Java Web Project referencing another Java project

Question

I have a Java Project, for which I'm now creating a Web interface, using a Dynamic Web Project from Eclipse. The Web project consists of a single servlet and two JSP's. Something like this:

/JavaApplication
  /src
  /lib
  /resources
/WebApplication
  /src
    /Servlet.java
  /WebContent
    /WEB-INF
    index.jsp
    other.jsp

Now, I need to reference JavaApplication from WebApplication, in order to use its classes to process web requests. What's the best way to accomplish this ? My idea is to create a .jar of the JavaApplication, containing all the .class files, /resources, and /libs. In this way, I could include the .jar in the web application, and I could have a single .war file that contained the entire application.

What do you think? How is this problem typically solved ?

Note: I don't want to convert the Java Project into a Web project.

Answer 1

Typically you would create an API interface using remote service beans from the Java application that expose the methods that you want to invoke in the web application. You would include a proxy of the API interface with your web application that calls the remote service bean in the Java application. Remember that you will need to register the remote bean in the web.xml file.

Answer 2

Under Eclipse, you can declare Project References for a given project, the web application in your case. To do so, right click on your web application project, then go for Properties > Project References and select the JavaApplication project. This should allow you to call code from the JavaApplication project from the WebApplication without having to build a WAR. This is a solution for development.

For standard deployment (outside the IDE), you should indeed create a standard WAR. To do so, you'll have to package your JavaApplication as a JAR including the .class files and the files under /resources but not the libraries it depends on (JARs under /lib). These dependencies will actually end up in the WEB-INF/lib directory of the WAR, beside the JAR of your JavaApplication. These steps are typically automated with tools like Ant or Maven.

Answer 3

Consider moving up to EAR level, if your web container supports that.

The tricky part with shared code is where should the common code be put. A copy pr web application? A copy in the web container? Overdoing the "share these classes" might end up in class loader problems.

If you are creating two separate web applications refactor common java code into a separate Eclipse project and refer to it from both WAR projects.

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EDIT: Apparently I have misread the problem description, and thought you asked about an existing and a new web application sharing code.

If you have an Eclipse project with your application, and another with your web frontend, then you can let your application export the necessary resources which the "Export WAR" in Eclipse JEE can wrap up in a jar file and put in WEB-INF/lib for you. You need to say this explicitly with a checkmark in Properties -> Java EE Module Dependencies for your web project. Expect you have to experiment a bit - this took me a while to learn.

Answer 4

In Eclipse project properties, add the project to the Java Build Path (under the Projects tab). Then go to Java EE Module Dependencies entry in the project properties and tick the project in question as dependency. Now Eclipse will take care about doing the right thing to create a WAR out of this all.