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写了一个Servlet的程序,程序目的在于显示客户端提交的多值变量,开发环境是:jboss4.0+ecplipse3.1+JDK1.5,代码如下:
package com.Servelet;
import java.io.*;
import javax.servlet.ServletException;
import javax.servlet.http.*;
import javax.servlet.http.HttpServletResponse;
public class MultiChoiceServlet extends javax.servlet.http.HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/htmllchatset=gb2312");
request.setCharacterEncoding("gb2312");
PrintWriter out=response.getWriter();
String[] paramValues=request.getParameterValues("checkbox1");
String temp=new String("");
for(int i=0;i<paramValues.length;i++)temp+=paramValues[i]+" ";
out.println("你喜欢吃的水果有:"+temp+"。");
}
}
HTML代码,我就不写了。每次运行的时候,服务器总是报500错误,报错时的内容如下:
type Exception report
message
description The server encountered an internal error () that prevented it from fulfilling this request.
exception
java.lang.NullPointerException
com.servlet.MultiChoiceServlet.doPost(MultiChoiceServlet.java:30)(就是这句:for(int i=0;i<paramValues.length;i++)temp+=paramValues[i]+" ";)
javax.servlet.http.HttpServlet.service(HttpServlet.java:709)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
请教那位高手,能够帮我解答一下。问题是在那里。 |
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