记一次难产的spring boot之hello world!

开始一次spring boot之旅，结果发现2分钟的demo硬是花半天时间才出来hello world！记录下中间的过程。

学习文档：https://docs.spring.io/spring-boot/docs/current/reference/htmlsingle/

本地环境jdkjdk1.8.0_65，新建一个maven项目，参看文中的pom文件，

<?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>

<groupId>com.qnvip</groupId>
<artifactId>demo</artifactId>
<version>0.0.1-SNAPSHOT</version>

<!-- Inherit defaults from Spring Boot -->
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.5.1.RELEASE</version>
</parent>

<!-- Add typical dependencies for a web application -->
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
</dependencies>

<!-- Package as an executable jar -->
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>

</project>

新建一个类

/**
* Hello world!
*
*/
@RestController
@EnableAutoConfiguration
public class App {

@RequestMapping("/")
String home() {
return "Hello World!";
}

public static void main(String[] args) throws Exception {
SpringApplication.run(App.class, args);
}
}

mvn spring-boot:run启动

结果报错

java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Tomcat].StandardHost[localhost].TomcatEmbeddedContext[]]
at java.util.concurrent.FutureTask.report(FutureTask.java:122) [na:1.8.0_65]
at java.util.concurrent.FutureTask.get(FutureTask.java:192) [na:1.8.0_65]
at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:939) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:872) [tomcat-embed-core-8.5.11.jar:8.5.11]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) [tomcat-embed-core-8.5.11.jar:8.5.11]
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1419) [tomcat-embed-core-8.5.11.jar:8.5.11]
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1409) [tomcat-embed-core-8.5.11.jar:8.5.11]
at java.util.concurrent.FutureTask.run(FutureTask.java:266) [na:1.8.0_65]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_65]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_65]
at java.lang.Thread.run(Thread.java:745) [na:1.8.0_65]
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Tomcat].StandardHost[localhost].TomcatEmbeddedContext[]]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:167) [tomcat-embed-core-8.5.11.jar:8.5.11]
... 6 common frames omitted
Caused by: org.apache.catalina.LifecycleException: Failed to start component [Pipeline[StandardEngine[Tomcat].StandardHost[localhost].TomcatEmbeddedContext[]]]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:167) [tomcat-embed-core-8.5.11.jar:8.5.11]
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5099) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) [tomcat-embed-core-8.5.11.jar:8.5.11]
... 6 common frames omitted
Caused by: org.apache.catalina.LifecycleException: Failed to start component [org.apache.catalina.authenticator.NonLoginAuthenticator[]]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:167) [tomcat-embed-core-8.5.11.jar:8.5.11]
at org.apache.catalina.core.StandardPipeline.startInternal(StandardPipeline.java:170) ~[tomcat-embed-core-8.5.11.jar:8.5.11]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) [tomcat-embed-core-8.5.11.jar:8.5.11]
... 8 common frames omitted
Caused by: java.lang.NoSuchMethodError: javax.servlet.ServletContext.getVirtualServerName()Ljava/lang/String;
at org.apache.catalina.authenticator.AuthenticatorBase.startInternal(AuthenticatorBase.java:1137) ~[tomcat-embed-core-8.5.11.jar:8.5.11]

没有javax.servlet.ServletContext.getVirtualServerName()这个方法，然后再看了下默认使用的tomcat/8.5.11，然后找到这个版本的tocmat，查看里面的servlet-api.jar，果然没有这个方法，那么指定一个tomcat版本，网上搜下最新版本为9.0.0.M17，果断在pom中添加指向这个版本

<properties>
<tomcat.version>9.0.0.M17</tomcat.version>
</properties>

现来mvn spring-boot:run

结果还是报错

[WARNING]
java.lang.reflect.InvocationTargetException
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:497)
at org.springframework.boot.maven.AbstractRunMojo$LaunchRunner.run(AbstractRunMojo.java:527)
at java.lang.Thread.run(Thread.java:745)
Caused by: org.springframework.context.ApplicationContextException: Unable to start embedded container; nested exception is java.lang.NoSuchMethodError: org.apache.catalina.Context.addServletMapping(Ljava/lang/String;Ljava/lang/String;)V
at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.onRefresh(EmbeddedWebApplicationContext.java:137)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:536)
at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:122)
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:737)
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:370)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:314)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1162)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1151)
at com.qnvip.demo.App.main(App.java:22)
... 6 more

查看mvn引入的jar，tomcat-embed-core-9.0.0.M17.jar 中确实没有这个方法，难道9太新了，要换8？！

换了tomcat/8.0.23试了下

又出了新的错误

java.lang.reflect.InvocationTargetException
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:497)
at org.springframework.boot.maven.AbstractRunMojo$LaunchRunner.run(AbstractRunMojo.java:527)
at java.lang.Thread.run(Thread.java:745)
Caused by: org.springframework.context.ApplicationContextException: Unable to start embedded container; nested exception is java.lang.NoClassDefFoundError: org/apache/juli/logging/LogFactory
at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.onRefresh(EmbeddedWebApplicationContext.java:137)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:536)
at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:122)
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:737)
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:370)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:314)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1162)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1151)
at com.qnvip.demo.App.main(App.java:22)
... 6 more

好吧，都到这里了，再引入tomcat-juli

<dependency>
<groupId>org.apache.tomcat</groupId>
<artifactId>tomcat-juli</artifactId>
<version>9.0.0.M17</version>
</dependency>

终于能启动了，但是不完美，中间过程报错

java.lang.NoSuchMethodError: javax.servlet.ServletContext.getVirtualServerName()Ljava/lang/String;
at org.apache.tomcat.websocket.server.WsServerContainer.<init>(WsServerContainer.java:147) ~[tomcat-embed-websocket-8.0.23.jar:8.0.23]
at org.apache.tomcat.websocket.server.WsSci.init(WsSci.java:131) ~[tomcat-embed-websocket-8.0.23.jar:8.0.23]
at org.apache.tomcat.websocket.server.WsContextListener.contextInitialized(WsContextListener.java:39) ~[tomcat-embed-websocket-8.0.23.jar:8.0.23]
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4729) [tomcat-embed-core-8.0.23.jar:8.0.23]
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5167) [tomcat-embed-core-8.0.23.jar:8.0.23]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) [tomcat-embed-core-8.0.23.jar:8.0.23]
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1409) [tomcat-embed-core-8.0.23.jar:8.0.23]
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1399) [tomcat-embed-core-8.0.23.jar:8.0.23]
at java.util.concurrent.FutureTask.run(FutureTask.java:266) [na:1.8.0_65]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_65]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_65]
at java.lang.Thread.run(Thread.java:745) [na:1.8.0_65]

2017-03-01 16:16:37.544 ERROR 14032 --- [ost-startStop-1] o.apache.catalina.core.StandardContext   : One or more listeners failed to start. Full details will be found in the appropriate container log file
2017-03-01 16:16:37.546 ERROR 14032 --- [ost-startStop-1] o.apache.catalina.core.StandardContext   : Context [] startup failed due to previous errors
2017-03-01 16:16:37.923  INFO 14032 --- [           main] s.w.s.m.m.a.RequestMappingHandlerAdapter : Looking for @ControllerAdvice: org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@4ecad335: startup date [Wed Mar 01 16:16:35 CST 2017]; root of context hierarchy
2017-03-01 16:16:38.031  INFO 14032 --- [           main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/]}" onto java.lang.String com.qnvip.demo.App.home()
2017-03-01 16:16:38.038  INFO 14032 --- [           main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error]}" onto public org.springframework.http.ResponseEntity<java.util.Map<java.lang.String, java.lang.Object>> org.springframework.boot.autoconfigure.web.BasicErrorController.error(javax.servlet.http.HttpServletRequest)
2017-03-01 16:16:38.041  INFO 14032 --- [           main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error],produces=[text/html]}" onto public org.springframework.web.servlet.ModelAndView org.springframework.boot.autoconfigure.web.BasicErrorController.errorHtml(javax.servlet.http.HttpServletRequest,javax.servlet.http.HttpServletResponse)
2017-03-01 16:16:38.096  INFO 14032 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/webjars/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2017-03-01 16:16:38.097  INFO 14032 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2017-03-01 16:16:38.178  INFO 14032 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/**/favicon.ico] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2017-03-01 16:16:38.369  INFO 14032 --- [           main] o.s.j.e.a.AnnotationMBeanExporter        : Registering beans for JMX exposure on startup
2017-03-01 16:16:38.472  INFO 14032 --- [           main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat started on port(s): 8080 (http)
2017-03-01 16:16:38.479  INFO 14032 --- [           main] com.qnvip.demo.App                       : Started App in 4.005 seconds (JVM running for 8.011)

这个问题有点不对啊，又回头去查看tomcat-embed-core-8.0.23.jar，确认有没有这个方法，结果是有的。

再仔细看下报错日志，错误似乎是从jdk1.8.0_65中出来的，而不是项目中，jdk1.8.0_65\jre\lib\ext\servlet-api.jar中也有这个类，难道是这个类出了问题？

好吧，试着从apache-tomcat-9.0.0.M17中拷一个jar文件去覆盖，结果完善启动了，顺利的出现hello world!

似乎可以得出以下结论：

spring boot 1.5.1.RELEASE不兼容tomcat9，但是官方文档上并没有写，只写着tomcat7+

但是事情还没完，从最后的问题上来看和网上搜索的情况来下（并没有搜到多少同类的问题），难道问题一开始就出现在jdk上？我再把pom文件恢复到最初的样子，不再指定tomcat，项目再启动，成功了！

所以难道spring boot1.5.1也不支持jdk8?，官方说明是支持jdk7+，凌乱了~~~~

所以这里肯定还有其它问题存在，不知道有没有人也碰到我的问题，交流一下