BAEL-1039: Introduction to Derive4J (#5845)

libraries/pom.xml

@@ -717,6 +717,12 @@
             <version>${suanshu.version}</version>
         </dependency>
 
+        <dependency>
+            <groupId>org.derive4j</groupId>
+            <artifactId>derive4j</artifactId>
+            <version>${derive4j.version}</version>
+            <optional>true</optional>
+        </dependency>
     </dependencies>
 
     <repositories>
@@ -952,6 +958,7 @@
         <fugue.version>4.5.1</fugue.version>
         <maven-bundle-plugin.version>3.3.0</maven-bundle-plugin.version>
         <maven-jar-plugin.version>3.0.2</maven-jar-plugin.version>
+        <derive4j.version>1.1.0</derive4j.version>
     </properties>
 
 </project>

libraries/src/main/java/com/baeldung/derive4j/adt/Either.java

@@ -0,0 +1,10 @@
+package com.baeldung.derive4j.adt;
+
+import org.derive4j.Data;
+
+import java.util.function.Function;
+
+@Data
+interface Either<A,B>{
+    <X> X match(Function<A, X> left, Function<B, X> right);
+}

libraries/src/main/java/com/baeldung/derive4j/lazy/LazyRequest.java

@@ -0,0 +1,21 @@
+package com.baeldung.derive4j.lazy;
+
+import org.derive4j.Data;
+import org.derive4j.Derive;
+import org.derive4j.Make;
+
+@Data(value = @Derive(
+    inClass = "{ClassName}Impl",
+    make = {Make.lazyConstructor, Make.constructors}
+))
+public interface LazyRequest {
+    interface Cases<R>{
+        R GET(String path);
+        R POST(String path, String body);
+        R PUT(String path, String body);
+        R DELETE(String path);
+    }
+
+    <R> R match(LazyRequest.Cases<R> method);
+}
+

libraries/src/main/java/com/baeldung/derive4j/pattern/HTTPRequest.java

@@ -0,0 +1,15 @@
+package com.baeldung.derive4j.pattern;
+
+import org.derive4j.Data;
+
+@Data
+interface HTTPRequest {
+    interface Cases<R>{
+        R GET(String path);
+        R POST(String path, String body);
+        R PUT(String path, String body);
+        R DELETE(String path);
+    }
+
+     <R> R match(Cases<R> method);
+}

libraries/src/main/java/com/baeldung/derive4j/pattern/HTTPResponse.java

@@ -0,0 +1,19 @@
+package com.baeldung.derive4j.pattern;
+
+public class HTTPResponse {
+    private int  statusCode;
+    private String responseBody;
+
+    public int getStatusCode() {
+        return statusCode;
+    }
+
+    public String getResponseBody() {
+        return responseBody;
+    }
+
+    public HTTPResponse(int statusCode, String responseBody) {
+        this.statusCode = statusCode;
+        this.responseBody = responseBody;
+    }
+}

libraries/src/main/java/com/baeldung/derive4j/pattern/HTTPServer.java

@@ -0,0 +1,17 @@
+package com.baeldung.derive4j.pattern;
+
+
+public class HTTPServer {
+    public static String GET_RESPONSE_BODY = "Success!";
+    public static String PUT_RESPONSE_BODY = "Resource Created!";
+    public static String POST_RESPONSE_BODY = "Resource Updated!";
+    public static String DELETE_RESPONSE_BODY = "Resource Deleted!";
+
+    public HTTPResponse acceptRequest(HTTPRequest request) {
+       return HTTPRequests.caseOf(request)
+                .GET((path) -> new HTTPResponse(200, GET_RESPONSE_BODY))
+                .POST((path,body) -> new HTTPResponse(201, POST_RESPONSE_BODY))
+                .PUT((path,body) -> new HTTPResponse(200, PUT_RESPONSE_BODY))
+                .DELETE(path -> new HTTPResponse(200, DELETE_RESPONSE_BODY));
+    }
+}

libraries/src/test/java/com/baeldung/derive4j/adt/EitherUnitTest.java

@@ -0,0 +1,33 @@
+package com.baeldung.derive4j.adt;
+
+import org.assertj.core.api.Assertions;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mockito;
+import org.mockito.junit.MockitoJUnitRunner;
+
+import java.util.Optional;
+import java.util.function.Function;
+@RunWith(MockitoJUnitRunner.class)
+public class EitherUnitTest {
+    @Test
+    public void testEitherIsCreatedFromRight() {
+       Either<Exception, String> either = Eithers.right("Okay");
+       Optional<Exception> leftOptional = Eithers.getLeft(either);
+       Optional<String> rightOptional = Eithers.getRight(either);
+       Assertions.assertThat(leftOptional).isEmpty();
+       Assertions.assertThat(rightOptional).hasValue("Okay");
+
+    }
+
+    @Test
+    public void testEitherIsMatchedWithRight() {
+        Either<Exception, String> either = Eithers.right("Okay");
+        Function<Exception, String> leftFunction = Mockito.mock(Function.class);
+        Function<String, String> rightFunction = Mockito.mock(Function.class);
+        either.match(leftFunction, rightFunction);
+        Mockito.verify(rightFunction, Mockito.times(1)).apply("Okay");
+        Mockito.verify(leftFunction, Mockito.times(0)).apply(Mockito.any(Exception.class));
+    }
+
+}

libraries/src/test/java/com/baeldung/derive4j/lazy/LazyRequestUnitTest.java

@@ -0,0 +1,28 @@
+package com.baeldung.derive4j.lazy;
+
+import org.junit.Assert;
+import org.junit.Test;
+import org.mockito.Mockito;
+
+import java.util.function.Supplier;
+
+public class LazyRequestUnitTest {
+
+    @Test
+    public void givenLazyContstructedRequest_whenRequestIsReferenced_thenRequestIsLazilyContructed() {
+        LazyRequestSupplier mockSupplier = Mockito.spy(new LazyRequestSupplier());
+
+        LazyRequest request = LazyRequestImpl.lazy(() -> mockSupplier.get());
+        Mockito.verify(mockSupplier, Mockito.times(0)).get();
+        Assert.assertEquals(LazyRequestImpl.getPath(request), "http://test.com/get");
+        Mockito.verify(mockSupplier, Mockito.times(1)).get();
+
+    }
+
+    class LazyRequestSupplier implements Supplier<LazyRequest> {
+        @Override
+        public LazyRequest get() {
+            return LazyRequestImpl.GET("http://test.com/get");
+        }
+    }
+}

libraries/src/test/java/com/baeldung/derive4j/pattern/HTTPRequestUnitTest.java

@@ -0,0 +1,22 @@
+package com.baeldung.derive4j.pattern;
+
+import org.junit.Assert;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+public class HTTPRequestUnitTest {
+    public static HTTPServer server;
+
+    @BeforeClass
+    public static void setUp() {
+        server = new HTTPServer();
+    }
+
+    @Test
+    public void givenHttpGETRequest_whenRequestReachesServer_thenProperResponseIsReturned() {
+        HTTPRequest postRequest = HTTPRequests.POST("http://test.com/post", "Resource");
+        HTTPResponse response = server.acceptRequest(postRequest);
+        Assert.assertEquals(201, response.getStatusCode());
+        Assert.assertEquals(HTTPServer.POST_RESPONSE_BODY, response.getResponseBody());
+    }
+}