Ajax + Servlet错误500 - 内部服务器错误java.lang.NullPointerException

时间：2015-07-09 22:52:09

标签： java ajax oracle servlets

这是我的第一个问题，我不会问我是否花了很长时间在这里寻找答案。所以就这样了。

我试图制作一个简单的CRUD应用程序，因为我想学习一些基本的ajax + servlets + java web开发，我的问题可能与响应有关，我不知道如何处理它，sql插件已完成，但当它返回到应用程序时，它返回到servlet给我一个500错误代码。

所以，这是我的代码和一些照片，我希望你能帮助我！感谢。

AJAX代码 

//Get XMLHTTP Object
function getXMLHTTPObject() {
        var xmlhttpObject = null;
        try {
                // For Old Microsoft Browsers
                xmlhttpObject = new ActiveXObject("Msxml2.XMLHTTP");
        } catch (e) {
                try {
                        // For Microsoft IE 6.0+
                        xmlhttpObject = new ActiveXObject("Microsoft.XMLHTTP");
                } catch (e1) {
                        // No Browser accepts the XMLHTTP Object then false
                        xmlhttpObject = false;
                }
        }
        if (!xmlhttpObject && typeof XMLHttpRequest != 'undefined') {
                // For Mozilla, Opera Browsers
                xmlhttpObject = new XMLHttpRequest();
        }
        // Mandatory Statement returning the ajax object created
        return xmlhttpObject;
}

// Change the value of the outputText field
function setAjaxOutput() {
    document.getElementById("res").innerHTML = xmlhttpObject.responseText;

}

function handleServerResponse() {
    //Poner aqui un print para saber que paso con readyState

        if (xmlhttpObject.readyState == 4) {
            console.log("ReadyState " +xmlhttpObject.readyState);
                if (xmlhttpObject.status == 200) {
                        setAjaxOutput();
                } else {
                     console.log("ReadyState " +xmlhttpObject.status);
                        //alert("Error during AJAX call. Please try again");
                }
        }
}

// Implement business logic
function doAjaxCall() {
        xmlhttpObject = getXMLHTTPObject();
        if (xmlhttpObject != null) {
                var URL = "servlet?action=ingresar&nombre=" + document.getElementById('firstname').value.toString() + "&apellido="+ document.getElementById('lastname').value.toString();
                xmlhttpObject.open("POST", URL, true);
                xmlhttpObject.setRequestHeader("Content-type", "application/x-www-form-urlencoded");   
                console.log(xmlhttpObject);
                 xmlhttpObject.onreadystatechange = handleServerResponse;
                xmlhttpObject.send(null);
        }
}

服务代码 

    /*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package servlet;

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 *
 * @author compract
 */
public class servlet extends HttpServlet {

    /**
     * Processes requests for both HTTP <code>GET</code> and <code>POST</code>
     * methods.
     *
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        try {
            /* TODO output your page here. You may use following sample code. */
            out.println("<!DOCTYPE html>");
            out.println("<html>");
            out.println("<head>");
            out.println("<title>Servlet servlet</title>");            
            out.println("</head>");
            out.println("<body>");
            out.println("<h1>Servlet servlet at " + request.getContextPath() + "</h1>");
            out.println("</body>");
            out.println("</html>");
        } finally {
            out.close();
        }
    }

    // <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
    /**
     * Handles the HTTP <code>GET</code> method.
     *
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }

    /**
     * Handles the HTTP <code>POST</code> method.
     *
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    protected void Mensaje (HttpServletRequest request, HttpServletResponse response) throws IOException
    {
           PrintWriter out = response.getWriter();
        try {
            /* TODO output your page here. You may use following sample code. */
            out.println("<!DOCTYPE html>");
            out.println("<html>");
            out.println("<head>");
            out.println("<title>Servlet servlet</title>");            
            out.println("</head>");
            out.println("<body>");
            out.println("<h1> El dato se ha insertado correctamente </h1>");
            out.println("</body>");
            out.println("</html>");
        } finally {
            out.close();
        }
    }
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        //processRequest(request, response);
        //hizo error porque no habia este parametro
          String action = request.getParameter("action");
          boolean usuarioregistrado = false;
            if (action.equals("ingresar")) {
        String nombre = request.getParameter("nombre");
         String apellido = request.getParameter("apellido");
         Usuario.Usuario u = new Usuario.Usuario();
         u.setNombre(nombre);
        u.setApellidoPaterno(apellido);
        u.registrarUsuario();
        usuarioregistrado = true;
       // Mensaje(request, response);  
            }
            if (usuarioregistrado) {
                response.setContentType("text/plain");  
                response.setCharacterEncoding("UTF-8"); 
                response.getWriter().write(request.getParameter("nombre")); 
            } 
            else {
                //nothing to show
                response.setStatus(HttpServletResponse.SC_NO_CONTENT);
            }
    }

    /**
     * Returns a short description of the servlet.
     *
     * @return a String containing servlet description
     */
    @Override
    public String getServletInfo() {
        return "Short description";
    }// </editor-fold>

}

HTML JSP 

    <%-- 
    Document   : index
    Created on : 8/07/2015, 03:37:12 PM
    Author     : compract
--%>

<%@page contentType="text/html" pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
        <link rel="stylesheet" type="text/css" href="style.css" />
        <!-- Importamos javascript -->
        <script language="JavaScript" type="text/javascript" src="ajax.js"></script>
        <title>Usuarios</title>
    </head>
    <body>
       <div id="header">
<h1>Usuarios</h1>
</div>
        <!-- Inputs y comandos -->
        <div id="inputsycomandos">
<!-- Hacemos llamada -->
<form action="servlet" method="POST">
    <table border="0">
    <thead>
        <tr>
            <th colspan="2">Ingrese los datos del nuevo usuario:</th>
        </tr>
    </thead>
    <tbody>
        <tr>
            <td>Nombre del usuario:</td>
            <td> <input type="text" name="firstname" id="firstname"> </td>
        </tr>
        <tr>
            <td>Apellido del usuario:</td>
            <td><input type="text" name="lastname" id="lastname"></td>
        </tr>
        <tr>
            <td><button id="ingresarnuevo" type="submit">Registrar</button></td>
            <td><button id="cancelar">Cancelar</button></td>
        </tr>
         <tr>
             <td>  <button id="registrarconajax" onclick="doAjaxCall()">Registrar-Ajax</button></td>
            <td></td>
        </tr>


    </tbody>
</table>

</form>
<p id="res">
</div>

        <div id="datatable">
<h1>Usuarios</h1>

</div>

        <div id="footer">

</div>

    </body>
</html>

类别数据库 

   package Usuario;

import java.sql.*;

/**
 *
 * @author compract
 */
public class Usuario {
    String idUsuario;
    String nombre;
    String apellidoPaterno;

    public String getIdUsuario() {
        return idUsuario;
    }

    public void setIdUsuario(String idUsuario) {
        this.idUsuario = idUsuario;
    }

    public String getNombre() {
        return nombre;
    }

    public void setNombre(String nombre) {
        this.nombre = nombre;
    }

    public String getApellidoPaterno() {
        return apellidoPaterno;
    }

    public void setApellidoPaterno(String apellidoPaterno) {
        this.apellidoPaterno = apellidoPaterno;
    }

      public void registrarUsuario()
    {
        SingletonConectar.singletonConectar sin =  SingletonConectar.singletonConectar.getDbCon();
        try {

             String query = "INSERT INTO USUARIOS(ID_USUARIO, NOMBRE_USUARIO,APELLIDO_USUARIO) VALUES (null, ?,?)";
             PreparedStatement preparedStmt = sin.db.conn.prepareStatement(query);
                preparedStmt.setString (1, nombre);
                preparedStmt.setString (2, apellidoPaterno);
             preparedStmt.execute();  


        } catch (Exception e) {    
   {
   }
        }
    }

}

WEB XML 

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">

    <servlet>
        <servlet-name>servlet</servlet-name>
        <servlet-class>servlet.servlet</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>servlet</servlet-name>
        <url-pattern>/servlet</url-pattern>
    </servlet-mapping>
    <session-config>
        <session-timeout>
            30
        </session-timeout>
    </session-config>
    <welcome-file-list>
        <welcome-file>index.jsp</welcome-file>
    </welcome-file-list>
</web-app>

0 个答案:

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