Added methods to add filter relatively in ServerHttpSecurity

Addition of two new methods addFilterBefore and addFilterAfter in
ServerHttpSecurity to allow addition of WebFilter before and after of
specified order

Fixes: gh-6138

Author: ankurpathak

config/src/main/java/org/springframework/security/config/web/server/ServerHttpSecurity.java

@@ -288,6 +288,32 @@ public ServerHttpSecurity addFilterAt(WebFilter webFilter, SecurityWebFiltersOrd
 		return this;
 	}
 
+	/**
+	 * Adds a {@link WebFilter} before specific position.
+	 * @param webFilter the {@link WebFilter} to add
+	 * @param order the place before which to insert the {@link WebFilter}
+	 * @return the {@link ServerHttpSecurity} to continue configuring
+	 * @since 5.2.0
+	 * @author Ankur Pathak
+	 */
+	public ServerHttpSecurity addFilterBefore(WebFilter webFilter, SecurityWebFiltersOrder order) {
+		this.webFilters.add(new OrderedWebFilter(webFilter, order.getOrder() - 1));
+		return this;
+	}
+
+	/**
+	 * Adds a {@link WebFilter} after specific position.
+	 * @param webFilter the {@link WebFilter} to add
+	 * @param order the place after which to insert the {@link WebFilter}
+	 * @return the {@link ServerHttpSecurity} to continue configuring
+	 * @since 5.2.0
+	 * @author Ankur Pathak
+	 */
+	public ServerHttpSecurity addFilterAfter(WebFilter webFilter, SecurityWebFiltersOrder order) {
+		this.webFilters.add(new OrderedWebFilter(webFilter, order.getOrder() + 1));
+		return this;
+	}
+
 	/**
 	 * Gets the ServerExchangeMatcher that determines which requests apply to this HttpSecurity instance.
 	 * @return the ServerExchangeMatcher that determines which requests apply to this HttpSecurity instance.

config/src/test/java/org/springframework/security/config/web/server/ServerHttpSecurityTests.java

@@ -34,6 +34,8 @@
 import org.mockito.Mock;
 import org.mockito.junit.MockitoJUnitRunner;
 
+import org.springframework.security.web.server.context.SecurityContextServerWebExchangeWebFilter;
+import org.springframework.web.server.WebFilterChain;
 import reactor.core.publisher.Mono;
 import reactor.test.publisher.TestPublisher;
 
@@ -190,6 +192,30 @@ public void csrfServerLogoutHandlerAppliedIfCsrfIsEnabled() {
 				.isEqualTo(Arrays.asList(SecurityContextServerLogoutHandler.class, CsrfServerLogoutHandler.class));
 	}
 
+	@Test
+	@SuppressWarnings("unchecked")
+	public void addFilterAfterIsApplied(){
+		SecurityWebFilterChain securityWebFilterChain =  this.http.addFilterAfter(new TestWebFilter(), SecurityWebFiltersOrder.SECURITY_CONTEXT_SERVER_WEB_EXCHANGE).build();
+		List filters = securityWebFilterChain.getWebFilters().map(WebFilter::getClass).collectList().block();
+
+		assertThat(filters).isNotNull()
+				.isNotEmpty()
+				.containsSequence(SecurityContextServerWebExchangeWebFilter.class, TestWebFilter.class);
+
+	}
+
+	@Test
+	@SuppressWarnings("unchecked")
+	public void addFilterBeforeIsApplied(){
+		SecurityWebFilterChain securityWebFilterChain =  this.http.addFilterBefore(new TestWebFilter(), SecurityWebFiltersOrder.SECURITY_CONTEXT_SERVER_WEB_EXCHANGE).build();
+		List filters = securityWebFilterChain.getWebFilters().map(WebFilter::getClass).collectList().block();
+
+		assertThat(filters).isNotNull()
+				.isNotEmpty()
+				.containsSequence(TestWebFilter.class, SecurityContextServerWebExchangeWebFilter.class);
+
+	}
+
 	private <T extends WebFilter> Optional<T> getWebFilter(SecurityWebFilterChain filterChain, Class<T> filterClass) {
 		return (Optional<T>) filterChain.getWebFilters()
 				.filter(Objects::nonNull)
@@ -214,4 +240,12 @@ Mono<String> pathWithinApplicationFromContext() {
 				.map(e -> e.getRequest().getPath().pathWithinApplication().value());
 		}
 	}
+
+	private static class TestWebFilter implements WebFilter {
+
+		@Override
+		public Mono<Void> filter(ServerWebExchange exchange, WebFilterChain chain) {
+			return chain.filter(exchange);
+		}
+	}
 }