https://jira.baeldung.com/browse/BAEL-7787

Author: Michaelin007

spring-reactive-modules/spring-reactive-client-2/src/main/java/com/baeldung/memoization/FibonacciMemoization.java

@@ -0,0 +1,30 @@
+package com.baeldung.memoization;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class FibonacciMemoization {
+
+    private static final Map<Integer, Long> cache = new HashMap<>();
+    private static Logger logger = LoggerFactory.getLogger(FibonacciMemoization.class);
+
+    static long fibonacci(int n) {
+        if (n <= 1) {
+            return n;
+        }
+
+        if (cache.containsKey(n)) {
+            return cache.get(n);
+        }
+
+        long result = fibonacci(n - 1) + fibonacci(n - 2);
+        logger.info("First occurrence of " + n);
+        cache.put(n, result);
+
+        return result;
+    }
+
+}

spring-reactive-modules/spring-reactive-client-2/src/main/java/com/baeldung/memoization/MemoizationWithMonoCache.java

@@ -0,0 +1,28 @@
+package com.baeldung.memoization;
+
+import org.springframework.web.reactive.function.client.WebClient;
+import reactor.core.publisher.Mono;
+
+import java.io.IOException;
+import java.time.Duration;
+import java.util.concurrent.atomic.AtomicInteger;
+
+public class MemoizationWithMonoCache {
+
+    static WebClient client = WebClient.create("https://jsonplaceholder.typicode.com/users");
+
+    static AtomicInteger counter = new AtomicInteger(0);
+
+    static Mono<User> retrieveOneUser(int id) {
+        return client.get()
+            .uri("/{id}", id)
+            .retrieve()
+            .bodyToMono(User.class)
+            .doOnSubscribe(i -> counter.incrementAndGet())
+            .onErrorResume(Mono::error);
+    }
+
+    int getCounter() {
+        return counter.get();
+    }
+}

spring-reactive-modules/spring-reactive-client-2/src/main/java/com/baeldung/memoization/User.java

@@ -0,0 +1,35 @@
+package com.baeldung.memoization;
+
+public class User {
+    private int id;
+    private String name;
+
+    public User() {
+    }
+
+    public User(int id, String name) {
+        this.id = id;
+        this.name = name;
+    }
+
+    public int getId() {
+        return id;
+    }
+
+    public void setId(int id) {
+        this.id = id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    @Override
+    public String toString() {
+        return "User{" + "id=" + id + ", name='" + name + '\'' + '}';
+    }
+}

spring-reactive-modules/spring-reactive-client-2/src/test/java/com/baeldung/memoization/FibonacciMemoizationUnitTest.java

@@ -0,0 +1,18 @@
+package com.baeldung.memoization;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class FibonacciMemoizationUnitTest {
+
+    @Test
+    void givenFibonacciNumber_whenFirstOccurenceIscache_thenReturnCacheResultOnSecondCall() {
+
+        assertEquals(5, FibonacciMemoization.fibonacci(5));
+        assertEquals(2, FibonacciMemoization.fibonacci(3));
+        assertEquals(55, FibonacciMemoization.fibonacci(10));
+        assertEquals(21, FibonacciMemoization.fibonacci(8));
+    }
+
+}

spring-reactive-modules/spring-reactive-client-2/src/test/java/com/baeldung/memoization/MemoizationWithMonoCacheUnitTest.java

@@ -0,0 +1,41 @@
+package com.baeldung.memoization;
+
+import org.junit.jupiter.api.Test;
+import reactor.core.Disposable;
+import reactor.core.publisher.Mono;
+import reactor.test.StepVerifier;
+
+import java.util.concurrent.atomic.AtomicReference;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class MemoizationWithMonoCacheUnitTest {
+
+    @Test
+    void givenRetrievedUser_whenTheCallToRemoteIsCache_thenReturnInvocationCountAndCompareResult() {
+
+        MemoizationWithMonoCache memoizationWithMonoCache = new MemoizationWithMonoCache();
+
+        Mono<User> userCall = MemoizationWithMonoCache.retrieveOneUser(1)
+            .cache();
+        AtomicReference<User> firstUser = new AtomicReference<>();
+        AtomicReference<User> secondUser = new AtomicReference<>();
+
+        Disposable firstUserCall = userCall.map(user -> {
+                firstUser.set(user);
+                return user.getName();
+            })
+            .subscribe();
+
+        Disposable secondUserCall = userCall.map(user -> {
+                secondUser.set(user);
+                return user.getName();
+            })
+            .subscribe();
+
+        assertEquals(1, memoizationWithMonoCache.getCounter());
+        assertEquals(firstUser.get(), secondUser.get());
+
+    }
+
+}

spring-reactive-modules/spring-reactive-client-2/src/test/java/com/baeldung/memoization/RetrieveAndExchangeBenchmark.java

@@ -0,0 +1,38 @@
+package com.baeldung.memoization;
+
+import com.baeldung.webclientretrievevsexchange.User;
+import org.openjdk.jmh.annotations.*;
+import org.springframework.web.reactive.function.client.WebClient;
+import reactor.core.publisher.Mono;
+
+import java.util.concurrent.TimeUnit;
+
+@State(Scope.Benchmark)
+@BenchmarkMode(Mode.AverageTime)
+@Warmup(iterations = 3, time = 10, timeUnit = TimeUnit.MICROSECONDS)
+@Measurement(iterations = 3, time = 10, timeUnit = TimeUnit.MICROSECONDS)
+public class RetrieveAndExchangeBenchmark {
+    private WebClient client;
+
+    @Setup
+    public void setup() {
+        this.client = WebClient.create("https://jsonplaceholder.typicode.com/users");
+    }
+
+    @Benchmark
+    public Mono<User> retrieveOneUserUsingRetrieveMethod() {
+        return client.get()
+            .uri("/1")
+            .retrieve()
+            .bodyToMono(com.baeldung.webclientretrievevsexchange.User.class)
+            .onErrorResume(Mono::error);
+    }
+
+    @Benchmark
+    public Mono<User> retrieveOneUserUsingRetrieveMethodCache() {
+        Mono<User> cal = retrieveOneUserUsingRetrieveMethod().cache();
+        Mono<User> cal2 = retrieveOneUserUsingRetrieveMethod().cache();
+        return cal2;
+    }
+
+}

spring-reactive-modules/spring-reactor/src/main/java/com/baeldung/memoization/FibonacciMemoization.java

@@ -0,0 +1,4 @@
+package com.baeldung.memoization;
+
+public class FibonacciMemoization {
+}

spring-reactive-modules/spring-reactor/src/main/java/com/baeldung/memoization/MemoizationWithMonoCache.java

@@ -0,0 +1,4 @@
+package com.baeldung.memoization;
+
+public class MemoizationWithMonoCache {
+}

spring-reactive-modules/spring-reactor/src/main/java/com/baeldung/memoization/User.java

@@ -0,0 +1,4 @@
+package com.baeldung.memoization;
+
+public class User {
+}

spring-reactive-modules/spring-reactor/src/test/java/com/baeldung/memoization/FibonacciMemoizationUnitTest.java

@@ -0,0 +1,7 @@
+package com.baeldung.memoization;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class FibonacciMemoizationUnitTest {
+
+}