Add flag to make sure we don't validate checksum twice

.changes/next-release/bugfix-AWSSDKforJavav2-89a97c3.json

@@ -0,0 +1,5 @@
+{
+    "category": "AWS SDK for Java v2", 
+    "type": "bugfix", 
+    "description": "Preserve computedChecksum in `ChecksumValidatingInputStream` so that it doesn't throw error if it validates more than once. See [#873](https://github.com/aws/aws-sdk-java-v2/issues/873)"
+}

services/s3/src/it/java/software/amazon/awssdk/services/s3/GetObjectIntegrationTest.java

@@ -23,12 +23,14 @@
 import java.io.File;
 import java.io.IOException;
 import java.nio.file.Path;
+import java.util.Properties;
 import org.junit.AfterClass;
 import org.junit.BeforeClass;
 import org.junit.Test;
 import software.amazon.awssdk.core.ResponseInputStream;
 import software.amazon.awssdk.core.client.config.ClientOverrideConfiguration;
 import software.amazon.awssdk.core.interceptor.ExecutionInterceptor;
+import software.amazon.awssdk.core.sync.RequestBody;
 import software.amazon.awssdk.core.sync.ResponseTransformer;
 import software.amazon.awssdk.services.s3.GetObjectAsyncIntegrationTest.AssertingExecutionInterceptor;
 import software.amazon.awssdk.services.s3.model.GetObjectRequest;
@@ -41,6 +43,7 @@ public class GetObjectIntegrationTest extends S3IntegrationTestBase {
     private static final String BUCKET = temporaryBucketName(GetObjectIntegrationTest.class);
 
     private static final String KEY = "some-key";
+    private static final String PROPERTY_KEY = "properties";
 
     private final GetObjectRequest getObjectRequest = GetObjectRequest.builder()
                                                                       .bucket(BUCKET)
@@ -71,6 +74,18 @@ public void toInputStream() throws Exception {
         }
     }
 
+
+    @Test
+    public void toInputStream_loadFromProperties() throws IOException {
+        s3.putObject(b -> b.bucket(BUCKET).key(PROPERTY_KEY), RequestBody.fromString("test: test"));
+        try (ResponseInputStream<GetObjectResponse> object = s3.getObject(b -> b.bucket(BUCKET).key(PROPERTY_KEY),
+                                                                          ResponseTransformer.toInputStream())) {
+            Properties properties = new Properties();
+            properties.load(object);
+            assertThat(properties.getProperty("test")).isEqualTo("test");
+        }
+    }
+
     @Test
     public void toFile() throws Exception {
         Path path = RandomTempFile.randomUncreatedFile().toPath();

services/s3/src/main/java/software/amazon/awssdk/services/s3/checksums/ChecksumValidatingInputStream.java

@@ -32,6 +32,9 @@ public class ChecksumValidatingInputStream extends InputStream implements Aborta
     private long strippedLength;
     private byte[] streamChecksum = new byte[CHECKSUM_SIZE];
     private long lengthRead = 0;
+    // Preserve the computed checksum because some InputStream readers (e.g., java.util.Properties) read more than once at the
+    // end of the stream.
+    private Integer computedChecksum;
 
     /**
      * Creates an input stream using the specified Checksum, input stream, and length.
@@ -171,11 +174,14 @@ public int getStreamChecksum() {
 
     private void validateAndThrow() {
         int streamChecksumInt = getStreamChecksum();
-        int computedChecksumInt = ByteBuffer.wrap(checkSum.getChecksumBytes()).getInt();
-        if (streamChecksumInt != computedChecksumInt) {
+        if (computedChecksum == null) {
+            computedChecksum = ByteBuffer.wrap(checkSum.getChecksumBytes()).getInt();
+        }
+
+        if (streamChecksumInt != computedChecksum) {
             throw SdkClientException.builder().message(
                 String.format("Data read has a different checksum than expected. Was %d, but expected %d",
-                              computedChecksumInt, streamChecksumInt)).build();
+                              computedChecksum, streamChecksumInt)).build();
         }
     }