spring-cloud-gateway启动踩坑及解决
本人使用的版本是2.1.2,以下只记录几个小问题，但确实实实在在的把个人恶心的要死要活的找不到办法，几经挣扎，最终解决。
更可恨的是开发的过程中，没有出现异常，后来由于项目组其它人加了依赖，不知不觉对项目的兼容造成了英雄，真的是被撞的头破血流，才找到原因
1、webflux与mvc不兼容如类路径中引用了webmvc会导致项目启动不起来
异常1
org.springframework.context.ApplicationContextException: Unable to start web server; nested exception is org.springframework.context.ApplicationContextException: Unable to start ServletWebServerApplicationContext due to missing ServletWebServerFactory bean.
异常2
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type ’org.springframework.core.convert.ConversionService’ available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Qualifier(value=webFluxConversionService)}
解决办法，找到依赖webmvc的jar包，将webmvc排除即可，如
<dependency> <groupId>${project.groupId}</groupId> <artifactId>core</artifactId> <version>${project.version}</version> <exclusions><!-- 1. webflux与webmvc不兼容，否则会项目启动不起来--><exclusion> <groupId>org.springframework</groupId> <artifactId>spring-webmvc</artifactId></exclusion></dependency>2、webflux使用netty作为容器
不能使用tomcat，表现形式为网关工作转发正常，目标服务返回数据也正常，但是网关会无法解析返回的数据并最终由网关将数据返回给客户端
java.lang.ClassCastException: org.springframework.core.io.buffer.DefaultDataBufferFactory cannot be cast to org.springframework.core.io.buffer.NettyDataBufferFactory
解决办法
https://github.com/spring-cloud/spring-cloud-gateway/issues/145
找到将tomcat依赖进来的jar包，然后排除即可。需要注意的是，要看清楚自己项目依赖的tomcat具体的maven坐标。
然后排除即可
<dependency> <groupId>${project.groupId}</groupId> <artifactId>core</artifactId> <version>${project.version}</version> <exclusions> <!-- 1. webflux与webmvc不兼容，否则会项目启动不起来 2. webflux使用Netty作为容器，如果使用tomcat，接口转发正常，但是会导致服务间的数据无法解析 java.lang.ClassCastException: org.springframework.core.io.buffer.DefaultDataBufferFactory cannot be cast to org.springframework.core.io.buffer.NettyDataBufferFactory --> <exclusion> <groupId>org.springframework</groupId> <artifactId>spring-webmvc</artifactId> </exclusion> <exclusion> <groupId>org.springframework.bootk</groupId> <artifactId>spring-boot-starter-tomcat</artifactId> </exclusion> <exclusion> <groupId>org.apache.tomcat.embed</groupId> <artifactId>tomcat-embed-core</artifactId> </exclusion> <exclusion> <groupId>org.apache.tomcat.embed</groupId> <artifactId>tomcat-embed-el</artifactId> </exclusion> <exclusion> <groupId>org.apache.tomcat.embed</groupId> <artifactId>tomcat-embed-websocket</artifactId> </exclusion> </exclusions></dependency>3、后来实验了下
关于1webflux和mvc不兼容项目启动不起来的异常，如果项目中存在了tomcat的用来，则抛出的异常是
org.springframework.context.ApplicationContextException: Unable to start web server; nested exception is org.springframework.context.ApplicationContextException: Unable to start ServletWebServerApplicationContext due to missing ServletWebServerFactory bean.
而如果没有依赖tomcat则抛出的异常是
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type ’org.springframework.core.convert.ConversionService’ available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Qualifier(value=webFluxConversionService)}
很坑得spring cloud gateway 异常Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type ’org.springframework.core.convert.ConversionService’ available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Qualifier(value=webFluxConversionService)}at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoMatchingBeanFound(DefaultListableBeanFactory.java:1655) ~[spring-beans-5.1.7.RELEASE.jar:5.1.7.RELEASE]at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1214) ~[spring-beans-5.1.7.RELEASE.jar:5.1.7.RELEASE]at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1168) ~[spring-beans-5.1.7.RELEASE.jar:5.1.7.RELEASE]at org.springframework.beans.factory.support.ConstructorResolver.resolveAutowiredArgument(ConstructorResolver.java:857) ~[spring-beans-5.1.7.RELEASE.jar:5.1.7.RELEASE]at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:760) ~[spring-beans-5.1.7.RELEASE.jar:5.1.7.RELEASE]... 101 common frames omitted
这个异常是因为spring cloud gateway 是webflux 项目，引了含有web-starter得项目就会出现冲突。因为Hystrix-dashboard中含有web-starter，所以出现冲突。
以上为个人经验，希望能给大家一个参考，也希望大家多多支持好吧啦网。
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