Accessing EJBs Locally -- OpenEJB embedded in your app, server, or IDE

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Accessing EJBs Locally OpenEJB embedded in your app, server, or IDE

Accessing EJBs locally
Passing initialization parameters
Set the openejb.home variable
Embedded OpenEJB FAQ
Why do I need so many OpenEJB specific files to implement a client?
What Security Service do I get?

## Accessing EJBs locally

If you wish to access ejbs locally and not in client/server mode, for example if your application is a server or other middleware, you can do so by embedding OpenEJB as a library and accessing ejbs through OpenEJB's built-in IntraVM (Local) Server.

NOTE

OpenEJB can be initialized and invoked directly as an API. You would do this if you need closer integration with OpenEJB, you wish to distribute beans using your own distributed object protocol, or if you need very advanced control over transaction and security context propogation. See the OpenEJB Specification for more information.

In this case, your application, server, or other middleware accesses beans as you would from any other EJB Server. The EJB Server just happens to be running in the same virtual machine as your application. This EJB Server is thusly called the IntraVM Server, and, for all intense purposes, your application or server is an IntraVM Client.

Try something like this for a simple IntraVM (Local) Client:

c:\my\app\MyEjbApplication.java

    import java.util.Properties;
    import javax.naming.Context;
    import javax.naming.InitialContext;
    import javax.rmi.PortableRemoteObject;
    import FooHome;

    public class MyEjbApplication {

    public static void main( String args[]) {
      try{

        Properties properties = new Properties();

        properties.put(Context.INITIAL_CONTEXT_FACTORY,
            "org.openejb.client.LocalInitialContextFactory");

        InitialContext ctx = new InitialContext(properties);

        Object obj = ctx.lookup("my/bean/Foo");

        FooHome ejbHome = (FooHome)
            PortableRemoteObject.narrow(obj, FooHome.class);

      } catch (Exception e){
        e.printStackTRace();
      }
    }
    }

That would be the simplest spec compliant client you could create. If you don't care about spec compliance and just want to "cheat", you can do this:

c:\my\app\MyEjbApplication.java

    import javax.naming.InitialContext;
    import FooHome;

    public class MyEjbApplication {

    public static void main( String args[]) {
      try{

        FooHome ejbHome = (FooHome)new InitialContext().lookup(
                                "java:openejb/ejb/my/bean/Foo");

      } catch (Exception e){
        e.printStackTRace();
      }
    }
    }

Now keep in mind, that is not spec compliant. Also keep in mind that we provide it as a convenience, so if there is something you don't like or think should be changed, send code.

## Passing initialization parameters

When accessing OpenEJB in local (intra-vm) mode, the IntraVM server will instantiate OpenEJB for you. When it instantiates OpenEJB, it puts default values for the items in the Properties object OpenEJB needs to actually instantiate.

If you want to pass OpenEJB specific parameters, you can do this in two ways:

1. Call init yourself before any JNDI calls are made
2. Pass the parameters in the InitialContext hashtable

Refer to the OpenEJB Specification for information on the init method or the parameters you can pass to OpenEJB.

Here is an example of passing the initialization parameters in to OpenEJB via the first InitialContext creation. I stress, this is only applicable the very first time and InitialContext is created within your Virtual Machine. After that, OpenEJB will have been initialized and the parameters will be ignored.

c:\my\app\MyEjbApplication.java

    import FooHome;
    import java.util.Properties;
    import javax.naming.Context;
    import javax.naming.InitialContext;
    import javax.rmi.PortableRemoteObject;

    public class MyEjbApplication {

    public static void main( String args[]) {
      try{

        Properties p = new Properties();

        p.put(Context.INITIAL_CONTEXT_FACTORY,
              "org.openejb.client.LocalInitialContextFactory");

        p.put("openejb.home", "c:\\dir\\openejb");

        p.put("openejb.configuration",
              "c:\\my\\app\\conf\\openejb.conf");

        InitialContext ctx = new InitialContext( p );

        Object obj = ctx.lookup("my/bean/Foo");

        FooHome ejbHome = (FooHome)
            PortableRemoteObject.narrow(obj,FooHome.class);

      } catch (Exception e){
        e.printStackTRace();
      }
    }
    }

## Set the openejb.home variable

If you use OpenEJB Local Server, you are actually using OpenEJB as an embedded library. This means when your application starts, OpenEJB will be starting too, in your virtual machine. Odds are you will not want to execute your application in the directory where OpenEJB was installed, but will want to execute your application where you are developing it. This is fine, but you will need to tell OpenEJB where it was installed. To do this, set the "openejb.home" system variable.

For example, if OpenEJB was unpacked in the directory in c:\dir\openejb, you can set the openejb.home variable as a java vm flag as follows.

c:\my\app> java -Dopenejb.home=c:\dir\openejb MyEjbApplication

You can also set the openejb.home variable by calling System.setProperty(...) in your application before any calls to the OpenEJB Local Server are made.

c:\my\app\MyEjbApplication.java

    ...
    public static void main(String args[]) {

      System.setProperty("openejb.home", "c:\\dir\\openejb");
      ...

    }
    ...

As mentioned above, you can pass OpenEJB parameters on your first call to the Local Server.

c:\my\app\MyEjbApplication.java

    ...
    public static void main( String args[]) {

      Properties p = new Properties();

      p.put(Context.INITIAL_CONTEXT_FACTORY,
            "org.openejb.client.LocalInitialContextFactory");

      p.put("openejb.home", "c:\\dir\\openejb");

      InitialContext ctx = new InitialContext( p );
      ...
    }
    ...

When OpenEJB is started, it will look for its configuration files in the OPENJB_HOME/conf directory. The paths to beans in your openejb.conf file are also resolved relative to the openejb.home variable.

Here is an example of this. The openejb.home variable, which we will refer to as OPENEJB_HOME, is set to "c:\dir\openejb". The following relative path in your openejb.conf file will be resolved assuming OPENEJB_HOME as the base path.

openejb.conf

    <openejb>
    ...

    <Deployments dir="beans\" />
    </openejb>

The above deployment path, "beans\", would automatically be expanded to "c:\dir\openejb\beans".

If you want tell OpenEJB to look outside the OPENEJB_HOME, then use an absolute file path as shown below.

openejb.conf

    <openejb>
    ...

    <Deployments dir="beans\" />
    <Deployments dir="c:\my\app\my\beans\" />
    </openejb>

OpenEJB can look in any number of directories for beans, just add those directories to your openejb.conf file as such.

openejb.conf

    <openejb>
    ...

    <Deployments dir="beans\" />
    <Deployments dir="c:\my\app\my\beans\" />
    <Deployments dir="c:\my\special\beans\" />
    <Deployments dir="c:\foo\ejbs\" />
    <Deployments dir="d:\files\ejbjars\" />
    </openejb>

Furthermore, you can add jars individually to OpenEJB's deployment path by naming the jar directly.

openejb.conf

    <openejb>
    ...

    <Deployments dir="beans\" />
    <Deployments dir="c:\my\app\my\beans\" />
    <Deployments dir="c:\my\special\beans\" />
    <Deployments dir="c:\foo\ejbs\" />
    <Deployments dir="d:\files\ejbjars\" />
    <Deployments jar="c:\the\very\special.jar" />
    </openejb>

## Embedded OpenEJB FAQ

### Why do I need so many OpenEJB specific files to implement a client?

This is the bane you face when running OpenEJB in the same VM, you have to configure OpenEJB as well as your client. Any server has configuration files, you can't change that. When you run the server in the same vm as your application, you take on some additional responsibility. But as I mentioned, we are implementing some things to make even that "additional" responsibility more transparent.

When your clients run OpenEJB in the same VM using the IntraVM Server, you're using OpenEJB as an embedded EJB Server just like InstantDB and Cloudscape are embedded databases servers. Just like InstantDB and Cloudscape, OpenEJB needs configuration files and other files to do it's job.

OpenEJB is the only EJB server that I know of that you can run as an embedded library, so the fact that you can even do it is a real feather in our cap. If anyone knows of another, please tell me.

In fact, anyone already using InstantDB or Cloudscape as embedded database servers in a product could just as easily use OpenEJB as an embedded EJB Server and add instant EJB support to the product as well. OpenEJB can easily play with InstantDB or Cloudscape, so it would be pretty slick. This would be extremely useful for IDEs like Visual Cafe, JBuilder, Visual Age, etc.

### What Security Service do I get?

OpenEJB doesn't come with a valid SecurityService, this has been considered the role of the application server vendor since the beginning of the project. However, no app servers have yet created a SecurityService as we had hoped. Months down the road, we will create a simple SecurityService provider if one is not contributed.

OpenEJB can do without a server and use the IntraVM Server, but it still needs a SecurityService, therefore, a fake SecurityService implementation is used by default. This PseudoSecurityService just allows you to use OpenEJB without a valid security service, it basically says everyone is a valid user.

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