jeecg使用内嵌tomcat进行调试开发时需要注意的问题

按照我的这篇文章基于内嵌的tomcat7进行开发搭建好开发环境后，运行EmbededTomcat后报以下错误：

java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Tomcat].StandardHost[localhost].StandardContext[/jeecg]]
	at java.util.concurrent.FutureTask.report(FutureTask.java:122)
	at java.util.concurrent.FutureTask.get(FutureTask.java:188)
	at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:1123)
	at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:816)
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
	at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1575)
	at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1565)
	at java.util.concurrent.FutureTask.run(FutureTask.java:262)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
	at java.lang.Thread.run(Thread.java:744)
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Tomcat].StandardHost[localhost].StandardContext[/jeecg]]
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:154)
	... 6 more
Caused by: java.lang.NoSuchMethodError: javax.servlet.ServletContext.getClassLoader()Ljava/lang/ClassLoader;
	at org.apache.catalina.startup.WebappServiceLoader.load(WebappServiceLoader.java:90)
	at org.apache.catalina.startup.ContextConfig.processServletContainerInitializers(ContextConfig.java:1577)
	at org.apache.catalina.startup.ContextConfig.webConfig(ContextConfig.java:1281)
	at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:889)
	at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:386)
	at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:117)
	at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:90)
	at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5412)
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
	... 6 more

检查后发现是因为tomcat7使用的是servlet3.0,而jeecg的pom.xml中引用的是2.5版本的servlet jar包，修改成3.0即可，如下：

<!-- web依赖包 -->
		<!--
		<dependency>
			<groupId>javax.servlet</groupId>
			<artifactId>servlet-api</artifactId>
			<version>2.5</version>
			<scope>provided</scope>
		</dependency>
		-->
		<dependency>
			<groupId>javax.servlet</groupId>
			<artifactId>javax.servlet-api</artifactId>
			<version>3.0.1</version>
			<scope>provided</scope>
		</dependency>
		
		<!--
		<dependency>
			<groupId>javax.servlet</groupId>
			<artifactId>jsp-api</artifactId>
			<version>2.0</version>
			<scope>provided</scope>
		</dependency>
		-->
		<dependency>
			<groupId>javax.servlet</groupId>
			<artifactId>jstl</artifactId>
			<version>1.2</version>
		</dependency>

修改完成后，再启动EmbbdTomcat，启动成功。

接着使用http://localhost:8080/jeecg/ 访问管理界面，报以下异常：

java.lang.NoSuchMethodError: javax.servlet.jsp.JspFactory.getJspApplicationContext(Ljavax/servlet/ServletContext;)Ljavax/servlet/jsp/JspApplicationContext;
	at org.apache.jasper.compiler.Validator$ValidateVisitor.<init>(Validator.java:515)
	at org.apache.jasper.compiler.Validator.validateExDirectives(Validator.java:1845)
	at org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:218)
	at org.apache.jasper.compiler.Compiler.compile(Compiler.java:374)
	at org.apache.jasper.compiler.Compiler.compile(Compiler.java:354)
	at org.apache.jasper.compiler.Compiler.compile(Compiler.java:341)
	at org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:657)
	at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:357)
	at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:395)
	at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:770)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
	at com.alibaba.druid.support.http.WebStatFilter.doFilter(WebStatFilter.java:140)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:504)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:421)
	at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1074)
	at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:611)
	at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.lang.Thread.run(Thread.java:744)

应该还是javax.servlet版本的问题，在编绎jsp时出错了，仔细检查发现工程的classpath下还是有两个版本的servelt,如图：

应该是这两个版本的servlet api冲突了，应该去掉2.3这个版本就好了，但具体是哪里引用到了2.3的servlet呢？

在工程根进入cmd命令行使用mvn dependency:tree命令查看jar包依赖关系也没有发现有什么引用到了这个包，比较奇怪

用mvn clean清除工程，再mvn eclipse:eclipse生成工程文件后，这个2.3的servlet版本在classpath版本就没掉了！

再次mvn war:war后运行EmbbdTomcat，访问首页未出错，显示的却是hellow world！发现进入了jeecg默认的 index.jsp页面，没有按照web.xml中设置的进入到/webpage/login/login.jsp

<welcome-file-list>
		<welcome-file>/webpage/login/login.jsp</welcome-file>
	</welcome-file-list>

晕！，只好修改index.jsp了让进入index.jsp时再跳转到/webpage/login/login.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<jsp:forward page="/webpage/login/login.jsp" />

ok!终于可以访问了！