Java Servlet如何获取请求的参数值？

小灰灰 2021-02-13 16:57 736阅读 0赞

## Servlet如何获取请求的参数 ##

> 使用Request常用API来获取参数  
> 这里演示的表单的提交  
> 用到的是`getParameter()`和`getParameterValues()`

相关代码：

//ParamrterServlet.java
    package servlet;
    
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    import java.util.ArrayList;
    import java.util.Arrays;
    
    public class ParameterServlet extends HttpServlet { 
    
        @Override
        protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 
            String username = req.getParameter("username");
            String password = req.getParameter("password");
            String[] hobby = req.getParameterValues("hobby");
    
            System.out.println("用户名：" + username);
            System.out.println("密码：" + password);
            System.out.println("兴趣爱好：" + Arrays.asList(hobby));
        }
    
        @Override
        protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 
    // 设置请求体字符集为UTF-8
            req.setCharacterEncoding("UTF-8");
            String username = req.getParameter("username");
            String password = req.getParameter("password");
            String[] hobby = req.getParameterValues("hobby");
    
            System.out.println("用户名：" + username);
            System.out.println("密码：" + password);
            System.out.println("兴趣爱好：" + Arrays.asList(hobby));
        }
    }

<!DOCTYPE html>
    <html lang="en">
    <head>
        <meta charset="UTF-8">
        <title>Title</title>
    </head>
    <body>
        <form action="http://localhost:8080/Java_Web01_war_exploded/parameterServlet" method="post">
            用户名：<input type="text" name="username"><br>
            密码：<input type="text" name="password"><br>
            兴趣爱好：
            <input type="checkbox" name="hobby" value="java">java
            <input type="checkbox" name="hobby" value="cpp">c++
            <input type="checkbox" name="hobby" value="PHP">PHP
            <input type="checkbox" name="hobby" value="HTML">HTML<br>
            <input type="submit" value="提交（POST请求）">
    
        </form>
    
        <form action="http://localhost:8080/Java_Web01_war_exploded/parameterServlet" method="get">
            用户名：<input type="text" name="username"><br>
            密码：<input type="text" name="password"><br>
            兴趣爱好：
            <input type="checkbox" name="hobby" value="java">java
            <input type="checkbox" name="hobby" value="cpp">c++
            <input type="checkbox" name="hobby" value="PHP">PHP
            <input type="checkbox" name="hobby" value="HTML">HTML<br>
            <input type="submit" value="提交（GET请求）">
    
        </form>
    
    </body>
    </html>

## 如果POST请求传递出现乱码(传递中文时)如何解决? ##

> 在doPost方法中加入：  
> `req.setCharacterEncoding("UTF-8");`  
> 注意：这个API得加在第一行，只对后面的获取请求参数传递生效，对于前面的请求参数不会生效