spring-cloud-gateway啟動踩坑及解決
本人使用的版本是2.1.2,以下只記錄幾個小問題，但確實實實在在的把個人惡心的要死要活的找不到辦法，幾經掙扎，最終解決。
更可恨的是開發的過程中，沒有出現異常，后來由于項目組其它人加了依賴，不知不覺對項目的兼容造成了英雄，真的是被撞的頭破血流，才找到原因
1、webflux與mvc不兼容如類路徑中引用了webmvc會導致項目啟動不起來
異常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.
異常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)}
解決辦法，找到依賴webmvc的jar包，將webmvc排除即可，如
<dependency> <groupId>${project.groupId}</groupId> <artifactId>core</artifactId> <version>${project.version}</version> <exclusions><!-- 1. webflux與webmvc不兼容，否則會項目啟動不起來--><exclusion> <groupId>org.springframework</groupId> <artifactId>spring-webmvc</artifactId></exclusion></dependency>2、webflux使用netty作為容器
不能使用tomcat，表現形式為網關工作轉發正常，目標服務返回數據也正常，但是網關會無法解析返回的數據并最終由網關將數據返回給客戶端
java.lang.ClassCastException: org.springframework.core.io.buffer.DefaultDataBufferFactory cannot be cast to org.springframework.core.io.buffer.NettyDataBufferFactory
解決辦法
https://github.com/spring-cloud/spring-cloud-gateway/issues/145
找到將tomcat依賴進來的jar包，然后排除即可。需要注意的是，要看清楚自己項目依賴的tomcat具體的maven坐標。
然后排除即可
<dependency> <groupId>${project.groupId}</groupId> <artifactId>core</artifactId> <version>${project.version}</version> <exclusions> <!-- 1. webflux與webmvc不兼容，否則會項目啟動不起來 2. webflux使用Netty作為容器，如果使用tomcat，接口轉發正常，但是會導致服務間的數據無法解析 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、后來實驗了下
關于1webflux和mvc不兼容項目啟動不起來的異常，如果項目中存在了tomcat的用來，則拋出的異常是
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.
而如果沒有依賴tomcat則拋出的異常是
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 異常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
這個異常是因為spring cloud gateway 是webflux 項目，引了含有web-starter得項目就會出現沖突。因為Hystrix-dashboard中含有web-starter，所以出現沖突。
以上為個人經驗，希望能給大家一個參考，也希望大家多多支持好吧啦網。
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