Exposing a Java class as a MXBean
This Java tutorial extends Java ExecutorService for multi-threading -- coding question and tutorial by exposing it as an MXBean so that MXBean properties can be viewed and set via JConsole as demonstrated below.
Step 1: The changes from the previous tutorial are
1. It implements SumEngineMXBean interface with the naming convention suffix MXBean and the methods that needs to be exposed must be defined.
2. The thread pool size is managed via threadPoolSize variable and it needs to have getThreadPoolSize( ) and setThreadPoolSize(int threadPoolSize) methods to view and modify this variable JConsole, which is a JMX console to monitor your JVM.
3. The getRequestsCount( ) is also managed via JMX to view the requests counts via JConsole.
package com.mycompany.metrics; import java.util.LinkedList; import java.util.List; import java.util.concurrent.Callable; import java.util.concurrent.ExecutionException; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.Future; import java.util.concurrent.atomic.AtomicInteger; public class SumEngine implements SumEngineMXBean{ private final AtomicInteger requestsCount = new AtomicInteger(); private ExecutorService executionService = null; private int threadPoolSize = 1; //executes requests to sum public void execute(SumRequest... request) { executionService = Executors.newFixedThreadPool(threadPoolSize); //create a thread pool List<Callable<SumResponse>> tasks = createExecuteTasks(request); List<Future<SumResponse>> results = execute(tasks); for (Future<SumResponse> result : results) { try { System.out.println(Thread.currentThread().getName() + ": Response = " + result.get()); } catch (InterruptedException e) { e.printStackTrace(); } catch (ExecutionException e) { e.printStackTrace(); } } //initiates an orderly shutdown of thread pool executionService.shutdown(); } //create tasks private List<Callable<SumResponse>> createExecuteTasks(SumRequest[] requests) { List<Callable<SumResponse>> tasks = new LinkedList<Callable<SumResponse>>(); executingRequests(requests.length); for (SumRequest req : requests) { Callable<SumResponse> task = createTask(req); tasks.add(task); } return tasks; } //increment the requests counter private void executingRequests(int count) { requestsCount.addAndGet(count); } //creates callable (i.e executable or runnable tasks) private Callable<SumResponse> createTask(final SumRequest request) { // anonymous implementation of Callable. // Pre Java 8's way of creating closures Callable<SumResponse> task = new Callable<SumResponse>() { @Override public SumResponse call() throws Exception { System.out.println(Thread.currentThread().getName() + ": Request = " + request); SumProcessor<SumRequest, SumResponse> processor = new SumProcessorImpl<>(); SumResponse result = processor.sum(request); return result; } }; return task; } //executes the tasks private <T> List<Future<T>> execute(List<Callable<T>> tasks) { List<Future<T>> result = null; try { //invokes the sum(sumRequest) method by executing the closure call() inside createTask result = executionService.invokeAll(tasks); } catch (InterruptedException e) { e.printStackTrace(); } return result; } public int getRequestsCount(){ return requestsCount.get(); } public int getThreadPoolSize() { return threadPoolSize; } @Override public void setThreadPoolSize(int threadPoolSize) { this.threadPoolSize = threadPoolSize; } }
Step 2: The test class SumEngineTest that runs forever in an endless while loop. This allows you to monitor your app via JConsole as it runs. For example, change the threadPoolSize and view both the threadPoolSize and requestsCount. THe MBean server lines are also added to register the MXBean.
package com.mycompany.metrics; import java.lang.management.ManagementFactory; import java.util.ArrayList; import java.util.List; import java.util.concurrent.TimeUnit; import javax.management.MBeanServer; import javax.management.ObjectName; public class SumEngineTest { public static void main(String[] args) throws Exception { SumEngine se = new SumEngine(); //Register with MBeanServer MBeanServer mbs = ManagementFactory.getPlatformMBeanServer(); ObjectName name = new ObjectName("com.mycompany.metrics:type=SumEngine"); mbs.registerMBean(se, name); List<SumRequest> list = new ArrayList<>(); //run for ever while (true) { // sums 1+2, 2+3, 3+4, etc for (int i = 1; i <= 5; i++) { SumRequest req = new SumRequest(); req.setOperand1(i); req.setOperand2(i + 1); list.add(req); } SumRequest[] req = new SumRequest[list.size()]; se.execute((SumRequest[]) list.toArray(req)); // sleep for 5 seconds TimeUnit.SECONDS.sleep(5); list.clear(); } } }
Step 3: Run the SumEngineTest, and wherever the engine is running, go to the DOS command prompt and type jconsole. This pops up the jconsole GUI. Connect to com.mycompany.metrics.SumEngineTest.
You can try increase the threadPoolSize and check the output to see if more threads are used. Also, look at the other tabs memory, threads, overview, etc.
Labels: JMX
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