[Destinations] Custom Destination Service Parameters and Chaining

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

@@ -2,6 +2,7 @@
 
 import java.util.HashMap;
 import java.util.Map;
+import java.util.Set;
 
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
@@ -36,6 +37,18 @@ public Option<Object> get( @Nonnull final String key )
         return Option.of(parameters.get(key));
     }
 
+    /**
+     * Get all defined options.
+     *
+     * @return A set of all option keys.
+     * @since 5.22.0
+     */
+    @Nonnull
+    public Set<String> getOptionKeys()
+    {
+        return Set.copyOf(parameters.keySet());
+    }
+
     /**
      * Creates a builder for instantiating {@link DestinationOptions} objects.
      *

cloudplatform/connectivity-destination-service/src/main/java/com/sap/cloud/sdk/cloudplatform/connectivity/DestinationRetrievalStrategy.java

@@ -4,6 +4,9 @@
 import static com.sap.cloud.sdk.cloudplatform.connectivity.DestinationRetrievalStrategy.TokenForwarding.REFRESH_TOKEN;
 import static com.sap.cloud.sdk.cloudplatform.connectivity.DestinationRetrievalStrategy.TokenForwarding.USER_TOKEN;
 
+import java.util.ArrayList;
+import java.util.List;
+
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 
@@ -30,6 +33,8 @@ final class DestinationRetrievalStrategy
     private final String token;
     @Nullable
     private String fragment;
+    @Nonnull
+    private final List<Header> additionalHeaders = new ArrayList<>();
 
     static DestinationRetrievalStrategy withoutToken( @Nonnull final OnBehalfOf behalf )
     {
@@ -68,6 +73,12 @@ DestinationRetrievalStrategy withFragmentName( @Nonnull final String fragmentNam
         return this;
     }
 
+    DestinationRetrievalStrategy withAdditionalHeaders( @Nonnull final List<Header> additionalHeaders )
+    {
+        this.additionalHeaders.addAll(additionalHeaders);
+        return this;
+    }
+
     enum TokenForwarding
     {
         USER_TOKEN,

cloudplatform/connectivity-destination-service/src/main/java/com/sap/cloud/sdk/cloudplatform/connectivity/DestinationRetrievalStrategyResolver.java

@@ -116,13 +116,15 @@ DestinationRetrieval prepareSupplier( @Nonnull final DestinationOptions options
                 .getFragmentName(options)
                 .peek(it -> log.debug("Found fragment name '{}'.", it))
                 .getOrNull();
+        final List<Header> additionalHeaders = DestinationServiceOptionsAugmenter.getAdditionalHeaders(options);
+        additionalHeaders.forEach(it -> log.debug("Found additional header: {}.", it));
 
         log
             .debug(
                 "Loading destination from reuse-destination-service with retrieval strategy {} and token exchange strategy {}.",
                 retrievalStrategy,
                 tokenExchangeStrategy);
-        return prepareSupplier(retrievalStrategy, tokenExchangeStrategy, refreshToken, fragmentName);
+        return prepareSupplier(retrievalStrategy, tokenExchangeStrategy, refreshToken, fragmentName, additionalHeaders);
     }
 
     /**
@@ -161,7 +163,8 @@ DestinationRetrieval prepareSupplier(
         @Nonnull final DestinationServiceRetrievalStrategy retrievalStrategy,
         @Nonnull final DestinationServiceTokenExchangeStrategy tokenExchangeStrategy,
         @Nullable final String refreshToken,
-        @Nullable final String fragmentName )
+        @Nullable final String fragmentName,
+        @Nonnull final List<Header> additionalHeaders )
         throws DestinationAccessException
     {
         log
@@ -198,6 +201,9 @@ DestinationRetrieval prepareSupplier(
         if( fragmentName != null ) {
             strategy.withFragmentName(fragmentName);
         }
+        if( !additionalHeaders.isEmpty() ) {
+            strategy.withAdditionalHeaders(additionalHeaders);
+        }
         return new DestinationRetrieval(() -> destinationRetriever.apply(strategy), strategy.behalf());
     }
 

cloudplatform/connectivity-destination-service/src/main/java/com/sap/cloud/sdk/cloudplatform/connectivity/DestinationServiceAdapter.java

@@ -185,17 +185,24 @@ private HttpUriRequest prepareRequest( final String servicePath, final Destinati
         log.debug("Querying Destination Service via URI {}.", requestUri);
         final HttpUriRequest request = new HttpGet(requestUri);
 
-        final String headerName = switch( strategy.tokenForwarding() ) {
-            case USER_TOKEN -> "x-user-token";
-            case REFRESH_TOKEN -> "x-refresh-token";
-            case NONE -> null;
-        };
-        if( headerName != null ) {
-            request.addHeader(headerName, strategy.token());
+        if( !servicePath.startsWith("/v1/destinations") && !servicePath.startsWith("/v2/destinations") ) {
+            // additional headers and settings are only needed for single destination requests
+            return request;
+        }
+
+        switch( strategy.tokenForwarding() ) {
+            case USER_TOKEN -> request.addHeader("x-user-token", strategy.token());
+            case REFRESH_TOKEN -> request.addHeader("x-refresh-token", strategy.token());
+            case NONE -> {
+                /* nothing to do in this case */ }
         }
         if( strategy.fragment() != null ) {
             request.addHeader("x-fragment-name", strategy.fragment());
         }
+        for( final Header h : strategy.additionalHeaders() ) {
+            request.addHeader(h.getName(), h.getValue());
+        }
+
         return request;
     }
 

cloudplatform/connectivity-destination-service/src/main/java/com/sap/cloud/sdk/cloudplatform/connectivity/DestinationServiceOptionsAugmenter.java

@@ -1,6 +1,7 @@
 package com.sap.cloud.sdk.cloudplatform.connectivity;
 
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 
 import javax.annotation.Nonnull;
@@ -23,7 +24,8 @@ public class DestinationServiceOptionsAugmenter implements DestinationOptionsAug
     static final String DESTINATION_TOKEN_EXCHANGE_STRATEGY_KEY = "scp.cf.destinationTokenExchangeStrategy";
     static final String X_REFRESH_TOKEN_KEY = "x-refresh-token";
     static final String X_FRAGMENT_KEY = "X-fragment-name";
-    static final String CROSS_LEVEL_SETTING = "crossLevelSetting";
+    static final String CROSS_LEVEL_SETTING_KEY = "crossLevelSetting";
+    static final String CUSTOM_HEADER_KEY = "customHeader.";
 
     private final Map<String, Object> parameters = new HashMap<>();
 
@@ -125,7 +127,7 @@ public DestinationServiceOptionsAugmenter fragmentName( @Nonnull final String fr
     @Nonnull
     public DestinationServiceOptionsAugmenter crossLevelConsumption( @Nonnull final CrossLevelScope scope )
     {
-        parameters.put(CROSS_LEVEL_SETTING, scope);
+        parameters.put(CROSS_LEVEL_SETTING_KEY, scope);
         return this;
     }
 
@@ -168,6 +170,28 @@ String getSuffix()
         }
     }
 
+    /**
+     * Adds custom headers to the destination request. Use this to add parameters that are not directly supported by the
+     * SDK. For example, use this to achieve destination chaining.
+     * <p>
+     * <strong>Note:</strong> Any secret values added as custom headers here will <strong>not</strong> be masked in log
+     * output and may appear in plain text on debug log level.
+     *
+     * @param headers
+     *            The headers to be added.
+     * @return The same augmenter that called this method.
+     * @since 5.22.0
+     */
+    @Beta
+    @Nonnull
+    public DestinationServiceOptionsAugmenter customHeaders( @Nonnull final Header... headers )
+    {
+        for( final Header header : headers ) {
+            parameters.put(CUSTOM_HEADER_KEY + header.getName(), header.getValue());
+        }
+        return this;
+    }
+
     @Override
     public void augmentBuilder( @Nonnull final DestinationOptions.Builder builder )
     {
@@ -238,8 +262,28 @@ static Option<String> getFragmentName( @Nonnull final DestinationOptions options
     static Option<CrossLevelScope> getCrossLevelScope( @Nonnull final DestinationOptions options )
     {
         return options
-            .get(CROSS_LEVEL_SETTING)
+            .get(CROSS_LEVEL_SETTING_KEY)
             .filter(CrossLevelScope.class::isInstance)
             .map(CrossLevelScope.class::cast);
     }
+
+    @Nonnull
+    static List<Header> getAdditionalHeaders( @Nonnull final DestinationOptions options )
+    {
+        return options
+            .getOptionKeys()
+            .stream()
+            .filter(it -> it.startsWith(CUSTOM_HEADER_KEY))
+            .map(it -> it.replaceFirst(CUSTOM_HEADER_KEY, ""))
+            .map(headerName -> {
+                final String headerValue =
+                    options
+                        .get(CUSTOM_HEADER_KEY + headerName)
+                        .filter(String.class::isInstance)
+                        .map(String.class::cast)
+                        .get();
+                return new Header(headerName, headerValue);
+            })
+            .toList();
+    }
 }

cloudplatform/connectivity-destination-service/src/test/java/com/sap/cloud/sdk/cloudplatform/connectivity/DestinationRetrievalStrategyResolverTest.java

@@ -9,12 +9,10 @@
 import static com.sap.cloud.sdk.cloudplatform.connectivity.DestinationServiceTokenExchangeStrategy.EXCHANGE_ONLY;
 import static com.sap.cloud.sdk.cloudplatform.connectivity.DestinationServiceTokenExchangeStrategy.FORWARD_USER_TOKEN;
 import static com.sap.cloud.sdk.cloudplatform.connectivity.DestinationServiceTokenExchangeStrategy.LOOKUP_ONLY;
-import static com.sap.cloud.sdk.cloudplatform.connectivity.DestinationServiceTokenExchangeStrategy.LOOKUP_THEN_EXCHANGE;
 import static com.sap.cloud.sdk.cloudplatform.connectivity.OnBehalfOf.NAMED_USER_CURRENT_TENANT;
 import static com.sap.cloud.sdk.cloudplatform.connectivity.OnBehalfOf.TECHNICAL_USER_CURRENT_TENANT;
 import static com.sap.cloud.sdk.cloudplatform.connectivity.OnBehalfOf.TECHNICAL_USER_PROVIDER;
 import static com.sap.cloud.sdk.cloudplatform.connectivity.XsuaaTokenMocker.mockXsuaaToken;
-import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatThrownBy;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.eq;
@@ -26,6 +24,7 @@
 import static org.mockito.Mockito.verifyNoMoreInteractions;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 import java.util.function.Function;
 
@@ -209,7 +208,8 @@ void testExceptionsAreThrownOnIllegalCombinations()
                     .executeWithTenant(
                         c._3(),
                         () -> softly
-                            .assertThatThrownBy(() -> sut.prepareSupplier(c._1(), c._2(), null, null))
+                            .assertThatThrownBy(
+                                () -> sut.prepareSupplier(c._1(), c._2(), null, null, Collections.emptyList()))
                             .as("Expecting '%s' with '%s' and '%s' to throw.", c._1(), c._2(), c._3())
                             .isInstanceOf(DestinationAccessException.class)));
 
@@ -235,7 +235,8 @@ void testExceptionsAreThrownForImpossibleTokenExchanges()
                     ALWAYS_PROVIDER,
                     DestinationServiceTokenExchangeStrategy.LOOKUP_THEN_EXCHANGE,
                     null,
-                    null);
+                    null,
+                    Collections.emptyList());
 
         TenantAccessor
             .executeWithTenant(
@@ -260,7 +261,7 @@ void testDefaultStrategies()
         sut.prepareSupplier(DestinationOptions.builder().build());
         sut.prepareSupplierAllDestinations(DestinationOptions.builder().build());
 
-        verify(sut).prepareSupplier(CURRENT_TENANT, FORWARD_USER_TOKEN, null, null);
+        verify(sut).prepareSupplier(CURRENT_TENANT, FORWARD_USER_TOKEN, null, null, Collections.emptyList());
         verify(sut).prepareSupplierAllDestinations(CURRENT_TENANT);
     }
 
@@ -274,7 +275,12 @@ void testDefaultNonXsuaaTokenStrategy()
         sut.prepareSupplierAllDestinations(DestinationOptions.builder().build());
 
         verify(sut)
-            .prepareSupplier(CURRENT_TENANT, DestinationServiceTokenExchangeStrategy.LOOKUP_THEN_EXCHANGE, null, null);
+            .prepareSupplier(
+                CURRENT_TENANT,
+                DestinationServiceTokenExchangeStrategy.LOOKUP_THEN_EXCHANGE,
+                null,
+                null,
+                Collections.emptyList());
         verify(sut).prepareSupplierAllDestinations(CURRENT_TENANT);
     }
 
@@ -305,6 +311,6 @@ void testFragmentName()
 
         sut.prepareSupplier(opts);
 
-        verify(sut).prepareSupplier(any(), any(), eq(null), eq(fragmentName));
+        verify(sut).prepareSupplier(any(), any(), eq(null), eq(fragmentName), any());
     }
 }