Lazily initializing and reuse a single shared instance

Author: gcatanese

src/main/java/com/adyen/Client.java

@@ -4,9 +4,11 @@
 import com.adyen.enums.Region;
 import com.adyen.httpclient.AdyenHttpClient;
 import com.adyen.httpclient.ClientInterface;
+import java.io.Closeable;
+import java.io.IOException;
 import javax.net.ssl.SSLContext;
 
-public class Client {
+public class Client implements Closeable {
   private ClientInterface httpClient;
   private Config config;
   public static final String LIB_NAME = "adyen-java-api-library";
@@ -157,13 +159,23 @@ public String toString() {
   }
 
   public ClientInterface getHttpClient() {
-    return this.httpClient == null ? new AdyenHttpClient() : this.httpClient;
+    if (this.httpClient == null) {
+      this.httpClient = new AdyenHttpClient();
+    }
+    return this.httpClient;
   }
 
   public void setHttpClient(ClientInterface httpClient) {
     this.httpClient = httpClient;
   }
 
+  @Override
+  public void close() throws IOException {
+    if (this.httpClient != null) {
+      this.httpClient.close();
+    }
+  }
+
   public Config getConfig() {
     return config;
   }

src/main/java/com/adyen/httpclient/AdyenHttpClient.java

@@ -69,6 +69,8 @@ public class AdyenHttpClient implements ClientInterface {
 
   private static final String CHARSET = "UTF-8";
   private Proxy proxy;
+  private volatile CloseableHttpClient sharedHttpClient;
+  private final Object lock = new Object();
 
   public Proxy getProxy() {
     return proxy;
@@ -78,6 +80,29 @@ public void setProxy(Proxy proxy) {
     this.proxy = proxy;
   }
 
+  @Override
+  public void close() throws IOException {
+    synchronized (lock) {
+      if (sharedHttpClient != null) {
+        sharedHttpClient.close();
+        sharedHttpClient = null;
+      }
+    }
+  }
+
+  private CloseableHttpClient getOrCreateHttpClient(Config config) {
+    CloseableHttpClient client = sharedHttpClient;
+    if (client != null) {
+      return client;
+    }
+    synchronized (lock) {
+      if (sharedHttpClient == null) {
+        sharedHttpClient = createCloseableHttpClient(config);
+      }
+      return sharedHttpClient;
+    }
+  }
+
   @Override
   public String request(String endpoint, String requestBody, Config config)
       throws IOException, HTTPClientException {
@@ -125,20 +150,19 @@ public String request(
       ApiConstants.HttpMethod httpMethod,
       Map<String, String> params)
       throws IOException, HTTPClientException {
-    try (CloseableHttpClient httpclient = createCloseableHttpClient(config)) {
-      HttpUriRequestBase httpRequest =
-          createRequest(
-              endpoint, requestBody, config, isApiKeyRequired, requestOptions, httpMethod, params);
+    CloseableHttpClient httpclient = getOrCreateHttpClient(config);
+    HttpUriRequestBase httpRequest =
+        createRequest(
+            endpoint, requestBody, config, isApiKeyRequired, requestOptions, httpMethod, params);
 
-      // Execute request with a custom response handler
-      AdyenResponse response = httpclient.execute(httpRequest, new AdyenResponseHandler());
+    // Execute request with a custom response handler
+    AdyenResponse response = httpclient.execute(httpRequest, new AdyenResponseHandler());
 
-      if (response.getStatus() < 200 || response.getStatus() >= 300) {
-        throw new HTTPClientException(
-            response.getStatus(), "HTTP Exception", response.getHeaders(), response.getBody());
-      }
-      return response.getBody();
+    if (response.getStatus() < 200 || response.getStatus() >= 300) {
+      throw new HTTPClientException(
+          response.getStatus(), "HTTP Exception", response.getHeaders(), response.getBody());
     }
+    return response.getBody();
   }
 
   HttpUriRequestBase createRequest(

src/main/java/com/adyen/httpclient/ClientInterface.java

@@ -23,10 +23,14 @@
 import com.adyen.Config;
 import com.adyen.constants.ApiConstants;
 import com.adyen.model.RequestOptions;
+import java.io.Closeable;
 import java.io.IOException;
 import java.util.Map;
 
-public interface ClientInterface {
+public interface ClientInterface extends Closeable {
+
+  @Override
+  default void close() throws IOException {}
 
   String request(String endpoint, String requestBody, Config config)
       throws IOException, HTTPClientException;

src/test/java/com/adyen/httpclient/ClientTest.java

@@ -285,4 +285,20 @@ public void testRequestWithHttpHeaders() throws Exception {
     assertNotNull(wwwAuthenticate);
     assertEquals("www-authenticate-header", wwwAuthenticate.getValue());
   }
+
+  @Test
+  public void testGetHttpClientReturnsSameInstance() {
+    Client client = new Client("apiKey", Environment.TEST);
+    ClientInterface first = client.getHttpClient();
+    ClientInterface second = client.getHttpClient();
+    assertSame(first, second);
+  }
+
+  @Test
+  public void testClientCloseIsIdempotent() throws Exception {
+    Client client = new Client("apiKey", Environment.TEST);
+    client.getHttpClient();
+    client.close();
+    client.close();
+  }
 }