英文:
Java Servlet Form Post issue : getParameters() return null values
问题
我在这里是你的中文翻译，以下是你提供的内容的翻译部分：
我在这里是一个新人，不是以英语为母语的 :).
所以，我编写了一个表单，通过Java Servlet使用POST方法发送简单的值。
起初，它可以使用request.getParameter()正常工作，我不知道我做了什么，但现在不再起作用了。
package servlets;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;public class Authentification extends HttpServlet{public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {res.setContentType("text/html");PrintWriter writer = res.getWriter();writer.println("<h1>欢迎访问我们的新网站</h1>");writer.println("<body>");//表单writer.println("<form action=\"Authentification\" method=\"post\" class=\"form\">");//登录writer.println("<div class=\"\">");writer.println("<label for=\"login\">登录：");writer.println("<input type=\"text\" name=\"login\"/>");writer.println("</label>");writer.println("</div>");//密码writer.println("<div class=\"\">");writer.println("<label for=\"pwd\">密码：");writer.println("<input type=\"text\" name=\"pwd\"/>");writer.println("</label>");writer.println("</div>");//表单按钮writer.println("<div class=\"button\">");writer.println("<button type=\"submit\" name=\"button_connexion\" value=\"Se_connecter\">连接</button>");writer.println("</div>");writer.println("</form>");//前往注册链接writer.println("<a href=\"/ProjetWeb2020/Inscription\">是新用户吗？前往注册</a>");writer.println("</body>");}public void doPost(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {res.setContentType("text/html");PrintWriter writer = res.getWriter();String login, pwd;login=req.getParameter("Login");pwd=req.getParameter("Pwd");if(login==null && pwd==null){writer.println("<h1>不好意思！</h1>");}//JSONObject obj=services.Authentification.loginUtilisateur(login, pwd);writer.println("<h2>登录名为：" + login + "</h2>");writer.println("<h2>密码为：" + pwd + "</h2>");}}
至此为止，不再提供结果。我将非常乐意为你提供任何回答 :)。
英文:
i am new here and not native english speaker :).
So, i programmed a form that sent simple values via a post method within a java servlet.
At first, it worked with request.getParameter(), i don't know what i did, but it doesn't work anymore.
package servlets;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;//import services.*;//import org.json.JSONException;//import org.json.JSONObject;public class Authentification extends HttpServlet{public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {res.setContentType("text/html");PrintWriter writer = res.getWriter();writer.println("<h1>Bienvenue sur notre nouveau site WEB</h1>");writer.println("<body>");//Formwriter.println("<form action="+"Authentification"+" method="+"post"+" class="+"form"+">");//loginwriter.println("<div class="+">");writer.println("<label for="+"login"+">Login:");writer.println("<input type="+"text"+" name="+"login"+"/>");writer.println("</label>");writer.println("</div>");//passwordwriter.println("<div class="+">");writer.println("<label for="+"pwd"+">Password:");writer.println("<input type="+"text"+" name="+"pwd"+"/>");writer.println("</label>");writer.println("</div>");//button formwriter.println("<div class="+"button"+">");writer.println("<button type="+"submit"+" name="+"button_connexion"+" value="+"Se_connecter"+">Connexion</button>");writer.println("</div>");writer.println("</form>");//aller sur le lien de l'inscriptionwriter.println("<a href="+"/ProjetWeb2020/Inscription"+">T'es nouveau?Par ici l'inscription</a>");writer.println("</body>");}public void doPost(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {res.setContentType("text/html");PrintWriter writer = res.getWriter();String login, pwd;login=req.getParameter("Login");pwd=req.getParameter("Pwd");if(login==null && pwd==null){writer.println("<h1>Not good!</h1>");}//JSONObject obj=services.Authentification.loginUtilisateur(login, pwd);writer.println("<h2>login is:"+login+"</h2>");writer.println("<h2>pwd is:"+pwd+"</h2>");}}
And the result i don't want no more.
I will aprecciate any answer with great pleasure 
答案1
得分: 1
好的，以下是您提供的代码的中文翻译部分：
所以，非常感谢大家，尤其是 Swati 提供的解决方案。是的，这个问题是关于“反斜杠”的一个拼写错误。我给您正确的代码：
package servlets;
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;
//import services.*;
//import org.json.JSONException;
//import org.json.JSONObject;
public class Authentification extends HttpServlet{
public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {res.setContentType("text/html");PrintWriter writer = res.getWriter();writer.println("<h1>欢迎访问我们的新网站</h1>");writer.println("<body>");//表单writer.println("<form action=\"Authentification\" method=\"post\" class=\"form\">");//登录writer.println("<div class=\"\">");writer.println("<label for=\"login\">登录：");writer.println("<input type=\"text\" name=\"login\"/>");writer.println("</label>");writer.println("</div>");//密码writer.println("<div class=\"\">");writer.println("<label for=\"pwd\">密码：");writer.println("<input type=\"text\" name=\"pwd\"/>");writer.println("</label>");writer.println("</div>");//按钮表单writer.println("<div class=\"button\">");writer.println("<button type=\"submit\" name=\"button_connexion\" value=\"Se_connecter\">连接</button>");writer.println("</div>");writer.println("</form>");//跳转到注册链接writer.println("<a href=\"/ProjetWeb2020/Inscription\">新来的？这边进行注册</a>");writer.println("</body>");}public void doPost(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {res.setContentType("text/html");PrintWriter writer = res.getWriter();String login, pwd;login=req.getParameter("login");pwd=req.getParameter("pwd");if(login==null && pwd==null){writer.println("<h1>不好意思！</h1>");}//JSONObject obj=services.Authentification.loginUtilisateur(login, pwd);writer.println("<h2>登录名是：" + login + "</h2>");writer.println("<h2>密码是：" + pwd + "</h2>");}
}
以及HTML页面的语法（您可以在我之前的评论中查看旧的HTML代码）：
欢迎访问我们的新网站
新来的？这边进行注册
```
故事寓意：注意使用“"”，在HTML代码中使用反斜杠来处理字符串！
<details><summary>英文:</summary>So, thank you everybody, and especially Swati for the solution. Yes, the issue as a typo thing about "backslash".I give you the correct code:
package servlets;
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;
//import services.*;
//import org.json.JSONException;
//import org.json.JSONObject;
public class Authentification extends HttpServlet{
public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {res.setContentType("text/html");PrintWriter writer = res.getWriter();writer.println("<h1>Bienvenue sur notre nouveau site WEB</h1>");writer.println("<body>");//Formwriter.println("<form action="+"\"Authentification\""+" method="+"\"post\""+" class="+"\"form\""+">");//loginwriter.println("<div class=\" \">");writer.println("<label for="+"\"login\""+">Login:");writer.println("<input type="+"\"text\""+" name="+"\"login\""+"/>");writer.println("</label>");writer.println("</div>");//passwordwriter.println("<div class=\" \">");writer.println("<label for="+"\"pwd\""+">Password:");writer.println("<input type="+"\"text\""+" name="+"\"pwd\""+"/>");writer.println("</label>");writer.println("</div>");//button formwriter.println("<div class="+"\"button\""+">");writer.println("<button type="+"\"submit\""+" name="+"\"button_connexion\""+" value="+"\"Se_connecter\""+">Connexion</button>");writer.println("</div>");writer.println("</form>");//aller sur le lien de l'inscriptionwriter.println("<a href="+"/ProjetWeb2020/Inscription"+">T'es nouveau?Par ici l'inscription</a>");writer.println("</body>");}public void doPost(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {res.setContentType("text/html");PrintWriter writer = res.getWriter();String login, pwd;login=req.getParameter("login");pwd=req.getParameter("pwd");if(login==null && pwd==null){writer.println("<h1>Not good!</h1>");}//JSONObject obj=services.Authentification.loginUtilisateur(login, pwd);writer.println("<h2>login is:"+login+"</h2>");writer.println("<h2>pwd is:"+pwd+"</h2>");}
}
And the syntax of the html page:(you can check the ancient html code in my previous comments)
<h1>Bienvenue sur notre nouveau site WEB</h1>
<body>
<form action="Authentification" method="post" class="form">
<div class=" ">
<label for="login">Login:
<input type="text" name="login"/>
</label>
</div>
<div class=" ">
<label for="pwd">Password:
<input type="text" name="pwd"/>
</label>
</div>
<div class="button">
<button type="submit" name="button_connexion" value="Se_connecter">Connexion</button>
</div>
</form>
<a href=/ProjetWeb2020/Inscription>T'es nouveau?Par ici l'inscription</a>
</body>
Moral of the story:be careful with " ", use Backslash in strings for html code!</details># 答案2**得分**: 0更改访问时的参数名称。login=req.getParameter("login");pwd=req.getParameter("pwd");它将起作用。<details><summary>英文:</summary>change the param names while accessing.login=req.getParameter("login");pwd=req.getParameter("pwd");it will work.</details>
专注分享java语言的经验与见解，让所有开发者获益！
评论