Question

我下面有一个jps，下面的代码带有源和目标下拉列表，以及一个“ Execute”按钮，它将调用servlet。

服务端将根据所选的值执行某些操作。

JSP代码：

<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
    <head>
     <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
        <title/>
    </head>
    <form action="MySourceEnv" method="POST">
        <select name="SourceEnv" >      
            <option>10.100.10.11</option>      
            <option>10.100.10.12</option>      
        </select>   
    </form>
    <form action="MyDestEnv" method="POST">
        <select name="DestEnv" >      
            <option>10.100.10.11</option>      
            <option>10.100.10.12</option>      
        </select>   
    </form>
    <body>
        <button onclick="location.href = 'http://localhost:7500/Project_1/JavaServlet';" id="RedirectButton" > Execute</button>
    </body>
</html>

Servlet代码：

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

public class JavaServletClass extends HttpServlet {

    public void init() throws ServletException {
    }

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        String SourceEnvParam = request.getParameter("SourceEnv");
        out.println("<h1>" + SourceEnvParam + "</h1>");
        LogicMethod(SourceEnvParam);
    }

    private void LogicMethod(String SourceEnvParam) throws IOException {
        // Some logic here
    }

    public void destroy() {
    }
}

当单击执行按钮并调用servlet时，我得到 request.getParameter（“ SourceEnv”）的值为Null。

我在这里怎么了？

Answer 1

我认为您的html代码中存在问题。首先，您从体内创建了两种形式，具有两种作用。但是您用

定义了另一个动作

<button onclick="location.href = 'http://localhost:7500/Project_1/JavaServlet';" id="RedirectButton" > Execute</button>.

尝试这样编写您的jsp页面

<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
    <head>

        <title> name<title/>
    </head>

    <body>
      <form action="JavaServletClass" method="GET">
        <select name="SourceEnv" >      
            <option>10.100.10.11</option>      
            <option>10.100.10.12</option>      
        </select>  
       <select name="DestEnv" >      
            <option>10.100.10.11</option>      
            <option>10.100.10.12</option>      
        </select> 
<button type="submit" value="Submit">Submit</button> 
</form>
</body>
</html>

从JSP调用servlet时request.getParameter中的空值

1 个答案: