为啥spring webflux默认选择jetty然后失败？

Posted 2023-02-27

【中文标题】为啥spring webflux默认选择jetty然后失败？

【英文标题】：Why spring webflux is choosing jetty by default and then failing?为什么spring webflux默认选择jetty然后失败？

【发布时间】：2018-05-24 13:38:50

【问题描述】：

我正在尝试运行基于 Spring boot 2.0.0.M7 的应用程序。

这是我在 build.gradle 中与 spring 相关的依赖项：

compile "org.springframework.boot:spring-boot-starter-webflux:2.0.0.M7"
compile "org.springframework.boot:spring-boot-starter-data-ldap:2.0.0.M7"
compile "org.springframework.boot:spring-boot-starter-actuator:2.0.0.M7"

根据自动配置报告，是否有可能告诉为什么 spring 默认要使用 Jetty 作为响应式引擎（实际上，根据 spring 文档，reactor Netty 是默认引擎）

spring boot 自动配置报告（摘录）：

ReactiveWebServerConfiguration.ReactorNettyAutoConfiguration:
  Did not match:
     - @ConditionalOnMissingBean (types: org.springframework.boot.web.reactive.server.ReactiveWebServerFactory; SearchStrategy: all) found beans of type'org.springframework.boot.web.reactive.server.ReactiveWebServerFactory'jettyReactiveWebServerFactory (OnBeanCondition)
  Matched:
     - @ConditionalOnClass found required class 'reactor.ipc.netty.http.server.HttpServer'; @ConditionalOnMissingClass did not find unwanted class (OnClassCondition)

ReactiveWebServerAutoConfiguration#defaultReactiveWebServerCustomizer matched:
      - @ConditionalOnMissingBean (types: org.springframework.boot.autoconfigure.web.reactive.DefaultReactiveWebServerCustomizer; SearchStrategy: all) did not find any beans (OnBeanCondition)

   ReactiveWebServerConfiguration.JettyAutoConfiguration matched:
      - @ConditionalOnClass found required class 'org.eclipse.jetty.server.Server'; @ConditionalOnMissingClass did not find unwanted class (OnClassCondition)
      - @ConditionalOnMissingBean (types: org.springframework.boot.web.reactive.server.ReactiveWebServerFactory; SearchStrategy: all) did not find any beans (OnBeanCondition)

我在应用程序启动期间遇到的异常：

[0;39morg.springframework.context.ApplicationContextException: Unable to start reactive web server; nested exception is java.lang.NoClassDefFoundError: org/eclipse/jetty/servlet/ServletHolder
    at org.springframework.boot.web.reactive.context.ReactiveWebServerApplicationContext.onRefresh(ReactiveWebServerApplicationContext.java:64)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:543)
    at org.springframework.boot.web.reactive.context.ReactiveWebServerApplicationContext.refresh(ReactiveWebServerApplicationContext.java:49)
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:750)
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:386)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:327)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1245)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1233)
    at com.xyz.abc.routing.web.ApiApplication.main(ApiApplication.java:14)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.springframework.boot.loader.MainMethodRunner.run(MainMethodRunner.java:48)
    at org.springframework.boot.loader.Launcher.launch(Launcher.java:87)
    at org.springframework.boot.loader.Launcher.launch(Launcher.java:50)
    at org.springframework.boot.loader.JarLauncher.main(JarLauncher.java:51)
Caused by: java.lang.NoClassDefFoundError: org/eclipse/jetty/servlet/ServletHolder
    at org.springframework.boot.web.embedded.jetty.JettyReactiveWebServerFactory.createJettyServer(JettyReactiveWebServerFactory.java:96)
    at org.springframework.boot.web.embedded.jetty.JettyReactiveWebServerFactory.getWebServer(JettyReactiveWebServerFactory.java:87)
    at org.springframework.boot.web.reactive.context.ReactiveWebServerApplicationContext.createWebServer(ReactiveWebServerApplicationContext.java:87)
    at org.springframework.boot.web.reactive.context.ReactiveWebServerApplicationContext.onRefresh(ReactiveWebServerApplicationContext.java:61)
    ... 16 common frames omitted
Caused by: java.lang.ClassNotFoundException: org.eclipse.jetty.servlet.ServletHolder
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at org.springframework.boot.loader.LaunchedURLClassLoader.loadClass(LaunchedURLClassLoader.java:93)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    ... 20 common frames omitted

如何让 Spring 使用 reactor netty？

【问题讨论】：

如果您查看报告是使用Netty 匹配的规则。您的依赖项列表中有一些东西正在添加 Jetty。运行 gradle dependencies 以查看 Jetty 中的内容。

【参考方案1】：

正如 Marten 所提到的，检查您的依赖项以获取 Jetty Server 依赖项。 Spring Boot 正在寻找 org.eclipse.jetty.server.Server 类作为您选择 Jetty 作为服务器的信号。

试试./gradlew dependencies，看看这个依赖来自哪里。

【讨论】：

如果一个依赖需要 Jetty 来运行自己的功能，没有办法告诉 spring 仍然使用 netty？