关于java.lang.NumberFormatException: For input string: ""的异常是怎么回事

qq_32970387 2016-11-01 09:18:33

新人小白看了半天没弄明白为什么取不到参数
下面是传给servlet参数的第一个jsp页面
<title>Insert title here</title>
</head>
<body>
<form action="/NewWeb/type" method="post">
<table width="400" border="1">
<tr>
<td align="center">序号</td>
<td align="center">参数类别</td>
<td align="center">操作</td>
</tr>
<c:forEach items="${types }" var="t" varStatus="status">
<tr>
<td align="center">${t.typeid }</td>
<td align="center">${t.typename }</td>
<td>
<a href="/NewWeb/type?tup=update&tid=${t.typeid }">修改</a>
|
<a href="/NewWeb/type?tup=delete&tid=${t.typeid } ">删除</a>
|
<a href="/NewWeb/param?tid=${t.typeid }">编辑参数</a>
</td>
</tr>
</c:forEach>

</table>
</form>

</body>
</html>
下面这个是上面的jsp页面获取tid的jsp页面
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<form action="/NewWeb/type" method="post">
<table width="400" border="1">
<tr>
<td align="center">序号</td>
<td align="center">参数类别</td>
<td align="center">操作</td>
</tr>
<c:forEach items="${types }" var="t" varStatus="status">
<tr>
<td align="center">${t.typeid }</td>
<td align="center">${t.typename }</td>
<td>
<a href="/NewWeb/type?tup=update&tid=${t.typeid }">修改</a>
|
<a href="/NewWeb/type?tup=delete&tid=${t.typeid } ">删除</a>
|
<a href="/NewWeb/param?tid=${t.typeid }">编辑参数</a>
</td>
</tr>
</c:forEach>

</table>
</form>

</body>
</html>
下面这个是servlet页面
package com.kt.servlet;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.kt.service.ParamService;

public class ParamServlet extends HttpServlet {

ParamService ps = new ParamService();

/**
*
*/
private static final long serialVersionUID = 1L;

@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {

doPost(req, resp);
}

@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
String pup = req.getParameter("pup");

// 从Type.jsp页面获取的获取参数的typeid(tid)
// String tid = req.getParameter("typeid");
// int itid = tid == null ? 0 : Integer.parseInt(tid);
//
// req.setAttribute("tid", itid);
// req.setAttribute("params", ps.selectByTypeid(itid));
// req.getRequestDispatcher("Param.jsp").forward(req, resp);

if ("update".equals(pup)) {
String paramid = req.getParameter("pid");
int iparamid = paramid == null ? 0 : Integer.parseInt(paramid);

req.setAttribute("params", ps.selectById(iparamid));
req.getRequestDispatcher("ParamEdit.jsp").forward(req, resp);

} else if ("delete".equals(pup)) {

String pid = req.getParameter("pid");
int ipid = pid == null ? 0 : Integer.parseInt(pid);

String tid = req.getParameter("tid");
int itid = tid == null ? 0 : Integer.parseInt(tid);

ps.deleteParam(ipid);

req.setAttribute("params", ps.selectByTypeid(itid));
req.setAttribute("tid", tid);

req.getRequestDispatcher("Param.jsp").forward(req, resp);

} else if ("edit".equals(pup)) {
String pname = req.getParameter("paranname");

String pid = req.getParameter("paramid");
int ipid = pid == null ? 0 : Integer.parseInt(pid);

String typeid = req.getParameter("typeid");
int itypeid = typeid == null ? 0 : Integer.parseInt(typeid);

ps.updateParam(pname, ipid, itypeid);

req.setAttribute("params", ps.selectByTypeid(itypeid));
req.getRequestDispatcher("Param.jsp").forward(req, resp);

} else {
// 从Type.jsp页面获取的获取参数的typeid(tid)
String tid2 = req.getParameter("tid");
int itid2 = tid2 == null ? 0 : Integer.parseInt(tid2);

// req.setAttribute("tid", itid2);
req.setAttribute("params", ps.selectByTypeid(itid2));
req.getRequestDispatcher("Param.jsp").forward(req, resp);

}

}

}
下面是报错
严重: Servlet.service() for servlet [ParamServlet] in context with path [/NewWeb] threw exception
java.lang.NumberFormatException: For input string: ""
at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
at java.lang.Integer.parseInt(Integer.java:592)
at java.lang.Integer.parseInt(Integer.java:615)
at com.kt.servlet.ParamServlet.doPost(ParamServlet.java:55)
at com.kt.servlet.ParamServlet.doGet(ParamServlet.java:25)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:624)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at com.kt.util.EncodingFilter.doFilter(EncodingFilter.java:27)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:218)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:956)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:442)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1083)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:640)
at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2517)
at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2506)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:745)
55行和25行报错