Keep separation of concerns of JsonContentHandler and JsonFieldTypeResolver.

Author: Mathias Düsterhöft

spring-restdocs-core/src/main/java/org/springframework/restdocs/payload/AbstractFieldsSnippet.java

@@ -161,17 +161,15 @@ protected Map<String, Object> createModel(Operation operation) {
 			content = verifyContent(
 					this.subsectionExtractor.extractSubsection(content, contentType));
 		}
-		ContentHandler contentHandler = ContentTypeHandlerFactory.create(content,
-				contentType);
+		ContentHandler contentHandler = ContentHandler.forContent(content, contentType);
 
 		validateFieldDocumentation(contentHandler);
 
 		List<FieldDescriptor> descriptorsToDocument = new ArrayList<>();
 		for (FieldDescriptor descriptor : this.fieldDescriptors) {
 			if (!descriptor.isIgnored()) {
 				try {
-					Object type = contentHandler.getFieldTypeResolver()
-							.determineFieldType(descriptor);
+					Object type = contentHandler.resolveFieldType(descriptor);
 					descriptorsToDocument.add(copyWithType(descriptor, type));
 				}
 				catch (FieldDoesNotExistException ex) {

spring-restdocs-core/src/main/java/org/springframework/restdocs/payload/ContentHandler.java

@@ -18,13 +18,15 @@
 
 import java.util.List;
 
+import org.springframework.http.MediaType;
+
 /**
  * A handler for the content of a request or response.
  *
  * @author Andy Wilkinson
  * @author Mathias Düsterhöft
  */
-interface ContentHandler {
+interface ContentHandler extends FieldTypeResolver {
 
 	/**
 	 * Finds the fields that are missing from the handler's payload. A field is missing if
@@ -49,10 +51,26 @@ interface ContentHandler {
 	String getUndocumentedContent(List<FieldDescriptor> fieldDescriptors);
 
 	/**
-	 * Return a {@link FieldTypeResolver} that can be used for the content type this
-	 * ContentHandler can process.
-	 * @return a {@link FieldTypeResolver}
+	 * Create a {@link ContentHandler} for the given content type and payload.
+	 * @param content the payload
+	 * @param contentType the content type
+	 * @return the ContentHandler
+	 * @throws PayloadHandlingException if no known ContentHandler can handle the content
 	 */
-	FieldTypeResolver getFieldTypeResolver();
+	static ContentHandler forContent(byte[] content, MediaType contentType) {
+
+		try {
+			return new JsonContentHandler(content);
+		}
+		catch (Exception je) {
+			try {
+				return new XmlContentHandler(content);
+			}
+			catch (Exception xe) {
+				throw new PayloadHandlingException("Cannot handle " + contentType
+						+ " content as it could not be parsed as JSON or XML");
+			}
+		}
+	}
 
 }

spring-restdocs-core/src/main/java/org/springframework/restdocs/payload/ContentTypeHandlerFactory.java

@@ -34,8 +34,7 @@ public interface FieldTypeResolver {
 	 * @return the {@link FieldTypeResolver}
 	 */
 	static FieldTypeResolver forContent(byte[] content, MediaType contentType) {
-		return ContentTypeHandlerFactory.create(content, contentType)
-				.getFieldTypeResolver();
+		return ContentHandler.forContent(content, contentType);
 	}
 
 	/**
@@ -44,6 +43,6 @@ static FieldTypeResolver forContent(byte[] content, MediaType contentType) {
 	 * @param fieldDescriptor the field descriptor
 	 * @return the type of the field
 	 */
-	Object determineFieldType(FieldDescriptor fieldDescriptor);
+	Object resolveFieldType(FieldDescriptor fieldDescriptor);
 
 }

spring-restdocs-core/src/main/java/org/springframework/restdocs/payload/FieldTypeResolver.java

@@ -32,11 +32,14 @@
  * A {@link ContentHandler} for JSON content.
  *
  * @author Andy Wilkinson
+ * @author Mathias Düsterhöft
  */
-class JsonContentHandler implements ContentHandler {
+class JsonContentHandler implements ContentHandler, FieldTypeResolver {
 
 	private final JsonFieldProcessor fieldProcessor = new JsonFieldProcessor();
 
+	private final JsonFieldTypeResolver fieldTypeResolver = new JsonFieldTypeResolver();
+
 	private final ObjectMapper objectMapper = new ObjectMapper()
 			.enable(SerializationFeature.INDENT_OUTPUT);
 
@@ -122,11 +125,6 @@ public String getUndocumentedContent(List<FieldDescriptor> fieldDescriptors) {
 		return null;
 	}
 
-	@Override
-	public FieldTypeResolver getFieldTypeResolver() {
-		return new JsonFieldTypeResolver(readContent());
-	}
-
 	private boolean describesSubsection(FieldDescriptor fieldDescriptor) {
 		return fieldDescriptor instanceof SubsectionDescriptor;
 	}
@@ -147,4 +145,30 @@ private boolean isEmpty(Object object) {
 		return ((List<?>) object).isEmpty();
 	}
 
+	@Override
+	public Object resolveFieldType(FieldDescriptor fieldDescriptor) {
+		if (fieldDescriptor.getType() == null) {
+			return this.fieldTypeResolver.resolveFieldType(fieldDescriptor,
+					readContent());
+		}
+		if (!(fieldDescriptor.getType() instanceof JsonFieldType)) {
+			return fieldDescriptor.getType();
+		}
+		JsonFieldType descriptorFieldType = (JsonFieldType) fieldDescriptor.getType();
+		try {
+			JsonFieldType actualFieldType = this.fieldTypeResolver
+					.resolveFieldType(fieldDescriptor, readContent());
+			if (descriptorFieldType == JsonFieldType.VARIES
+					|| descriptorFieldType == actualFieldType
+					|| (fieldDescriptor.isOptional()
+							&& actualFieldType == JsonFieldType.NULL)) {
+				return descriptorFieldType;
+			}
+			throw new FieldTypesDoNotMatchException(fieldDescriptor, actualFieldType);
+		}
+		catch (FieldDoesNotExistException ex) {
+			return fieldDescriptor.getType();
+		}
+	}
+
 }

spring-restdocs-core/src/main/java/org/springframework/restdocs/payload/JsonContentHandler.java

@@ -26,45 +26,14 @@
  * Resolves the type of a field in a JSON request or response payload.
  *
  * @author Andy Wilkinson
- * @author Mathias Düsterhöft
  */
-class JsonFieldTypeResolver implements FieldTypeResolver {
-
-	private final Object content;
+class JsonFieldTypeResolver {
 
 	private final JsonFieldProcessor fieldProcessor = new JsonFieldProcessor();
 
-	JsonFieldTypeResolver(Object content) {
-		this.content = content;
-	}
-
-	@Override
-	public Object determineFieldType(FieldDescriptor fieldDescriptor) {
-		if (fieldDescriptor.getType() == null) {
-			return resolveFieldType(fieldDescriptor);
-		}
-		if (!(fieldDescriptor.getType() instanceof JsonFieldType)) {
-			return fieldDescriptor.getType();
-		}
-		JsonFieldType descriptorFieldType = (JsonFieldType) fieldDescriptor.getType();
-		try {
-			JsonFieldType actualFieldType = resolveFieldType(fieldDescriptor);
-			if (descriptorFieldType == JsonFieldType.VARIES
-					|| descriptorFieldType == actualFieldType
-					|| (fieldDescriptor.isOptional()
-							&& actualFieldType == JsonFieldType.NULL)) {
-				return descriptorFieldType;
-			}
-			throw new FieldTypesDoNotMatchException(fieldDescriptor, actualFieldType);
-		}
-		catch (FieldDoesNotExistException ex) {
-			return fieldDescriptor.getType();
-		}
-	}
-
-	JsonFieldType resolveFieldType(FieldDescriptor fieldDescriptor) {
+	JsonFieldType resolveFieldType(FieldDescriptor fieldDescriptor, Object payload) {
 		ExtractedField extractedField = this.fieldProcessor
-				.extract(fieldDescriptor.getPath(), this.content);
+				.extract(fieldDescriptor.getPath(), payload);
 		Object value = extractedField.getValue();
 		if (value instanceof Collection && extractedField.getType() == PathType.MULTI) {
 			JsonFieldType commonType = null;

spring-restdocs-core/src/main/java/org/springframework/restdocs/payload/JsonFieldTypeResolver.java

@@ -47,7 +47,7 @@
  *
  * @author Andy Wilkinson
  */
-class XmlContentHandler implements ContentHandler, FieldTypeResolver {
+class XmlContentHandler implements ContentHandler {
 
 	private final DocumentBuilder documentBuilder;
 
@@ -146,11 +146,6 @@ public String getUndocumentedContent(List<FieldDescriptor> fieldDescriptors) {
 		return null;
 	}
 
-	@Override
-	public FieldTypeResolver getFieldTypeResolver() {
-		return this;
-	}
-
 	private void removeLeafNodes(List<Node> candidates) {
 		boolean changed = true;
 		while (changed) {
@@ -195,7 +190,7 @@ private String prettyPrint(Document document) {
 	}
 
 	@Override
-	public Object determineFieldType(FieldDescriptor fieldDescriptor) {
+	public Object resolveFieldType(FieldDescriptor fieldDescriptor) {
 		if (fieldDescriptor.getType() != null) {
 			return fieldDescriptor.getType();
 		}

spring-restdocs-core/src/main/java/org/springframework/restdocs/payload/XmlContentHandler.java

@@ -37,7 +37,7 @@ public class FieldTypeResolverTests {
 	@Test
 	public void returnJsonFieldTypeResolver() {
 		assertThat(FieldTypeResolver.forContent("{\"field\": \"value\"}".getBytes(),
-				MediaType.APPLICATION_JSON)).isInstanceOf(JsonFieldTypeResolver.class);
+				MediaType.APPLICATION_JSON)).isInstanceOf(JsonContentHandler.class);
 	}
 
 	@Test

spring-restdocs-core/src/test/java/org/springframework/restdocs/payload/FieldTypeResolverTests.java

@@ -36,6 +36,69 @@ public class JsonContentHandlerTests {
 	@Rule
 	public ExpectedException thrown = ExpectedException.none();
 
+	@Test
+	public void typeForFieldWithNullValueMustMatch() {
+		this.thrown.expect(FieldTypesDoNotMatchException.class);
+		new JsonContentHandler("{\"a\": null}".getBytes())
+				.resolveFieldType(new FieldDescriptor("a").type(JsonFieldType.STRING));
+	}
+
+	@Test
+	public void typeForFieldWithNotNullAndThenNullValueMustMatch() {
+		this.thrown.expect(FieldTypesDoNotMatchException.class);
+		new JsonContentHandler("{\"a\":[{\"id\":1},{\"id\":null}]}".getBytes())
+				.resolveFieldType(
+						new FieldDescriptor("a[].id").type(JsonFieldType.STRING));
+	}
+
+	@Test
+	public void typeForFieldWithNullAndThenNotNullValueMustMatch() {
+		this.thrown.expect(FieldTypesDoNotMatchException.class);
+		new JsonContentHandler("{\"a\":[{\"id\":null},{\"id\":1}]}".getBytes())
+				.resolveFieldType(
+						new FieldDescriptor("a.[].id").type(JsonFieldType.STRING));
+	}
+
+	@Test
+	public void typeForOptionalFieldWithNumberAndThenNullValueIsNumber() {
+		Object fieldType = new JsonContentHandler(
+				"{\"a\":[{\"id\":1},{\"id\":null}]}\"".getBytes())
+						.resolveFieldType(new FieldDescriptor("a[].id").optional());
+		assertThat((JsonFieldType) fieldType).isEqualTo(JsonFieldType.NUMBER);
+	}
+
+	@Test
+	public void typeForOptionalFieldWithNullAndThenNumberIsNumber() {
+		Object fieldType = new JsonContentHandler(
+				"{\"a\":[{\"id\":null},{\"id\":1}]}".getBytes())
+						.resolveFieldType(new FieldDescriptor("a[].id").optional());
+		assertThat((JsonFieldType) fieldType).isEqualTo(JsonFieldType.NUMBER);
+	}
+
+	@Test
+	public void typeForFieldWithNumberAndThenNullValueIsVaries() {
+		Object fieldType = new JsonContentHandler(
+				"{\"a\":[{\"id\":1},{\"id\":null}]}\"".getBytes())
+						.resolveFieldType(new FieldDescriptor("a[].id"));
+		assertThat((JsonFieldType) fieldType).isEqualTo(JsonFieldType.VARIES);
+	}
+
+	@Test
+	public void typeForFieldWithNullAndThenNumberIsVaries() {
+		Object fieldType = new JsonContentHandler(
+				"{\"a\":[{\"id\":null},{\"id\":1}]}".getBytes())
+						.resolveFieldType(new FieldDescriptor("a[].id"));
+		assertThat((JsonFieldType) fieldType).isEqualTo(JsonFieldType.VARIES);
+	}
+
+	@Test
+	public void typeForOptionalFieldWithNullValueCanBeProvidedExplicitly() {
+		Object fieldType = new JsonContentHandler("{\"a\": null}".getBytes())
+				.resolveFieldType(
+						new FieldDescriptor("a").type(JsonFieldType.STRING).optional());
+		assertThat((JsonFieldType) fieldType).isEqualTo(JsonFieldType.STRING);
+	}
+
 	@Test
 	public void failsFastWithNonJsonContent() {
 		this.thrown.expect(PayloadHandlingException.class);