Question

我的代码来自java eclipse keplero，我的项目是一个servlet（服务器），它通过XMLRequest与chrome（客户端）的扩展进行通信。我已经使用了GET和POST，并且servlet可以在case之间通信，但是request.getParameter在每种情况下都是null。

的web.xml：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
<display-name>XMLFinal</display-name>
<welcome-file-list>
<welcome-file>index.html</welcome-file>
<welcome-file>index.htm</welcome-file>
<welcome-file>index.jsp</welcome-file>
<welcome-file>default.html</welcome-file>
<welcome-file>default.htm</welcome-file>
<welcome-file>default.jsp</welcome-file>
</welcome-file-list>
</web-app>

的index.html：

<!DOCTYPE html>
<html>
<head>
<meta charset="ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
<form method = "get" action = "main">
Data: <input type="text" name="data">
<input type="submit" value = "send">
</form>
</body>
</html>

main.java

import java.io.BufferedReader;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Collection;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import netscape.javascript.JSObject;

/**
 * Servlet implementation class main
 */
@WebServlet("/main")
public class main extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
public main() {
    super();
    // TODO Auto-generated constructor stub
}

/**
 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
 */

//server funziona in invio, il segnale in ricezione non funziona ancora
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {


    //guardare file index.html
    System.out.println(request.getParameter("data"));



    response.setContentType("text/plain");
    response.setCharacterEncoding("UTF-8");

    //
    response.getWriter().write("GET");

}

/**
 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
 */
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // TODO Auto-generated method stub

    //guardare file index.html
    System.out.println(request.getParameter("data"));



    response.setContentType("text/plain");
    response.setCharacterEncoding("UTF-8");

    //invio segnale funzionante 
    response.getWriter().write("POST2");
}

private void getHeadersInfo() {
    // TODO Auto-generated method stub
}
}

我在登录页面上有所改进，以创建一个简单的表单并且运行完美但我需要来自js客户端的数据：

loadXMLRequest();

function loadXMLRequest()
{
    var xmlhttp;

//da testare su Chrome Firefox Opera IE 7 o superiore
if (window.XMLHttpRequest)
{
    xmlhttp = new XMLHttpRequest();

    //arrivo del segnale
    xmlhttp.open("GET","http://localhost:8080/XMLFinal/main?ciao",true);
    xmlhttp.setRequestHeader("Content-Type","text/plain");
    alert("questi sono  i dati da inviare : ciao"");

    xmlhttp.send();
    alert("Message sent");

    //apertura pagina web risposta giunta ed in elaborazione
    //window.open(xmlhttp.responseText);
    xmlhttp.onreadystatechange=function()
    {
        if (xmlhttp.readyState==0)
        {
            alert("request not initialized");
        }

        if (xmlhttp.readyState==1)
        {
            alert("server connection established");
        }

        if (xmlhttp.readyState==2)
        {
            alert("request received");
        }

        if (xmlhttp.readyState==3)
        {
            alert("processing request");
        }

        if (xmlhttp.readyState==4)
        {
            alert("request finished and response is ready");
            alert(xmlhttp.responseText);

            //nessun dato ricevuto possibile shutdown del server
            if(xmlhttp.responseText=="")
            {

            }
            else
            {
                //windows.open(xmlhttp.responseText);
            }
        }

        if (xmlhttp.readyState==200)
        {
            alert("OK");
            alert(xmlhttp.responseText);
        }

        if (xmlhttp.readyState==404)
        {
            alert("Page not found");
        }
    }


}
else
{
    //per IE 6 o inferiore
    xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");

    alert("Microsoft alert");
}

}

Answer 1

名称是密钥

您的代码说

System.out.println(request.getParameter("http"));

并且您的表单上写着

<input type="text" name="data">

将第一个更改为

System.out.println(request.getParameter("data"));

或第二个

<input type="text" name="http">

Answer 2

你正在接听电话，即

xmlhttp.open("GET","http://localhost:8080/XMLFinal/main?ciao",true);

因此，从servlet调用doGet(-,-)方法，但是在doGet(-,-)方法下你已经编写了

System.out.println(request.getParameter("http"));

应该替换为

System.out.println(request.getParameter("data"));

您已使用doPost(-,-)方法正确编写。

但我总是不想写冗余代码。在doGet()和{ doPost()，您可以在常用方法中编写代码，并从do ***方法调用相同的方法。即，

protected void processRequest(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {

希望这会对你有所帮助。

可以发送数据，但request.getParameter总是== null

2 个答案:

名称是密钥