Inside the Application Server
Before we look at deploying an application, we will quickly run over the internals of WebSphere Application Server (WAS). The anatomy of WebSphere Application Server is quite detailed, so for now, we will briefly explain the important parts of WebSphere Application Server.
The figure below shows the basic architecture model for a WebSphere Application Server JVM.
An important thing to remember is that the WebSphere product code base is the same for all operating-systems (platforms). The Java applications that are deployed are written once and can be deployed to all versions of a given WebSphere release without any code changes.
JVM
All WebSphere Application Servers are essentially Java Virtual Machines (JVMs). IBM has implemented the J2EE application server model in a way which maximizes the J2EE specification and also provides many enhancements creating specific features for WAS. J2EE applications are deployed to an Application Server.
Web container
A common type of business application is a web application. The WAS web container is essentially a Java-based web server contained within an application server’s JVM, which serves the web component of an application to the client browser.
Virtual hosts
A virtual host is a configuration element which is required for the web container to receive HTTP requests. As in most web server technologies, a single machine may be required to host multiple applications and appear to the outside world as multiple machines. Resources that are associated with a particular virtual host are designed to not share data with resources belonging to another virtual host, even if the virtual hosts share the same physical machine. Each virtual host is given a logical name and assigned one or more DNS aliases by which it is known. A DNS alias is the TCP/ host name and port number that are used to request a web resource, for example: <hostname>:9080/<servlet>.
By default, two virtual host aliases are created during installation. One for the administration console called admin_host and another called default_host which is assigned as the default virtual host alias for all application deployments unless overridden during the deployment phase. All web applications must be mapped to a virtual host, otherwise web browser clients cannot access the application that is being served by the web container.
Environment settings
WebSphere uses Java environment variables to control settings and properties relating to the server environment. WebSphere variables are used to configure product path names, such as the location of a database driver, for example, ORACLE_JDBC_DRIVER_PATH, and environmental values required by internal WebSphere services and/or applications.
Resources
Configuration data is stored in XML files in the underlying configuration repository of the WebSphere Application Server. Resource definitions are a fundamental part of J2EE administration. Application logic can vary depending on the business requirement and there are several types of resource types that can be used by an application. Below is a list of some of the most commonly used resource types.
|
Resource Types |
Description |
|
JDBC (Java database connectivity) |
Used to define providers and data sources |
|
URL Providers |
Used to define end-points for external services for example web services… |
|
JMS Providers |
Used to defined messaging configurations for Java Message Service, MQ connection factories and queue destinations etc. |
|
Mail Providers |
Enable applications to send and receive mail, typically use the SMTP protocol. |
JNDI
The Java Naming and Directory Interface (JNDI) is employed to make applications more portable. JNDI is essentially an API for a directory service which allows Java applications to look up data and objects via a name. JNDI is a lookup service where each resource can be given a unique name. Naming operations, such as lookups and binds, are performed on contexts. All naming operations begin with obtaining an initial context. You can view the initial context as a starting point in the namespace. Applications use JNDI lookups to find a resource using a known naming convention. Administrators can override the resource the application is actually connecting to without requiring a reconfiguration or code change in the application. This level of abstraction using JNDI is fundamental and required for the proper use of WebSphere by applications.
Application file types
There are three file types we work with in Java applications. Two can be installed via the WebSphere deployment process. One is known as an EAR file, and the other is a WAR file. The third is a JAR file (often re-usable common code) which is contained in either the WAR or EAR format. The explanation of these file types is shown in the following table:
|
File Type |
Description |
|
JAR file |
A JAR file (or Java ARchive) is used for organising many files into one. The actual internal physical layout is much like a ZIP file. A JAR is generally used to distribute Java classes and associated metadata. In J2EE applications the JAR file often contains utility code, shared libraries and EJBS. An EJB is a server-side model that encapsulates the business logic of an application and is one of several Java APIs in the Java Platform, Enterprise Edition with its own specification. You can visit http://java.sun.com/products/ejb/ for information on EJBs. |
|
EAR file |
An Enterprise Archive file represents a J2EE application that can be deployed in a WebSphere application server. EAR files are standard Java archive files (JAR) and have the file extension .ear. An EAR file can consist of the following:
The modules that make up the EAR file are themselves packaged in archive files specific to their types. For example, a Web module contains Web archive files and an EJB module contains Java archive files. EAR files also contain a deployment descriptor (an XML file called application.xml) that describes the contents of the application and contains instructions for the entire application, such as security settings to be used in the run-time environment… |
|
WAR file |
A WAR file (Web Application) is essentially a JAR file used to encapsulate a collection of JavaServer Pages (JSP), servlets, Java classes, HTML and other related files which may include XML and other file types depending on the web technology used. For information on JSP and Servlets, you can visit http://java.sun.com/products/jsp/.
A WAR file also has its own deployment descriptor called “web.xml” which is used to configure the WAR file and can contain instruction for resource mapping and security. |
When an EJB module or web module is installed as a standalone application, it is automatically wrapped in an Enterprise Archive (EAR) file by the WebSphere deployment process and is managed on disk by WebSphere as an EAR file structure. So, if a WAR file is deployed, WebSphere will convert it into an EAR file.
Deploying an application
As WebSphere administrators, we are asked to deploy applications. These applications may be written in-house or delivered by a third-party vendor. Either way, they will most often be provided as an EAR file for deployment into WebSphere. For the purpose of understanding a manual deployment, we are now going to install a default application. The default application can be located in the <was_root>/installableApps folder. The following steps will show how we deploy the EAR file.
Open the administration console and navigate to the Applications section and click on New Application as shown below:
You now see the option to create one of the following three types of applications:
|
Application Type |
Description |
|
Enterprise Application
|
EAR file on a server configured to hold installable Web Applications, (WAR), Java archives, library files, and other resource files. |
|
Business Level Application
|
A business-level application is an administration model similar to a server or cluster. However, it lends itself to the configuration of applications as a single grouping of modules. |
|
Asset
|
An asset represents one or more application binary files that are stored in an asset repository such as Java archives, library files, and other resource files. Assets can be shared between applications. |
Click on New Enterprise Application.
As seen in the following screenshot, you will be presented with the option to either browse locally on your machine for the file or remotely on the Application Server’s file system. Since the EAR file we wish to install is on the server, we will choose the Remote file system option.
It can sometimes be quicker to deploy large applications by first using Secure File Transfer Protocol (SFTP) to move the file to the application server’s file system and then using remote, as opposed to transferring via local browse, which will do an HTTP file transfer which takes more resources and can be slower.
The following screenshot depicts the path to the new application:
Click Browse…. You will see the name of the application server node. If there is more than one profile, select the appropriate instance. You will then be able to navigate through a web-based version of the Linux file system as seen in the following screenshot:
Locate the DefaultApplication.ear file. It will be in a folder called installableApps located in the root WebSphere install folder, for example, <was_root>/installableApps as shown in the previous screenshot.
Click Next to begin installing the EAR file.
On the Preparing for the application installation page, choose the Fast Path option. There are two options to choose.
|
Install option |
Description |
|
Fast Path |
The deployment wizard will skip advanced settings and only prompt for the absolute minimum settings required for the deployment. |
|
Detailed |
The wizard will allow, at each stage of the installation, for the user to override any of the J2EE properties and configurations available to an EAR file. |
The Choose to generate default bindings and mappings setting allows the user to accept the default settings for resource mappings or override with specific values. Resource mappings will exist depending on the complexity of the EAR. Bindings are JNDI to resource mappings. Each EAR file has pre-configured XML descriptors which specify the JNDI name that the application resource uses to map to a matching (application server) provided resource. An example would be a JDBC data source name which is referred to as jdbc/mydatasource, whereas the actual data source created in the application server might be called jdbc/datasource1. By choosing the Detailed option, you get prompted by the wizard to decide on how you want to map the resource bindings. By choosing the Fast Path option, you are allowing the application to use its pre-configured default JNDI names.
We will select Fast Path as demonstrated in the following screenshot:
Click on Next.
In the next screen, we are given the ability to fill out some specific deployment options. Below is a list of the options presented in this page.