爬坑记(7) :HTTP Status 500 - Unable to compile class for JSP

简述

开发使用tomcat7进行测试，maven项目。服务器上tomcat8，部署上服务器启动ok，访问就报错。

HTTP Status 500 - Unable to compile class for JSP:
type Exception report

message Unable to compile class for JSP:

description The server encountered an internal error that prevented it from fulfilling this request.

exception

org.apache.jasper.JasperException: Unable to compile class for JSP: 

An error occurred at line: [71] in the generated java file: [/usr/local/apache-tomcat-8.0.22/work/Catalina/localhost/Session/org/apache/jsp/jsp/index_jsp.java]
The method getDispatcherType() is undefined for the type HttpServletRequest

Stacktrace:
    org.apache.jasper.compiler.DefaultErrorHandler.javacError(DefaultErrorHandler.java:102)
    org.apache.jasper.compiler.ErrorDispatcher.javacError(ErrorDispatcher.java:198)
    org.apache.jasper.compiler.JDTCompiler.generateClass(JDTCompiler.java:450)
    org.apache.jasper.compiler.Compiler.compile(Compiler.java:361)
    org.apache.jasper.compiler.Compiler.compile(Compiler.java:336)
    org.apache.jasper.compiler.Compiler.compile(Compiler.java:323)
    org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:580)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:356)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:396)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:340)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    org.springframework.web.servlet.view.InternalResourceView.renderMergedOutputModel(InternalResourceView.java:168)
    org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:303)
    org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1228)
    org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1011)
    org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:955)
    org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:877)
    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:966)
    org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:857)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:622)
    org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:842)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
    org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)

通过网上查找发现，这是tomcat8才会出错，因为tomcat8没有处理好容器和应用jar包冲突的问题。但是当配置了servlet-api.jar之后，就可能会与tomcat容器中的jar包冲突，导致出现以上问题，无法找到jsp，该问题在tomcat8即以上才会出现，在tomcat7即以下是没有问题的。

解决

• 1.把tomcat8 lib下的这个servlet-api.jar干掉。
• 2.把maven的依赖设置包不参与打包。添加scope限制为provided。（一劳永逸）
  实际情况：先把依赖排除掉（依赖少的化可以一个个点开查找，多的话可以使用idea依赖树进行筛选排除），在引入，不然会包编译错误，然后设置依赖范围。

<dependency>
            <groupId>javax.servlet.jsp.jstl</groupId>
            <artifactId>jstl-api</artifactId>
            <version>1.2</version>
            <!-- 排除掉主动添加OK设置级别scope -->
            <exclusions>
                <exclusion>
                    <groupId>javax.servlet</groupId>
                    <artifactId>servlet-api</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupId>taglibs</groupId>
            <artifactId>standard</artifactId>
            <version>1.1.2</version>
        </dependency>
        <!-- 打包不参与,防止tomcat8自带serlet-api冲突  -->
          <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>servlet-api</artifactId>
            <version>2.5</version>
            <scope>provided</scope>
        </dependency>

    </dependencies>