将变量从脚本传递到 jsp - null 指针

Question

Struggling to pass a variable from a scriplet in one jsp to the 'calling jsp'

assetedit.jsp posts a binary stream to upload.jsp. upload.jsp proceses that stream and determines a filepath which I want to make available in assedit.jsp but the returned value always produces null pointer.

I am obviously doing something fundamentally wrong, I even tried asynch in the post to 'stop' the jsp in case things were happening too fast.

Thoughts appreciated.

assetedit.jsp -

//post binary to upload.jsp
$.ajax({
url: '/wz/upload.jsp',
data: decodedstring,
type: 'POST',
contentType: false,
processData: false,
}).done(function(data) {
console.log(data);
});     

upload.jsp (some lines removed to make easier to understand -

<%
try {
String root = getServletContext().getRealPath("/uploads/"); 
BufferedInputStream bis = new BufferedInputStream(request.getInputStream());
String nm = System.currentTimeMillis() + ".jpg";
String filepath = root + "/" + nm;
String realpath = (filepath.substring(filepath.lastIndexOf("/") - 7));
System.out.println("realpath is   "  + realpath);
pageContext.setAttribute("pathtogo", realpath);

}
fos.close();
bis.close();
);
} catch (Exception ex) {
ex.printStackTrace();
}
%>

assetedit.jsp -

<%
String str = request.getAttribute("pathtogo").toString();
System.out.println("pathtogo is   "  + str);
%>  

also tried (in assetedit.jsp) -

<%
        String name=(pageContext.getAttribute("pathtogo").toString()); 
        System.out.println("pathtogo is "+name); 
%>

resulting in - Uncaught TypeError: getElemRefs(...) is null

Thoughts appreciated, do I need to do another post in upload.jsp to send pathtogo back to assetedit.jsp?

Ralph

Answer 1

Can you try to use Session Scope, in order to pass appropriate variables between different JSP Pages.

pageContext.setAttribute("pathtogo",realPath,PageContext.SESSION_SCOPE);  
    
pageContext.getAttribute("pathtogo",PageContext.SESSION_SCOPE);  

https://docs.oracle.com/javaee/6/api/javax/servlet/jsp/PageContext.html

---- Edited ----

ok lets try something else:

upload.jsp

session.setAttribute("pathtogo",realPath);

assetedit.jsp -

<%
String str = (String)session.getAttribute("pathtogo");

System.out.println("pathtogo is   "  + str);
%>  

or String.valueOf(session.getAttribute("pathtogo"));