BAEL-4615: Create and Detect Memory Leak in Java (#14060)
This commit is contained in:
Eugene Kovko
GitHub
parent
2091146702
commit
7317f0816d
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@ -5,3 +5,4 @@ This module contains articles about performance of Java applications
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### Relevant Articles:
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- [Possible Root Causes for High CPU Usage in Java](https://www.baeldung.com/java-high-cpu-usage-causes)
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- [External Debugging With JMXTerm](https://www.baeldung.com/java-jmxterm-external-debugging)
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- [Create and Detect Memory Leaks in Java](https://www.baeldung.com/java-create-detect-memory-leaks)
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@ -13,4 +13,11 @@
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<version>0.0.1-SNAPSHOT</version>
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</parent>
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<dependencies>
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<dependency>
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<groupId>net.datafaker</groupId>
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<artifactId>datafaker</artifactId>
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<version>1.6.0</version>
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</dependency>
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</dependencies>
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</project>
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@ -0,0 +1,35 @@
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package com.baeldung.lapsedlistener;
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import static com.baeldung.lapsedlistener.UserGenerator.generateUser;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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public class LapsedListenerRunner {
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private static final Logger logger = LoggerFactory.getLogger(LapsedListenerRunner.class);
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private static final MovieQuoteService movieQuoteService = new MovieQuoteService();
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static {
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movieQuoteService.start();
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}
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public static void main(String[] args) {
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while (true) {
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User user = generateUser();
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logger.debug("{} logged in", user.getName());
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user.subscribe(movieQuoteService);
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userUsingService();
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logger.debug("{} logged out", user.getName());
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}
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}
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private static void userUsingService() {
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try {
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Thread.sleep(10);
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} catch (InterruptedException e) {
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e.printStackTrace();
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}
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}
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}
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@ -0,0 +1,47 @@
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package com.baeldung.lapsedlistener;
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import java.util.ArrayList;
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import java.util.List;
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import java.util.concurrent.Executors;
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import java.util.concurrent.ScheduledExecutorService;
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import java.util.concurrent.TimeUnit;
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import net.datafaker.Faker;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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public class MovieQuoteService implements Subject {
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private static final Logger logger = LoggerFactory.getLogger(MovieQuoteService.class);
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private final ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);
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private final List<Observer> observers = new ArrayList<>();
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private final Faker faker = new Faker();
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@Override
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public void attach(Observer observer) {
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logger.debug("Current number of subscribed users: {}", observers.size());
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observers.add(observer);
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}
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@Override
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public void detach(Observer observer) {
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observers.remove(observer);
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}
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@Override
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public void notifyObservers() {
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String quote = faker.movie().quote();
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logger.debug("New quote: {}", quote);
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for (Observer observer : observers) {
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logger.debug("Notifying user: {}", observer);
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observer.update(quote);
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}
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}
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public void start() {
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scheduler.scheduleAtFixedRate(this::notifyObservers, 0, 1, TimeUnit.SECONDS);
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}
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public int numberOfSubscribers() {
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return observers.size();
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}
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}
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@ -0,0 +1,9 @@
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package com.baeldung.lapsedlistener;
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public interface Observer {
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void update(String latestNews);
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void subscribe(Subject subject);
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void unsubscribe(Subject subject);
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}
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@ -0,0 +1,9 @@
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package com.baeldung.lapsedlistener;
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public interface Subject {
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void attach(Observer observer);
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void detach(Observer observer);
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void notifyObservers();
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}
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@ -0,0 +1,70 @@
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package com.baeldung.lapsedlistener;
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public class User implements Observer {
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private final String name;
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private final String email;
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private final String phone;
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private final String street;
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private final String city;
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private final String state;
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private final String zipCode;
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public User(String name, String email, String phone, String street, String city, String state, String zipCode) {
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this.name = name;
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this.email = email;
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this.phone = phone;
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this.street = street;
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this.city = city;
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this.state = state;
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this.zipCode = zipCode;
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}
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public String getName() {
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return name;
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}
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public String getEmail() {
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return email;
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}
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public String getPhone() {
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return phone;
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}
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public String getStreet() {
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return street;
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}
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public String getCity() {
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return city;
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}
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public String getState() {
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return state;
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}
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public String getZipCode() {
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return zipCode;
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}
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@Override
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public void update(final String quote) {
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// user got updated with a new quote
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}
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@Override
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public void subscribe(final Subject subject) {
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subject.attach(this);
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}
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@Override
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public void unsubscribe(final Subject subject) {
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subject.detach(this);
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}
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@Override
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public String toString() {
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return "User [name=" + name + "]";
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}
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}
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@ -0,0 +1,23 @@
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package com.baeldung.lapsedlistener;
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import net.datafaker.Faker;
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public class UserGenerator {
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private UserGenerator() {
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}
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private static final Faker faker = new Faker();
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public static User generateUser() {
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String name = faker.name().fullName();
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String email = faker.internet().emailAddress();
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String phone = faker.phoneNumber().cellPhone();
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String street = faker.address().streetAddress();
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String city = faker.address().city();
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String state = faker.address().state();
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String zipCode = faker.address().zipCode();
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return new User(name, email, phone, street, city, state, zipCode);
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}
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}
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@ -0,0 +1,24 @@
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package com.baeldung.lapsedlistener;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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import org.junit.jupiter.api.Test;
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class MovieQuoteServiceTest {
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@Test
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void whenSubscribeToService_thenServiceHasOneSubscriber() {
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MovieQuoteService service = new MovieQuoteService();
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service.attach(UserGenerator.generateUser());
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assertEquals(1, service.numberOfSubscribers());
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}
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@Test
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void whenUnsubscribeFromService_thenServiceHasNoSubscribers() {
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MovieQuoteService service = new MovieQuoteService();
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User user = UserGenerator.generateUser();
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service.attach(user);
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service.detach(user);
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assertEquals(0, service.numberOfSubscribers());
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}
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}
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