[BAEL-3313] spring-cloud/spring-cloud-gateway | Writing custom Spring Cloud Gateway Filters -- address comments (#8251)

* Addressed comments:
* Removed Global filter bean with @Order annotation, now using class that implements Ordered
* Added logic to actually mutate the request entity (and the exchange) for the Modify Request example
* changed endpoint for languageServiceEndpoint in the chain requests example

* removed order from first simple global filter, since well be covering that with other global filter

spring-cloud/spring-cloud-gateway/src/main/java/com/baeldung/springcloudgateway/customfilters/filters/factories/ChainRequestGatewayFilterFactory.java

@@ -28,14 +28,14 @@ public class ChainRequestGatewayFilterFactory extends AbstractGatewayFilterFacto
 
     @Override
     public List<String> shortcutFieldOrder() {
-        return Arrays.asList("endpoint", "defaultLanguage");
+        return Arrays.asList("languageServiceEndpoint", "defaultLanguage");
     }
 
     @Override
     public GatewayFilter apply(Config config) {
         return (exchange, chain) -> {
             return client.get()
-                .uri(config.getEndpoint())
+                .uri(config.getLanguageServiceEndpoint())
                 .exchange()
                 .flatMap(response -> {
                     return (response.statusCode()
@@ -45,8 +45,7 @@ public class ChainRequestGatewayFilterFactory extends AbstractGatewayFilterFacto
                 .map(range -> {
                     exchange.getRequest()
                         .mutate()
-                        .headers(h -> h.setAcceptLanguage(range))
+                        .headers(h -> h.setAcceptLanguage(range));
-                        .build();
 
                     String allOutgoingRequestLanguages = exchange.getRequest()
                         .getHeaders()
@@ -65,18 +64,18 @@ public class ChainRequestGatewayFilterFactory extends AbstractGatewayFilterFacto
     }
 
     public static class Config {
-        private String endpoint;
+        private String languageServiceEndpoint;
         private String defaultLanguage;
 
         public Config() {
         }
 
-        public String getEndpoint() {
+        public String getLanguageServiceEndpoint() {
-            return endpoint;
+            return languageServiceEndpoint;
         }
 
-        public void setEndpoint(String endpoint) {
+        public void setLanguageServiceEndpoint(String languageServiceEndpoint) {
-            this.endpoint = endpoint;
+            this.languageServiceEndpoint = languageServiceEndpoint;
         }
 
         public String getDefaultLanguage() {

spring-cloud/spring-cloud-gateway/src/main/java/com/baeldung/springcloudgateway/customfilters/filters/factories/LoggingGatewayFilterFactory.java

@@ -40,7 +40,7 @@ public class LoggingGatewayFilterFactory extends AbstractGatewayFilterFactory<Lo
                     if (config.isPostLogger())
                         logger.info("Post GatewayFilter logging: " + config.getBaseMessage());
                 }));
-        }, -2);
+        }, 1);
     }
 
     public static class Config {

spring-cloud/spring-cloud-gateway/src/main/java/com/baeldung/springcloudgateway/customfilters/filters/factories/ModifyRequestGatewayFilterFactory.java

@@ -12,6 +12,9 @@ import org.slf4j.LoggerFactory;
 import org.springframework.cloud.gateway.filter.GatewayFilter;
 import org.springframework.cloud.gateway.filter.factory.AbstractGatewayFilterFactory;
 import org.springframework.stereotype.Component;
+import org.springframework.util.LinkedMultiValueMap;
+import org.springframework.web.server.ServerWebExchange;
+import org.springframework.web.util.UriComponentsBuilder;
 
 @Component
 public class ModifyRequestGatewayFilterFactory extends AbstractGatewayFilterFactory<ModifyRequestGatewayFilterFactory.Config> {
@@ -45,8 +48,7 @@ public class ModifyRequestGatewayFilterFactory extends AbstractGatewayFilterFact
 
                 exchange.getRequest()
                     .mutate()
-                    .headers(h -> h.setAcceptLanguageAsLocales(Collections.singletonList(requestLocale)))
+                    .headers(h -> h.setAcceptLanguageAsLocales(Collections.singletonList(requestLocale)));
-                    .build();
             }
 
             String allOutgoingRequestLanguages = exchange.getRequest()
@@ -56,8 +58,20 @@ public class ModifyRequestGatewayFilterFactory extends AbstractGatewayFilterFact
                 .map(range -> range.getRange())
                 .collect(Collectors.joining(","));
 
-            logger.info("Modify Request output - Request contains Accept-Language header: " + allOutgoingRequestLanguages);
+            logger.info("Modify request output - Request contains Accept-Language header: {}", allOutgoingRequestLanguages);
-            return chain.filter(exchange);
+
+            ServerWebExchange modifiedExchange = exchange.mutate()
+                .request(originalRequest -> originalRequest.uri(UriComponentsBuilder.fromUri(exchange.getRequest()
+                    .getURI())
+                    .replaceQueryParams(new LinkedMultiValueMap<String, String>())
+                    .build()
+                    .toUri()))
+                .build();
+
+            logger.info("Removed all query params: {}", modifiedExchange.getRequest()
+                .getURI());
+
+            return chain.filter(modifiedExchange);
         };
     }
 

spring-cloud/spring-cloud-gateway/src/main/java/com/baeldung/springcloudgateway/customfilters/filters/global/FirstPreLastPostGlobalFilter.java

@@ -0,0 +1,31 @@
+package com.baeldung.springcloudgateway.customfilters.filters.global;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.cloud.gateway.filter.GatewayFilterChain;
+import org.springframework.cloud.gateway.filter.GlobalFilter;
+import org.springframework.core.Ordered;
+import org.springframework.stereotype.Component;
+import org.springframework.web.server.ServerWebExchange;
+
+import reactor.core.publisher.Mono;
+
+@Component
+public class FirstPreLastPostGlobalFilter implements GlobalFilter, Ordered {
+
+    final Logger logger = LoggerFactory.getLogger(FirstPreLastPostGlobalFilter.class);
+
+    @Override
+    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
+        logger.info("First Pre Global Filter");
+        return chain.filter(exchange)
+            .then(Mono.fromRunnable(() -> {
+                logger.info("Last Post Global Filter");
+            }));
+    }
+
+    @Override
+    public int getOrder() {
+        return -1;
+    }
+}

spring-cloud/spring-cloud-gateway/src/main/java/com/baeldung/springcloudgateway/customfilters/filters/global/LoggingGlobalFiltersConfigurations.java

@@ -5,7 +5,6 @@ import org.slf4j.LoggerFactory;
 import org.springframework.cloud.gateway.filter.GlobalFilter;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
-import org.springframework.core.annotation.Order;
 
 import reactor.core.publisher.Mono;
 
@@ -23,17 +22,4 @@ public class LoggingGlobalFiltersConfigurations {
                 }));
         };
     }
-
-    @Bean
-    @Order(-1)
-    public GlobalFilter FirstPreLastPostGlobalFilter() {
-        return (exchange, chain) -> {
-            logger.info("First Pre Global Filter");
-            return chain.filter(exchange)
-                .then(Mono.fromRunnable(() -> {
-                    logger.info("Last Post Global Filter");
-                }));
-        };
-    }
-
 }

spring-cloud/spring-cloud-gateway/src/main/java/com/baeldung/springcloudgateway/customfilters/filters/global/LoggingGlobalPreFilter.java

@@ -4,14 +4,13 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.cloud.gateway.filter.GatewayFilterChain;
 import org.springframework.cloud.gateway.filter.GlobalFilter;
-import org.springframework.core.Ordered;
 import org.springframework.stereotype.Component;
 import org.springframework.web.server.ServerWebExchange;
 
 import reactor.core.publisher.Mono;
 
 @Component
-public class LoggingGlobalPreFilter implements GlobalFilter, Ordered {
+public class LoggingGlobalPreFilter implements GlobalFilter {
 
     final Logger logger = LoggerFactory.getLogger(LoggingGlobalPreFilter.class);
 
@@ -20,9 +19,4 @@ public class LoggingGlobalPreFilter implements GlobalFilter, Ordered {
         logger.info("Global Pre Filter executed");
         return chain.filter(exchange);
     }
-
-    @Override
-    public int getOrder() {
-        return 0;
-    }
 }

spring-cloud/spring-cloud-gateway/src/main/resources/customfilters-global-application.properties

@@ -9,8 +9,8 @@ spring.cloud.gateway.routes[0].filters[1]=Logging=My Custom Message, true, true
 #spring.cloud.gateway.routes[0].filters[1].args[preLogger]=true
 #spring.cloud.gateway.routes[0].filters[1].args[postLogger]=true
 
-spring.cloud.gateway.routes[0].filters[2]=ModifyRequest=en
+spring.cloud.gateway.routes[0].filters[2]=ModifyResponse
-spring.cloud.gateway.routes[0].filters[3]=ModifyResponse
+spring.cloud.gateway.routes[0].filters[3]=ModifyRequest=en
 spring.cloud.gateway.routes[0].filters[4]=ChainRequest=http://localhost:8082/resource/language, fr
 
 management.endpoints.web.exposure.include=*

spring-cloud/spring-cloud-gateway/src/test/java/com/baeldung/springcloudgateway/customfilters/CustomFiltersLiveTest.java

@@ -45,6 +45,8 @@ public class CustomFiltersLiveTest {
 
         response.expectStatus()
             .isOk()
+            .expectHeader()
+            .doesNotExist("Bael-Custom-Language-Header")
             .expectBody(String.class)
             .isEqualTo("Service Resource");
 
@@ -60,7 +62,8 @@ public class CustomFiltersLiveTest {
             .haveAtLeastOne(eventContains("Pre GatewayFilter logging: My Custom Message"))
             .haveAtLeastOne(eventContains("Post GatewayFilter logging: My Custom Message"))
             // Modify Request
-            .haveAtLeastOne(eventContains("Modify Request output - Request contains Accept-Language header:"))
+            .haveAtLeastOne(eventContains("Modify request output - Request contains Accept-Language header:"))
+            .haveAtLeastOne(eventContainsExcept("Removed all query params: ", "locale"))
             // Modify Response
             .areNot(eventContains("Added custom header to Response"))
             // Chain Request
@@ -75,16 +78,33 @@ public class CustomFiltersLiveTest {
 
         response.expectStatus()
             .isOk()
+            .expectHeader()
+            .exists("Bael-Custom-Language-Header")
             .expectBody(String.class)
             .isEqualTo("Service Resource");
 
         assertThat(LoggerListAppender.getEvents())
             // Modify Response
-            .haveAtLeastOne(eventContains("Added custom header to Response"));
+            .haveAtLeastOne(eventContains("Added custom header to Response"))
+            .haveAtLeastOne(eventContainsExcept("Removed all query params: ", "locale"));
     }
 
+    /**
+     * This condition will be successful if the event contains a substring
+     */
     private Condition<ILoggingEvent> eventContains(String substring) {
         return new Condition<ILoggingEvent>(entry -> (substring == null || (entry.getFormattedMessage() != null && entry.getFormattedMessage()
             .contains(substring))), String.format("entry with message '%s'", substring));
     }
+
+    /**
+     * This condition will be successful if the event contains a substring, but not another one
+     */
+    private Condition<ILoggingEvent> eventContainsExcept(String substring, String except) {
+        return new Condition<ILoggingEvent>(entry -> (substring == null || (entry.getFormattedMessage() != null && entry.getFormattedMessage()
+            .contains(substring)
+            && !entry.getFormattedMessage()
+                .contains(except))),
+            String.format("entry with message '%s'", substring));
+    }
 }