Update solution

Author: newtork

datamodel/odata-client/src/main/java/com/sap/cloud/sdk/datamodel/odata/client/request/ODataRequestBatch.java

@@ -93,7 +93,7 @@ public ODataRequestBatch(
         this.uuidProvider = uuidProvider;
         this.batchUuid = uuidProvider.get();
         this.headers.remove(HttpHeaders.ACCEPT); // batch request does not require Accept header
-        this.bufferStrategy = ResponseBufferStrategy.DISABLED;
+        this.requestResultFactory = ODataRequestResultFactory.WITHOUT_BUFFER;
     }
 
     @Nonnull

datamodel/odata-client/src/main/java/com/sap/cloud/sdk/datamodel/odata/client/request/ODataRequestGeneric.java

@@ -93,7 +93,7 @@ public abstract class ODataRequestGeneric implements ODataRequestExecutable
      * The response buffer strategy to use for this request.
      */
     @Nonnull
-    ResponseBufferStrategy bufferStrategy = ResponseBufferStrategy.ENABLED;
+    ODataRequestResultFactory requestResultFactory = ODataRequestResultFactory.WITH_BUFFER;
 
     ODataRequestGeneric(
         @Nonnull final String servicePath,
@@ -149,14 +149,6 @@ public void addListener( @Nonnull final ODataRequestListener listener )
         listeners.add(listener);
     }
 
-    /**
-     * Disable pre-buffering of http response entity.
-     */
-    public void disableHttpResponseBuffering()
-    {
-        bufferStrategy = ResponseBufferStrategy.DISABLED;
-    }
-
     /**
      * Replace a header in the OData HTTP request.
      *
@@ -243,8 +235,7 @@ public void addQueryParameter( @Nonnull final String key, @Nullable final String
     {
         return Try
             .ofSupplier(httpOperation)
-            .map(bufferStrategy.getHandler())
-            .map(response -> new ODataRequestResultGeneric(this, response, httpClient))
+            .map(response -> requestResultFactory.create(this, response, httpClient))
             .andThenTry(ODataHealthyResponseValidator::requireHealthyResponse);
     }
 

datamodel/odata-client/src/main/java/com/sap/cloud/sdk/datamodel/odata/client/request/ODataRequestRead.java

@@ -7,6 +7,7 @@
 
 import org.apache.http.client.HttpClient;
 
+import com.google.common.annotations.Beta;
 import com.google.common.net.UrlEscapers;
 import com.sap.cloud.sdk.datamodel.odata.client.ODataProtocol;
 import com.sap.cloud.sdk.datamodel.odata.client.expression.ODataResourcePath;
@@ -134,4 +135,14 @@ public ODataRequestResultGeneric execute( @Nonnull final HttpClient httpClient )
                 : tryExecuteWithCsrfToken(httpClient, request::requestGet);
         return result.get();
     }
+
+    /**
+     * Disable pre-buffering of http response entity.
+     */
+    @Beta
+    public ODataRequestResultResource.Executable withoutResponseBuffering()
+    {
+        requestResultFactory = ODataRequestResultFactory.WITHOUT_BUFFER;
+        return httpClient -> (ODataRequestResultResource) this.execute(httpClient);
+    }
 }

datamodel/odata-client/src/main/java/com/sap/cloud/sdk/datamodel/odata/client/request/ODataRequestReadByKey.java

@@ -7,6 +7,7 @@
 
 import org.apache.http.client.HttpClient;
 
+import com.google.common.annotations.Beta;
 import com.sap.cloud.sdk.datamodel.odata.client.ODataProtocol;
 import com.sap.cloud.sdk.datamodel.odata.client.expression.ODataResourcePath;
 import com.sap.cloud.sdk.datamodel.odata.client.query.StructuredQuery;
@@ -128,4 +129,14 @@ public ODataRequestResultGeneric execute( @Nonnull final HttpClient httpClient )
                 : tryExecuteWithCsrfToken(httpClient, request::requestGet);
         return result.get();
     }
+
+    /**
+     * Disable pre-buffering of http response entity.
+     */
+    @Beta
+    public ODataRequestResultResource.Executable withoutResponseBuffering()
+    {
+        requestResultFactory = ODataRequestResultFactory.WITHOUT_BUFFER;
+        return httpClient -> (ODataRequestResultResource) this.execute(httpClient);
+    }
 }

datamodel/odata-client/src/main/java/com/sap/cloud/sdk/datamodel/odata/client/request/ODataRequestResultFactory.java

@@ -0,0 +1,42 @@
+package com.sap.cloud.sdk.datamodel.odata.client.request;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
+import org.apache.http.HttpResponse;
+import org.apache.http.client.HttpClient;
+import org.apache.http.entity.BufferedHttpEntity;
+import org.apache.http.message.BasicHttpResponse;
+
+import io.vavr.control.Option;
+import io.vavr.control.Try;
+
+/**
+ * Enum representing the strategy for buffering HTTP responses.
+ */
+@FunctionalInterface
+interface ODataRequestResultFactory
+{
+    ODataRequestResultGeneric create(
+        @Nonnull final ODataRequestGeneric oDataRequest,
+        @Nonnull final HttpResponse httpResponse,
+        @Nullable final HttpClient httpClient );
+
+    /**
+     * Strategy that does not buffer the response.
+     */
+    ODataRequestResultFactory WITHOUT_BUFFER = ODataRequestResultResource::new;
+
+    /**
+     * Strategy that buffers the response by creating a copy of it.
+     */
+    ODataRequestResultFactory WITH_BUFFER = ( oDataRequest, httpResponse, httpClient ) -> {
+        final BasicHttpResponse copy = new BasicHttpResponse(httpResponse.getStatusLine());
+        Option.of(httpResponse.getLocale()).peek(copy::setLocale);
+        Option.of(httpResponse.getAllHeaders()).peek(copy::setHeaders);
+        Option
+            .of(httpResponse.getEntity())
+            .peek(entity -> Try.run(() -> copy.setEntity(new BufferedHttpEntity(entity))));
+        return new ODataRequestResultGeneric(oDataRequest, copy, httpClient);
+    };
+}

datamodel/odata-client/src/main/java/com/sap/cloud/sdk/datamodel/odata/client/request/ODataRequestResultGeneric.java

@@ -147,7 +147,8 @@ public ODataRequestResultGeneric withNumberDeserializationStrategy(
      * Method that allows consumers to disable buffering HTTP response entity. Note that once this is disabled, HTTP
      * responses can only be streamed/read once
      *
-     * @deprecated Please use {@link ODataRequestGeneric#disableHttpResponseBuffering()} instead.
+     * @deprecated Please use {@link ODataRequestRead#withoutResponseBuffering()} or
+     *             {@link ODataRequestReadByKey#withoutResponseBuffering()} instead.
      */
     @Deprecated
     public void disableBufferingHttpResponse()

datamodel/odata-client/src/main/java/com/sap/cloud/sdk/datamodel/odata/client/request/ODataRequestResultResource.java

@@ -0,0 +1,64 @@
+package com.sap.cloud.sdk.datamodel.odata.client.request;
+
+import java.io.IOException;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
+import org.apache.http.HttpResponse;
+import org.apache.http.client.HttpClient;
+import org.apache.http.util.EntityUtils;
+
+import com.google.common.annotations.Beta;
+
+import lombok.EqualsAndHashCode;
+import lombok.extern.slf4j.Slf4j;
+
+/**
+ * OData request result for reading entities. The connection is not yet closed.
+ */
+@Slf4j
+@Beta
+@EqualsAndHashCode( callSuper = true )
+public class ODataRequestResultResource extends ODataRequestResultGeneric implements AutoCloseable
+{
+    /**
+     * Default constructor.
+     *
+     * @param oDataRequest
+     *            The original OData request
+     * @param httpResponse
+     *            The original Http response
+     * @param httpClient
+     *            The Http client used to execute the request
+     */
+    ODataRequestResultResource(
+        @Nonnull final ODataRequestGeneric oDataRequest,
+        @Nonnull final HttpResponse httpResponse,
+        @Nullable final HttpClient httpClient )
+    {
+        super(oDataRequest, httpResponse, httpClient);
+    }
+
+    @Override
+    public void close()
+    {
+        try {
+            EntityUtils.consume(getHttpResponse().getEntity());
+        }
+        catch( final IOException e ) {
+            log.warn("Failed to close the HTTP response entity.", e);
+        }
+    }
+
+    /**
+     * Interface for executing OData requests that return a resource which must be closed.
+     */
+    @FunctionalInterface
+    public interface Executable extends ODataRequestExecutable
+    {
+        @Nonnull
+        @Override
+        ODataRequestResultResource execute( @Nonnull final HttpClient httpClient );
+    }
+}

datamodel/odata-client/src/main/java/com/sap/cloud/sdk/datamodel/odata/client/request/ResponseBufferStrategy.java

@@ -182,19 +182,20 @@ void testDisabledBuffer()
         httpResponse.setEntity(new InputStreamEntity(inputStream, json.length()));
 
         // system under test
-        oDataRequest.disableHttpResponseBuffering();
-        final ODataRequestResultGeneric testResult = new ODataRequestResultGeneric(oDataRequest, httpResponse);
-
-        // sanity checks do not consume the response
-        assertThat(testResult.getHeaderValues("Content-Length")).isEmpty();
-        assertThat(testResult.getHttpResponse().getStatusLine().getStatusCode()).isEqualTo(200);
-
-        // true-positive, successfully read once
-        assertThat(testResult.asListOfMaps()).isEmpty();
-
-        // true-negative, no second read possible
-        assertThatThrownBy(testResult::asListOfMaps)
-            .isInstanceOf(ODataDeserializationException.class)
-            .hasMessageContaining("Unable to read OData 4.0 response.");
+        try(
+            final ODataRequestResultResource testResult =
+                new ODataRequestResultResource(oDataRequest, httpResponse, null) ) {
+            // sanity checks do not consume the response
+            assertThat(testResult.getHeaderValues("Content-Length")).isEmpty();
+            assertThat(testResult.getHttpResponse().getStatusLine().getStatusCode()).isEqualTo(200);
+
+            // true-positive, successfully read once
+            assertThat(testResult.asListOfMaps()).isEmpty();
+
+            // true-negative, no second read possible
+            assertThatThrownBy(testResult::asListOfMaps)
+                .isInstanceOf(ODataDeserializationException.class)
+                .hasMessageContaining("Unable to read OData 4.0 response.");
+        }
     }
 }

datamodel/odata-client/src/test/java/com/sap/cloud/sdk/datamodel/odata/client/request/ODataRequestResultGenericTest.java

@@ -4,6 +4,7 @@
 import static org.assertj.core.api.Assertions.assertThatCode;
 import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
 
+import java.io.IOException;
 import java.time.OffsetDateTime;
 import java.util.List;
 import java.util.UUID;
@@ -310,10 +311,14 @@ void testExceptionWhenUnbufferedHttpEntityIsAccessedMultipleTimes()
         final ODataRequestRead request =
             new ODataRequestRead("TripPinRESTierService", "People", "$count=true&$format=json", ODataProtocol.V4);
 
-        request.disableHttpResponseBuffering();
-        final ODataRequestResultGeneric result = request.execute(httpClient);
-        assertThat(result.asMap()).containsKeys("value", "@odata.count");
-        assertThatExceptionOfType(ODataDeserializationException.class).isThrownBy(() -> result.getInlineCount());
+        try( final ODataRequestResultResource result = request.withoutResponseBuffering().execute(httpClient) ) {
+
+            // first access successful
+            assertThat(result.asMap()).containsKeys("value", "@odata.count");
+
+            // second access fails
+            assertThatExceptionOfType(ODataDeserializationException.class).isThrownBy(result::getInlineCount);
+        }
     }
 
     @Test
@@ -322,9 +327,17 @@ void testWhenUnbufferedHttpEntityIsAccessedAfterAccessingBufferedHttpEntity()
         final ODataRequestRead request =
             new ODataRequestRead("TripPinRESTierService", "People", "$count=true&$format=json", ODataProtocol.V4);
 
-        request.disableHttpResponseBuffering();
-        final ODataRequestResultGeneric result = request.execute(httpClient);
+        @SuppressWarnings( "resource" ) // let's assume user is forgetting try-with-resources
+        final ODataRequestResultGeneric result = request.withoutResponseBuffering().execute(httpClient);
+
+        // first access successful
         assertThat(result.asMap()).containsKeys("value", "@odata.count");
-        assertThat(result.getInlineCount()).isEqualTo(20);
+
+        // second access fails
+        assertThatExceptionOfType(ODataDeserializationException.class)
+            .isThrownBy(result::getInlineCount)
+            .havingRootCause()
+            .isInstanceOf(IOException.class)
+            .withMessage("Attempted read from closed stream.");
     }
 }