Hi,
I have some error during the invocation of a bean inside an Aspect, and I also
would like to have some suggestions about initialization of beans inside an
aspect class.
1. I am trying to invoke a bean [2] inside my aspects class [1], but in the end
I get the following error [4]. It seems that the @Autowired parameter didn't
initialize the bean. My configuration file is in [3]. What am I doing wrong?
2. I want that the bean will be invoked one time during initialization. So,
even the `map` function is called multiple times, the bean is already
initialized.
Another solution is, I want (I don't know if it is possible), that the bean
will be initialized when the pointcut `map` or `reduce` is invoked by the first
time.
Are these requests possible to do?
Thanks,
[1] My aspect class @Aspect @Configurable @Component public class
MapReduceAspects {
@Autowired MedusaDigestsdigests;
@Before("execution(* map(..))")
public void mymap(JoinPoint joinPoint) {
System.out.println("My Map Execution: " + joinPoint.getArgs() +":" +
joinPoint.getTarget());
Object[] obj = joinPoint.getArgs();
if (obj.length >0) {
byte[] key = convertToBytes(obj[0]);
byte[] value = convertToBytes(obj[1]);
digests.updateDigest(key, value);
}
}
@Before("execution(* reduce(..))")
public void myreduce(JoinPoint joinPoint) { System.out.println("My Reduce
Execution");
Object[] obj = joinPoint.getArgs();
if (obj.length >0) {
byte[] key = convertToBytes(obj[0]);
byte[] value = convertToBytes(obj[1]);
digests.updateDigest(key, value);
}
}
}
[1] My aspect
@Component public class MedusaDigests {
private final StringMD5 ="MD5";
private MessageDigestmda =null;
public MedusaDigests() {
try {
mda = MessageDigest.getInstance(MD5);
}catch (NoSuchAlgorithmException e) {
// TODO Auto-generated catch block e.printStackTrace();
}
}
[3] My beans-aspects.xml
<?xml version="1.0" encoding="UTF-8"?> <beans
xmlns="http://www.springframework.org/schema/beans";
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance";
xmlns:aop="http://www.springframework.org/schema/aop";
xmlns:context="http://www.springframework.org/schema/context";
xsi:schemaLocation="http://www.springframework.org/schema/aop
http://www.springframework.org/schema/aop/spring-aop-3.2.xsd
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.2.xsd";>
<aop:aspectj-autoproxy proxy-target-class="true"/>
<!--<aop:include name="mapreduceAspect"/>--> <!--<aop:include
name="jobClient"/>--> <!--</aop:aspectj-autoproxy>-->
<!--<context:load-time-weaver/>--> <context:component-scan
base-package="org.apache.hadoop.mapred"/>
<bean id="mapreduceAspect"
class="org.apache.hadoop.mapred.aspects.MapReduceAspects"
factory-method="aspectOf" autowire="byType" />
<bean id="medusaDigests" class="org.apache.hadoop.mapred.MedusaDigests"/>
</beans>
[4] the error that I get
WARNING: job_local138234703_0001
java.lang.Exception: java.lang.NullPointerException
at
org.apache.hadoop.mapred.LocalJobRunner$Job.runTasks(LocalJobRunner.java:462)
at
org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:522)
Caused by: java.lang.NullPointerException
at
org.apache.hadoop.mapred.aspects.MapReduceAspects.mymap(MapReduceAspects.java:50)
at
org.apache.hadoop.mapred.examples.DummyWordCount$Map.map(DummyWordCount.java:32)
at
org.apache.hadoop.mapred.examples.DummyWordCount$Map.map(DummyWordCount.java:1)
at org.apache.hadoop.mapreduce.Mapper.run(Mapper.java:146)
at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:787)
at org.apache.hadoop.mapred.MapTask.run(MapTask.java:341)
at
org.apache.hadoop.mapred.LocalJobRunner$Job$MapTaskRunnable.run(LocalJobRunner.java:243)
at
java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
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