Why I need to do this: In my application I have some JAR file for connecting to MYSQL DB, now I have to extend this API so that my application can communicate to MongoDB.To do this I have to make changes in existing JAR file.
I don't have the source code of the JAR files so I de-compiled it, used the code to implement the interfaces, now I am unable to make a JAR file because may be the de-compiler did not de-compile the classes properly in the first place. So I separately compiled the newly written classes, I want some of the new classes to overwrite the existing ones.
I know that tomcat looks for classes in the following order:
1. System class loader classes
2. /WEB-INF/classes of your web application
3. /WEB-INF/lib/*.jar of your web application
so I put new classes in /WEB-INF/classes/ directory.
My tomcat server is still not using the newly added classes, is there any way to know which class is my class loader using and how to make it load the newly added classes?
Related
I'd like to include a resource file (e.g. some xml config file) in my bundle and make it visible to all other bundles in the container. Is it possible without using the Fragment-Host manifest header? I'd like this resource file to always be visible in the classpath of all bundles running alongside my bundle, even those that do not exist yet, but will potentially be added in future.
EDIT:
To clarify - that resource must be available passively, i.e. the other bundles should be able to find it in their classpath, and not by refering to any special API or service of my bundle.
Some more background - my environment is a bit messy but I have no control over it and cannot change its existing bundles. The only way I can modify it is by adding my own bundles. That environment includes several copies of the ch.qos.logback.classic bundle. When logback starts up, it looks for specific XML config files in the classpath. If it doesn't find any of them, then its default behaviour is to print everything to stdout with debug level. This environment was previously used to host a GUI application so it didn't matter that much before, but now I am trying to adapt it so I can use some of its functionality in headless mode. So now it becomes important to me to be able to configure it in such a way that only warning and errors are printed to the console.
In general, no you cannot do this. Class-space isolation is at the heart of OSGi, but you want to put a resource in the class loader of one bundle and make it visible to all other bundles. That's not OSGi, it's the global application classpath.
The only thing you can do to add to the internal classpath of a specific bundle is to write a fragment which attaches to that bundle. A fragment can attach to multiple host bundles, but only if those hosts have the same symbolic name, i.e. because they are different versions of the same bundle. See OSGi R6 Core Specification, section 3.14.
You did however state that the bundles you want to attach are all copies of ch.qos.logback.classic. If that means they all have that exact symbolic name then perhaps a fragment will work after all.
You can not change the classpath of other bundles this way.
What you can do is retrieve the classloader of your bundle from your bundleContext. You can give this classloader to another bundle to retrieve your resource.
ClassLoader cl = context.getBundle().adapt(BundleWiring.class).getClassLoader();
Another option is to give the other bundle the URL of the resource.
As long as the resource is on the classpath, any bundle can access the resource if it can get hold of the class loader of the bundle that contains the resource.
For example:
ClassLoader classLoaderOfBundleWithResource = ...
classLoaderOfBundleWithResource.getResourceAsStream("org/example/resource.xml");
From a maintenance and API point of view, I would not recommend exposing a resource that way. Java types are much better suited therefore. Instead, let the resource bundle export a class that gives clients access to the contents of the resource.
For example:
public class XmlDocumentProvider {
public InputStream openDocument() {
return getClass().getResourceAsStream("resource.xml");
}
}
Assuming that both the resource.xml and the XmlDocumentProvider reside in the same package, openDocument will return the resource content just like in the first example.
I've an desktop application that implements Serializable class, but now I'm translating it to an web app with servlets, I use Netbeans for this work,I have the following code:
InputStream input = ClassLoader.getSystemResourceAsStream(file_input);
Where file_input is an bytecode fyle from an object serialized before, I don't know where I should put this file because in the desktop application I put it in the same dir where I had my classes.
(I have the file, I don't need to create it).
First of all, don't use ClassLoader#getSystemResourceAsStream() in a Java EE web application, ever. Instead, use ClassLoader#getResourceAsStream(). I would also put big question marks around using ClassLoader#getSystemResourceAsStream() in a Java SE desktop application, for sure if it's intended to be distributable, but that aside.
The ClassLoader ultimately loads resources from the classpath. So all you need to do is to make sure that the file is placed in one of the paths which are by default covered by the webapp's runtime classpath, or to add the new path to the file to the webapp's runtime classpath through a server specific configuration setting, such as shared.loader property of Tomcat's /conf/catalina.properties.
One of the default paths covered by the webapp's runtime classpath is the /WEB-INF/classes folder of the WAR. From IDE project's perspective, just drop the file in the root folder of the "Java Source" (src) folder, there where you have all your Java packages and classes. The IDE will take care that it ultimately ends up in /WEB-INF/classes of the built WAR file.
I by the way still assume that you are not creating the file from inside the webapp, as you explicitly told. That wouldn't work. If you actually need to have write access as well, you're going to need an absolute disk file system path instead. You can always make it configureable by providing it as a VM argument or environment variable, for example.
This is for Struts 1.x (I'm using 1.3.10).
I've noticed that Struts is unable to pick up resource bundles in the ApplicationResources.properties file if it is not placed somewhere in the default classpath (e.g., com.abc.SomePackage).
For instance, if I put the ApplicationResources.properties file in a custom folder /WEB-INF/strutsResources and configure the struts-config.xml thus:
<message-resources parameter="/WEB-INF/strutsResources/ApplicationResources"/>
I've read that the resources need to be on the classpath so I've also tried adding the /WEB-INF/strutsResources folder to the classpath. It still does not pick up the resource keys.
I've double-checked that the strutsResources folder is actually deployed to the server (I'm using Glassfish v3), so the file is there, it's just not being parsed.
P.S.
If you're wondering why I'm trying to do this, I just wanted to organize my code a little better ("better," IMO). Since the ApplicationResources.properties file is not really a class, I wanted to place it in a resources folder by itself.
I've checked that placing the ApplicationResources file in a package in the src directory works just fine.
Ultimately, the answer is yes. You can play some interesting games by configuring a custom className and/or factory and get messages however you want (including from a database) and so on. This allows you to customize whatever you want*.
I agree the resources aren't a class, but putting them on the classpath is a common practice, and allows resources to be loaded as a resource, e.g., from inside a jar. I'm sympathetic, but I'd leave it as-is.
*Like reversing all the text; a fun prank to play on your co-workers and QA department.
Its best leave it on the classpath.
It's stadard practise to include properties files on the classpath, especially if you're planning on packaging it up in your WAR/EAR. You're keeping it under WEB-INF so you gain no benefit from moving it off the classpath, and you'll just confuse other developers who have to work on the project and you've had to put a hack in to make this work.
If you want to keep your files external to your deployable WAR/EAR then that's a valid reason for not using the classpath. Typically this will require some configuration as part of your deployment to specify where the file is to reside.
For example specify the location using
a JVM argument (e.g. -Dprops.file=/config/myapp.properites)
lookup from a JNDI resource
use a PropertiesFactoryBean if you're using the Spring framework (I
use Spring's ApplicationContext with Struts 1 MVC)
read properties from a database writing your own
ApplicationPropertiesDAO class that initialises itself durnig your
applications bootstrap process (e.g. Spring application contact,
Servlet in web.xml, Listener in web.xml, etc)
I am new to Eclipse plugin development, and I am trying to develop a plugin where I am required to load a class which is selected in the Navigator.
Can you please instruct me how can I load a class or create a classloader from eclipse plugin, to load a class in the eclipse workbench which is using my plugin.
Thanks in advance.
Regards
Gillani
You need to create a URLClassLoader. You may want it to be parented or not, depending on your security concerns. If parented by an OSGi bundle class loader, then the user will have access to all of the classes in that particular bundle and this may be a back door to the user getting runtime access to the entire Eclipse platform (and access the plugin registry and the OSGi services, etc). The user can also call System.exit(). This may not be a problem on a single user system, but it is something to think about, especially if the user may be downloading unverified scripts from the internet.
That being said, you need to do something like this:
Instantiate a URLClassLoader and add the URLs of the directories containing the class files you will want to load.
if you want the classes to have access to the Eclipse runtime, then set the parent loader to be
((BundleHost) Activator.getBundleContext().getBundle()).getLoaderProxy().getBundleLoader()
Add all of the directories corresponding to URLs where the user can load classes from. But, you must include all dependencies in order to load the classes.
This should be enough to load the classes you require.
I know this can be done as there are other modules out there that have this, but I'm just not getting it to work.
I have created a custom module for a DotNetNuke site. I want to be able to create a class object within the module to hold the information about that object. I can create the object and everything complies. But when I go to use the object in the code-behind it states that the object is not defined. I'm not really sure where to go from here.
This is the beginning of the View.ascx.vb :
Namespace Modules.VacationForms
Public MustInherit Class View
Inherits PortalModuleBase
This is the object class beginning:
Namespace Modules.VacationForms
Public MustInherit Class Vacation
I'm really not sure why this is not working. I did download another module code to compare and as far as I can tell everything is the same. Any help is appreciated.
Are you using a Web Site Project or a Web Application Project? The Web Application project will allow you to compile all of your code together (the only issue here might be the the Root Namespace setting in your project, but, assuming both classes are in the same project, that shouldn't be it). If you're in the Web Site project (e.g. developing directly in the DNN solution), then your code won't get compiled in the traditional sense, but will be on-demand compiled by DNN. It only does that for code behind files associated with requested controls/pages (e.g. your View.ascx.vb) and code files in the App_Code folder. I would guess that your hangup is that your Vacation class' code file isn't in the App_Code folder.
It looks you are not using the Web Application Project for module development. Easiest thing to do is install module development templates (from dotnetnuke.codeplex.com download starterkit package of your dnn version).
If your module is too simple and you don't want to do that, OR you don't want to install the templates in your pc, you can do following:
If you are using a vs version that is not using WAP by default, get the installation from web.
create a new folder for your dnn module in DesktopModules directory in root
add a new WAP project in that folder.
remove web.config from that folder, go to properties and point build output director to your dnn site's bin directory (../../bin will work most of the time)
Once you are done with that, all your code will start working as expected.
Good thing about this is, all your .vb and .ascx.vb files will be compiled in a single dll that you can distribute as a package easily.
Hope this helps