cannot be resolved to a type

问题

I am trying to use HTTP Authentication in my JSP code. But I am getting error on MyAuthenticator cannot be resolved to a type. Is the sytax correct for the code that I have writtent in jsp page. Any suggestions will be appreciated..

    <%@ page language="java" import="java.net.Authenticator,java.net.PasswordAuthentication,java.io.BufferedReader,java.net.*,java.io.*" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<%

String urlToQuery = request.getParameter("url");
System.out.println(" " +urlToQuery);
//URL url = new URL(urlToQuery);



//InputStream in = conn.getInputStream();

String urlString = "";
String username = "";
String password = "";
Authenticator.setDefault(new MyAuthenticator(username, password));
URL url = new URL(urlToQuery);
URLConnection conn = url.openConnection();
InputStream content = (InputStream) url.getContent();
BufferedReader in = new BufferedReader(new InputStreamReader(content));
String line;
while ((line = in.readLine()) != null) {
  System.out.println(line);
}
System.out.println("Done.");

 class MyAuthenticator extends Authenticator {
    private String username, password;

    public MyAuthenticator(String user, String pass) {
      username = user;
      password = pass;
    }

    protected PasswordAuthentication getPasswordAuthentication() {
      System.out.println("Requesting Host  : " + getRequestingHost());
      System.out.println("Requesting Port  : " + getRequestingPort());
      System.out.println("Requesting Prompt : " + getRequestingPrompt());
      System.out.println("Requesting Protocol: " + getRequestingProtocol());
      System.out.println("Requesting Scheme : " + getRequestingScheme());
      System.out.println("Requesting Site  : " + getRequestingSite());
      return new PasswordAuthentication(username, password.toCharArray());
    }
  }



%>

<%=line %>

回答1:

Do not define inner classes in JSPs. Consider a JSP like a simple method.

A JSP is something like(1):

public class MyJSP extends Servlet {
  public void service(HttpRequest request, HttpResponse response) {
     /** JSP CODE HERE **/
  }
}

Defining an inner class should be done as an anonimous inner class:

 Authenticator.setDefault(new Authenticator() {
   protected getPasswordAuthentication() {
     System.out.println("Requesting Host  : " + getRequestingHost());
     System.out.println("Requesting Port  : " + getRequestingPort());
     ...
   }
 });

Not sure what would I do to pass parameters (I only have used the simplest anonymous inner classes).

Anyway for anything that is going to be used from outside methods, I would use a public class (in its own file) and avoid all these troubles.

(1)Not exactly this, but you get the idea.

回答2:

<% ... %> leads JSP to treat the code contents as statements. Therefore you class becomes a local class following the same scope rules as local variables (that is, you must declare the class earlier than using it). I didn't test it, but if you rewrite your code to:

    <%@ page language="java" import="java.net.Authenticator,java.net.PasswordAuthentication,java.io.BufferedReader,java.net.*,java.io.*" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<%

class MyAuthenticator extends Authenticator {
    private String username, password;

    public MyAuthenticator(String user, String pass) {
      username = user;
      password = pass;
    }

    protected PasswordAuthentication getPasswordAuthentication() {
      System.out.println("Requesting Host  : " + getRequestingHost());
      System.out.println("Requesting Port  : " + getRequestingPort());
      System.out.println("Requesting Prompt : " + getRequestingPrompt());
      System.out.println("Requesting Protocol: " + getRequestingProtocol());
      System.out.println("Requesting Scheme : " + getRequestingScheme());
      System.out.println("Requesting Site  : " + getRequestingSite());
      return new PasswordAuthentication(username, password.toCharArray());
    }
  }

String urlToQuery = request.getParameter("url");
System.out.println(" " +urlToQuery);
//URL url = new URL(urlToQuery);



//InputStream in = conn.getInputStream();

String urlString = "";
String username = "";
String password = "";
Authenticator.setDefault(new MyAuthenticator(username, password));
URL url = new URL(urlToQuery);
URLConnection conn = url.openConnection();
InputStream content = (InputStream) url.getContent();
BufferedReader in = new BufferedReader(new InputStreamReader(content));
String line;
while ((line = in.readLine()) != null) {
  System.out.println(line);
}
System.out.println("Done.");





%>

<%=line %>

Then MyAuthenticator should be resolvable in your code.

Consider moving the Java class to a separate file to make your code more readable.

来源：https://stackoverflow.com/questions/6513050/cannot-be-resolved-to-a-type