Question

我正在尝试使用JSTL标记将User类中的属性username设置为newUser，但是当我输入以下链接http://localhost:8082/LoginApp/seccuss.jsp时，我会收到以下错误。 setProperty如何标记JSTL中的单词？

seccusss.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1" import="org.user.dto.User" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Seccuss</title>
</head>
<body>

<h3>login Successful</h3>

<jsp:useBean id="user" class="org.user.dto.User" scope="request">
   <jsp:setProperty property="username" name="newUser"/>
</jsp:useBean>
Hello <jsp:getProperty property="username" name="user"/>

</body>
</html>

用户类：

package org.user.dto;

public class User {

    private String username;
    private String userId;


    public String getUsername() {
        return username;
    }
    public void setUsername(String userName) {
        this.username = userName;
    }
    public String getUserId() {
        return userId;
    }
    public void setUserId(String userId) {
        this.userId = userId;
    }

}

错误消息：

Mai 29, 2016 1:18:03 PM org.apache.catalina.core.StandardWrapperValve invoke
SCHWERWIEGEND: Servlet.service() for servlet [jsp] in context with path [/LoginApp] threw exception [An exception occurred processing JSP page /seccuss.jsp at line 22

19: 
20: <%--The previous code line with JSTL --%>
21: <jsp:useBean id="user" class="org.user.dto.User" scope="request">
22:    <jsp:setProperty property="username" name="newUser"/>
23: </jsp:useBean>
24: Hello <jsp:getProperty property="username" name="user"/>
25: 


Stacktrace:] with root cause
java.lang.NullPointerException
    at org.apache.jasper.runtime.JspRuntimeLibrary.internalIntrospecthelper(JspRuntimeLibrary.java:320)
    at org.apache.jasper.runtime.JspRuntimeLibrary.introspecthelper(JspRuntimeLibrary.java:306)
    at org.apache.jsp.seccuss_jsp._jspService(seccuss_jsp.java:108)
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:439)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:395)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)
    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 org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
    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:436)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1078)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:625)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Unknown Source)

Answer 1

您要在标记中提供name属性的值，“ newUser ”必须是bean的名称，例如用户，就像您在标记中所做的那样。还提供值属性，否则将打印 null

试试这个。

<jsp:useBean id="user" class="com.model.User" scope="request">
   <jsp:setProperty property="username" name="user" value="hiren"/>
</jsp:useBean>
Hello <jsp:getProperty property="username" name="user"/>

使用JSTL将该属性设置为默认值

1 个答案: