Added fluent api mapper for SSLFactory (#577)

* Added fluent api mapper

* Added test

* Applied feedback

* Refactored to lazy mapping

* Renamed method

README.md

@@ -100,6 +100,7 @@ libraryDependencies += "io.github.hakky54" % "sslcontext-kickstart" % "8.3.7"
      - [Global SSL configuration](#global-ssl-configuration)
      - [Logging certificate validation](#logging-detailed-certificate-validation)
      - [Logging detailed KeyManager flow, input and output](#logging-detailed-keymanager-flow-input-and-output)
+     - [Fluently mapping SSLFactory](#fluently-mapping-sslfactory)
    - [Returnable values from the SSLFactory](#returnable-values-from-the-sslfactory)
 3. [Additional mappers for specific libraries](#additional-mappers-for-specific-libraries)
    - [Netty](#netty)
@@ -1096,6 +1097,37 @@ KeyIdentifier [
 ]]
 ```
 
+### Fluently mapping SSLFactory
+The SSLFactory can be mapped easily if it needs additional intermediate steps before it can be used fully used, such as using it with a Netty or Apache client. Below is an example for Netty with Spring WebClient.
+
+```java
+import io.netty.handler.ssl.SslContext;
+import nl.altindag.ssl.SSLFactory;
+import nl.altindag.ssl.netty.util.NettySslUtils;
+import org.springframework.http.client.reactive.ReactorClientHttpConnector;
+import org.springframework.web.reactive.function.client.WebClient;
+import reactor.netty.http.client.HttpClient;
+
+import javax.net.ssl.SSLException;
+
+public class App {
+
+    public static void main(String[] args) throws SSLException {
+      WebClient webClient = SSLFactory.builder()
+                .withDefaultTrustMaterial()
+                .build()
+                .map(NettySslUtils::forClient)
+                .map(SslContextBuilder::build)
+                .map(sslContext -> HttpClient.create().secure(sslSpec -> sslSpec.sslContext(sslContext)))
+                .map(ReactorClientHttpConnector::new)
+                .map(httpConnector -> WebClient.builder().clientConnector(httpConnector).build()) 
+                .get();
+    }
+
+}
+```
+
+
 ### Returnable values from the SSLFactory
 The SSLFactory provides different kinds of returnable values, see below for all the options:
 

sslcontext-kickstart/src/main/java/nl/altindag/ssl/SSLFactory.java

@@ -25,8 +25,10 @@
 import nl.altindag.ssl.trustmanager.trustoptions.TrustAnchorTrustOptions;
 import nl.altindag.ssl.trustmanager.trustoptions.TrustStoreTrustOptions;
 import nl.altindag.ssl.util.HostnameVerifierUtils;
+import nl.altindag.ssl.util.Function;
 import nl.altindag.ssl.util.KeyManagerUtils;
 import nl.altindag.ssl.util.KeyStoreUtils;
+import nl.altindag.ssl.util.Box;
 import nl.altindag.ssl.util.SSLContextUtils;
 import nl.altindag.ssl.util.SSLParametersUtils;
 import nl.altindag.ssl.util.SSLSessionUtils;
@@ -155,6 +157,15 @@ public SSLEngine getSSLEngine(String peerHost, Integer peerPort) {
         }
     }
 
+    /**
+     * Returns a cardboard box to further process the SSLFactory instance.
+     * The helper {@link Box} class provides a mapping method to map the
+     * source in a functional way.
+     */
+    public <T> Box<T> map(Function<SSLFactory, T> mapper) {
+        return Box.of(this).map(mapper);
+    }
+
     public static Builder builder() {
         return new Builder();
     }

sslcontext-kickstart/src/main/java/nl/altindag/ssl/util/Box.java

@@ -0,0 +1,64 @@
+/*
+ * Copyright 2019 Thunderberry.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package nl.altindag.ssl.util;
+
+import nl.altindag.ssl.exception.GenericException;
+
+import java.util.function.Supplier;
+
+/**
+ * @author Hakan Altindag
+ */
+@FunctionalInterface
+public interface Box<T> {
+
+    ValueHolder<T> valueHolder();
+
+    static <T> Box<T> of(T value) {
+        return () -> ValueHolder.wrap(() -> value);
+    }
+
+    default <R> Box<R> map(Function<? super T, ? extends R> mapper) {
+        return () -> ValueHolder.wrap(() -> {
+            final T value = valueHolder().get();
+
+            try {
+                return mapper.apply(value);
+            } catch (Exception e) {
+                throw new GenericException(e);
+            }
+        });
+    }
+
+    default T get() {
+        return valueHolder().get();
+    }
+
+    @FunctionalInterface
+    interface ValueHolder<T> {
+
+        Supplier<T> valueSupplier();
+
+        default T get() {
+            return valueSupplier().get();
+        }
+
+        static <U> ValueHolder<U> wrap(Supplier<U> supplier) {
+            return () -> supplier;
+        }
+    }
+
+}

sslcontext-kickstart/src/main/java/nl/altindag/ssl/util/Function.java

@@ -0,0 +1,26 @@
+/*
+ * Copyright 2019 Thunderberry.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package nl.altindag.ssl.util;
+
+/**
+ * @author Hakan Altindag
+ */
+@FunctionalInterface
+public interface Function<T, R> {
+
+    R apply(T t) throws Exception;
+
+}

sslcontext-kickstart/src/test/java/nl/altindag/ssl/SSLFactoryShould.java

@@ -1949,6 +1949,18 @@ void haveConsistentParameterConfiguration() throws IOException {
         assertThat(sslEngine.getWantClientAuth()).isFalse();
     }
 
+    @Test
+    void mapSslFactoryInternalsInFunctionalWay() {
+        SSLParameters sslParameters = SSLFactory.builder()
+                .withDefaultTrustMaterial()
+                .build()
+                .map(SSLFactory::getSSLEngine)
+                .map(SSLEngine::getSSLParameters)
+                .get();
+
+        assertThat(sslParameters).isNotNull();
+    }
+
     @Test
     void throwIllegalArgumentExceptionWhenCertificateIsAbsent() {
         List<Certificate> certificates = Collections.emptyList();

sslcontext-kickstart/src/test/java/nl/altindag/ssl/util/BoxShould.java

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2019 Thunderberry.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package nl.altindag.ssl.util;
+
+import nl.altindag.ssl.exception.GenericException;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+/**
+ * @author Hakan Altindag
+ */
+class BoxShould {
+
+    @Test
+    void wrapAnyExceptionInGenericException() {
+        Box<String> stringBox = Box.of("")
+                .map(value -> {
+                    throw new RuntimeException("KABOOM");
+                });
+
+        assertThatThrownBy(stringBox::get)
+                .isInstanceOf(GenericException.class)
+                .hasRootCauseMessage("KABOOM");
+    }
+}