Fix prefixPath double encoding

Fixes gh-3769
Signed-off-by: Sebastien <[email protected]>

Author: SebHeuze

spring-cloud-gateway-server-mvc/src/main/java/org/springframework/cloud/gateway/server/mvc/filter/BeforeFilterFunctions.java

@@ -195,7 +195,8 @@ public static Function<ServerRequest, ServerRequest> prefixPath(String prefix) {
 
 			String newPath = uri.getRawPath() + request.uri().getRawPath();
 
-			URI prefixedUri = UriComponentsBuilder.fromUri(request.uri()).replacePath(newPath).build().toUri();
+			URI prefixedUri = UriComponentsBuilder.fromUri(request.uri())
+					.replacePath(newPath).build(true).toUri();
 			return ServerRequest.from(request).uri(prefixedUri).build();
 		};
 	}

spring-cloud-gateway-server-mvc/src/test/java/org/springframework/cloud/gateway/server/mvc/filter/BeforeFilterFunctionsTests.java

@@ -245,4 +245,32 @@ void rewritePathWithEnDashAndSpace() {
 			.isEqualTo("/modified/path/with%E2%80%93en%E2%80%93dashes%20and%20spaces");
 	}
 
+	@Test
+	void prefixPath() {
+		MockHttpServletRequest servletRequest = MockMvcRequestBuilders
+				.get("http://localhost/get").buildRequest(null);
+
+		ServerRequest request = ServerRequest.create(servletRequest,
+				Collections.emptyList());
+
+		ServerRequest modified = BeforeFilterFunctions.prefixPath("/prefix")
+				.apply(request);
+
+		assertThat(modified.uri().getRawPath()).isEqualTo("/prefix/get");
+	}
+
+	@Test
+	void prefixEncodedPath() {
+		MockHttpServletRequest servletRequest = MockMvcRequestBuilders
+				.get("http://localhost/get/é").buildRequest(null);
+
+		ServerRequest request = ServerRequest.create(servletRequest,
+				Collections.emptyList());
+
+		ServerRequest modified = BeforeFilterFunctions.prefixPath("/pre fix")
+				.apply(request);
+
+		assertThat(modified.uri().getRawPath()).isEqualTo("/pre%20fix/get/%C3%A9");
+	}
+
 }