Spring Cloud Gateway not starting when deployed as WAR showing webFluxConversionService error - spring

Question

I'm trying to do a sample with Spring Cloud Gateway for JWT authentication and URL routing purpose.
All is running well when i run as a JAVA application or using Embedded Tomcat Container but when the same is deployed to a Tomcat server as a War, then i ge the below dependency injection error.
APPLICATION FAILED TO START
Description:
Parameter 4 of method routeDefinitionRouteLocator in org.springframework.cloud.gateway.config.GatewayAutoConfiguration required a bean of type 'org.springframework.core.convert.ConversionService' that could not be found.
The injection point has the following annotations:
- #org.springframework.beans.factory.annotation.Qualifier(value=webFluxConversionService)
Action:
Consider defining a bean of type 'org.springframework.core.convert.ConversionService' in your configuration.
I have tried adding jars related to spring web flux but the error did not go
my POM.XML
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.6.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.gateway</groupId>
<artifactId>gateway</artifactId>
<version>1.0</version>
<packaging>war</packaging>
<name>gateway</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>1.8</java.version>
<spring-cloud.version>Greenwich.SR2</spring-cloud.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
</dependency>
<dependency>
<groupId>io.jsonwebtoken</groupId>
<artifactId>jjwt</artifactId>
<version>0.9.1</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-jdbc</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-gateway</artifactId>
</dependency>
<!-- https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-starter-tomcat -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-tomcat</artifactId>
<scope>provided</scope>
</dependency>
<!-- https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-starter-webflux -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-webflux</artifactId>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<!-- https://mvnrepository.com/artifact/org.springframework/spring-web-reactive -->
</dependencies>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-dependencies</artifactId>
<version>${spring-cloud.version}</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
<build>
<finalName>mxgateway</finalName>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
<plugin> <artifactId>maven-war-plugin</artifactId>
<configuration> <outputDirectory>E:/apache-tomcat-9.0.22/webapps</outputDirectory>
</configuration> </plugin>
</plugins>
</build>
</project>
The gateway configuration is
package com.gateway.gateway;
import java.util.ArrayList;
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.boot.web.servlet.support.SpringBootServletInitializer;
import org.springframework.cloud.gateway.route.RouteLocator;
import org.springframework.cloud.gateway.route.builder.RouteLocatorBuilder;
import org.springframework.cloud.gateway.route.builder.RouteLocatorBuilder.Builder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import com.gateway.gateway.bean.ProgramRouteDetail;
import com.gateway.gateway.security.CustomGatewayFilter;
#SpringBootApplication
#Configuration
public class GatewayApplication extends SpringBootServletInitializer{
#Autowired
CustomGatewayFilter customGatewayFilter;
public static void main(String[] args) {
SpringApplication.run(GatewayApplication.class, args);
}
public List<ProgramRouteDetail> filterRequest(){
List<ProgramRouteDetail> programRouteDetails = new ArrayList<ProgramRouteDetail>();
for(int i =0;i<=2;i++){
ProgramRouteDetail detail = new ProgramRouteDetail();
detail.setDestUri("http://localhost:9090");
detail.setProgramId("users");
detail.setPath("/user/**");
programRouteDetails.add(detail);
}
return programRouteDetails;
}
#Override
protected SpringApplicationBuilder configure(
SpringApplicationBuilder builder) {
return builder.sources(GatewayApplication.class);
}
public RouteLocator constructRouteAndFilters(RouteLocatorBuilder builder ){
Builder routes = builder.routes();
List<ProgramRouteDetail> programRouteDetails = filterRequest();
for(ProgramRouteDetail programDetail : programRouteDetails){
routes.route(p -> p.path(programDetail.getPath()).filters(f->f.filter(customGatewayFilter)).uri(programDetail.getDestUri()));
}
return routes.build();
}
#Bean
public RouteLocator myRoutes(RouteLocatorBuilder builder) {
return constructRouteAndFilters(builder);
}
}

Answer 1

Spring Cloud Gateway does not support WAR deployments. It is based on Spring Webflux and Spring Boot does not support war deployments of webflux.
From the documentation:
Because Spring WebFlux does not strictly depend on the Servlet API and
applications are deployed by default on an embedded Reactor Netty
server, War deployment is not supported for WebFlux applications.