严重: Servlet.service() for servlet jsp threw exceptionjava.lang.NullPointerException	at org.apache.jsp.index_jsp._jspInit(index_jsp.java:23)	at org.apache.jasper.runtime.HttpJspBase.init(HttpJspBase.java:52)	at org.apache.jasper.servlet.JspServletWrapper.getServlet(JspServletWrapper.java:159)	at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:329)	at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)	at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)	at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)	at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845)	at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)	at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)	at java.lang.Thread.run(Thread.java:744)

原因：jar包依赖冲突，两种方式解决；

1、把servlet的jar的依赖范围改成provided <scope>provided</scope>

2、在pom.xml中，查找servlet关键字，删除跟servlet相关的jar包依赖