Allow stripPrefix to be less strict about contextPaths

.gitignore

@@ -21,3 +21,4 @@ _site/
 *.swo
 .vscode/
 .flattened-pom.xml
+.devcontainer/

spring-cloud-gateway-server/src/main/java/org/springframework/cloud/gateway/filter/factory/StripPrefixGatewayFilterFactory.java

@@ -79,8 +79,11 @@ public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
 					newPath.append('/');
 				}
 
-				ServerHttpRequest newRequest = request.mutate().path(newPath.toString()).build();
-
+				ServerHttpRequest.Builder requestBuilder = request.mutate().path(newPath.toString());
+				if (!(config.getEnforceContextPath())) {
+					requestBuilder.contextPath(null);
+				}
+				ServerHttpRequest newRequest = requestBuilder.build();
 				exchange.getAttributes().put(GATEWAY_REQUEST_URL_ATTR, newRequest.getURI());
 
 				return chain.filter(exchange.mutate().request(newRequest).build());
@@ -89,7 +92,7 @@ public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
 			@Override
 			public String toString() {
 				return filterToStringCreator(StripPrefixGatewayFilterFactory.this).append("parts", config.getParts())
-						.toString();
+						.append("enforeContextPath", config.getEnforceContextPath()).toString();
 			}
 		};
 	}
@@ -98,6 +101,8 @@ public static class Config {
 
 		private int parts = 1;
 
+		private boolean enforceContextPath = true;
+
 		public int getParts() {
 			return parts;
 		}
@@ -106,6 +111,14 @@ public void setParts(int parts) {
 			this.parts = parts;
 		}
 
+		public boolean getEnforceContextPath() {
+			return enforceContextPath;
+		}
+
+		public void setEnforceContextPath(boolean enforceContextPath) {
+			this.enforceContextPath = enforceContextPath;
+		}
+
 	}
 
 }

spring-cloud-gateway-server/src/main/java/org/springframework/cloud/gateway/route/builder/GatewayFilterSpec.java

@@ -742,6 +742,20 @@ public GatewayFilterSpec stripPrefix(int parts) {
 		return filter(getBean(StripPrefixGatewayFilterFactory.class).apply(c -> c.setParts(parts)));
 	}
 
+	/**
+	 * Strips the prefix from the path of the request before it is routed by the Gateway.
+	 * @param parts the number of parts of the path to remove
+	 * @param enforeContextPath whether the resulting path must contain the context-path
+	 * defined for the application
+	 * @return a {@link GatewayFilterSpec} that can be used to apply additional filters
+	 */
+	public GatewayFilterSpec stripPrefix(int parts, boolean enforceContextPath) {
+		return filter(getBean(StripPrefixGatewayFilterFactory.class).apply(c -> {
+			c.setParts(parts);
+			c.setEnforceContextPath(enforceContextPath);
+		}));
+	}
+
 	/**
 	 * A filter which changes the URI the request will be routed to by the Gateway by
 	 * pulling it from a header on the request.