request请求转换成对象。

1）前端post数据过来，key和val键值对会有很多，这个时候往后端进行插值的时候，最好将这些键值对转换成对象进行处理。

使用common-beanutils 来将前端传递过来的map直接转换成对象。

依赖jar包：

前端代码的name属性要和后端bean对象属性一致！

   <h1>测试POST</h1>
   <form action="/bean" method="post">
     <input type="text" name="username">用户名字
     <input type="password" name="passowrd">用户密码
     <button type="submit">提交</button>
   </form>
   </body>
 </html>

后端代码：

 package jd.com.bean_test;

 import org.apache.commons.beanutils.BeanUtils;

 import javax.servlet.ServletException;
 import javax.servlet.annotation.WebServlet;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 import java.io.IOException;
 import java.util.Map;

 @WebServlet(name = "Servlet_Bean")
 public class Servlet_Bean extends HttpServlet {
     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws  ServletException, IOException {
         //只能针对post请求 不乱码。
         request.setCharacterEncoding("utf-8");
         Map<String,String[]> data=request.getParameterMap();
         User user_obj=new User();
         try {
             BeanUtils.populate(user_obj,data);
         }catch (Exception ex){
             ex.printStackTrace();
             throw  new RuntimeException("转换出问题！");
         }
         System.out.println(user_obj);

     }

     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

     }
 }

 package jd.com.bean_test;

 public class User {
     private String username;
     private String passowrd;
     public  User(){}

     public void setUsername(String username) {
         this.username = username;
     }

     public void setPassowrd(String passowrd) {
         this.passowrd = passowrd;
     }

     public String getUsername() {
         return username;
     }

     public String getPassowrd() {
         return passowrd;
     }

     @Override
     public String toString() {
         return username+" "+passowrd;
     }
 }