tomcat - 关于JSP里的Java语句嵌入问题

问题描述

问 题

是这样的,我用的是Intellij 导入了一个MyEclipse的包（该包已部署在服务器上，所以是没有大错误的）。

然后在一个jsp文件出现了个问题：

莫名奇妙地println变成了红色，执行的时候就直接抛出异常了。
今天刚接触JavaWeb不太懂，到底是怎么回事呢？

异常：

type Exception report

message An exception occurred processing JSP page /blackphones.jsp at line 15

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

exception

org.apache.jasper.JasperException: An exception occurred processing JSP page /blackphones.jsp at line 15

12: <%
13:     String [] phones = (String []) request.getAttribute("blackphones");
14: 
15:     out.println("褰撳墠鏈� + phones.length + "涓墜鏈哄彿鐮侊細<br/><br/>");
16:     
17:     for(String phone : phones){
18:         out.println(phone + "&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;");


Stacktrace:
    org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:575)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:477)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:395)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    com.aspire.mmlite.server.servlet.LogFilter.doFilter(LogFilter.java:63)
root cause

java.lang.NullPointerException
    org.apache.jsp.blackphones_jsp._jspService(blackphones_jsp.java:96)
    org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:439)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:395)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    com.aspire.mmlite.server.servlet.LogFilter.doFilter(LogFilter.java:63)

解决方案

字符串数组没有实例化一个大小给它～length属性是空的

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