Struts2封装数据核心机制 Struts2-3mode

封装的类Users.java

package com.cj.pojo;

public class Users {
    private String username;
    private String password;
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
}

servlet实现 有两个(BaseServlet.java和LoginServlet.java)

BaseServlet

package com.cj.servlet;

import java.io.IOException;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.Enumeration;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class BaseServlet
 */
@WebServlet("/BaseServlet")
public class BaseServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public BaseServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doPost(request, response);
    }


    //当请求发送到action 之前
        //调用MloginAction类中getModel()获取要将表单数据封装到哪个实例化的对象中
        //获得到该对象之后,我们可以获得 类类型
        //获得类 类型之后,获得类中的属性
        //request,getParameters获得  表单提交的所有数据名
        //从而获取值
        //如果表单提交的name值与实体类中属性名一致
        //那么我们将获得表单中的数据 封装到us对象当中去
    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        try {
            //在程序运行时 获取当前类的getModel方法对象
            Method method = this.getClass().getDeclaredMethod("getModel", null);
            //通过invoke方法 调用本类中的该方法 获得实体类对象
            Object object = method.invoke(this, null);
            //通过实体类对象获得 类类型
            Class cl = object.getClass();
            //通过类类型获得 类中的属性对象数组
            Field[] fi = cl.getDeclaredFields();
            //通过request获得所有的 表单中提交的name值
            Enumeration en = request.getParameterNames();
            //循环枚举中的值
            while (en.hasMoreElements()) {
                //获得枚举中的值
                String fieldName = en.nextElement().toString();
                //循环类中所有的属性对象
                for(int i=0;i<fi.length;i++){

                    if (fieldName.equals(fi[i].getName())) {
                        fi[i].setAccessible(true);//尤为重要,可以被外部赋值
                        fi[i].set(object, request.getParameter(fieldName));
                    }
                }
            }
            //调用默认的方法  执行处理
            Method method2 = this.getClass().getDeclaredMethod("execute", null);
            //获得返回的url字符串
            Object url = method2.invoke(this, null);
            //根据返回的字符串 跳转页面
            request.getRequestDispatcher(String.valueOf(url)).forward(request, response);
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

}

LoginServlet 继承于 BaseServlet

package com.cj.servlet;

import java.io.IOException;
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 com.cj.pojo.Users;

/**
 * Servlet implementation class LoginServlet
 */
@WebServlet("/LoginServlet")
public class LoginServlet extends BaseServlet {

    private Users us = new Users();

    public String execute() throws Exception {
        // TODO Auto-generated method stub
        System.out.println("自动封装数据后的结果");
        System.out.println(us.getUsername());
        System.out.println(us.getPassword());
        return "/index.jsp";
    }

    public Users getModel() {
        // TODO Auto-generated method stub
        return us;
    }

}

index.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
    <%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!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=UTF-8">
<title>Insert title here</title>
</head>
<body>
  <form action="<%=path %>/servlet/LoginServlet" method="post">
            username:<input type="text" name="username"><br>
            password:<input type="password" name="password"><br>
            <input type="submit" value="tijiao">
   </form>
</body>
</html>