As of Play 2.0, it appears that there is no longer a way of creating a module for an existing Play application, other than by creating a new Play application. Having searched around a bit, I came across these instructions, which indicate that I must (or at least should) delete any routes created in the new module (application), and that the module's application.conf file is really just a stub that is required in order for the module to be recognized as a Play application.
I am new to Play, but apparently there used to be a console command ('new-module') for generating a module, which presumably created only those files which were needed for the module to be discovered by the application. It seems to me like it would still be useful to be able to quickly create a new module in this way, especially if registering a new module from the console also added the module to your build, and to the repository of your choice, thus removing the requirement for (as much) manual wiring.
I would also like to be able to maintain Play modules upon which my application depends as part of the same codebase/build, such that, when I make changes to a module, they are picked up at application compile time (for example, when play is ~ running and and a changed file is saved). Does this already happen with modules registered as dependencies, or must I rebuild modules independently of my application?
Because I am a newcomer, I'm not positive that there isn't a way to do accomplish these tasks in an automated manner. There is a chapter on packages and modules listed in the Play for Scala book (Part III, chapter 9), but the book is not yet complete and that chapter is, unfortunately, yet unwritten.
If an experienced Play! developer would be so kind as to either confirm that the instructions to which I linked above are still the recommended procedure for creating a module and registering/maintaining it as a dependency, or else list a better procedure, I would greatly appreciate it.
Most of the information is valid.
To Play 2.x there is no difference between a regular library and a Play module (a library which itself depends on the play library jar).
The part about the routes file is still valid, but they introduced 'Sub-Router composition' to give you some extra freedom (search for 'Allow more modularization for your projects' on the highlight page).
Libraries (and thus Play modules) are referenced in the Build.scala file with version, for example:
"play.modules.mailer" %% "play-mailer" % "1.1.0"
If you are developing a module yourself you could use the 'publish-local' command to make sure other projects on your computer can find the dependency. Because modules are essentially versioned libraries you need to compile them separately from your application. However no-one is preventing you from running scripts to automate things.
Related
Use Play Framework as a component got a server up, but configuring the file system paths for routes file, views, etc, give or take having to take care of a thread pool for the embedded play server is a different story. Basing on the aforementioned, I started a template for including play as a library, but it remains unclear how to wire the paths, hopefully in an IDE-import friendly way too, so that Play can be nicely used in an existing non-play project, as a library.
How do you configure the file system paths for the routes file and views?
What else should be handled for being as robust as running as the framework?
Anything special for bundling the project for deploy with Play now included?
Motivation: Adding Play to a project, in the current state of affairs, means wrapping the project definition and structure around Play, and losing full compilation in sbt (because only run completes the compilation when using the play sbt plugin). As future Spray support is vague and Akka http is beta-ish, using Play as a library seems to plug a hole.
Somehow this didn't pop up in google, until someone suggested the link on gitter: https://www.playframework.com/documentation/2.5.x/ScalaEmbeddingPlay
Note that an application.conf file containing the required crypto secret can simply sit under src/main/resources in this embedded mode (up until you want to override it for production as per the documentation about it). This is quite enough for a REST server.
However now back to the docs, in case you want more than REST:
This can be used in conjunction with the Twirl template compiler and Play routes compiler
So for Play view templates (which are twirl templates really), refer to the repo I mention in the question body, in which #JonasAnso kindly enabled exactly that.
Considering that I am developing an end-user software program (as an uberjar) I am wondering what my options are to make it possible for the user to download a plugin and load that during runtime.
The plugin(s) should come compiled and without source code, so sth. like load is not an option.
What existing libraries (or ways of Java...?) exist to build this on?
EDIT: If you are not sure I would also be satisfied with a way that costs a reboot/-start of the main-program. However, what is important is that the source-code won't be included in any JAR file (neither main application nor plugin-jars, see :omit-source of Leiningen documentation).
To add a jar during runtime, use pomegranate which lets you add a .jar file to the classpath. Plugins of your software should be regular Clojure libs that follow certain conventions that you need to establish:
Make them provide (e. g. in an edn) a symbol to an object implementing a constructor/destructor mechanism such as the Lifecycle protocol in Stuart Sierras component library. In runtime, require and resolve that symbol, start the resulting object and hand it over to rest your programs plugin coordination facilities.
Provide a public API in your program that allows the plugins to interact with it in ways that you coordinate asynchronously e. g. with clojure.core.async (don't let one plugin block the entire program).
Make sure that the plugins have a coordinated way to expose their functionality to each other only if they desire so to enable a high degree of modularity among your plugins. Make sure that your plugin loader is capable of detecting dependencies among plugins and is capable of loading and unloading them in the right order.
I've not tried it myself, but you should in theory be able to get OSGi to work with Clojure.
There's a Clojure / OSGi integration library here:
https://github.com/aav/clojure.osgi
If I were to attempt to role my own solution, I would try using tools.namespace to load and unload plugins. I'm not entirely sure it will work, but it's certainly in the right direction. I think one key piece is that the plugin jars will have to be "installed" in a location that's already on the classpath.
Again, this is only the start of one possible solution. I haven't tried doing this.
Can go run dynamically in order to be used for a plugin based application ?
In eclipse, we can create some plugins that Eclipse can run dynamically.
Would the same thing be possible in Go ?
I'll argue that those are two separate problems :
having dynamic load
having plugins
The first one is simply no : A Go program is statically linked, which means you can't add code to a running program. And which also means you must compile the program to let it integrate plugins.
Fortunately, you can define a program accepting plugins in Go as in most languages, and Go, with interfaces and fast compilation doesn't make that task hard.
Here are two possible approaches :
Solution 1 : Plugin integrated in the main program
Similarly to Eclipse plugins, we can integrate the "plugins" in the main program memory, by simply recompiling the program. In this sense we can for example say that database drivers are plugins.
This may not feel as simple as in Java, as you must have a recompilation and you must in some point of your code import the "plugin" (see how it's done for database drivers) but, given the standardization of Go regarding directories and imports, it seems easy to handle that with a simple makefile importing the plugin and recompiling the application.
Given the ease and speed of compilation in Go, and the standardization of package structure, this seems to me to be a very viable solution.
Solution 2 : Separate process
It's especially easy in Go to communicate and to handle asynchronous calls. Which means you could define a solution based on many process communicating by named pipes (or any networking solution). Note that there is a rpc package in Go. This would probably be efficient enough for most programs and the main program would be able to start and stop the plugin processes. This could very well feel similar to what you have in Eclipse with the added benefits of memory space protection.
A last note from somebody who wrote several Eclipse plugins : you don't want that mess; keep it simple.
Go 1.8 supports plugins (to be released soon Feb 2017.)
https://tip.golang.org/pkg/plugin/
As dystroy already said, it's not possible to load packages at runtime.
In the future (or today with limitations) it may be possible to have this feature with projects like go-eval, which is "the beginning of an interpreter for Go".
A few packages I found to do this:
https://golang.org/pkg/net/rpc/
https://github.com/hashicorp/go-plugin
https://github.com/natefinch/pie
I think (see below) that I would like to structure a Clojure project as multiple modules, with ordered dependencies - just like Maven lets me do with multi-modules projects.
But I can't see how to do this with Leiningen - all I can see is the checkouts fix described in the FAQ which doesn't seem to be as powerful.
Will lein do this? Should I be using Gradle instead? Or is this kind of thing not needed?
Some more context: I am wondering how to architect a modular application that supports plugins (which I imagine means jars dumped on the classpath). And am wondering to what extent I can structure that as a core + plugins (I am thinking I should be able to do something with Clojure's dynamic code loading and not have to go with Java/OSGi). So I guess the driving motivation for a single project comes from wanting some way of packaging everything (the core + default plugins) as a single blob that is easy for the end user, but which can also be divided up (and which is built and tested in fragments, testing the logical independence of each module). More general advice about this is welcome
Update
A possible solution that wasn't mentioned below is using a Maven plugin - I assume that supports everything Maven does, but compiles Clojure, so will work with nested modules, etc.
First, it does not seem like Leiningen supports a module hierarchy like Maven does. The checkouts are the next closest thing it has. It should be sufficient though to develop a modular application in Clojure though.
For the project structure, I would have an API project, a "core" project, the plugins themselves, and a separate packaging project. The core and the plugins should only depend on the API. Which build tool you use to create the packaging project is up to you. Gradle would probably be more effective at handling the packaging, however having the "checkout" functionality Leiningen offers could make development of the system as a whole easier.
I would take a look at the code for Leiningen and Noir to figure out how to effectively handle this.
For dynamically loading the plugins, I would start with looking how Noir handles it in two of their files:
server.clj has namespace loading for all files under a particular namespace. Under the hood it uses tools.namespace, but you can easily see how it's used to require every namespace under a particular base. This is how Leiningen handles custom tasks as well - the base definition for the task should be in the leiningen.$task namespace.
core.clj has what I would use for plugin registration. In summary, use a map under an atom and add plugins to that map. I would advice wrapping the registration with a macro to keep your code cleaner.
What I listed above should be sufficient if you don't need to handle adding plugins at run time. If you don't have every plugin on the classpath during start-up, I would recommend utilizing pomegranite to add entries to the classpath. You can see an example in classpath.clj.
I completed my very first project in zend framework!! Thanks to stackoverflow community!!
While uploading files, i didn't know how to include zend library so i uploaded the whole library in the /library folder of my project base.
Is there a way to determine which library is used and which in not (like compilation that automatically copies dependent files to library folder incase webhost does not provide zend library ..)? i would be awfully bad to manually add each file and test weather the particular library is added or not.
This answer essentially says don't worry about including the whole library. I usually put the whole library in the project library folder, just like you did.
But if it is truly problematic to include the whole library, you could take a look at Jani Hartikainen's Packageizer which, at least in a previous form that I played with, allowed you to specify the components you needed and it would chase the dependencies and wrap them in a neat little package.
Disk space is cheap. Just have the entire ./Zend library directory (and maybe ./ZendX, if you are using that) into your own library directory where it will used. With autoloading, nothing that isn't being used will take up any significant memory. taking even 5 minutes trying to figure out is time (and therefore money) that is more usefully spent writing code.
I wonder if it would be worthwhile/reliable to subclass the autoloader for this and have it optionally log each class it loads during site operation (sort of how Zend_Translate can log untranslated strings).
You could have it turned off normally but in your testing environment you would turn it on (via your application.ini), and have it build your dependency list while your unit tests are running.