Add InputStreamSourceToByteArrayConverter

Add an `InputStreamSourceToByteArrayConverter` that can be used to
convert from an `InputStreamSource` (such as a `Resource`) to a
byte array.

Closes gh-21285

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/convert/ApplicationConversionService.java

@@ -116,6 +116,7 @@ public class ApplicationConversionService extends FormattingConversionService {
 		registry.addConverter(new StringToDataSizeConverter());
 		registry.addConverter(new NumberToDataSizeConverter());
 		registry.addConverter(new StringToFileConverter());
+		registry.addConverter(new InputStreamSourceToByteArrayConverter());
 		registry.addConverterFactory(new LenientStringToEnumConverterFactory());
 		registry.addConverterFactory(new LenientBooleanToEnumConverterFactory());
 	}

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/convert/InputStreamSourceToByteArrayConverter.java

@@ -0,0 +1,55 @@
+/*
+ * Copyright 2012-2020 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.convert;
+
+import java.io.IOException;
+
+import org.springframework.boot.origin.Origin;
+import org.springframework.core.convert.converter.Converter;
+import org.springframework.core.io.InputStreamSource;
+import org.springframework.core.io.Resource;
+import org.springframework.util.FileCopyUtils;
+
+/**
+ * {@link Converter} to convert from an {@link InputStreamSource} to a {@code byte[]}.
+ *
+ * @author Phillip Webb
+ */
+class InputStreamSourceToByteArrayConverter implements Converter<InputStreamSource, byte[]> {
+
+	@Override
+	public byte[] convert(InputStreamSource source) {
+		try {
+			return FileCopyUtils.copyToByteArray(source.getInputStream());
+		}
+		catch (IOException ex) {
+			throw new IllegalStateException("Unable to read from " + getName(source), ex);
+		}
+	}
+
+	private String getName(InputStreamSource source) {
+		Origin origin = Origin.from(source);
+		if (origin != null) {
+			return origin.toString();
+		}
+		if (source instanceof Resource) {
+			return ((Resource) source).getDescription();
+		}
+		return "input stream source";
+	}
+
+}

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/convert/InputStreamSourceToByteArrayConverterTests.java

@@ -0,0 +1,106 @@
+/*
+ * Copyright 2012-2020 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.convert;
+
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
+import java.util.stream.Stream;
+
+import org.junit.jupiter.params.provider.Arguments;
+
+import org.springframework.boot.origin.Origin;
+import org.springframework.boot.origin.OriginProvider;
+import org.springframework.core.convert.ConversionFailedException;
+import org.springframework.core.convert.ConversionService;
+import org.springframework.core.io.InputStreamSource;
+import org.springframework.core.io.Resource;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
+import static org.mockito.BDDMockito.given;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.withSettings;
+
+/**
+ * Tests for {@link InputStreamSourceToByteArrayConverter}.
+ *
+ * @author Phillip Webb
+ */
+class InputStreamSourceToByteArrayConverterTests {
+
+	@ConversionServiceTest
+	void convertConvertsSource(ConversionService conversionService) {
+		InputStreamSource source = () -> new ByteArrayInputStream(new byte[] { 0, 1, 2 });
+		assertThat(conversionService.convert(source, byte[].class)).containsExactly(0, 1, 2);
+	}
+
+	@ConversionServiceTest
+	void convertWhenFailsWithIOExceptionThrowsException(ConversionService conversionService) throws Exception {
+		InputStreamSource source = mock(InputStreamSource.class);
+		given(source.getInputStream()).willThrow(IOException.class);
+		assertThatExceptionOfType(ConversionFailedException.class)
+				.isThrownBy(() -> conversionService.convert(source, byte[].class))
+				.withCauseExactlyInstanceOf(IllegalStateException.class)
+				.withMessageContaining("Unable to read from input stream source");
+	}
+
+	@ConversionServiceTest
+	void convertWhenFailsWithIOExceptionFromOriginProviderThrowsException(ConversionService conversionService)
+			throws Exception {
+		Origin origin = new TestOrigin("mylocation");
+		InputStreamSource source = mock(InputStreamSource.class, withSettings().extraInterfaces(OriginProvider.class));
+		given(source.getInputStream()).willThrow(IOException.class);
+		given(((OriginProvider) source).getOrigin()).willReturn(origin);
+		assertThatExceptionOfType(ConversionFailedException.class)
+				.isThrownBy(() -> conversionService.convert(source, byte[].class))
+				.withCauseExactlyInstanceOf(IllegalStateException.class)
+				.withMessageContaining("Unable to read from mylocation");
+	}
+
+	@ConversionServiceTest
+	void convertWhenFailsWithIOExceptionFromResourceThrowsException(ConversionService conversionService)
+			throws Exception {
+		Resource source = mock(Resource.class);
+		given(source.getInputStream()).willThrow(IOException.class);
+		given(source.getDescription()).willReturn("myresource");
+		assertThatExceptionOfType(ConversionFailedException.class)
+				.isThrownBy(() -> conversionService.convert(source, byte[].class))
+				.withCauseExactlyInstanceOf(IllegalStateException.class)
+				.withMessageContaining("Unable to read from myresource");
+	}
+
+	static Stream<? extends Arguments> conversionServices() {
+		return ConversionServiceArguments
+				.with((service) -> service.addConverter(new InputStreamSourceToByteArrayConverter()));
+	}
+
+	private static class TestOrigin implements Origin {
+
+		private final String string;
+
+		TestOrigin(String string) {
+			this.string = string;
+		}
+
+		@Override
+		public String toString() {
+			return this.string;
+		}
+
+	}
+
+}