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BAEL-3768 - spatialguru.net@gmail.com (#9385) 

* Add implementation of BeanPostProcessor and BeanFactoryPostProcessor for ticket

* Continue processing beans if annotation not found on one or more

* Add integration test

* Simplify code
This commit is contained in:
Mark Thomas 2020-05-28 15:34:00 -05:00 committed by GitHub
parent 6cd7bfba80
commit 135c3160ac
10 changed files with 379 additions and 1 deletions
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24
spring-core-4/pom.xml
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@ -24,6 +24,16 @@
<artifactId>spring-core</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-expression</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>28.2-jre</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-test</artifactId>
@ -42,6 +52,18 @@
<version>${junit-jupiter.version}</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.awaitility</groupId>
<artifactId>awaitility</artifactId>
<version>4.0.2</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.assertj</groupId>
<artifactId>assertj-core</artifactId>
<version>2.9.1</version>
<scope>test</scope>
</dependency>
</dependencies>
<build>
@ -60,4 +82,4 @@
<spring.boot.version>2.2.2.RELEASE</spring.boot.version>
</properties>
</project>
</project>

39
spring-core-4/src/main/java/com/baeldung/postprocessor/GlobalEventBus.java Normal file
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@ -0,0 +1,39 @@
package com.baeldung.postprocessor;
import com.google.common.eventbus.AsyncEventBus;
import com.google.common.eventbus.EventBus;
import java.util.concurrent.Executors;
@SuppressWarnings("ALL")
public final class GlobalEventBus {
public static final String GLOBAL_EVENT_BUS_EXPRESSION = "T(com.baeldung.postprocessor.GlobalEventBus).getEventBus()";
private static final String IDENTIFIER = "global-event-bus";
private static final GlobalEventBus GLOBAL_EVENT_BUS = new GlobalEventBus();
private final EventBus eventBus = new AsyncEventBus(IDENTIFIER, Executors.newCachedThreadPool());
private GlobalEventBus() {
}
public static GlobalEventBus getInstance() {
return GlobalEventBus.GLOBAL_EVENT_BUS;
}
public static EventBus getEventBus() {
return GlobalEventBus.GLOBAL_EVENT_BUS.eventBus;
}
public static void subscribe(Object obj) {
getEventBus().register(obj);
}
public static void unsubscribe(Object obj) {
getEventBus().unregister(obj);
}
public static void post(Object event) {
getEventBus().post(event);
}
}

63
spring-core-4/src/main/java/com/baeldung/postprocessor/GuavaEventBusBeanFactoryPostProcessor.java Normal file
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@ -0,0 +1,63 @@
package com.baeldung.postprocessor;
import com.google.common.eventbus.EventBus;
import java.util.Iterator;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.aop.framework.Advised;
import org.springframework.aop.support.AopUtils;
import org.springframework.beans.BeansException;
import org.springframework.beans.FatalBeanException;
import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.core.annotation.AnnotationUtils;
import org.springframework.expression.Expression;
import org.springframework.expression.ExpressionException;
import org.springframework.expression.spel.standard.SpelExpressionParser;
@SuppressWarnings("ALL")
public class GuavaEventBusBeanFactoryPostProcessor implements BeanFactoryPostProcessor {
private final Logger logger = LoggerFactory.getLogger(this.getClass());
private final SpelExpressionParser expressionParser = new SpelExpressionParser();
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
for (Iterator<String> names = beanFactory.getBeanNamesIterator(); names.hasNext(); ) {
Object proxy = this.getTargetObject(beanFactory.getBean(names.next()));
final Subscriber annotation = AnnotationUtils.getAnnotation(proxy.getClass(), Subscriber.class);
if (annotation == null)
continue;
this.logger.info("{}: processing bean of type {} during initialization", this.getClass().getSimpleName(),
proxy.getClass().getName());
final String annotationValue = annotation.value();
try {
final Expression expression = this.expressionParser.parseExpression(annotationValue);
final Object value = expression.getValue();
if (!(value instanceof EventBus)) {
this.logger.error("{}: expression {} did not evaluate to an instance of EventBus for bean of type {}",
this.getClass().getSimpleName(), annotationValue, proxy.getClass().getSimpleName());
return;
}
final EventBus eventBus = (EventBus)value;
eventBus.register(proxy);
} catch (ExpressionException ex) {
this.logger.error("{}: unable to parse/evaluate expression {} for bean of type {}", this.getClass().getSimpleName(),
annotationValue, proxy.getClass().getName());
}
}
}
private Object getTargetObject(Object proxy) throws BeansException {
if (AopUtils.isJdkDynamicProxy(proxy)) {
try {
return ((Advised)proxy).getTargetSource().getTarget();
} catch (Exception e) {
throw new FatalBeanException("Error getting target of JDK proxy", e);
}
}
return proxy;
}
}

87
spring-core-4/src/main/java/com/baeldung/postprocessor/GuavaEventBusBeanPostProcessor.java Normal file
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@ -0,0 +1,87 @@
package com.baeldung.postprocessor;
import com.google.common.eventbus.EventBus;
import java.util.function.BiConsumer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.aop.framework.Advised;
import org.springframework.aop.support.AopUtils;
import org.springframework.beans.BeansException;
import org.springframework.beans.FatalBeanException;
import org.springframework.beans.factory.config.DestructionAwareBeanPostProcessor;
import org.springframework.core.annotation.AnnotationUtils;
import org.springframework.expression.Expression;
import org.springframework.expression.ExpressionException;
import org.springframework.expression.spel.standard.SpelExpressionParser;
/**
* A {@link DestructionAwareBeanPostProcessor} which registers/un-registers subscribers to a Guava {@link EventBus}. The class must
* be annotated with {@link Subscriber} and each subscribing method must be annotated with
* {@link com.google.common.eventbus.Subscribe}.
*/
@SuppressWarnings("ALL")
public class GuavaEventBusBeanPostProcessor implements DestructionAwareBeanPostProcessor {
private final Logger logger = LoggerFactory.getLogger(this.getClass());
private final SpelExpressionParser expressionParser = new SpelExpressionParser();
@Override
public void postProcessBeforeDestruction(final Object bean, final String beanName) throws BeansException {
this.process(bean, EventBus::unregister, "destruction");
}
@Override
public boolean requiresDestruction(Object bean) {
return true;
}
@Override
public Object postProcessBeforeInitialization(final Object bean, final String beanName) throws BeansException {
return bean;
}
@Override
public Object postProcessAfterInitialization(final Object bean, final String beanName) throws BeansException {
this.process(bean, EventBus::register, "initialization");
return bean;
}
private void process(final Object bean, final BiConsumer<EventBus, Object> consumer, final String action) {
Object proxy = this.getTargetObject(bean);
final Subscriber annotation = AnnotationUtils.getAnnotation(proxy.getClass(), Subscriber.class);
if (annotation == null)
return;
this.logger.info("{}: processing bean of type {} during {}", this.getClass().getSimpleName(), proxy.getClass().getName(),
action);
final String annotationValue = annotation.value();
try {
final Expression expression = this.expressionParser.parseExpression(annotationValue);
final Object value = expression.getValue();
if (!(value instanceof EventBus)) {
this.logger.error("{}: expression {} did not evaluate to an instance of EventBus for bean of type {}",
this.getClass().getSimpleName(), annotationValue, proxy.getClass().getSimpleName());
return;
}
final EventBus eventBus = (EventBus)value;
consumer.accept(eventBus, proxy);
} catch (ExpressionException ex) {
this.logger.error("{}: unable to parse/evaluate expression {} for bean of type {}", this.getClass().getSimpleName(),
annotationValue, proxy.getClass().getName());
}
}
private Object getTargetObject(Object proxy) throws BeansException {
if (AopUtils.isJdkDynamicProxy(proxy)) {
try {
return ((Advised)proxy).getTargetSource().getTarget();
} catch (Exception e) {
throw new FatalBeanException("Error getting target of JDK proxy", e);
}
}
return proxy;
}
}

34
spring-core-4/src/main/java/com/baeldung/postprocessor/StockTrade.java Normal file
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@ -0,0 +1,34 @@
package com.baeldung.postprocessor;
import java.util.Date;
public class StockTrade {
private final String symbol;
private final int quantity;
private final double price;
private final Date tradeDate;
public StockTrade(String symbol, int quantity, double price, Date tradeDate) {
this.symbol = symbol;
this.quantity = quantity;
this.price = price;
this.tradeDate = tradeDate;
}
public String getSymbol() {
return this.symbol;
}
public int getQuantity() {
return this.quantity;
}
public double getPrice() {
return this.price;
}
public Date getTradeDate() {
return this.tradeDate;
}
}

7
spring-core-4/src/main/java/com/baeldung/postprocessor/StockTradeListener.java Normal file
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@ -0,0 +1,7 @@
package com.baeldung.postprocessor;
@FunctionalInterface
public interface StockTradeListener {
void stockTradePublished(StockTrade trade);
}

36
spring-core-4/src/main/java/com/baeldung/postprocessor/StockTradePublisher.java Normal file
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@ -0,0 +1,36 @@
package com.baeldung.postprocessor;
import com.google.common.eventbus.AllowConcurrentEvents;
import com.google.common.eventbus.Subscribe;
import java.util.HashSet;
import java.util.Set;
@Subscriber
public class StockTradePublisher {
private final Set<StockTradeListener> stockTradeListeners = new HashSet<>();
public void addStockTradeListener(StockTradeListener listener) {
synchronized (this.stockTradeListeners) {
this.stockTradeListeners.add(listener);
}
}
public void removeStockTradeListener(StockTradeListener listener) {
synchronized (this.stockTradeListeners) {
this.stockTradeListeners.remove(listener);
}
}
@Subscribe
@AllowConcurrentEvents
private void handleNewStockTradeEvent(StockTrade trade) {
// publish to DB, send to PubNub, whatever you want here
final Set<StockTradeListener> listeners;
synchronized (this.stockTradeListeners) {
listeners = new HashSet<>(this.stockTradeListeners);
}
listeners.forEach(li -> li.stockTradePublished(trade));
}
}

21
spring-core-4/src/main/java/com/baeldung/postprocessor/Subscriber.java Normal file
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@ -0,0 +1,21 @@
package com.baeldung.postprocessor;
import java.lang.annotation.ElementType;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
* An annotation which indicates which Guava {@link com.google.common.eventbus.EventBus} a Spring bean wishes to subscribe to.
*/
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Inherited
public @interface Subscriber {
/**
* A SpEL expression which selects the {@link com.google.common.eventbus.EventBus}.
*/
String value() default GlobalEventBus.GLOBAL_EVENT_BUS_EXPRESSION;
}

23
spring-core-4/src/test/java/com/baeldung/postprocessor/PostProcessorConfiguration.java Normal file
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@ -0,0 +1,23 @@
package com.baeldung.postprocessor;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
public class PostProcessorConfiguration {
@Bean
public GlobalEventBus eventBus() {
return GlobalEventBus.getInstance();
}
@Bean
public GuavaEventBusBeanPostProcessor eventBusBeanPostProcessor() {
return new GuavaEventBusBeanPostProcessor();
}
@Bean
public StockTradePublisher stockTradePublisher() {
return new StockTradePublisher();
}
}

46
spring-core-4/src/test/java/com/baeldung/postprocessor/StockTradeIntegrationTest.java Normal file
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@ -0,0 +1,46 @@
package com.baeldung.postprocessor;
import java.time.Duration;
import java.util.Date;
import java.util.Objects;
import java.util.concurrent.atomic.AtomicBoolean;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import static org.assertj.core.api.Assertions.assertThat;
import static org.awaitility.Awaitility.await;
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes = {PostProcessorConfiguration.class})
public class StockTradeIntegrationTest {
@Autowired
private StockTradePublisher stockTradePublisher;
@Test
public void givenValidConfig_whenTradePublished_thenTradeReceived() {
Date tradeDate = new Date();
StockTrade stockTrade = new StockTrade("AMZN", 100, 2483.52d, tradeDate);
AtomicBoolean assertionsPassed = new AtomicBoolean(false);
StockTradeListener listener = trade -> assertionsPassed.set(this.verifyExact(stockTrade, trade));
this.stockTradePublisher.addStockTradeListener(listener);
try {
GlobalEventBus.post(stockTrade);
await().atMost(Duration.ofSeconds(2L))
.untilAsserted(() -> assertThat(assertionsPassed.get()).isTrue());
} finally {
this.stockTradePublisher.removeStockTradeListener(listener);
}
}
private boolean verifyExact(StockTrade stockTrade, StockTrade trade) {
return Objects.equals(stockTrade.getSymbol(), trade.getSymbol())
&& Objects.equals(stockTrade.getTradeDate(), trade.getTradeDate())
&& stockTrade.getQuantity() == trade.getQuantity()
&& stockTrade.getPrice() == trade.getPrice();
}
}