在我的网络应用程序中，我有一个 Item 类
public class Item {
private Long item_id;
private String name;
...
}
...
<servlet-mapping>
<servlet-name>edititemservlet</servlet-name>
<url-pattern>/edititem</url-pattern>
</servlet-mapping>
...
在列出项目时，我尝试使用
<a href="<c:url value="editItem?itemId=${item.item_id}" />" >${item.name}</a>
这行得通。但是，当我尝试以下使用时
<c:url value="editItem" var="editItemurl">
<c:param name="itemId" value="${item.item_id}" />
</c:url>
<c:forEach var="item" items="${items}" varStatus="itemslistCount">
<tr><td>${itemslistCount.count} </td>
<td><a href="${editItemurl}" >${item.name}</a></td>
我希望得到相同的结果。但这会导致 NumbeFformatException 。
java.lang.NumberFormatException: For input string: ""
java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)
java.lang.Long.parseLong(Long.java:424)
我试图打印 ${editItemurl} 并显示一个空字符串。
知道如何纠正这个吗？
谢谢
标记
ps：这是堆栈跟踪
java.lang.NumberFormatException: For input string: ""
at java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)
at java.lang.Long.parseLong(Long.java:424)
at java.lang.Long.parseLong(Long.java:461)
at myshop.servlets.ItemEditServlet.doGet(Unknown Source)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:470)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:857)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
at java.lang.Thread.run(Thread.java:619)