked /etc/network interface and it seems there is no problem. I have checked /etc/resolv.conf and it seems OK I have checked /etc/nsswitch.conf and only host section is different from old one which old system has hosts: files mdns4_minimal [NOTFOUND=return] dns mdns4 and then I have checked time host -t A services.myapp.com and I got real 0m0.355s user 0m0.010s sys 0m0.020s and I have checked apache2 HostnameLookups : find /etc/apache2/ -type f | xargs grep -i HostnameLookups It returned : /etc/apache2/apache2.conf:# HostnameLookups: Log the names of clients or just their IP addresses /etc/apache2/apache2.conf:HostnameLookups Off and now what can I have to check for boosting my system as before?

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• nginx reverse proxy to apache mod_wsgi doesn't work

  - by user11243

  I'm trying to run a django site with apache mod-wsgi with nginx as the front-end to reverse proxy into apache. In my Apache ports.conf file: NameVirtualHost 192.168.0.1:7000 Listen 192.168.0.1:7000 <VirtualHost 192.168.0.1:7000> DocumentRoot /var/apps/example/ ServerName example.com WSGIDaemonProcess example WSGIProcessGroup example Alias /m/ /var/apps/example/forum/skins/ Alias /upfiles/ /var/apps/example/forum/upfiles/ <Directory /var/apps/example/forum/skins> Order deny,allow Allow from all </Directory> WSGIScriptAlias / /var/apps/example/django.wsgi </VirtualHost> In my nginx config: server { listen 80; server_name example.com; location / { include /usr/local/nginx/conf/proxy.conf; proxy_pass http://192.168.0.1:7000; proxy_redirect default; root /var/apps/example/forum/skins/; } #error_page 404 /404.html; # redirect server error pages to the static page /50x.html error_page 500 502 503 504 /50x.html; location = /50x.html { root html; } } After restarting both apache and nginx, nothing works, example.com simply hangs or serves index.html in my /var/www/ folder. I'd appreciate any advice to point me in the right direction. I've tried several tutorials online to no avail.

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• Hibernate: "Field 'id' doesn't have a default value"

  - by André Neves

  Hi, all. I'm facing what I think is a simple problem with Hibernate, but can't get over it (Hibernate forums being unreachable certainly doesn't help). I have a simple class I'd like to persist, but keep getting: SEVERE: Field 'id' doesn't have a default value Exception in thread "main" org.hibernate.exception.GenericJDBCException: could not insert: [hibtest.model.Mensagem] at org.hibernate.exception.SQLStateConverter.handledNonSpecificException(SQLStateConverter.java:103) at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:91) [ a bunch more ] Caused by: java.sql.SQLException: Field 'id' doesn't have a default value [ a bunch more ] The relevant code for the persisted class is: package hibtest.model; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.Id; import javax.persistence.Inheritance; import javax.persistence.InheritanceType; @Entity @Inheritance(strategy = InheritanceType.JOINED) public class Mensagem { protected Long id; protected Mensagem() { } @Id @GeneratedValue public Long getId() { return id; } public Mensagem setId(Long id) { this.id = id; return this; } } And the actual running code is just plain: SessionFactory factory = new AnnotationConfiguration() .configure() .buildSessionFactory(); { Session session = factory.openSession(); Transaction tx = session.beginTransaction(); Mensagem msg = new Mensagem("YARR!"); session.save(msg); tx.commit(); session.close(); } I tried some "strategies" within the GeneratedValue annotation but it just doesn't seem to work. Initializing id doesn't help either! (eg Long id = 20L). Could anyone shed some light? EDIT 2: confirmed: messing with@GeneratedValue(strategy = GenerationType.XXX) doesn't solve it SOLVED: recreating the database solved the problem

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• Is it okay to implement reference counting through composition?

  - by Billy ONeal

  Most common re-usable reference counted objects use private inheritance to implement re-use. I'm not a huge fan of private inheritance, and I'm curious if this is an acceptable way of handling things: class ReferenceCounter { std::size_t * referenceCount; public: ReferenceCounter() : referenceCount(NULL) {}; ReferenceCounter(ReferenceCounter& other) : referenceCount(other.referenceCount) { if (!referenceCount) { referenceCount = new std::size_t(1); other.referenceCount = referenceCount; } else { ++(*referenceCount); } }; ReferenceCounter& operator=(const ReferenceCounter& other) { ReferenceCounter temp(other); swap(temp); return *this; }; void swap(ReferenceCounter& other) { std::swap(referenceCount, other.referenceCount); }; ~ReferenceCounter() { if (referenceCount) { --(*referenceCount); if (!*referenceCount) delete referenceCount; } }; operator bool() const { return referenceCount && (*referenceCount != 0); }; }; class SomeClientClass { HANDLE someHandleThingy; ReferenceCounter objectsStillActive; public: SomeClientClass() { //Construct handle thingy } ~SomeClientClass() { if (objectsStillActive) return; //Release resources }; }; or are there subtle problems with this I'm not seeing?

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• ASP.NET MVC UpdateModel doesn't update inherited public properties??

  - by mrjoltcola

  I refactored some common properties into a base class and immediately my model updates started failing. UpdateModel() and TryUpdateModel() do not seem to update inherited public properties. I cannot find detailed info on MSDN nor Google as to the rules or semantics of these methods. The docs are terse (http://msdn.microsoft.com/en-us/library/dd470933.aspx), simply stating: Updates the specified model instance using values from the controller's current value provider. Well that leads us to believe it is as simple as that. It makes no mention of limitations with inheritance. My assumption is the methods are reflecting on the top class only, ignoring base properties, but this seems to be an ugly shortcoming, if so. SOLVED: Eep, this turned out to have nothing to do with inheritance. My base class was implemented with public fields, not properties. Switching them to formal properties (adding {get; set; }) was all I needed. This has bitten me before, I keep wanting to use simple, public fields.

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• Runtime Exception when using Custom Healthmonitoring event in medium trust

  - by Elementenfresser

  Hi, I'm using custom healthmonitoring events in ASP.NET We recently moved to a new server with default High Trust Permissions. Literature says that healthmonitoring and custom events should work under Medium or higher trust (http://msdn.microsoft.com/en-us/library/bb398933.aspx). Problem is it doesn't. In less than high trust I get a SecurityException saying The application attempted to perform an operation not allowed by the security policy It works in Full trust or when I remove the inheritance of System.Web.Management.WebErrorEvent. Any suggestions anyone? Here is the super simple code behind with a custom event defined: public partial class Default : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { try { CallCustomEvent(); } catch (Exception ex) { Response.Write(ex.Message); throw ex; } } /// <summary> /// this metho is never called due to lacking permissions... /// </summary> private void CallCustomEvent() { try { //do something useful here } catch (Exception) { //code to instantiate the forbidden inheritance... WebBaseEvent.Raise(new CustomEvent()); } } } /// <summary> /// custom error inheriting WebErrorEvent which is not allowed in high trust? can't believe that... /// </summary> public class CustomEvent : WebErrorEvent { public CustomEvent() : base("test", HttpContext.Current.Request, 100001, new ApplicationException("dummy")) { } } and the Web Config excerpt for high trust: <system.web> <trust level="High" originUrl="" />

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• C#'s equivalent to VB.Net's DirectCast?

  - by Collin Sauve

  This has probably been asked before, but if it has, I can't find it. Does C# have an equivalent to VB.Net's DirectCast? I am aware that it has () casts and the 'as' keyword, but those line up to CType and TryCast. To be clear, these keywords do the following; CType/() casts: If it is already the correct type, cast it, otherwise look for a type converter and invoke it. If no type converter is found, throw an InvalidCastException. TryCast/"as" keyword: If it is the correct type, cast it, otherwise return null. DirectCast: If it is the correct type, cast it, otherwise throw an InvalidCastException. EDIT: After I have spelled out the above, some people have still responded that () is equivalent, so I will expand further upon why this is not true. DirectCast only allows for either Narrowing or Widening conversions on inheritance tree, it does not support conversions across different branches like () does. ie: C#, this compiles and runs: //This code uses a type converter to go across an inheritance tree double d = 10; int i = (int)d; VB.Net, this does NOT COMPILE 'Direct cast can only go up or down a branch, never across to a different one. Dim d as Double= 10 Dim i as Integer = DirectCast(d, Integer) The equivalent in VB.Net to my C# code is CType: 'This compiles and runs Dim d as Double= 10 Dim i as Integer = CType(d, Integer) (Edit again, I was originally using strings, I changed it to double... sorry)

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• Interface vs Abstract Class (general OO)

  - by Kave

  Hi, I have had recently two telephone interviews where I've been asked about the differences between an Interface and an Abstract class. I have explained every aspect of them I could think of, but it seems they are waiting for me to mention something specific, and I dont know what it is. From my experience I think the following is true, if i am missing a major point please let me know: Interface: Every single Method declared in an Interface will have to be implemented in the subclass. Only Events, Delegates, Properties (C#) and Methods can exist in a Interface. A class can implement multiple Interfaces. Abstract Class Only Abstract methods have to be implemented by the subclass. An Abstract class can have normal methods with implementations. Abstract class can also have class variables beside Events, Delegates, Properties and Methods. A class can only implement one abstract class only due non-existence of Multi-inheritance in C#. 1) After all that the interviewer came up with the question What if you had an Abstract class with only abstract methods, how would that be different from an interface? I didnt know the answer but I think its the inheritance as mentioned above right? 2) An another interviewer asked me what if you had a Public variable inside the interface, how would that be different than in Abstract Class? I insisted you can't have a public variable inside an interface. I didn't know what he wanted to hear but he wasn't satisfied either. Many Thanks for clarification, Kave See Also: When to use an interface instead of an abstract class and vice versa Interfaces vs. Abstract Classes How do you decide between using an Abstract Class and an Interface?

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• Hibernate: Querying objects by attributes of inherited classes

  - by MichaelD

  Hi all, I ran into a problem with Hibernate concerning queries on classes which use inheritance. Basically I've the following class hierarchy: @Entity @Table( name = "recording" ) class Recording { ClassA attributeSet; ... } @Entity @Inheritance( strategy = InheritanceType.JOINED ) @Table( name = "classA" ) public class ClassA { String Id; ... } @Entity @Table( name = "ClassB1" ) @PrimaryKeyJoinColumn( name = "Id" ) public class ClassB1 extends ClassA { private Double P1300; private Double P2000; } @Entity @Table( name = "ClassB2" ) @PrimaryKeyJoinColumn( name = "Id" ) public class ClassB2 extends ClassA { private Double P1300; private Double P3000; } The hierarchy is already given like this and I cannot change it easily. As you can see ClassB1 and ClassB2 inherit from ClassA. Both classes contain a set of attributes which sometimes even have the same names (but I can't move them to ClassA since there are possible more sub-classes which do not use them). The Recording class references one instance of one of this classes. Now my question: What I want to do is selecting all Recording objects in my database which refer to an instance of either ClassB1 or ClassB2 with e.g. the field P1300 == 15.5 (so this could be ClassB1 or ClassB2 instances since the P1300 attribute is declared in both classes). What I tried is something like this: Criteria criteria = session.createCriteria(Recording.class); criteria.add( Restrictions.eq( "attributeSet.P1300", new Double(15.5) ) ); criteria.list(); But since P1300 is not an attribute of ClassA hibernate throws an exception telling me: could not resolve property: P1300 of: ClassA How can I tell hibernate that it should search in all subclasses to find the attribute I want to filter? Thanks MichaelD

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• Security Exception when using Custom ASP.NET Healthmonitoring event in medium trust

  - by Elementenfresser

  Hi, I'm using custom healthmonitoring events in ASP.NET We recently moved to a new server with default High Trust Permissions. Literature says that healthmonitoring and custom events should work under Medium or higher trust (http://msdn.microsoft.com/en-us/library/bb398933.aspx). Problem is - it doesn't. In less than full trust I get a SecurityException saying The application attempted to perform an operation not allowed by the security policy It works in Full trust or when I remove the inheritance of System.Web.Management.WebErrorEvent. Any suggestions anyone? Here is the super simple code behind with a custom event defined: public partial class Default : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { try { CallCustomEvent(); } catch (Exception ex) { Response.Write(ex.Message); throw ex; } } /// <summary> /// this metho is never called due to lacking permissions... /// </summary> private void CallCustomEvent() { try { //do something useful here } catch (Exception) { //code to instantiate the forbidden inheritance... WebBaseEvent.Raise(new CustomEvent()); } } } /// <summary> /// custom error inheriting WebErrorEvent which is not allowed in high trust? can't believe that... /// </summary> public class CustomEvent : WebErrorEvent { public CustomEvent() : base("test", HttpContext.Current.Request, 100001, new ApplicationException("dummy")) { } } and the Web Config excerpt for high trust: <system.web> <trust level="High" originUrl="" />

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• How To Create a Flexible Plug-In Architecture?

  - by justkt

  A repeating theme in my development work has been the use of or creation of an in-house plug-in architecture. I've seen it approached many ways - configuration files (XML, .conf, and so on), inheritance frameworks, database information, libraries, and others. In my experience: A database isn't a great place to store your configuration information, especially co-mingled with data Attempting this with an inheritance hierarchy requires knowledge about the plug-ins to be coded in, meaning the plug-in architecture isn't all that dynamic Configuration files work well for providing simple information, but can't handle more complex behaviors Libraries seem to work well, but the one-way dependencies have to be carefully created. As I seek to learn from the various architectures I've worked with, I'm also looking to the community for suggestions. How have you implemented a solid plug-in architecture? What was your worst failure (or the worst failure you've seen)? What would you do if you were going to implement a new plug-in architecture? What SDK or open source project that you've worked with has the best example of a good architecture? A few examples I've been finding on my own: Perl's Module::Plugable An SO question with a list for Java (including Sever Provider Interfaces) An SO question for C++ pointing to a Dr. Dobbs article These examples seem to play to various language strengths. Is a good plugin architecture necessarily tied to the language? Is it best to use tools to create a plugin architecture, or to do it on one's own following models?

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• Java downcasting dilemma

  - by Shades88

  please have a look at this code here. class Vehicle { public void printSound() { System.out.print("vehicle"); } } class Car extends Vehicle { public void printSound() { System.out.print("car"); } } class Bike extends Vehicle{ public void printSound() { System.out.print("bike"); } } public class Test { public static void main(String[] args) { Vehicle v = new Car(); Bike b = (Bike)v; v.printSound(); b.printSound(); Object myObj = new String[]{"one", "two", "three"}; for (String s : (String[])myObj) System.out.print(s + "."); } } Executing this code will give ClassCastException saying inheritance.Car cannot be cast to inheritance.Bike. Now look at the line Object myObj = new String[]{"one", "two", "three"};. This line is same as Vehicle v = new Car(); right? In both lines we are assigning sub class object to super class reference variable. But downcasting String[]myObj is allowed but (Bike)v is not. Please help me understand what is going on around here.

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• How do I DRY up business logic between sever-side Ruby and client-side Javascript?

  - by James A. Rosen

  I have a Widget model with inheritance (I'm using Single-Table Inheritance, but it's equally valid for Class-per-Table). Some of the subclasses require a particular field; others do not. class Widget < ActiveRecord ALL_WIDGET_TYPES = [FooWidget, BarWidget, BazWidget] end class FooWidget < Widget validates_presence_of :color end class BarWidget < Widget # no color field end class BazWidget < Widget validates_presence_of :color end I'm building a "New Widget" form (app/views/widgets/new.html.erb) and would like to dynamically show/hide the color field based on a <select> for widget_type. <% form_for @widget do |f| %> <%= f.select :type, Widget::ALL_WIDGET_TYPES %> <div class='hiddenUnlessWidgetTypeIsFooOrBaz'> <%= f.label :color %> <%= f.text_field :color %> </div> <% end %> I can easily write some jQuery to watch for onChange events on widget_type, but that would mean putting some sort of WidgetTypesThatRequireColor constant in my Javascript. Easy enough to do manually, but it is likely to get disconnected from the Widget model classes. I would prefer not to output Javascript directly in my view, though I have considered using content_for(:js) and have a yield :js in my template footer. Any better ideas?

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