I am working on a new web application using Scala with Lift. I want to make it reusable so others might install it on their own servers for their own needs. I come out of a PHP background where it is common practice to create an install form asking for database connection details. This information is stored in a configuration file and used by the rest of the PHP application for connecting to the database. It is extremely convenient for the user because everything is contained within the directory storing the PHP files. They are free to define everything else. My Java/Scala background has all been enterprise work where an application was only intended to run on the database we setup for it. It was not meant to be installed on others' web servers or with different databases.
So my question is how is this typically done for the Java/Scala world? If there are open source applications implementing the mainstream solution, feel free to point me to those too.
I use this to set up the database:
val vendor =
new StandardDBVendor(
Props.get("db.driver") openOr "org.h2.Driver",
Props.get("db.url") openOr "jdbc:h2:mem:db;AUTO_SERVER=TRUE",
Props.get("db.user"),
Props.get("db.password"))
LiftRules.unloadHooks.append(vendor.closeAllConnections_! _)
DB.defineConnectionManager(DefaultConnectionIdentifier, vendor)
The 'Props' referred to will then be (by default) in the file default.props in the props directory in resources.
Updated: This is what I do on servers in production. With 'Props.whereToLook' you provide a function that retrieves an input stream of the configuration. This can be a file as in the example below or you could for example fetch it over network socket.
You will probably let the application to fail with an error dialog.
val localFile = () => {
val file = new File("/opt/jb/myapp/etc/myapp.props")
if (file.exists) Full(new FileInputStream(file)) else Empty
}
Props.whereToLook = () => (("local", localFile) :: Nil)
I am not sure if I am missing your points.
By default, Lift use Scala source file(Boot.scala) to configure all the settings, because Lift doesn't wanna introduce other language into the framework, however you can override some of the configurations using a .properties file.
In Java/Scala world, we use .properties file. It's just a plain text file used for configuration or localization etc,just like text configuration files in PHP.
Lift Framework has it's default support for the external database configuration files, you check out the code in Boot.scala, that's if a .properties file existed, the database will initialized using the connection configuration, if it doesn't, it will use the source file configuration.
Related
OK, so I did the dumb thing and released production code (C#, VS2010) that targeted our development database (SQL Server 2008 R2). Luckily we are not using the production database yet so I didn't have the pain of trying to recover and synchronize everything...
But, I want to prevent this from happening again when it could be much more painful. My idea is to add a table I can query at startup and determine what database I am connected to by the value returned. Production would return "PROD" and dev and test would return other values, for example.
If it makes any difference, the application talks to a WCF service to access the database so I have endpoints in the config file, not actual connection strings.
Does this make sense? How have others addressed this problem?
Thanks,
Dave
The easiest way to solve this is to not have access to production accounts. Those are stored in the Machine.config file for our .net applications. In non-.net applications this is easily duplicated, by having a config file in a common location, or (dare I say) a registry entry which holds the account information.
Most of our servers are accessed through aliases too, so no one really needs to change the connection string from environment to environment. Just grab the user from the config and the server alias in the hosts file points you to the correct server. This also removes the headache from us having to update all our config files when we switch db instances (change hardware etc.)
So even with the click once deployment and the end points. You can publish the a new endpoint URI in a machine config on the end users desktop (I'm assuming this is an internal application), and then reference that in the code.
If you absolutely can't do this, as this might be a lot of work (last place I worked had 2000 call center people, so this push was a lot more difficult, but still possible). You can always have an automated build server setup which modifies the app.config file for you as a last step of building the application for you. You then ALWAYS publish the compiled code from the automated build server. Never have the change in the app.config for something like this be a manual step in the developer's process. This will always lead to problems at some point.
Now if none of this works, your final option (done this one too), which I hated, but it worked is to look up the value off of a mapped drive. Essentially, everyone in the company has a mapped drive to say R:. This is where you have your production configuration files etc. The prod account people map to one drive location with the production values, and the devs etc. map to another with the development values. I hate this option compared to the others, but it works, and it can save you in a pinch with others become tedious and difficult (due to say office politics, setting up a build server etc.).
I'm assuming your production server has a different name than your development server, so you could simply SELECT ##SERVERNAME AS ServerName.
Not sure if this answer helps you in a assumed .net environment, but within a *nix/PHP environment, this is how I handle the same situation.
OK, so I did the dumb thing and released production code
There are a times where some app behavior is environment dependent, as you eluded to. In order to provide this ability to check between development and production environments I added the following line to global /etc/profile/profile.d/custom.sh config (CentOS):
SERVICE_ENV=dev
And in code I have a wrapper method which will grab an environment variable based on name and localize it's value making it accessible to my application code. Below is a snippet demonstrating how to check the current environment and react accordingly (in PHP):
public function __call($method, $params)
{
// Reduce chatter on production envs
// Only display debug messages if override told us to
if (($method === 'debug') &&
(CoreLib_Api_Environment_Package::getValue(CoreLib_Api_Environment::VAR_LABEL_SERVICE) === CoreLib_Api_Environment::PROD) &&
(!in_array(CoreLib_Api_Log::DEBUG_ON_PROD_OVERRIDE, $params))) {
return;
}
}
Remember, you don't want to pepper your application logic with environment checks, save for a few extreme use cases as demonstrated with snippet. Rather you should be controlling access to your production databases using DNS. For example, within your development environment the following db hostname mydatabase-db would resolve to a local server instead of your actual production server. And when you push your code to the production environment, your DNS will correctly resolve the hostname, so your code should "just work" without any environment checks.
After hours of wading through textbooks and tutorials on MSBuild and app.config manipulation, I stumbled across something called SlowCheetah - XML Transforms http://visualstudiogallery.msdn.microsoft.com/69023d00-a4f9-4a34-a6cd-7e854ba318b5 that did what I needed it to do in less than hour after first stumbling across it. Definitely recommended! From the article:
This package enables you to transform your app.config or any other XML file based on the build configuration. It also adds additional tooling to help you create XML transforms.
This package is created by Sayed Ibrahim Hashimi, Chuck England and Bill Heibert, the same Hashimi who authored THE book on MSBuild. If you're looking for a simple ubiquitous way to transform your app.config, web.config or any other XML fie based on the build configuration, look no further -- this VS package will do the job.
Yeah I know I answered my own question but I already gave points to the answer that eventually pointed me to the real answer. Now I need to go back and edit the question based on my new understanding of the problem...
Dave
I' assuming yout production serveur has a different ip address. You can simply use
SELECT CONNECTIONPROPERTY('local_net_address') AS local_net_address
Is it possible to use connection strings in a Console app's app.config file in a single machine config file instead? So all console apps on the server can use the same file?
You could, but that would mean that any .NET application could gain access to your database.
I would advise against it, for several reaons:
A possible security hole.
Most developers would look for this information in app.config not machine.config.
You may end up sharing connection strings that only one or two applications need with all applications.
You can't limit what applications will be able to use the connection strings.
You will not be able to simply move the application to another machine, with the app.config file and have everything just work (you will also need to import the connection string information to the new machine.config).
You really should keep the configuration with the application that uses it.
I have a requirement to export to Microsoft Project from my company's program. As far as I've seen there are a few options:
Use one of the interchange formats, e.g. xml, mpx, mpd
Use the COM object model and automation to write the file
Buy a library that can write the files
The interchange formats have the problem that they will give you an import dialog when you open them, and if you want to save in a different format you need save as, and you need to select the file format before opening them. I.e. it's not a smooth experience for the customer.
Automation requires everyone who exports from our program to have MS Project installed, which is not acceptable.
The only library I could find was Aspose.Tasks which only writes into the Project XML format.
Does anyone know of any library that can write native mpp files? I've seen a post from Microsoft that they have no intention of documenting the file format, but there are some Project Viewers out there so someone must have done something with it? (Although reading from it can be done with an OleDB provider now that I think about it).
Anyone? Write MPP files?
The .NET Framework has the Microsoft.Office.Interop.MSProject set of classes. You could use them directly if your app is .NET, or write a dll in .NET and then reference that from your app.
I have never had reason to import or export Project files in non-native format but for kicks I just created and exported a simple Project in .XML format. Sure enough, when I open that file using the user interface I have to decide if I want to:
a) open as a new file,
b) Append the data to the active project or
c) Merge the data into the active project.
But, if I open the file using a VBA statement:
FileOpenEx ("Project1.xml")
I'm not troubled by the multiple-choice exam. If the default option provided by FileOpenEx is appropriate you could concoct a very simple procedure to which you could direct your users. I'm not sure if this meets your need?
I'm using Prism in my WPF application and up to now, I've been loading the modules via var moduleCatalog = new ConfigurationModuleCatalog();. I'd like to get the module catalog from a database. The Prism documentation indicates that this is possible, but it doesn't go into any details.
Has anyone done this and can provide some guidance?
This is a theoretical possibility, but it's not in any samples I've seen.
Basically what you'd do is either base64 encode the DLLs / Files into the database or zip them up and store them in one blob. You'd download them in your bootstrapper and copy them locally (in a temp directory) and then allows them to load normally from the filesystem using the DirectoryModuleCatalog. If you wanted it to be a bit more elegant, you could write your own ModuleCatalog that encapsulates this logic.
This is very similar to what I do... I actually download a zip file of all of the modules from a website at launch time and unzip them and load them with the DirectoryModuleCatalog.
You can write your own ModuleCatalog implementation by implementing IModuleCatalog. Your implementation can then populate the catalog by any means you define.
You could also use the CreateFromXAML overload that accepts a Stream and implement a webservice that delivers the ModuleCatalog in XAML over HTTP.
I'm working on a website in JSP (in GWT really, but on the server side, it's really just JSP), and I need to configure my database.
I know HOW to code in the database connection etc, but i'm wondering how/where the database config should be saved.
To clarify my doubt, let me give an example; in PHP, a website usualy has a config.php, where the user configures the database, user, etc (or an install.php generates it).
However, since JSP is bytecode, I can't code this info into my site and have the user modify it, nor can I modify it analogously to an install.php.
How should I handle this? what's the best/most common practice ? I've found NO examples of this. Mainly, where should the config file be stored?
There are several possibilities to do this, what I've seen done include:
Having database credentials in a special file, usually db.properties or some simple XML file that contain the required information (driver, url, username, password, any ORM parameters if needed). The properties file would be placed under WEB-INF or WEB-INF/classes; the downside of this approach is that the user would have to modify the file inside the WAR before deploying it to the application server.
Acquire the database connection via JNDI and expect it to be provided by the application server. This seems to be the most common way of doing this; on the upside, your WAR doesn't have to be changed, however, the downside is that configuring a JNDI data source is different for every application server and may be confusing if your system administrators are not experienced with Java technology.