Java 从JSP调用servlet时request.getParameter中的Null值_Java_Jsp_Servlets

Java 从JSP调用servlet时request.getParameter中的Null值

java jsp servlets

Java 从JSP调用servlet时request.getParameter中的Null值,java,jsp,servlets,Java,Jsp,Servlets,我有一个jps，下面是源代码和目标代码下拉列表，还有一个按钮“执行”，它将调用一个servlet servet将根据选择的值执行一些操作 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

我有一个jps，下面是源代码和目标代码下拉列表，还有一个按钮“执行”，它将调用一个servlet

servet将根据选择的值执行一些操作

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>

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() {
    }
}


10.100.10.11      
10.100.10.12      
10.100.10.11      
10.100.10.12      
执行

Servlet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>

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() {
    }
}

import java.io.*；
导入javax.servlet.*；
导入javax.servlet.http.*；
公共类JavaServletClass扩展了HttpServlet{
public void init（）引发ServletException{
}
public void doGet（HttpServletRequest请求，HttpServletResponse响应）抛出ServletException，IOException{
response.setContentType（“text/html”）；
PrintWriter out=response.getWriter（）；
字符串SourceEnvParam=request.getParameter（“SourceEnv”）；
out.println（“+SourceEnvParam+”）；
LogicMethod（SourceEnvParam）；
}
私有void LogicMethod（字符串SourceEnvParam）引发IOException{
//这里有些逻辑
}
公共空间销毁（）{
}
}

单击execute按钮并调用servlet时，我将request.getParameter（“SourceEnv”）的值设置为Null

我在这里怎么了？

我认为问题是在您的

html

代码中产生的。首先，你从你的身体中创造了两个形体，它有两个动作。但你定义了另一个动作

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

执行。

尝试这样编写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>


名称
10.100.10.11      
10.100.10.12      
10.100.10.11      
10.100.10.12      
提交

我认为问题产生在您的

html

代码中。首先，你从你的身体中创造了两个形体，它有两个动作。但你定义了另一个动作

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

执行。

尝试这样编写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>


名称
10.100.10.11      
10.100.10.12      
10.100.10.11      
10.100.10.12      
提交