Add support for URI path prefix modification

Fixes spring-projectsgh-944

spring-restdocs-core/src/main/java/org/springframework/restdocs/operation/preprocess/UriModifyingOperationPreprocessor.java

@@ -66,6 +66,8 @@ public class UriModifyingOperationPreprocessor implements OperationPreprocessor
 
 	private String port;
 
+	private String pathPrefix;
+
 	/**
 	 * Modifies the URI to use the given {@code scheme}. {@code null}, the default, will
 	 * leave the scheme unchanged.
@@ -99,6 +101,17 @@ public UriModifyingOperationPreprocessor port(int port) {
 		return port(Integer.toString(port));
 	}
 
+	/**
+	 * Modifies the URI to add the given path prefix.
+	 * @param pathPrefix the path prefix to add
+	 * @return {@code this}
+	 */
+	public UriModifyingOperationPreprocessor pathPrefix(String pathPrefix) {
+		this.pathPrefix = pathPrefix;
+		this.contentModifier.setPathPrefix(pathPrefix);
+		return this;
+	}
+
 	/**
 	 * Removes the port from the URI.
 	 * @return {@code this}
@@ -130,13 +143,17 @@ public OperationRequest preprocess(OperationRequest request) {
 				uriBuilder.port(null);
 			}
 		}
+		if (this.pathPrefix != null) {
+			String rawPath = request.getUri().getRawPath();
+			uriBuilder.replacePath(this.pathPrefix + ((rawPath != null) ? rawPath : ""));
+		}
 		URI modifiedUri = uriBuilder.build(true).toUri();
 		HttpHeaders modifiedHeaders = modify(request.getHeaders());
 		modifiedHeaders.set(HttpHeaders.HOST,
 				modifiedUri.getHost() + ((modifiedUri.getPort() != -1) ? ":" + modifiedUri.getPort() : ""));
 		return this.contentModifyingDelegate
-			.preprocess(new OperationRequestFactory().create(uriBuilder.build(true).toUri(), request.getMethod(),
-					request.getContent(), modifiedHeaders, modify(request.getParts()), request.getCookies()));
+				.preprocess(new OperationRequestFactory().create(uriBuilder.build(true).toUri(), request.getMethod(),
+						request.getContent(), modifiedHeaders, modify(request.getParts()), request.getCookies()));
 	}
 
 	@Override
@@ -169,14 +186,16 @@ private Collection<OperationRequestPart> modify(Collection<OperationRequestPart>
 	private static final class UriModifyingContentModifier implements ContentModifier {
 
 		private static final Pattern SCHEME_HOST_PORT_PATTERN = Pattern
-			.compile("(http[s]?)://([a-zA-Z0-9-\\.]+)(:[0-9]+)?");
+				.compile("(http[s]?)://([a-zA-Z0-9-\\.]+)(:[0-9]+)?");
 
 		private String scheme;
 
 		private String host;
 
 		private String port;
 
+		private String pathPrefix;
+
 		private void setScheme(String scheme) {
 			this.scheme = scheme;
 		}
@@ -189,6 +208,10 @@ private void setPort(String port) {
 			this.port = port;
 		}
 
+		private void setPathPrefix(String pathPrefix) {
+			this.pathPrefix = pathPrefix;
+		}
+
 		@Override
 		public byte[] modifyContent(byte[] content, MediaType contentType) {
 			String input;
@@ -204,7 +227,8 @@ public byte[] modifyContent(byte[] content, MediaType contentType) {
 
 		private String modify(String input) {
 			List<String> replacements = Arrays.asList(this.scheme, this.host,
-					StringUtils.hasText(this.port) ? ":" + this.port : this.port);
+					StringUtils.hasText(this.port) ? ":" + this.port : this.port,
+					this.pathPrefix);
 
 			int previous = 0;