如何从Java EE Server（JBoss）上同一个耳朵中的另一场战争中访问文件？

Question

So following problem: We have a load balancer with n servers behind it. On each server there is a PDF project (war) installed in ear together with a pdf-builder project in the same earfile (different war). I now want to read a pdf from the other war.

The problem is: I don't know the IP address of the server I'm running on and using the dns lookup I might end on the different server through the loadbalancer. Furthermore there might be problems with the access / security constraints since the server itself is not a valid user who has rights to make accesses to the pdf file locations of the pdf war project.

Is there a way to obtain something like getResourceAsStream() which works across different modules / war files within an ear?

Answer 1

You can move the .PDFs to a separate jar (ie pdf-builder.jar) and put it into the .EAR In the manifest of your .WAR ( META-INF/MANIFEST.MF ) put this line:

Class-Path: pdf-builder.jar

Now you can load the .PDFs using your class loader. This is J2EE compliant.

Answer 2

You need to provide absolute path to the file in order to access a resource which is not in current class path.

you can call

serverletContext.getRealpath("/");

will give the the path till the server node (context). From there you can navigate to the file.

One more way is, Jboss uses (or set) several environment variables while it bootstraps. You can use those properties in order to get the current node (like 'default'). Following two properties will give you the absolute path to current server node.

 System.getProperty("jboss.server.base.dir") + File.separator + System.getProperty("jboss.server.name") ; 

(Please use System.getenv('varname') if getProperty don't work). From there you can navigate. Here is the complete list of system varibles that jboss uses.

Answer 3

WARs are intended to be isolated from each other. They can see "up" into the application class loader (EAR level) but cannot access a peer's class loader. So while there may be a way to get it to work on your particular application server, doing so isn't advisable. If someone on the operations team changes deployment options down the line, they may not be aware that you're relying on that mechanism and would break the application in a (possibly) cryptic kind of manner.

Attempting to access a peer class loader like that violates Java EE (if not the letter of the spec, at least the spirit of it).

If you can't put static content on a separate server for access, at least put the static PDFs into a JAR (as been suggested by others) and deploy into the EAR. When do you that, don't forget to add the JAR entry to the manifest file of the declaring WAR (else it won't load the JAR into the application class loader).

Answer 4

1. Change the .war to .jar ( .ear ?) if deployment is not too often. For instance in the server lib directory if you do a daily restart.

2. Do not deploy a war, but upload the files to a fixed directory ie with rsync . This has my preference.

3. Do as @Rp- said, possibly unzipping.

Answer 5

I know I have not enough experience to answer such a question like this , so , all I can think of in a very , very rough sketch is setting each .war as a diferent Spring Context and then load it dynamically by setting the aprropiate mapping inside Springs MVC Framework.

Dynamically Loading Spring Contexts at Runtime

Loading Spring Resources as Dependent Jars

Web resources - Chapter 9 - Spring Reference