fix: [Destinations] Allow for Custom Proxy Config in ON_PREMISE Destinations

cloudplatform/connectivity-dwc/src/main/java/com/sap/cloud/sdk/cloudplatform/connectivity/MegacliteServiceBindingDestinationLoader.java

@@ -92,18 +92,21 @@ private Try<HttpDestination> tryGetConnectivityDestination(
 
     private Try<HttpDestination> toProxiedDestination( @Nonnull final HttpDestination base )
     {
+        final DefaultHttpDestination.Builder builder =
+            DefaultHttpDestination
+                .fromDestination(base)
+                // be sure to use exactly this instance of connectivityResolver since it has a cache attached
+                .headerProviders(connectivityResolver);
+        // don't override the proxy URL if it has been set explicitly/manually already
+        if( base.getProxyConfiguration().isDefined() ) {
+            return Try.of(builder::buildInternal);
+        }
         final Try<URI> proxyUrl = Try.of(connectivityResolver::getProxyUrl);
         if( proxyUrl.isFailure() ) {
             return Try
                 .failure(
                     new DestinationAccessException("Failed to resolve on-premise proxy URL.", proxyUrl.getCause()));
         }
-        final DefaultHttpDestination.Builder builder =
-            DefaultHttpDestination
-                .fromDestination(base)
-                // be sure to use exactly this instance of connectivityResolver since it has a cache attached
-                .headerProviders(connectivityResolver);
-
         return proxyUrl.map(builder::proxy).map(DefaultHttpDestination.Builder::buildInternal);
     }
 

cloudplatform/connectivity-dwc/src/test/java/com/sap/cloud/sdk/cloudplatform/connectivity/MegacliteServiceBindingDestinationLoaderTest.java

@@ -22,6 +22,7 @@
 
 import org.apache.http.HttpHeaders;
 import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.RegisterExtension;
 
@@ -315,6 +316,28 @@ void testConnectivityWithProviderTenant()
         assertThatThrownBy(() -> sut.getDestination(options)).isInstanceOf(DestinationAccessException.class);
     }
 
+    @Test
+    @DisplayName( "An already existing proxy configuration should not be overridden." )
+    void testConnectivityWithExistingProxyConfig()
+    {
+        final DefaultHttpDestination destination =
+            DefaultHttpDestination
+                .builder("foo")
+                .proxy(URI.create("http://bar"))
+                .proxyType(ProxyType.ON_PREMISE)
+                .buildInternal();
+
+        final ServiceBindingDestinationOptions options =
+            ServiceBindingDestinationOptions
+                .forService(MegacliteServiceBindingAccessor.CONNECTIVITY_BINDING)
+                .withOption(ProxyOptions.destinationToBeProxied(destination))
+                .build();
+        final HttpDestination result = sut.getDestination(options);
+
+        assertThat(result.getProxyConfiguration()).isNotEmpty();
+        assertThat(result.getProxyConfiguration().get().getUri()).isEqualTo(URI.create("http://bar"));
+    }
+
     @Test
     void testGetMandateConfiguration()
     {

cloudplatform/connectivity-oauth/src/main/java/com/sap/cloud/sdk/cloudplatform/connectivity/OAuth2ServiceBindingDestinationLoader.java

@@ -269,7 +269,7 @@ HttpDestination toProxiedDestination(
         final String destinationName =
             destinationToBeProxied.get(DestinationProperty.NAME).getOrElse("<unnamed-destination>");
         final DefaultHttpDestination.Builder destinationBuilder =
-            DefaultHttpDestination.fromDestination(destinationToBeProxied).proxy(proxyUrl);
+            DefaultHttpDestination.fromDestination(destinationToBeProxied);
 
         if( oAuth2Options.skipTokenRetrieval() ) {
             log.debug("Skipping OAuth2 token retrieval for proxied destination '{}'.", destinationName);
@@ -293,7 +293,11 @@ HttpDestination toProxiedDestination(
             destinationBuilder.keyStore(oAuth2Options.getClientKeyStore());
         }
 
-        return destinationBuilder.buildInternal();
+        // don't override the proxy URL if it has been set explicitly/manually already
+        if( destinationToBeProxied.getProxyConfiguration().isDefined() ) {
+            return destinationBuilder.buildInternal();
+        }
+        return destinationBuilder.proxy(proxyUrl).buildInternal();
     }
 
     DestinationHeaderProvider createHeaderProvider(

cloudplatform/connectivity-oauth/src/test/java/com/sap/cloud/sdk/cloudplatform/connectivity/OAuth2ServiceBindingDestinationLoaderTest.java

@@ -26,6 +26,7 @@
 import org.apache.http.HttpHeaders;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Test;
 import org.mockito.InOrder;
 import org.mockito.Mockito;
@@ -404,6 +405,31 @@ void testProxiedDestination()
                 eq(TEST_SERVICE));
     }
 
+    @Test
+    @DisplayName( "An already existing proxy configuration should not be overridden." )
+    void testConnectivityWithExistingProxyConfig()
+    {
+        final DefaultHttpDestination destination =
+            DefaultHttpDestination
+                .builder("foo")
+                .proxy(URI.create("http://bar"))
+                .proxyType(ProxyType.ON_PREMISE)
+                .buildInternal();
+        final HttpDestination result =
+            sut
+                .toProxiedDestination(
+                    destination,
+                    URI.create("yolo"),
+                    URI.create("foo"),
+                    credentials,
+                    OnBehalfOf.TECHNICAL_USER_CURRENT_TENANT,
+                    OAuth2Options.DEFAULT,
+                    TEST_SERVICE);
+
+        assertThat(result.getProxyConfiguration()).isNotEmpty();
+        assertThat(result.getProxyConfiguration().get().getUri()).isEqualTo(URI.create("http://bar"));
+    }
+
     @Test
     void testSkipTokenRetrieval()
     {

release_notes.md

@@ -16,6 +16,7 @@
 
 ### 📈 Improvements
 
+- Improve the `DefaultHttpDestination` builder API: For destinations with proxy type `ON_PREMISE` the proxy URL can now be customized by using the `proxy` method of the builder.
 - Dependency Updates:
   - SAP dependency updates:
     - Update [thing](https://link-to-thing) from `a.b.c` to `x.z.y`