问题描述：通过Spring Boot官方提供的方式，写出如下HelloWorld代码。
package cn.itcast.demo2;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Configuration;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
@Controller
@SpringBootApplication //声明是springboot的应用（入口）
@Configuration
public class HelloApplication {
@RequestMapping("hello")
@ResponseBody //经过消息转换器 直接在页面输出返回的字符串
public String hello(){
return "hello world";
}
public static void main(String[] args) {
SpringApplication.run(HelloApplication.class, args);
}
}
在运行main()方法时，抛出如下异常。
org.springframework.context.ApplicationContextException: Unable to start embedded container;
nested exception is java.lang.NoSuchMethodError: org.apache.tomcat.util.scan.StandardJarScanner.setJarScanFilter(Lorg/apache/tomcat/JarScanFilter;)V
at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.onRefresh(EmbeddedWebApplicationContext.java:137) ~[spring-boot-1.5.6.RELEASE.jar:1.5.6.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:537) ~[spring-context-4.3.10.RELEASE.jar:4.3.10.RELEASE]
at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:122) ~[spring-boot-1.5.6.RELEASE.jar:1.5.6.RELEASE]
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:693) [spring-boot-1.5.6.RELEASE.jar:1.5.6.RELEASE]
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:360) [spring-boot-1.5.6.RELEASE.jar:1.5.6.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:303) [spring-boot-1.5.6.RELEASE.jar:1.5.6.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1118) [spring-boot-1.5.6.RELEASE.jar:1.5.6.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1107) [spring-boot-1.5.6.RELEASE.jar:1.5.6.RELEASE]
at dolphin.springboot.controller.HelloWorld.main(HelloWorld.java:30) [classes/:na]
Caused by: java.lang.NoSuchMethodError: org.apache.tomcat.util.scan.StandardJarScanner.setJarScanFilter(Lorg/apache/tomcat/JarScanFilter;)V
at org.springframework.boot.context.embedded.tomcat.SkipPatternJarScanner$Tomcat8TldSkipSetter.setSkipPattern(SkipPatternJarScanner.java:106) ~[spring-boot-1.5.6.RELEASE.jar:1.5.6.RELEASE]
at org.springframework.boot.context.embedded.tomcat.SkipPatternJarScanner.setPatternToTomcat8SkipFilter(SkipPatternJarScanner.java:61) ~[spring-boot-1.5.6.RELEASE.jar:1.5.6.RELEASE]
at org.springframework.boot.context.embedded.tomcat.SkipPatternJarScanner.<init>(SkipPatternJarScanner.java:56) ~[spring-boot-1.5.6.RELEASE.jar:1.5.6.RELEASE]
at org.springframework.boot.context.embedded.tomcat.SkipPatternJarScanner.apply(SkipPatternJarScanner.java:87) ~[spring-boot-1.5.6.RELEASE.jar:1.5.6.RELEASE]
at org.springframework.boot.context.embedded.tomcat.TomcatEmbeddedServletContainerFactory.prepareContext(TomcatEmbeddedServletContainerFactory.java:209) ~[spring-boot-1.5.6.RELEASE.jar:1.5.6.RELEASE]
at org.springframework.boot.context.embedded.tomcat.TomcatEmbeddedServletContainerFactory.getEmbeddedServletContainer(TomcatEmbeddedServletContainerFactory.java:178) ~[spring-boot-1.5.6.RELEASE.jar:1.5.6.RELEASE]
at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.createEmbeddedServletContainer(EmbeddedWebApplicationContext.java:164) ~[spring-boot-1.5.6.RELEASE.jar:1.5.6.RELEASE]
at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.onRefresh(EmbeddedWebApplicationContext.java:134) ~[spring-boot-1.5.6.RELEASE.jar:1.5.6.RELEASE]
... 8 common frames omitted经检查，在org.apache.tomcat.util.scan.StandardJarScanner类中存在setJarScanFilter(Lorg/apache/tomcat/JarScanFilter;)方法，并且亲自测试，可以正常使用。而抛出异常却说没有此方法。
分析原因：1.存在重复的jar包。2.版本调整带来的影响。
经排查，发现MyEclipse Tomcat v9.0 Runtime Libraries包，和Maven Dependencies包中均包含org.apache.tomcat.util.scan.StandardJarScanner类。
于是，取消MyEclipse Tomcat v9.0 Runtime Libraries包，运行正常。
. ____ _ __ _ _
/\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
\\/ ___)| |_)| | | | | || (_| | ) ) ) )
' |____| .__|_| |_|_| |_\__, | / / / /
=========|_|==============|___/=/_/_/_/
:: Spring Boot :: (v1.5.2.RELEASE)
2018-11-24 18:58:08.986 INFO 8356 --- [ main] cn.itcast.demo2.HelloApplication : Starting HelloApplication on DESKTOP-SJH626H with PID 8356 (started by 佟永硕 in D:\JAVA学习\MyWorkSpace\itcast-springboot)
2018-11-24 18:58:08.988 INFO 8356 --- [ main] cn.itcast.demo2.HelloApplication : No active profile set, falling back to default profiles: default
2018-11-24 18:58:09.024 INFO 8356 --- [ main] ationConfigEmbeddedWebApplicationContext : Refreshing org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@7f416310: startup date [Sat Nov 24 18:58:09 CST 2018]; root of context hierarchy
2018-11-24 18:58:12.003 INFO 8356 --- [ main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat initialized with port(s): 8080 (http)
2018-11-24 18:58:14.664 INFO 8356 --- [ main] o.apache.catalina.core.StandardService : Starting service Tomcat
2018-11-24 18:58:14.665 INFO 8356 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet Engine: Apache Tomcat/8.5.11
2018-11-24 18:58:14.830 INFO 8356 --- [ost-startStop-1] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext
2018-11-24 18:58:14.830 INFO 8356 --- [ost-startStop-1] o.s.web.context.ContextLoader : Root WebApplicationContext: initialization completed in 5810 ms
2018-11-24 18:58:14.913 INFO 8356 --- [ost-startStop-1] o.s.b.w.servlet.ServletRegistrationBean : Mapping servlet: 'dispatcherServlet' to [/]
2018-11-24 18:58:14.916 INFO 8356 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean : Mapping filter: 'characterEncodingFilter' to: [/*]
2018-11-24 18:58:14.916 INFO 8356 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean : Mapping filter: 'hiddenHttpMethodFilter' to: [/*]
2018-11-24 18:58:14.917 INFO 8356 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean : Mapping filter: 'httpPutFormContentFilter' to: [/*]
2018-11-24 18:58:14.917 INFO 8356 --- [ost-startStop-1] o.s.b.w.servlet.FilterRegistrationBean : Mapping filter: 'requestContextFilter' to: [/*]
2018-11-24 18:58:15.283 INFO 8356 --- [ main] s.w.s.m.m.a.RequestMappingHandlerAdapter : Looking for @ControllerAdvice: org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@7f416310: startup date [Sat Nov 24 18:58:09 CST 2018]; root of context hierarchy
2018-11-24 18:58:15.328 INFO 8356 --- [ main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/hello]}" onto public java.lang.String cn.itcast.demo2.HelloApplication.hello()
2018-11-24 18:58:15.330 INFO 8356 --- [ 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)
2018-11-24 18:58:15.331 INFO 8356 --- [ 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)
2018-11-24 18:58:15.354 INFO 8356 --- [ main] o.s.w.s.handler.SimpleUrlHandlerMapping : Mapped URL path [/webjars/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2018-11-24 18:58:15.354 INFO 8356 --- [ main] o.s.w.s.handler.SimpleUrlHandlerMapping : Mapped URL path [/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2018-11-24 18:58:15.393 INFO 8356 --- [ main] o.s.w.s.handler.SimpleUrlHandlerMapping : Mapped URL path [/**/favicon.ico] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2018-11-24 18:58:15.521 INFO 8356 --- [ main] o.s.j.e.a.AnnotationMBeanExporter : Registering beans for JMX exposure on startup
2018-11-24 18:58:15.631 INFO 8356 --- [ main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat started on port(s): 8080 (http)
2018-11-24 18:58:15.635 INFO 8356 --- [ main] cn.itcast.demo2.HelloApplication : Started HelloApplication in 6.895 seconds (JVM running for 7.258)