This chapter is intended for advanced JOnAS users who require that some "external" services run along with the JOnAS server. A service is something that may be initialized, started, and stopped. JOnAS itself already defines a set of services, some of which are cornerstones of the JONAS Server. The JOnAS pre-defined services are listed in Configuring JOnAS services .
J2EE application developers may need to access other services, for example another Web container or a Versant container, for their components. Thus, it is important that such services be able to run along with the application server. To achieve this, it is possible to define them as JOnAS services.
This chapter describes how to define a new JOnAS service and how to specify which service should be started with the JOnAS server.
The customary way to define a new JOnAS service is to encapsulate it in a class whose interface is known by JOnAS. More precisely, such a class provides a way to initialize, start, and stop the service. Then, the jonas.properties file must be modified to make JOnAS aware of this service.
A JOnAS service is represented by a class that implements the interface
org.objectweb.jonas.service.Service
, and, thus should implement the following methods:
public void init(Context ctx) throws ServiceException;
public void start() throws ServiceException;
public void stop() throws ServiceException;
public boolean isStarted();
public String getName();
public void setName(String name);
It should also define a public constructor with no argument.
These methods will be called by JOnAS for initializing, starting, and stopping the service. Configuration parameters are provided to the initialization method through a naming context. This naming context is built from properties defined in the
jonas.properties
file as explained in
Section 1.2.2, “Modifying the jonas.properties file”.
The Service class should look like the following:
package a.b;
import javax.naming.Context;
import javax.naming.NamingException;
import org.objectweb.jonas.service.Service;
import org.objectweb.jonas.service.ServiceException;
.....
public class MyService implements Service {
private String name = null;
private boolean started = false;
.....
public void init(Context ctx) throws ServiceException {
try {
String p1 = (String) ctx.lookup("jonas.service.serv1.p1");
.....
} catch (NamingException e) {
throw new ServiceException("....", e);
}
.....
}
public void start() throws ServiceException {
.....
this.started = true;
}
public void stop() throws ServiceException {
if (this.started) {
this.started = false;
.....
}
}
public boolean isStarted() {
return this.started;
}
public String getName() {
return this.name;
}
public void setName(String name) {
this.name = name; }
}
The service is defined and its initialization parameters specified in the
jonas.properties
file. First, choose a name for the service (e.g. "serv1"), then do the following:
add this name to the
jonas.services
property; this property defines the set of services (comma-separated) that will be started with JOnAS,
in the order of this list
.
add a
jonas.service.serv1.class
property specifying the service class.
add as many
jonas.service.serv1.XXX
properties specifying the service initialization parameters, as will be made available to the service class via the Context argument of the
init
method.
This is illustrated as follows:
jonas.services .......,serv1 jonas.service.serv1.class a.b.MyService jonas.service.serv1.p1 value
The new service has been given a name in
jonas.properties
. With this name, it is possible to get a reference on the service implementation class by using the ServiceManager method:
getService(name)
. The following is an example of accessing a Service:
import org.objectweb.jonas.service.ServiceException;
import org.objectweb.jonas.service.ServiceManager;
MyService sv = null; // Get a reference on MyService.
try {
sv = (MyService) ServiceManager.getInstance().getService("serv1");
} catch (ServiceException e) {
Trace.errln("Cannot find MyService:"+e);
}
Refer to the JOnAS sources for more details about the classes mentioned in this section.
The existing JOnAS services are the following:
| Service name | Service class |
|---|---|
| registry | RegistryServiceImpl |
| ejb | EJBServiceImpl |
| web | CatalinaJWebContainerServiceImpl/JettyJWebContainerServiceImpl |
| ear | EarServiceImpl |
| dbm | DataBaseServiceImpl |
| jms | JmsServiceImpl |
| jmx | JmxServiceImpl |
| jtm | TransactionServiceImpl |
| MailServiceImpl | |
| resource | ResourceServiceImpl |
| security | JonasSecurityServiceImpl |
| ws | AxisWSService |
If all of these services are required, they will be launched in the following order: registry, jmx, security, jtm, dbm, mail, jms, resource, ejb, ws, web, ear, jmx, security, dbm, mail.
registry must be launched first. (Note that for reasons of compatability with previous versions of JOnAS, if registry is unintentionally not set as the first service to launch, JOnAS will automatically launch the registry service.)
Note that dbm , jms , resource , and ejb depend on jtm . Note that ear depends on ejb and web (that provide the ejb and web containers), thus these services must be launched before the ear service. Note that ear and web depends on ws, thus the ws service must be launched before the ear and web services. It is possible to launch a stand-alone Transaction Manager with only the registry and jtm services.
A
jonas.properties
file looks like the following:
... jonas.services registry,jmx,jtm,db,dbm,security,wm,wc,resource,ejb,ejb3,ws,web,ear,depmonitor jonas.service.registry.class org.ow2.jonas.registry.carol.CarolRegistryService jonas.service.registry.mode collocated jonas.service.jmx.class org.ow2.jonas.jmx.internal.JOnASJMXService jonas.service.jmx.secured false jonas.service.jmx.authentication.method jmx.remote.x.password.file jonas.service.jmx.authentication.parameter conf/jmx.passwords jonas.service.jmx.authorization.method jmx.remote.x.access.file jonas.service.jmx.authorization.parameter conf/jmx.access jonas.service.wc.class org.ow2.jonas.workcleaner.internal.JOnASWorkCleanerService jonas.service.wc.period 300 ...
The
org.objectweb.jonas.service.ServiceException
exception is defined for Services. Its type is
java.lang.RuntimeException.
and it can encapsulate any
java.lang.Throwable
.