Question

我在java文件中有一些html代码。在'textarea'元素下的'lower div'中有一个提交类型按钮。

我想知道如何识别此按钮是否已被点击？我已经阅读了一些答案，但没有受到它的好处。他们中的大多数人都说这样尝试String name = request.getParameter("Parameter_name") 如果name变量为null，则不会单击它，否则单击。

我使用了这种技术，发现名称变量总是在我点击按钮后返回null。这是我的代码

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.sql.*;

public class ProfileServlet extends HttpServlet{
    public void doPost(HttpServletRequest req,HttpServletResponse res){
        try{
            res.setContentType("text/html");
            PrintWriter pw = res.getWriter();
            pw.print("Under Construction");
            String fullname="",gender="",email="";
            //Database connection
            Class.forName("com.mysql.jdbc.Driver");
            Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/virtualcard","root","");
            PreparedStatement pst = con.prepareStatement("SELECT * FROM info WHERE name=?");
            String name = req.getParameter("username");//getting username from external html form
            pst.setString(1,name);
            ResultSet rs = pst.executeQuery();
            byte[] bytes = new byte[1024 * 1024 * 10];
            while(rs.next()){
                fullname = rs.getString(1);
                gender = rs.getString(4);
                email = rs.getString(5);
                Blob b = rs.getBlob(6);
                bytes= b.getBytes(1,(int)b.length());//here 1 represents first image
            }
            //internal html
            pw.print("<!DOCTYPE html>"+
                        "<html>\n"+
                            "<head>\n"+
                                "<title>Test Web</title>\n"+
                                "<link rel=\"stylesheet\" type=\"text/css\" href=\"../vcard/profile.css\">\n"+
                            "</head>\n"+
                            "<body>\n"+
                                "<div class=\"main\">\n"+
                                    "<div class=\"upper\">\n"+
                                            "<div class=\"image\">\n"+
                                            "<img src=\"\"style=\"width: 200px;height: 200px;border: 2px solid #D7EDC5\" />\n"+
                                            "</div>\n"+//image div ends here
                                            "<div class=\"bar\"></div>\n"+
                                            "<div class=\"info\">\n"+
                                                "Name       :"+" "+fullname+"<br><br>"+
                                                "Email      :"+" "+email+"<br><br>"+
                                                "Gender :"+" "+gender+"<br>"+
                                            "</div>\n"+//info div ends here
                                            "<div class=\"navigation\">\n"+
                                                "<a href=\"\">Account</a>\n"+
                                                "<a href=\"\">Logout</a>\n"+
                                            "</div>\n"+
                                    "</div>\n"+//div upper ends here
                                    "<hr>\n"+
                                    "<div class=\"lower\">\n"+
                                        "<div class=\"status\">\n"+
                                            "<textarea rows=\"10\" cols=\"60\" name=\"status2\" style=\"font-family: Impact\">\n"+
                                                "Hello There..."+
                                            "</textarea>\n"+
                                                "<input type=\"submit\" name=\"post\" value=\"Post\" />\n"+
                                        "</div>\n"+
                                    "</div>\n"+
                                "</div>\n"+
                            "</body>\n"+
                        "</html>");
        }catch(Exception ex){
            ex.printStackTrace();
        }
    }
}

HTML单一提交类型按钮在java中不起作用

0 个答案: