Immutable DefaultWebFilterChain

Issue: SPR-15517

spring-web/src/main/java/org/springframework/web/server/handler/DefaultWebFilterChain.java

@@ -40,21 +40,38 @@ public class DefaultWebFilterChain implements WebFilterChain {
 
 	private final WebHandler handler;
 
-	private volatile int index;
+	private final int index;
 
 
 	public DefaultWebFilterChain(WebHandler handler, WebFilter... filters) {
 		Assert.notNull(handler, "WebHandler is required");
 		this.filters = ObjectUtils.isEmpty(filters) ? Collections.emptyList() : Arrays.asList(filters);
 		this.handler = handler;
+		this.index = 0;
+	}
+
+	private DefaultWebFilterChain(DefaultWebFilterChain parent, int index) {
+		this.filters = parent.getFilters();
+		this.handler = parent.getHandler();
+		this.index = index;
+	}
+
+
+	public List<WebFilter> getFilters() {
+		return this.filters;
+	}
+
+	public WebHandler getHandler() {
+		return this.handler;
 	}
 
 
 	@Override
 	public Mono<Void> filter(ServerWebExchange exchange) {
 		if (this.index < this.filters.size()) {
-			WebFilter filter = this.filters.get(this.index++);
-			return filter.filter(exchange, this);
+			WebFilter filter = this.filters.get(this.index);
+			WebFilterChain chain = new DefaultWebFilterChain(this, this.index + 1);
+			return filter.filter(exchange, chain);
 		}
 		else {
 			return this.handler.handle(exchange);