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Adds StripContextPath filter (#4089)
* Fix StripPrefix and RewritePath filters including servlet context-path fixes: #4088 Signed-off-by: Garvit Joshi <garvitjoshi9@gmail.com> * Add documentation for StripContextPath filter Signed-off-by: Garvit Joshi <garvitjoshi9@gmail.com> --------- Signed-off-by: Garvit Joshi <garvitjoshi9@gmail.com>
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‎docs/modules/ROOT/nav.adoc‎

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*** xref:spring-cloud-gateway-server-webmvc/filters/setrequestheader.adoc[]
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*** xref:spring-cloud-gateway-server-webmvc/filters/setresponseheader.adoc[]
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*** xref:spring-cloud-gateway-server-webmvc/filters/setstatus.adoc[]
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*** xref:spring-cloud-gateway-server-webmvc/filters/stripcontextpath.adoc[]
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*** xref:spring-cloud-gateway-server-webmvc/filters/stripprefix.adoc[]
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*** xref:spring-cloud-gateway-server-webmvc/filters/retry.adoc[]
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*** xref:spring-cloud-gateway-server-webmvc/filters/requestsize.adoc[]

‎docs/modules/ROOT/pages/spring-cloud-gateway-server-webmvc/filters/stripcontextpath.adoc‎

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[[stripcontextpath-filter]]
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= `StripContextPath` Filter
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The `StripContextPath` filter removes the servlet context-path (configured via `server.servlet.context-path`) from the request URI before downstream filters process it.
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This is useful when path-manipulating filters like `StripPrefix`, `RewritePath`, or `PrefixPath` should operate on the same path that route predicates match against, without the context-path prefix.
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The `StripContextPath` filter must be placed before any path-manipulating filters in the filter chain.
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The following listing configures a `StripContextPath` filter:
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.application.yml
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[source,yaml]
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----
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server:
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servlet:
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context-path: /context
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spring:
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cloud:
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gateway:
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server:
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webmvc:
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routes:
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- id: strip_context_path_route
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uri: https://example.org
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predicates:
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- Path=/name/**
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filters:
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- StripContextPath
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- StripPrefix=1
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----
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.GatewaySampleApplication.java
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[source,java]
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----
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import static org.springframework.cloud.gateway.server.mvc.filter.BeforeFilterFunctions.stripContextPath;
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import static org.springframework.cloud.gateway.server.mvc.filter.BeforeFilterFunctions.stripPrefix;
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import static org.springframework.cloud.gateway.server.mvc.filter.BeforeFilterFunctions.uri;
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import static org.springframework.cloud.gateway.server.mvc.handler.GatewayRouterFunctions.route;
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import static org.springframework.cloud.gateway.server.mvc.handler.HandlerFunctions.http;
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@Configuration
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class RouteConfiguration {
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@Bean
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public RouterFunction<ServerResponse> gatewayRouterFunctionsStripContextPath() {
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return route("strip_context_path_route")
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.GET("/name/**", http())
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.before(uri("https://example.org"))
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.before(stripContextPath())
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.before(stripPrefix(1))
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.build();
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}
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}
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----
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With `server.servlet.context-path=/context`, when a request is made through the gateway to `/context/name/blue`, the `StripContextPath` filter removes the `/context` prefix, and then `StripPrefix` strips `/name`, resulting in a downstream request to `https://example.org/blue`.
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WARNING: The `StripContextPath` filter must be listed before `StripPrefix`, `RewritePath`, `PrefixPath`, or any other filter that operates on the request path. Filters execute in the order they are defined, and these filters need the context-path already removed to work correctly.

‎spring-cloud-gateway-server-webmvc/src/main/java/org/springframework/cloud/gateway/server/mvc/common/MvcUtils.java‎

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urls.add(url);
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}
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/**
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* Removes the servlet context-path prefix from the given path. This ensures
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* path-manipulating filters (e.g., StripPrefix, RewritePath) operate on the same path
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* that route predicates match against.
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* @param request the server request used to obtain the context path
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* @param path the path to strip the context path from (raw or decoded)
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* @return the path without the servlet context-path prefix
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*/
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public static String stripContextPath(ServerRequest request, String path) {
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String contextPath = request.servletRequest().getContextPath();
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if (StringUtils.hasText(contextPath) && path.startsWith(contextPath)) {
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path = path.substring(contextPath.length());
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if (path.isEmpty()) {
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path = "/";
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}
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}
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return path;
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}
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public static MultiValueMap<String, String> encodeQueryParams(MultiValueMap<String, String> params) {
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MultiValueMap<String, String> encodedQueryParams = new LinkedMultiValueMap<>(params.size());
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for (Map.Entry<String, List<String>> entry : params.entrySet()) {

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

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};
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}
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/**
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* Returns a filter function that strips the servlet context-path from the request
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* URI. Users should add this filter before path-manipulating filters (StripPrefix,
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* RewritePath, PrefixPath) when using {@code server.servlet.context-path}.
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* @return a function that strips the context-path from the request URI
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*/
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public static Function<ServerRequest, ServerRequest> stripContextPath() {
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return request -> {
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String rawPath = request.uri().getRawPath();
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String strippedPath = MvcUtils.stripContextPath(request, rawPath);
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if (!rawPath.equals(strippedPath)) {
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MvcUtils.addOriginalRequestUrl(request, request.uri());
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URI newUri = UriComponentsBuilder.fromUri(request.uri()).replacePath(strippedPath).build(true).toUri();
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return ServerRequest.from(request).uri(newUri).build();
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}
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return request;
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};
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}
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public static Function<ServerRequest, ServerRequest> stripPrefix() {
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return stripPrefix(1);
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}

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

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return ofResponseProcessor(AfterFilterFunctions.setResponseHeader(name, value));
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}
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@Shortcut
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static HandlerFilterFunction<ServerResponse, ServerResponse> stripContextPath() {
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return ofRequestProcessor(BeforeFilterFunctions.stripContextPath());
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}
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static HandlerFilterFunction<ServerResponse, ServerResponse> stripPrefix() {
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return stripPrefix(1);
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}

‎spring-cloud-gateway-server-webmvc/src/test/java/org/springframework/cloud/gateway/server/mvc/common/MvcUtilsTests.java‎

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/*
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* Copyright 2013-present the original author or authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* https://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.springframework.cloud.gateway.server.mvc.common;
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import java.util.Collections;
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import org.junit.jupiter.api.Test;
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import org.springframework.mock.web.MockHttpServletRequest;
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import org.springframework.test.web.servlet.request.MockMvcRequestBuilders;
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import org.springframework.web.servlet.function.ServerRequest;
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import static org.assertj.core.api.Assertions.assertThat;
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/**
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* @author Garvit Joshi
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*/
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class MvcUtilsTests {
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@Test
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void stripContextPathRemovesPrefix() {
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MockHttpServletRequest servletRequest = MockMvcRequestBuilders.get("http://localhost/context/path")
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.buildRequest(null);
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servletRequest.setContextPath("/context");
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ServerRequest request = ServerRequest.create(servletRequest, Collections.emptyList());
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assertThat(MvcUtils.stripContextPath(request, "/context/path")).isEqualTo("/path");
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}
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@Test
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void stripContextPathReturnsSlashWhenOnlyContextPath() {
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MockHttpServletRequest servletRequest = MockMvcRequestBuilders.get("http://localhost/context")
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.buildRequest(null);
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servletRequest.setContextPath("/context");
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ServerRequest request = ServerRequest.create(servletRequest, Collections.emptyList());
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assertThat(MvcUtils.stripContextPath(request, "/context")).isEqualTo("/");
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}
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@Test
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void stripContextPathNoOpWithoutContextPath() {
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MockHttpServletRequest servletRequest = MockMvcRequestBuilders.get("http://localhost/path").buildRequest(null);
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ServerRequest request = ServerRequest.create(servletRequest, Collections.emptyList());
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assertThat(MvcUtils.stripContextPath(request, "/path")).isEqualTo("/path");
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}
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}

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

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assertThat(result.uri().toString()).hasToString("http://localhost:77/depth3");
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}
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@Test
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void stripContextPath() {
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MockHttpServletRequest servletRequest = MockMvcRequestBuilders
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.get("http://localhost/context/depth1/depth2/depth3")
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.buildRequest(null);
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servletRequest.setContextPath("/context");
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ServerRequest request = ServerRequest.create(servletRequest, Collections.emptyList());
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ServerRequest result = BeforeFilterFunctions.stripContextPath().apply(request);
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assertThat(result.uri().getRawPath()).isEqualTo("/depth1/depth2/depth3");
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}
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@Test
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void stripContextPathWithoutContextPath() {
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MockHttpServletRequest servletRequest = MockMvcRequestBuilders.get("http://localhost/depth1/depth2/depth3")
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.buildRequest(null);
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ServerRequest request = ServerRequest.create(servletRequest, Collections.emptyList());
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ServerRequest result = BeforeFilterFunctions.stripContextPath().apply(request);
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assertThat(result.uri().getRawPath()).isEqualTo("/depth1/depth2/depth3");
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}
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@Test
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void stripPrefixWithContextPath() {
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MockHttpServletRequest servletRequest = MockMvcRequestBuilders
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.get("http://localhost/context/depth1/depth2/depth3")
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.buildRequest(null);
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servletRequest.setContextPath("/context");
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ServerRequest request = ServerRequest.create(servletRequest, Collections.emptyList());
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ServerRequest stripped = BeforeFilterFunctions.stripContextPath().apply(request);
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ServerRequest result = BeforeFilterFunctions.stripPrefix(2).apply(stripped);
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assertThat(result.uri().getRawPath()).isEqualTo("/depth3");
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}
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@Test
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void rewritePathWithContextPath() {
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MockHttpServletRequest servletRequest = MockMvcRequestBuilders.get("http://localhost/context/service/path")
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.buildRequest(null);
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servletRequest.setContextPath("/context");
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ServerRequest request = ServerRequest.create(servletRequest, Collections.emptyList());
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ServerRequest stripped = BeforeFilterFunctions.stripContextPath().apply(request);
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ServerRequest modified = BeforeFilterFunctions.rewritePath("/service/(?<remaining>.*)", "/${remaining}")
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.apply(stripped);
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assertThat(modified.uri().getRawPath()).isEqualTo("/path");
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}
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@Test
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void prefixPathWithContextPath() {
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MockHttpServletRequest servletRequest = MockMvcRequestBuilders.get("http://localhost/context/get")
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.buildRequest(null);
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servletRequest.setContextPath("/context");
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ServerRequest request = ServerRequest.create(servletRequest, Collections.emptyList());
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ServerRequest stripped = BeforeFilterFunctions.stripContextPath().apply(request);
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ServerRequest modified = BeforeFilterFunctions.prefixPath("/prefix").apply(stripped);
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assertThat(modified.uri().getRawPath()).isEqualTo("/prefix/get");
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}
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@Test
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void stripPrefixWithEncodedPath() {
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MockHttpServletRequest servletRequest = MockMvcRequestBuilders.get("http://localhost/depth1/depth2/depth3/é")

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