將值servlet傳遞給jsp
[英]Pass value servlet to jsp
問題描述
我想將值servlet傳遞給jsp。 在servlet中設置值並在jsp頁面中使用
我下面收到NullPointerException是我的代碼
jsp
<body>
<%
String message = (String) request.getAttribute("message");
out.println("Servlet communicated message to JSP: "+ message);
Vector vecObj = (Vector) request.getAttribute("vecBean");
out.println("Servlet to JSP communication of an object: "+vecObj.get(0));
%>
</body>
爪哇
public class ServletToJSP extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//communicating a simple String message.
String message = "Example source code of Servlet to JSP communication.";
request.setAttribute("message", message);
//communicating a Vector object
Vector vecObj = new Vector();
vecObj.add("Servlet to JSP communicating an object");
request.setAttribute("vecBean",vecObj);
//Servlet JSP communication
RequestDispatcher reqDispatcher = getServletConfig().getServletContext().getRequestDispatcher("javaPapers.jsp");
reqDispatcher.forward(request,response);
}
}
錯誤日志我沒有在web.xml中進行任何更改我沒有在web.xml中進行任何更改
org.apache.jasper.JasperException: An exception occurred processing JSP page /javaPapers.jsp at line 21
18: out.println("Servlet communicated message to JSP: "+ message);
19:
20: Vector vecObj = (Vector) request.getAttribute("vecBean");
21: out.println("Servlet to JSP communication of an object: "+vecObj.get(0));
22: %>
23: </body>
24: </html>
Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:553)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:457)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:391)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
root cause
java.lang.NullPointerException
org.apache.jsp.javaPapers_jsp._jspService(javaPapers_jsp.java:83)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:419)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:391)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
note The full stack trace of the root cause is available in the Apache Tomcat/7.0.12 logs.
1 個解決方案
解決方案1
0 2013-09-03 06:30:02
您可能會收到NullPointerException，因為“ reqDispatcher.forward（request，response）;” 一起創建一個新請求，由於請求對象中不存在vecObj，因此vecObj變為空。 代替使用reqDispatcher.forward，使用response.redirect。
servlet到jsp傳遞值
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