Chapter 7 Java EE Containers
This chapter explains how to configure the Java EE containers
included in the server. This chapter contains following sections:
About the Java EE Containers
This section describes the Java EE containers included with the Application Server.
Types of Java EE Containers
Java EE containers provide runtime support for Java EE application components.
Java EE application components use the protocols and methods of the container
to access other application components and services provided by the server.
The Application Server provides an application client container, an applet container, a Web container, and an EJB container.
For a diagram that shows the containers, see the section Application Server Architecture.
The Web Container
The Web Container is a Java EE container that hosts web applications.
The web container extends the web server functionality by providing developers
the environment to run servlets
and JavaServer
Pages (JSP files).
The EJB Container
Enterprise beans (EJB components) are Java programming language server
components that contain business logic. The EJB container provides local and
remote access to enterprise beans.
There are three types of enterprise beans: session beans, entity
beans, and message-driven beans. Session beans represent transient
objects and processes and typically are used by a single client. Entity beans
represent persistent data, typically maintained in a database. Message-driven
beans are used to pass messages asynchronously to application modules and
services.
The container is responsible for creating the enterprise bean, binding
the enterprise bean to the naming service so other application components can access the
enterprise bean, ensuring only authorized clients have access
to the enterprise bean’s methods, saving the bean’s state to persistent storage, caching the state of the bean, and activating or passivating the bean when necessary.
Sun Java System Application Server 9 conforms to Java EE 5 and EJB 3.0
specifications Therefore a JNDI name will be no longer be required for EJB
3.0 session beans that expose a Remote view. If a deployed Remote EJB 3.0
bean does not provide a global JNDI name, the container will assign it one
at runtime. The assigned JNDI name is the fully qualified class name of the
remote EJB's business interface. In addition, EJB clients that use the new
Remote EJB 3.0 client view will not be required to map their remote @EJB references
to a global JNDI name within sun-ejb-jar.xml. If a JNDI name has not been
associated with the ejb reference, the container will derive the default JNDI
name for the target EJB from its associated business interface.
Applications using this EJB 3.0 feature will no longer need sun-ejb-jar.xml or sun-application-client.xml configuration
files. The older method of providing a JNDI name in sun-ejb-jar.xml will
continue to work. It will also be possible for the application to map an ejb-reference or @EJB reference to a specific
global JNDI name.
See Also:
Configuring Java EE 5 Containers
Configuring Web Container Sessions
This section describes the HTTP session settings in the Web container.
HTTP sessions are unique web sessions that have their state data written to
a persistent store.
Configuring Session Timeout Value
Use the Admin Console to set the HTTP session timeout value. The session
timeout value represents the duration for which an HTTP session is valid.
In the Admin Console, go to Configuration> Web Container > Session
Properties. In the Session Timeout field, enter the number of seconds that
a session is valid.
For detailed instructions on setting the session timeout value, Click
Help in the Admin Console.
Configuring Manager Properties
The
session manager provides the means to configure how sessions are created and
destroyed, where session state is stored, and the maximum number of sessions.
To change the session manager settings in the Admin Console, go to
Configuration> Web Container > Manager Properties.
In the Manager Properties tab, set the following properties:
-
Reap Interval value. The Reap Interval field is the number
of seconds before the inactive session data is deleted from the store.
-
Max Sessions value. The Max Sessions field is the maximum
number of sessions allowed.
-
Set the Session Filename value. The Session Filename field
is the file that contains the session data.
-
Session ID Generator Classname value.
The Session ID Generator
Classname field allows you to specify a custom class for generating unique
session IDs. Only one session ID generator class per server instance is permitted,
and all instances in a cluster must use the same session ID generator to prevent
session key collision.
Custom session ID generator classes must
implement the com.sun.enterprise.util.uuid.UuidGenerator interface:
package com.sun.enterprise.util.uuid;
public interface UuidGenerator {
public String generateUuid();
public String generateUuid(Object obj); //obj is the session object
}
The class must be in the Application Server classpath.
For detailed instructions on setting the manager properties, Click Help
in the Admin Console.
Configuring Store Properties
To specify where the session store data will be saved, in the Admin Console,
go to Configuration > Web Container > Store Properties.
-
Set the Reap Interval field
The Reap Interval field is the number of seconds before the inactive
session data is deleted from the store.
-
Specify the directory where session data will be stored.
For detailed instructions on setting the session store properties, Click
Help in the Admin Console.
To configure the product.name property
By default, the web container returns an HTTP response header with an
attribute whose name is "Server" and value is the version of the Application
Server Software. For example, on Application Server 9 Platform Edition, the
value is: "Server: Sun Java System Application Server Enterprise Edition 9.0
FCS". Run the asadmin version command to view the version
of your installation. If you want to override this value, define a Java
Property named product.name in the server's configuration
and initialize it to the value of your choice. This value determines what
is returned by the server in the HTTP response. To change the property:
-
Start the Application Server and log in to Admin Console.
-
Click Application Server and click the JVM Settings tab.
-
Click Add JVM Option.
-
Enter the following value: -Dproduct.name="My Name".
Configuring the General EJB Settings
The following section describes settings that apply to all enterprise
bean containers on the server:
To override the defaults on a per-container basis, adjust the values
in the enterprise bean’s sun-ejb-jar.xml file. For
details, see the Sun Java System Application Server Platform Edition 9 Developer’s Guide.
Configuring Session Store Location
The Session Store Location field specifies the directory where passivated
beans and persisted HTTP sessions are stored on the file system.
Passivated beans are enterprise beans that have had their state written
to a file on the file system. Passivated beans typically have been idle
for a certain period of time, and are not currently being accessed by clients.
Similar to passivated beans, persisted HTTP sessions are individual
web sessions that have had their state written to a file on the file system.
The Commit Option field specifies how the container caches passivated entity bean instances between
transactions.
Option B caches entity bean instances between transactions, and is selected
by default. Option C disables caching.
Configuring EJB Pool Settings
The container maintains a pool of enterprise beans in order to respond
to client requests without the performance hit that results from creating
the beans. These settings only apply to stateless session beans and entity beans.
If you experience performance problems in an application that uses deployed
enterprise beans, creating a pool, or increasing the number of beans maintained
by an existing pool, can help increase the application’s performance.
By default, the container maintains a pool of enterprise beans.
To set the EJB pool properties using the Admin Console, go to Configuration
> EJB Container > EJB Settings.
-
Under Pool Settings in the Initial and Minimum Pool Size field
enter the minimum number of beans the container creates in the pool.
-
In the Maximum Pool Size field enter the maximum number of
beans the container maintains in the pool, at any time.
-
In the Pool Resize Quantity field enter the number of beans
that will be removed from the pool if they are idle for more than the time
specified in Pool Idle Timeout.
-
In the Pool Idle Timeout field enter the time, in seconds,
that a bean in the pool can remain idle before it will be removed from the
pool.
-
Restart the Application Server.
For detailed instructions on configuring the EJB pool, Click Help in
the Admin Console.
Configuring EJB Cache Settings
The container maintains a cache of enterprise bean data for the most
used enterprise beans. This allows the container to respond more quickly to
requests from other application modules for data from the enterprise beans.
This section applies only to stateful session beans and entity beans.
Cached enterprise beans are in one of three states: active, idle,
or passivated. An active enterprise bean is currently being accessed
by clients. An idle enterprise bean’s data is currently in the cache,
but no clients are accessing the bean. A passivated bean’s data is temporarily
stored, and read back into the cache if a client requests the bean.
To configure the EJB cache settings using the Admin Console, go to
Configuration > EJB Container > EJB Settings.
-
Adjust the maximum cache size in the Max Cache Size field.
Increase the maximum number of beans to cache to eliminate the overhead
of bean creation and destruction. However, if the cache is increased, the
server consumes more memory and resources. Be sure your operating environment
is sufficient for your cache settings.
-
Adjust the cache resize quantity in the Cache Resize Quantity
field.
When the maximum number of cached beans is reached, the
container removes a number of passivated beans from the backup store, set
to 32 by default.
-
Adjust the rate, in seconds, at which the cache cleanup is scheduled
for entity beans in the Cache
Idle Timeout field.
-
If a cached entity bean has been idle a certain amount of
time, it is passivated. That is, the bean’s state is written to a backup
store.
-
Adjust the time, in seconds, after which stateful session
beans are removed from the cache or passivated store in the Removal Timeout
field.
-
Configure the policy the container uses
to remove stateful session beans in the Removal Selection Policy field.
The container decides which stateful session beans to remove based on
the policy set in the Removal Selection Policy field. There are three possible
policies the container uses to remove beans from the cache:
The NRU policy removes a bean that hasn’t been used recently.
The FIFO policy removes the oldest bean in the cache. The LRU policy removes
the least recently accessed bean. By default, the NRU policy is used by the
container.
Entity beans are always removed using the FIFO policy.
-
Restart the Application Server.
For detailed instructions on configuring the EJB pool, Click Help in
the Admin Console.
Configuring the Message-Driven Bean Settings
The pool for message-driven beans is similar to the pool for session
beans described in Configuring EJB Pool Settings.
By default, the container maintains a pool of message-driven beans.
To adjust the configuration of this pool using the Admin Console, go
to Configuration > EJB Container > MDB Settings.
-
Under Pool Settings in the Initial and Minimum Pool Size field,
enter the minimum number of message beans the container creates in the pool.
-
In the Maximum Pool Size field, enter the maximum number of
beans the container maintains in the pool, at any time.
-
In the Pool Resize Quantity field, enter the number of beans
that are removed from the pool if they are idle for more than the time specified
in Pool Idle Timeout.
-
In the Pool Idle Timeout field, enter the time, in seconds,
that a bean in the pool can remain idle before it is removed from the pool.
-
Restart the Application Server.
For detailed instructions on configuring the MDB settings, Click Help
in the Admin Console.
Configuring the EJB Timer Service Settings
The timer service is a persistent and transactional notification service
provided by the enterprise bean container used to schedule notifications or
events used by enterprise beans. All enterprise beans except stateful session beans can receive notifications from the timer
service. Timers set by the service are not destroyed when the server is shut down or restarted.
To configure the EJB Timer Service using the Admin Console, go to Configuration
> EJB Container > EJB Timer Service.
-
Set the minimum delivery interval in milliseconds in the Minimum
Delivery Interval field.
Minimum Delivery Interval is the minimum
number of milliseconds allowed before the next timer expiration for a particular
timer can occur. Setting this interval too low can cause server overload.
-
Set the maximum number of attempts the timer service makes
to deliver the notification in the Maximum Redeliveries field.
-
Set the interval, in milliseconds, between redelivery attempts
in the Redelivery Interval field.
-
Specify the JNDI name of the JDBC resource that will be used
as the Timer Datasource.
-
Restart the Application Server.
Using an External Database With the Timer Service
By default, the timer service uses an embedded database to store timers.
You can set up the timer service to another database.
Sample timer database creation files are provided for Java
DB (Derby), PointBase, Oracle, Sybase, DB2, and MS SQL Server at install-dir/lib/install/databases/.
To use an external database with the Timer Service, first, set up a
JDBC resource for the selected database as described in Creating a JDBC Resource. Then go to Configuration > EJB Container > EJB Timer
Service and enter the JNDI name of the resource in the Timer DataSource field. Restart
the Application Server.
See the following for related information:
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