jsp要調用servlet中自定義的方法需要把自定的方法放在doPost或者doGet或者init方法中。
舉例如下：
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class HelloWorldServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
// TODO Auto-generated method stub
super.doGet(req, resp);
System.out.println("doGet");
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
// TODO Auto-generated method stub
super.doPost(req, resp);
//調用自定義方法
returnBack(req,resp);
System.out.println("doPost");
}

//這里是自定義方法
public void returnBack(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException
{
System.out.println("really！go home");
}
}

在JSP見面先用request把值存好了，然后跳到servlet去：
request.getRequestDispatcher("servlet的rul").forward(request, response);
在servlet里再調那方法

你好，不可以調用

jsp和servlet之間，可以互相傳值，但是因為存在先后關系，所以沒有調用一說，只有跳轉