OC4J - The "Other" Oracle Application Server

How does extensible markup language relate to the J2EE standalone version of Application Server? If "extensible markup language" sounds unfamiliar to you, perhaps you know it better by its acronym of XML. XML matters not to just to the J2EE version of Application Server, but to all versions. The manner in which XML matters is fairly significant: many configuration files are XML-based. If your DBA responsibilities include administering J2EE applications based upon Application Server, you face the learning hurdles of XML, Java and J2EE, how Oracle interfaces with Java (OC4J, more on that later), and Application Server itself. Chances are you have seen XML in action and may not have even noticed it. Oracle 10g's staging information uses a file named products.xml instead of products.jar.

If coming from a Forms and Reports Services standalone background, the J2EE version will be somewhat familiar, but even within this "known" territory, there are many differences. For example, using true or false: all versions of Application Server are installed using Oracle Universal Installer, so all you ever need to look for in the "Disk 1" directory is the setup.exe (or runInstaller) executable? As we will see later on, the answer is false.

This article is the first of a multi-part series focusing on Oracle's more Web-like version of Application Server, J2EE applications, and XML. Being able to differentiate the versions of Application Server (what is common, what is different), basic administration (using XML configuration files), performing a new type of installation, and acquiring an XML editing tool (free and lasts forever) are some of the topics that will be covered.

The different flavors of Application Server

Which version do you need, is it part of a bundle, and does it come in a standalone version? Part of the answer is shown in the version comparison matrix found under the Middleware (not Applications) link under "Products" at www.oracle.com (see http://www.oracle.com/appserver/appserver_family.html).

Scrolling down a bit on the page, the OC4J version shows the following availability by version.

Under product information for Application Server at OTN, you can expand a list of features for each version. The two tables below show a consolidated listing for each type. Common elements are aligned at the top.

 

The J2EE downloads (pure Java) version is of interest to us in that this version installs without Oracle Universal Installer. Click the "Pure Java" link and you will see several standalone versions (the product comparison matrix is somewhat misleading given that there is, in fact, a standalone version). Version 10.1.2.0.2 is a quick download (just over 35MB) and results in a compressed file named oc4j_extended.zip.

Reader's Note: For the purposes of this particular article, it is not necessary to install this product – finish reading before deciding whether or not you want to sample this version.

One thing to take note of is that Oracle Corporation is not consistent in how it refers to features. Sometimes OC4J is used, sometimes not. Is it Application Server Web Cache, or HTTP Server Web Cache?

Installing Oracle Application Server Containers for J2EE

Expand the zipped file and open the Readme.txt file. I staged the uncompressed version of the download under C:\oracle\oc4j. To perform the installation, you need the Java "java" executable (may have to add the C:\Program Files\Java\jdk1.5.0_02\bin folder to your path). To test your environment and setup, run "java –version" at a command prompt.

 C:\>java -version
 java version "1.5.0_02"
 Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_02-b09)
 Java HotSpot(TM) Client VM (build 1.5.0_02-b09, mixed mode, sharing)

In the j2ee\home directory, start the installation with java –jar oc4j.jar –install.

C:\oracle\oc4j\j2ee\home>java -jar oc4j.jar -install
Auto-unpacking C:\oracle\oc4j\j2ee\home\applications\dms0.war... done.
To enable in-process JSP compilation (which can be faster in some cases),
please add the path to your tools.jar in application.xml
Example:  <library path="../../../jdk/lib/tools.jar" />
Enter an admin password to use: oracle
Confirm admin password: oracle
If you are using J2SE 1.4 or higher, please ensure that all your imported classes are 
with in packages, as required by the Java Language Specification.
Installation done
C:\oracle\oc4j\j2ee\home>

If the installation was successful, the next step is to test it by starting an OC4J instance. This part should be familiar to Forms developers running a Developer Suite OC4J instance (used to run Forms on the Web without using Application Server).

C:\oracle\oc4j\j2ee\home>java -jar oc4j.jar
06/01/08 18:48:18 Oracle Application Server Containers for J2EE 10g (10.1.2.0.2) initialized
06/01/08 18:48:18 !!! No valid java compiler found !!!
06/01/08 18:48:18 javac.exe not found under C:\Program Files\Java\ 
jre1.5.0_02, please use a valid jdk or specify the location of your java 
compiler in server.xml using the <java-compiler .../> tag

Note the error about javac.exe not being found under C:\Program Files\Java\jre1.5.0_02. Let's see, which version – JDK or JRE – does javac come with? That would be JDK, so why is Oracle looking for javac under a Java Runtime Environment (JRE) installation path? I have JDK listed first in my path statement, not JRE, but that doesn't make a difference. The Standalone User's Guide (installs with the product) even mentions JDK as being a prerequisite, yet Oracle is looking for javac under JRE. Anyway, this leads into one of the topic areas for this series, namely that of XML-based configuration files.

XML Configuration Files

For an overview of all the files involved, Figure 2-1 shows a good representation. The specifics of these files will be covered later (along with an XML editor), but for now, the server.xml is what needs our attention.

The server.xml file is located in J2EE_HOME\j2ee\home\config, which resolves to C:\oracle\oc4j\j2ee\home\config given that I used C:\oracle\oc4j as my Oracle, oops, make that J2EE, home. The error message stated that a java-compiler tag needs to be used to set the JDK location. The default server.xml file does not contain this directive (more on what a directive is later, but for now, consider it to be a very close cousin of an HTML tag), so it must be added.

The contents of the server.xml file are shown below.

<?xml version="1.0" standalone="yes"?>
<!DOCTYPE application-server PUBLIC "Orion Application Server Config" 
"http://xmlns.oracle.com/ias/dtds/application-server-9_04.dtd">
<application-server application-directory="../applications" 
     deployment-directory="../application-deployments" connector-directory="../connectors">
    <rmi-config path="./rmi.xml"/>
    <!-- JMS-server config link, uncomment to activate the JMS service -->
    <jms-config path="./jms.xml"/>
    <j2ee-logging-config path="./j2ee-logging.xml" />
    <log>
        <file path="../log/server.log"/>
    </log>
    <global-application name="default" path="application.xml"/>
    <global-web-app-config path="global-web-application.xml"/>
    <!-- <web-site path="./secure-web-site.xml" /> -->
    <web-site path="./http-web-site.xml"/>
   <!-- Uncomment the following, to deploy these apps.
   <application name="callerInfo" path="../jazn/demo/callerInfo/callerInfo.ear" />
   <application name="ssoInfo" path="../jazn/demo/ssoInfo/build/ssoInfo.ear" />
   <application name="ejbsamples" path="../demo/ejb" />
   <application name="news" path="../applications/news.ear" />
   <application name="logger" path="../demo/messagelogger.ear" />
   <application name="petstore" path="../applications/estore-patched.ear" />
   <application name="ws_example" path="../demo/web_services/java_services/ws_example.ear" />
   <application name="ojspdemos" path="../demo/ojspdemos.ear" />
     -->
    <!-- Compiler, activate this to specify an alternative compiler such
         as jikes for EJB/JSP compiling. -->
    <!-- <compiler executable="jikes" classpath="/myjdkdir/jre/lib/rt.jar" /> -->
</application-server>

Directives, just like tags in HTML, have beginning and ending parts. Some tags are self-closing, like "br" , and some are not, like "table." With the server.xml file, the configuration part is between the "application-server" tags. Somewhere in between the opening and ending is good enough as far as adding java-compiler tag. Three usage notes for adding the java-compiler tag include:

• Provide a name of the compiler ("javac" in this case)
• Provide a path name using "bindir"
• For Windows-like paths, escape the back-slash character with another back-slash character

An example is shown below.

    <j2ee-logging-config path="./j2ee-logging.xml" />
    <java-compiler name="javac" 
                              bindir="C:\\Program Files\\Java\\jdk1.5.0_02\\bin" />
    <log>
        <file path="../log/server.log"/>
    </log>

Let's restart the OC4J instance and see what happens.

C:\oracle\oc4j\j2ee\home>java -jar oc4j.jar
06/01/08 20:52:37 Oracle Application Server Containers for J2EE 10g (10.1.2.0.2) initialized

Looks like a clean start. At this point, the basic webapp should be available. Access it via a URL of http://localhost:8888.

As another example, the Standalone User's Guide should be available at http://localhost:8888/standaloneguide.pdf. This URL suggests that where the PDF is located is also the Web server document root. The root (for me) is C:\oracle\oc4j\j2ee\home\default-web-app, and a simple test of trying to access other files within the default-web-app directory should prove this to be true.

Where is Enterprise Manager for this version of Application Server? Despite Oracle's Web site saying this version includes Enterprise Manager, it does not. The next version up – J2EE and Web Cache – is the minimum version type to get Enterprise Manager.

Just for grins, if you note that the contents of the server.xml file remind you of a simple HTML file, try opening this (or any) XML file in a browser.

In Closing

So far, we have seen a listing of the features included in the four types of installation for Application Server. Applications can be deployed via the standalone OC4J version, and administration can be performed via the direct editing of (many) XML files. Knowing the specifics of XML is not necessary, but it certainly helps to have an appreciation of the who-what-where of what Enterprise Manager changes when you, as the administrator, are making changes via the EM console.

» See All Articles by Columnist Steve Callan