request.getParameterValues()问题

0 0

request.getParameterValues()问题0

在一个JSP页面中，多个<input>的name一样，在servlet中用Map<Integer,String[]> map = new HashMap<Integer, String[]>();
map.put(id, request.getParameterValues(idStr));//这里的idStr就是
//<input> 的name
为什么
for(int i=0;i<map.size();i++){
System.out.println(map.size());
System.out.println(map.get(i).length);
/*for(int j=0;j<str.length;j++){
System.out.println(str[j]);
}*/
}
会报错?

2013-8-22 16:33:41 org.apache.catalina.core.StandardWrapperValve invoke
严重: Servlet.service() for servlet AddAnswerSheetServlet threw exception
java.lang.NullPointerException
	at com.answerSheetServlet.AddAnswerSheetServlet.doPost(AddAnswerSheetServlet.java:93)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
	at com.util.ChinaFilter.doFilter(ChinaFilter.java:16)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
	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:103)
	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.Http11AprProcessor.process(Http11AprProcessor.java:879)
	at org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:600)
	at org.apache.tomcat.util.net.AprEndpoint$Worker.run(AprEndpoint.java:1703)
	at java.lang.Thread.run(Thread.java:619)

JSP Servlet

2013年8月22日 16:48

muyexia521
2
0 0 9

2个答案按时间排序按投票排序

0 0

采纳的答案

String langtype[]=request.getParameterValues("idStr");

for (int i=0;i<size;i++)
{
out.println(langtype[i]+"");
}

上面是循环输出

你for 循环 map 要这么写。
Map<Integer,String> map = new LinkedHashMap<Integer,String>();
map.put(1, "星期一");
map.put(2, "星期二");
map.put(3, "星期三");
map.put(4, "星期四");
map.put(5, "星期五");
map.put(6, "星期六");
map.put(7, "星期日");

for(Map.Entry<Integer, String> entry: map.entrySet()) {
System.out.print(entry.getKey() + ":" + entry.getValue() + "\t");
}

2013年8月22日 16:56

Java_大猫
255
0 1 34

4条评论

0 0

map.put(key,value);
value=map.get(key);

map.put(id, request.getParameterValues(idStr));
for(int i=0;i<map.size();i++){
System.out.println(map.size());
System.out.println(map.get(i).length);
}

你上面的id=0吗？不然的话map.get(i)也就是map.get(0)是null，null也就不能length。List才是get(0),get(1)这样

2013年8月22日 17:12