spring-cloud-gateway启动踩坑及解决

spring-cloud-gateway启动踩坑

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

  ${project.groupId}core${project.version}  org.springframeworkspring-webmvc

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

  ${project.groupId}core${project.version}  org.springframeworkspring-webmvc org.springframework.bootkspring-boot-starter-tomcat org.apache.tomcat.embedtomcat-embed-core org.apache.tomcat.embedtomcat-embed-el org.apache.tomcat.embedtomcat-embed-websocket

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。