我在Spring，Maven和Tomcat交互中遇到了一些奇怪的行为。每次我在POM中使用jar包装时，都会抛出异常：
Severe: Servlet.service() for servlet jsp threw exception
java.lang.NullPointerException
at org.apache.jsp.index_jsp._jspInit(index_jsp.java:25)
at org.apache.jasper.runtime.HttpJspBase.init(HttpJspBase.java:52)
at org.apache.jasper.servlet.JspServletWrapper.getServlet(JspServletWrapper.java:164)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:340)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
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:127)
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:293)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:602)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
at java.lang.Thread.run(Thread.java:724)
否则，当我清理Tomcat时，会引发另一个异常（然后再次使用jar作为打包）：
org.apache.jasper.JasperException: /index.jsp(5,62) Unable to read TLD "META-INF/c.tld" from JAR file "file:/C:/tomcat/webapps/MyProject/WEB-INF/lib/jstl-1.2.jar": org.apache.jasper.JasperException: Failed to load or instantiate TagLibraryValidator class: org.apache.taglibs.standard.tlv.JstlCoreTLV
org.apache.jasper.compiler.DefaultErrorHandler.jspError(DefaultErrorHandler.java:40)
org.apache.jasper.compiler.ErrorDispatcher.dispatch(ErrorDispatcher.java:407)
org.apache.jasper.compiler.ErrorDispatcher.jspError(ErrorDispatcher.java:218)
org.apache.jasper.compiler.TagLibraryInfoImpl.<init>(TagLibraryInfoImpl.java:183)
org.apache.jasper.compiler.Parser.parseTaglibDirective(Parser.java:386)
org.apache.jasper.compiler.Parser.parseDirective(Parser.java:450)
org.apache.jasper.compiler.Parser.parseElements(Parser.java:1397)
org.apache.jasper.compiler.Parser.parse(Parser.java:130)
org.apache.jasper.compiler.ParserController.doParse(ParserController.java:255)
org.apache.jasper.compiler.ParserController.parse(ParserController.java:103)
org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:185)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:354)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:334)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:321)
org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:592)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:328)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
当我将POM改为战争包装时，一切都运行良好。为什么世界上Maven（仅）的jar包装与jstl-1.2.jar有关？什么是变通方法？谢谢！
编辑：Entyre POM
<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.mycompany</groupId>
<artifactId>tools</artifactId>
<version>1.5.1-SNAPSHOT</version>
<description>description text</description>
<packaging>war</packaging> <!-- <== ISSUE HERE! -->
<properties>
<!-- Generic properties -->
<java.version>1.6</java.version>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<!-- Web -->
<jsp.version>2.2</jsp.version>
<jstl.version>1.2</jstl.version>
<servlet.version>2.5</servlet.version>
<!-- Spring -->
<spring-framework.version>3.2.3.RELEASE</spring-framework.version>
<!-- Hibernate / JPA -->
<hibernate.version>4.2.1.Final</hibernate.version>
<!-- Logging -->
<logback.version>1.0.13</logback.version>
<slf4j.version>1.7.5</slf4j.version>
<!-- Test -->
<junit.version>4.11</junit.version>
</properties>
<dependencies>
<dependency>
<groupId>aopalliance</groupId>
<artifactId>aopalliance</artifactId>
<version>1.0</version>
</dependency>
<dependency>
<groupId>commons-logging</groupId>
<artifactId>commons-logging</artifactId>
<version>1.2</version>
</dependency>
<!-- Spring MVC -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>4.0.6.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-orm</artifactId>
<version>4.0.6.RELEASE</version>
</dependency>
<dependency>
<groupId>org.javassist</groupId>
<artifactId>javassist</artifactId>
<version>3.18.2-GA</version>
</dependency>
<!-- Spring and Transactions -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-tx</artifactId>
<version>4.0.6.RELEASE</version>
</dependency>
<!-- Other Web dependencies -->
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>jstl</artifactId>
<version>1.2</version>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>3.1.0</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>javax.servlet.jsp</groupId>
<artifactId>jsp-api</artifactId>
<version>2.2</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.32</version>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.apache.tomcat</groupId>
<artifactId>tomcat-dbcp</artifactId>
<version>8.0.11</version>
</dependency>
<dependency>
<groupId>org.apache.tomcat</groupId>
<artifactId>tomcat-jdbc</artifactId>
<version>8.0.11</version>
<scope>provided</scope>
</dependency>
<!-- Logging with SLF4J & LogBack -->
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.7.7</version>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-classic</artifactId>
<version>1.1.2</version>
<scope>runtime</scope>
</dependency>
<!-- Hibernate -->
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-entitymanager</artifactId>
<version>4.3.6.Final</version>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
<version>4.3.6.Final</version>
</dependency>
<!-- Test Artifacts -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-test</artifactId>
<version>4.0.6.RELEASE</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
<scope>test</scope>
</dependency>
</dependencies>
</project>