前端学习笔记：BeanUtils工具类的使用
BeanUtils的用法
====
BeanUtils的API docs:
https://docs.spring.io/spring/docs/current/javadoc-api/index.html?index-files/index-1.html
BeanUtils的作用：可以将jsp页面传过来的多个参数封装成一个对象。
一、搭建数据库
drop database if exists `pcd01`;
CREATE DATABASE IF NOT EXISTS `pcd01` CHARACTER SET `utf8` COLLATE `utf8_bin`;
USE `pcd01`;
DROP TABLE IF EXISTS `user`;
CREATE TABLE IF NOT EXISTS `user`(
`id` INT PRIMARY KEY AUTO_INCREMENT,
`username` VARCHAR(50) DEFAULT NULL,
`password` VARCHAR(50) DEFAULT NULL,
`nickname` VARCHAR(50) DEFAULT NULL
);
INSERT INTO `user` VALUES(NULL, "zhangsan", "123456", "张三");
INSERT INTO `user` VALUES(NULL, "lisi", "123456", "李四");
INSERT INTO `user` VALUES(NULL, "wangwu", "123456", "王五");
二、搭建项目
1. 创建工程：Create New Project-->Empty Project, Project name=exercises01, Finish
2. 创建项目：New-->Module-->Java Enterprise, Java EE version=Java EE 6, Additional Libraries and Frameworks=Web Application(3.0), Versions=3.0, 选中Create web.xml-->Next, Module name=exercise01
3. 在src文件夹下建立层级
servlet包：com.itcast.servlet
4. 导入jar包
在web/WEB-INF文件夹下建立文件夹lib，将jar包放入lib文件夹下，add as library, 所需要的jar包有：
BeanUtils的：commons-beanutils-1.9.4.jar, commons-logging-1.2.jar
5.配置tomcat
(1)Run-->Edit Configuration, 点击+，选Tomcat Server-->Local
(2)Name=tomcat8, 在Server标签页中，点击Configure按钮，Tomcat Home选择tomcat的安装目录，libraries选择tomcat安装目录下的lib文件夹，加入jsp-api.jar和servlet-api.jar
(3)在Deployment标签页中，Application context=/项目名称，即：Application context=/exercise01
三、核心代码
//file name: LoginServlet.java
package com.itcast.web;
import com.itcast.domain.User;
import org.apache.commons.beanutils.BeanUtils;
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.lang.reflect.InvocationTargetException;
import java.util.Map;
public class LoginServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//方式一：我们自己手动封装User对象
/*
//1.接收浏览器提交的数据
String username = request.getParameter("username");
String password = request.getParameter("password");
//2.将其封装成User对象 //目的：为了给大家讲解BeanUtils工具类的使用
User user = new User(0, username, password, "");
System.out.println(user);
//3.调用Service层的功能，根据封装后的对象，查询是否有该对象
//4.判断，如果存在，重定向到index.jsp
//5.判断，如果不存在，请求转发到login.jsp登陆页面
*/
//方式二：通过BeanUtils工具类实现，自动将数据封装成User对象
Map<String, String[]> map = request.getParameterMap();
User user = new User();
try {
BeanUtils.populate(user, map);
System.out.println(user);//从前端页面得到的结果：User{id=null, username='zhangsan', password='123456', nickname='张三'}
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
}
}
全部代码和笔记已经以资源的形式上传到CSDN，搜索关键字为：BeanUtils工具类的使用.zip
链接为：https://download.csdn.net/download/elizabethxxy/11953187
