一、get请求和post请求的区别

在Servlet中用来处理客户端请求需要用doGet()方法或doPost()方法中的request对象。

get请求：

get提交的数据会放在URL之后，以?分割URL和传输数据，参数之间以&相连

get方式明文传递，数据量小，不安全

效率高，浏览器默认请求方式为get请求

对应的Servlet的方法是doGet()

post请求：

post方法是把提交的数据放在HTTP包的body中

密文传递数据，数据量大，安全

效率没有get高

对应的Servlet的方法是doPost()

二、Request对象的应用

1、request主要方法

2、request获取数据

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>获取数据</title>
</head>
<body>
<form action="RequestServlet" method="post">
    <p><label>账号：</label><input type="text" name="user"></p>
    <p><label>密码：</label><input type="password" name="password"></p>
    <p><input type="submit" value="登录"></p>
</form>

</body>
</html>

package com.java.servlet;

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

@WebServlet(name = "RequestServlet", value = "/RequestServlet")
public class RequestServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String user = request.getParameter("user");
        String password = request.getParameter("password");
        System.out.println("user:"+user+"\npassword:"+password);

    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);

    }
}

3、设置请求的编码格式

控制台无法获取中文

package com.java.servlet;

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

@WebServlet(name = "RequestServlet", value = "/RequestServlet")
public class RequestServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");
        String user = request.getParameter("user");
        String password = request.getParameter("password");
        System.out.println("user:"+user+"\npassword:"+password);

    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);

    }
}

三、解决get请求收参乱码问题

get请求发送后，在服务器端获取中文数据产生乱码，是因为服务器和客户端沟通的编码不一致造成的，所以解决办法是在客户端和服务器之间设置一个统一的编码，之后就按照设置的编码进行数据的传输和接收。

在Tomcat7及以下版本，客户端以UTF-8的编码传输数据到服务器端，而服务器端的request对象使用的是ISO8859-1这个字符编码来接收数据，服务器和客户端沟通的编码不一致，因此会产生中文乱码。

解决办法：在接收到数据后，先获取request对象以ISO8859-1字符编码接收到的原始数据的字节数组，然后通过字节数组以指定的编码构建字符串，解决乱码问题。

Tomcat8的版本中get不会出现乱码了，因为服务器对url的编码格式可以自动转换

package com.java.servlet;

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

@WebServlet(name = "RequestServlet", value = "/RequestServlet")
public class RequestServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String user = request.getParameter("user");
        user = new String(user.getBytes("ISO8859-1"),"utf-8");
        String password = request.getParameter("password");
        System.out.println("user:"+user+"\npassword:"+password);

    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);

    }
}

四、解决post请求中文乱码问题

由于客户端是以UTF-8字符编码将表单数据传输到服务器端的，服务器端的字符编码格式为ISO8859-1，因此服务器端也需要设置以UTF-8字符编码进行接收。

解决方法：使用从ServletRequest接口继承而来的setCharacterEncoding(charset)方法进行统一的编码设置

package com.java.servlet;

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

@WebServlet(name = "RequestServlet", value = "/RequestServlet")
public class RequestServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);

    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");
        String user = request.getParameter("user");
        String password = request.getParameter("password");
        System.out.println("user:"+user+"\npassword:"+password);

    }
}