How to use EJB 3 timer in a weblogic 10 cluster environment
Although there are some articles talking about EJB 3 timers or job schedulers , we were not able to find any detailed instructions on how to make EJB 3 timer work in a weblogic cluster. In this article we will go through a sample project to show how EJB 3 timers are used in a weblogic cluster. The sample project will create two recurring timers, the first recurring timer will periodically print out some simple information, the second recurring timer will create a couple of one-timer timers, each of which will print out some information. In this article, we will show you how to use weblogic admin console to configure the cluster, how the application uses the related configuration from the console and how to invoke timers, also explain what problems we faced and how we solved them.
Environment:
web logic server 10.3.2, oracle database 11gR1, Eclipse Helios
Code:
Timer1SessionBeanLocal: local interface for creating timer
@Local
public
interface
Timer1SessionBeanLocal {
public
void
createTimer();
}
Timer1SessionBean: a recurring timer that prints out something
@Stateless
public
class
Timer1SessionBean
implements
Timer1SessionBeanLocal {
@Resource
TimerService
timerService
;
public
Timer1SessionBean() {
}
public
void
createTimer() {
timerService
.createTimer(
60000,
60000,
null
);
}
@Timeout
public
void
timeout(Timer arg0) {
System.
out
.println(
"recurring timer1 : "
+
new
Date());
}
}
Timer2SessionBean: a recurring timer that creates a bunch of one-time timers,al so the number of one-time timers created is roughly based on the maximum allowed number of active timers minus the number of active timers at that time.
@Stateless
public
class
Timer2SessionBean
implements
Timer2SessionBeanLocal {
@Resource
TimerService
timerService
;
@EJB
Timer3SessionBeanLocal
timer3Bean
;
public
Timer2SessionBean() {
}
public
void
createTimer() {
timerService
.createTimer(120000, 300000,
null
);
}
@Timeout
public
void
timeout(Timer arg0) {
System.
out
.println(
"recurring timer2 : "
+
new
Date());
// used to control the total number of threads running in the app
// use 10 as maximum in this example.
int
numberOfActiveTimers =
timer3Bean
.getCountOfActiveTimers();
if
(numberOfActiveTimers < 10) {
int
toCreateNum = 10 - numberOfActiveTimers;
for
(
int
i = 0; i < toCreateNum; i++) {
Timer3Info info =
new
Timer3Info();
// set start delays to be 30,60,90... seconds
info.setDelay(30000 * (i + 1));
timer3Bean
.createTimer(info);
}
}
System.
out
.println(
"Exit timeout in timer2"
);
}
}
Timer3SessionBean: one-time timer created by another timer, provides the number of active timers for this bean, and prints out something.
@Stateless
public
class
Timer3SessionBean
implements
Timer3SessionBeanLocal {
@Resource
TimerService
timerService
;
public
Timer3SessionBean() {
}
public
void
createTimer(Timer3Info timerInfo) {
timerService
.createTimer(timerInfo.getDelay(),
null
);
}
@Timeout
public
void
timeout(Timer arg0) {
System.
out
.println(
"one-time timer3 : "
+
new
Date());
}
/**
*
*
@return
the number of active timers
*/
public
int
getCountOfActiveTimers(){
int
retVal = 0;
try
{
//In rare occasions, could throw NullPointerException //because of a bug in weblogic
@SuppressWarnings
(
"unchecked"
)
Collection<Timer> timersCol =
timerService
.getTimers();
if
(timersCol !=
null
)
retVal = timersCol.size();
}
catch
(Exception e) {
//if it failed, use the maximum (10 in this example), so no //new timers can be created
retVal = 10;
}
return
retVal;
}
}
TestTimerCreateServlet: used to create recurring timers.
public
class
TestTimerCreateServlet
extends
HttpServlet {
private
static
final
long
serialVersionUID
= 1L;
@EJB
Timer1SessionBeanLocal
timer1
;
@EJB
Timer2SessionBeanLocal
timer2
;
/**
*
@see
HttpServlet#HttpServlet()
*/
public
TestTimerCreateServlet() {
super
();
}
/**
*
@see
HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
* response)
*/
protected
void
doGet(HttpServletRequest request,
HttpServletResponse response)
throws
ServletException, IOException {
System.
out
.println(
"start timer creation : "
+
new
Date());
try
{
timer1
.createTimer();
timer2
.createTimer();
}
catch
(Exception e) {
System.
out
.println(
"timer creation failed "
);
throw
new
RuntimeException(
"timer creation failed "
, e);
}
System.
out
.println(
"Done timer creation : "
);
}
/**
*
@see
HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
* response)
*/
protected
void
doPost(HttpServletRequest request,
HttpServletResponse response)
throws
ServletException, IOException {
doGet(request, response);
}
}
Overall, the code is quite simple. Some things are worth noting here is that local interfaces are used for the session beans, a servlet which needs to be invoked externally is used to create timers, also ‘
timerService
.getTimers()’ is used to find out the number of active timers for a session bean and also help control the number of running timers in the system, so the system will not be over stretched.
weblogic-ejb-jar.xml: some important configurations
<?
xml
version = "1.0" encoding = "UTF-8" ?>
<
wls:weblogic-ejb-jar
xmlns:wls = "http://xmlns.oracle.com/weblogic/weblogic-ejb-jar" xmlns:xsi = "http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation = "http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/ejb-jar_3_0.xsd http://xmlns.oracle.com/weblogic/weblogic-ejb-jar http://xmlns.oracle.com/weblogic/weblogic-ejb-jar/1.0/weblogic-ejb-jar.xsd" >
<!--weblogic -version:10.3.2-->
<
wls:weblogic-enterprise-bean
>
<
wls:ejb-name
>
Timer1SessionBean
</
wls:ejb-name
>
<
wls:stateless-session-descriptor
>
<
wls:timer-descriptor
>
<
wls:persistent-store-logical-name
>
timerst
</
wls:persistent-store-logical-name
>
</
wls:timer-descriptor
>
</
wls:stateless-session-descriptor
>
</
wls:weblogic-enterprise-bean
>
<
wls:weblogic-enterprise-bean
>
<
wls:ejb-name
>
Timer2SessionBean
</
wls:ejb-name
>
<
wls:stateless-session-descriptor
>
<
wls:timer-descriptor
>
<
wls:persistent-store-logical-name
>
timerst
</
wls:persistent-store-logical-name
>
</
wls:timer-descriptor
>
</
wls:stateless-session-descriptor
>
</
wls:weblogic-enterprise-bean
>
<
wls:weblogic-enterprise-bean
>
<
wls:ejb-name
>
Timer3SessionBean
</
wls:ejb-name
>
<
wls:stateless-session-descriptor
>
<
wls:timer-descriptor
>
<
wls:persistent-store-logical-name
>
timerst
</
wls:persistent-store-logical-name
>
</
wls:timer-descriptor
>
</
wls:stateless-session-descriptor
>
</
wls:weblogic-enterprise-bean
>
<
wls:timer-implementation
>
Clustered
</
wls:timer-implementation
>
</
wls:weblogic-ejb-jar
>
The most important things are that making sure the timers are cluster aware, and also using proper logical name for the persistent store (
timerst ), which will be configured in the administrator console.
Admin console configuration:
<
分享到：
评论