BAEL-3091: The Prototype Pattern in Java (changed code based on valid comments from a reader)

hystrix/.gitignore

@@ -0,0 +1,12 @@
+*.class
+
+#folders#
+/target
+/src/main/webapp/WEB-INF/classes
+*/META-INF/*
+
+# Packaged files #
+*.jar
+*.war
+*.ear
+*.iml

hystrix/README.md

@@ -0,0 +1,7 @@
+## Hystrix
+
+This module contains articles about Hystrix.
+
+### Relevant Articles:
+- [Hystrix Integration with Existing Spring Application](https://www.baeldung.com/hystrix-integration-with-spring-aop)
+- [Introduction to Hystrix](https://www.baeldung.com/introduction-to-hystrix)

hystrix/pom.xml

@@ -0,0 +1,59 @@
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>hystrix</artifactId>
+    <version>1.0</version>
+    <name>hystrix</name>
+
+    <parent>
+        <artifactId>parent-boot-1</artifactId>
+        <groupId>com.baeldung</groupId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../parent-boot-1</relativePath>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-tomcat</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-web</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-aop</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>com.netflix.hystrix</groupId>
+            <artifactId>hystrix-core</artifactId>
+            <version>${hystrix-core.version}</version>
+            <exclusions>
+                <exclusion>
+                    <artifactId>commons-logging</artifactId>
+                    <groupId>commons-logging</groupId>
+                </exclusion>
+            </exclusions>
+        </dependency>
+        <dependency>
+            <groupId>com.netflix.hystrix</groupId>
+            <artifactId>hystrix-metrics-event-stream</artifactId>
+            <version>${hystrix-metrics-event-stream.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>com.netflix.rxjava</groupId>
+            <artifactId>rxjava-core</artifactId>
+            <version>${rxjava-core.version}</version>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <!-- Hystrix -->
+        <hystrix-core.version>1.5.8</hystrix-core.version>
+        <rxjava-core.version>0.20.7</rxjava-core.version>
+        <!-- maven plugins -->
+        <hystrix-metrics-event-stream.version>1.5.8</hystrix-metrics-event-stream.version>
+    </properties>
+
+</project>

hystrix/src/main/java/com/baeldung/hystrix/AppConfig.java

@@ -0,0 +1,20 @@
+package com.baeldung.hystrix;
+
+import com.netflix.hystrix.contrib.metrics.eventstream.HystrixMetricsStreamServlet;
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.boot.web.servlet.ServletRegistrationBean;
+import org.springframework.context.annotation.Bean;
+
+@SpringBootApplication
+public class AppConfig {
+
+    public static void main(String[] args) {
+        SpringApplication.run(AppConfig.class, args);
+    }
+
+    @Bean
+    public ServletRegistrationBean adminServletRegistrationBean() {
+        return new ServletRegistrationBean(new HystrixMetricsStreamServlet(), "/hystrix.stream");
+    }
+}

hystrix/src/main/java/com/baeldung/hystrix/CommandHelloWorld.java

@@ -0,0 +1,19 @@
+package com.baeldung.hystrix;
+
+import com.netflix.hystrix.HystrixCommand;
+import com.netflix.hystrix.HystrixCommandGroupKey;
+
+class CommandHelloWorld extends HystrixCommand<String> {
+
+    private final String name;
+
+    CommandHelloWorld(String name) {
+        super(HystrixCommandGroupKey.Factory.asKey("ExampleGroup"));
+        this.name = name;
+    }
+
+    @Override
+    protected String run() {
+        return "Hello " + name + "!";
+    }
+}

hystrix/src/main/java/com/baeldung/hystrix/HystrixAspect.java

@@ -0,0 +1,83 @@
+package com.baeldung.hystrix;
+
+import com.netflix.hystrix.*;
+import org.aspectj.lang.ProceedingJoinPoint;
+import org.aspectj.lang.annotation.Around;
+import org.aspectj.lang.annotation.Aspect;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.stereotype.Component;
+
+import javax.annotation.PostConstruct;
+
+@Component
+@Aspect
+public class HystrixAspect {
+
+    private HystrixCommand.Setter config;
+    private HystrixCommandProperties.Setter commandProperties;
+    private HystrixThreadPoolProperties.Setter threadPoolProperties;
+
+    @Value("${remoteservice.command.execution.timeout}")
+    private int executionTimeout;
+
+    @Value("${remoteservice.command.sleepwindow}")
+    private int sleepWindow;
+
+    @Value("${remoteservice.command.threadpool.maxsize}")
+    private int maxThreadCount;
+
+    @Value("${remoteservice.command.threadpool.coresize}")
+    private int coreThreadCount;
+
+    @Value("${remoteservice.command.task.queue.size}")
+    private int queueCount;
+
+    @Value("${remoteservice.command.group.key}")
+    private String groupKey;
+
+    @Value("${remoteservice.command.key}")
+    private String key;
+
+
+    @Around("@annotation(com.baeldung.hystrix.HystrixCircuitBreaker)")
+    public Object circuitBreakerAround(final ProceedingJoinPoint aJoinPoint) {
+        return new RemoteServiceCommand(config, aJoinPoint).execute();
+    }
+
+    @PostConstruct
+    private void setup() {
+        this.config = HystrixCommand.Setter.withGroupKey(HystrixCommandGroupKey.Factory.asKey(groupKey));
+        this.config = config.andCommandKey(HystrixCommandKey.Factory.asKey(key));
+
+        this.commandProperties = HystrixCommandProperties.Setter();
+        this.commandProperties.withExecutionTimeoutInMilliseconds(executionTimeout);
+        this.commandProperties.withCircuitBreakerSleepWindowInMilliseconds(sleepWindow);
+
+        this.threadPoolProperties = HystrixThreadPoolProperties.Setter();
+        this.threadPoolProperties.withMaxQueueSize(maxThreadCount).withCoreSize(coreThreadCount).withMaxQueueSize(queueCount);
+
+        this.config.andCommandPropertiesDefaults(commandProperties);
+        this.config.andThreadPoolPropertiesDefaults(threadPoolProperties);
+    }
+
+    private static class RemoteServiceCommand extends HystrixCommand<String> {
+
+        private final ProceedingJoinPoint joinPoint;
+
+        RemoteServiceCommand(final Setter config, final ProceedingJoinPoint joinPoint) {
+            super(config);
+            this.joinPoint = joinPoint;
+        }
+
+        @Override
+        protected String run() throws Exception {
+            try {
+                return (String) joinPoint.proceed();
+            } catch (final Throwable th) {
+                throw new Exception(th);
+            }
+
+        }
+    }
+
+}

hystrix/src/main/java/com/baeldung/hystrix/HystrixCircuitBreaker.java

@@ -0,0 +1,11 @@
+package com.baeldung.hystrix;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+@Retention(RetentionPolicy.RUNTIME)
+@Target(ElementType.METHOD)
+public @interface HystrixCircuitBreaker {
+}

hystrix/src/main/java/com/baeldung/hystrix/HystrixController.java

@@ -0,0 +1,22 @@
+package com.baeldung.hystrix;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+@RestController
+public class HystrixController {
+
+    @Autowired
+    private SpringExistingClient client;
+
+    @RequestMapping("/withHystrix")
+    public String withHystrix() throws InterruptedException{
+        return client.invokeRemoteServiceWithHystrix();
+    }
+
+    @RequestMapping("/withOutHystrix")
+    public String withOutHystrix() throws InterruptedException{
+        return client.invokeRemoteServiceWithOutHystrix();
+    }
+}

hystrix/src/main/java/com/baeldung/hystrix/RemoteServiceTestCommand.java

@@ -0,0 +1,20 @@
+package com.baeldung.hystrix;
+
+import com.netflix.hystrix.HystrixCommand;
+import com.netflix.hystrix.HystrixCommandGroupKey;
+
+
+class RemoteServiceTestCommand extends HystrixCommand<String> {
+
+    private final RemoteServiceTestSimulator remoteService;
+
+    RemoteServiceTestCommand(Setter config, RemoteServiceTestSimulator remoteService) {
+        super(config);
+        this.remoteService = remoteService;
+    }
+
+    @Override
+    protected String run() throws Exception {
+        return remoteService.execute();
+    }
+}

hystrix/src/main/java/com/baeldung/hystrix/RemoteServiceTestSimulator.java

@@ -0,0 +1,16 @@
+package com.baeldung.hystrix;
+
+
+public class RemoteServiceTestSimulator {
+
+    private long wait;
+
+    RemoteServiceTestSimulator(long wait) throws InterruptedException {
+        this.wait = wait;
+    }
+
+    String execute() throws InterruptedException {
+        Thread.sleep(wait);
+        return "Success";
+    }
+}

hystrix/src/main/java/com/baeldung/hystrix/SpringExistingClient.java

@@ -0,0 +1,20 @@
+package com.baeldung.hystrix;
+
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.stereotype.Component;
+
+@Component("springClient")
+public class SpringExistingClient {
+
+    @Value("${remoteservice.timeout}")
+    private int remoteServiceDelay;
+
+    @HystrixCircuitBreaker
+    public String invokeRemoteServiceWithHystrix() throws InterruptedException{
+        return new RemoteServiceTestSimulator(remoteServiceDelay).execute();
+    }
+
+    public String invokeRemoteServiceWithOutHystrix() throws InterruptedException{
+        return new RemoteServiceTestSimulator(remoteServiceDelay).execute();
+    }
+}

hystrix/src/main/resources/application.properties

@@ -0,0 +1,8 @@
+remoteservice.command.group.key=RemoteServiceGroup
+remoteservice.command.key=RemoteServiceKey
+remoteservice.command.execution.timeout=10000
+remoteservice.command.threadpool.coresize=5
+remoteservice.command.threadpool.maxsize=10
+remoteservice.command.task.queue.size=5
+remoteservice.command.sleepwindow=5000
+remoteservice.timeout=15000

hystrix/src/main/resources/logback.xml

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<configuration>
+    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
+        <encoder>
+            <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n
+            </pattern>
+        </encoder>
+    </appender>
+
+    <root level="INFO">
+        <appender-ref ref="STDOUT" />
+    </root>
+</configuration>

hystrix/src/test/java/com/baeldung/hystrix/HystrixTimeoutManualTest.java

@@ -0,0 +1,132 @@
+package com.baeldung.hystrix;
+
+import com.netflix.hystrix.HystrixCommand;
+import com.netflix.hystrix.HystrixCommandGroupKey;
+import com.netflix.hystrix.HystrixCommandProperties;
+import com.netflix.hystrix.HystrixThreadPoolProperties;
+import com.netflix.hystrix.exception.HystrixRuntimeException;
+import org.junit.Test;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.equalTo;
+
+public class HystrixTimeoutManualTest {
+
+    @Test
+    public void givenInputBobAndDefaultSettings_whenCommandExecuted_thenReturnHelloBob() {
+        assertThat(new CommandHelloWorld("Bob").execute(), equalTo("Hello Bob!"));
+    }
+
+    @Test
+    public void givenSvcTimeoutOf100AndDefaultSettings_whenRemoteSvcExecuted_thenReturnSuccess()
+      throws InterruptedException {
+        HystrixCommand.Setter config = HystrixCommand
+          .Setter
+          .withGroupKey(HystrixCommandGroupKey.Factory.asKey("RemoteServiceGroup2"));
+
+        assertThat(new RemoteServiceTestCommand(config, new RemoteServiceTestSimulator(100)).execute(),
+          equalTo("Success"));
+    }
+
+    @Test(expected = HystrixRuntimeException.class)
+    public void givenSvcTimeoutOf10000AndDefaultSettings__whenRemoteSvcExecuted_thenExpectHRE() throws InterruptedException {
+        HystrixCommand.Setter config = HystrixCommand
+          .Setter
+          .withGroupKey(HystrixCommandGroupKey.Factory.asKey("RemoteServiceGroupTest3"));
+        new RemoteServiceTestCommand(config, new RemoteServiceTestSimulator(10_000)).execute();
+    }
+
+    @Test
+    public void givenSvcTimeoutOf5000AndExecTimeoutOf10000_whenRemoteSvcExecuted_thenReturnSuccess()
+      throws InterruptedException {
+
+        HystrixCommand.Setter config = HystrixCommand
+          .Setter
+          .withGroupKey(HystrixCommandGroupKey.Factory.asKey("RemoteServiceGroupTest4"));
+        HystrixCommandProperties.Setter commandProperties = HystrixCommandProperties.Setter();
+        commandProperties.withExecutionTimeoutInMilliseconds(10_000);
+        config.andCommandPropertiesDefaults(commandProperties);
+
+        assertThat(new RemoteServiceTestCommand(config, new RemoteServiceTestSimulator(500)).execute(),
+          equalTo("Success"));
+    }
+
+    @Test(expected = HystrixRuntimeException.class)
+    public void givenSvcTimeoutOf15000AndExecTimeoutOf5000__whenExecuted_thenExpectHRE()
+      throws InterruptedException {
+        HystrixCommand.Setter config = HystrixCommand
+          .Setter
+          .withGroupKey(HystrixCommandGroupKey.Factory.asKey("RemoteServiceGroupTest5"));
+        HystrixCommandProperties.Setter commandProperties = HystrixCommandProperties.Setter();
+        commandProperties.withExecutionTimeoutInMilliseconds(5_000);
+        config.andCommandPropertiesDefaults(commandProperties);
+        new RemoteServiceTestCommand(config, new RemoteServiceTestSimulator(15_000)).execute();
+    }
+
+    @Test
+    public void givenSvcTimeoutOf500AndExecTimeoutOf10000AndThreadPool__whenExecuted_thenReturnSuccess()
+      throws InterruptedException {
+
+        HystrixCommand.Setter config = HystrixCommand
+          .Setter
+          .withGroupKey(HystrixCommandGroupKey.Factory.asKey("RemoteServiceGroupThreadPool"));
+        HystrixCommandProperties.Setter commandProperties = HystrixCommandProperties.Setter();
+        commandProperties.withExecutionTimeoutInMilliseconds(10_000);
+        config.andCommandPropertiesDefaults(commandProperties);
+        config.andThreadPoolPropertiesDefaults(HystrixThreadPoolProperties.Setter()
+          .withMaxQueueSize(10)
+          .withCoreSize(3)
+          .withQueueSizeRejectionThreshold(10));
+
+        assertThat(new RemoteServiceTestCommand(config, new RemoteServiceTestSimulator(500)).execute(),
+          equalTo("Success"));
+    }
+
+    @Test
+    public void givenCircuitBreakerSetup__whenRemoteSvcCmdExecuted_thenReturnSuccess()
+      throws InterruptedException {
+
+        HystrixCommand.Setter config = HystrixCommand
+          .Setter
+          .withGroupKey(HystrixCommandGroupKey.Factory.asKey("RemoteServiceGroupCircuitBreaker"));
+        HystrixCommandProperties.Setter properties = HystrixCommandProperties.Setter();
+        properties.withExecutionTimeoutInMilliseconds(1000);
+
+        properties.withCircuitBreakerSleepWindowInMilliseconds(4000);
+        properties.withExecutionIsolationStrategy(
+          HystrixCommandProperties.ExecutionIsolationStrategy.THREAD);
+        properties.withCircuitBreakerEnabled(true);
+        properties.withCircuitBreakerRequestVolumeThreshold(1);
+
+        config.andCommandPropertiesDefaults(properties);
+
+        config.andThreadPoolPropertiesDefaults(HystrixThreadPoolProperties.Setter()
+          .withMaxQueueSize(1)
+          .withCoreSize(1)
+          .withQueueSizeRejectionThreshold(1));
+
+        assertThat(this.invokeRemoteService(config, 10_000), equalTo(null));
+        assertThat(this.invokeRemoteService(config, 10_000), equalTo(null));
+        assertThat(this.invokeRemoteService(config, 10_000), equalTo(null));
+        Thread.sleep(5000);
+
+        assertThat(new RemoteServiceTestCommand(config, new RemoteServiceTestSimulator(500)).execute(),
+          equalTo("Success"));
+        assertThat(new RemoteServiceTestCommand(config, new RemoteServiceTestSimulator(500)).execute(),
+          equalTo("Success"));
+        assertThat(new RemoteServiceTestCommand(config, new RemoteServiceTestSimulator(500)).execute(),
+          equalTo("Success"));
+    }
+
+    public String invokeRemoteService(HystrixCommand.Setter config, int timeout)
+      throws InterruptedException {
+        String response = null;
+        try {
+            response = new RemoteServiceTestCommand(config,
+              new RemoteServiceTestSimulator(timeout)).execute();
+        } catch (HystrixRuntimeException ex) {
+            System.out.println("ex = " + ex);
+        }
+        return response;
+    }
+}

hystrix/src/test/java/com/baeldung/hystrix/SpringAndHystrixIntegrationTest.java

@@ -0,0 +1,36 @@
+package com.baeldung.hystrix;
+
+import com.netflix.hystrix.exception.HystrixRuntimeException;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.junit4.SpringRunner;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.equalTo;
+
+@RunWith(SpringRunner.class)
+@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.DEFINED_PORT, classes = AppConfig.class)
+public class SpringAndHystrixIntegrationTest {
+
+    @Autowired
+    private HystrixController hystrixController;
+
+    @Rule
+    public final ExpectedException exception = ExpectedException.none();
+
+    @Test
+    public void givenTimeOutOf15000_whenClientCalledWithHystrix_thenExpectHystrixRuntimeException() throws InterruptedException {
+        exception.expect(HystrixRuntimeException.class);
+        hystrixController.withHystrix();
+    }
+
+    @Test
+    public void givenTimeOutOf15000_whenClientCalledWithOutHystrix_thenExpectSuccess() throws InterruptedException {
+        assertThat(hystrixController.withOutHystrix(), equalTo("Success"));
+    }
+
+}