Spring MVC模式示例（采用解耦控制器+校验器）

Product

package com.mstf.bean;

import java.io.Serializable;
/**
 * Product类，封装了一些信息，包含三个属性
 * @author wangzheng
 *
 */
public class Product implements Serializable {

	private static final long serialVersionUID = 1L;

	private String name;
	private String description;
	private float price;

	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getDescription() {
		return description;
	}
	public void setDescription(String description) {
		this.description = description;
	}
	public float getPrice() {
		return price;
	}
	public void setPrice(float price) {
		this.price = price;
	}

}

　　ProductForm

package com.mstf.bean.form;
/**
 * ProductForm是表单类
 * 作用：当数据校验失败时，用于保存和展示用户在原始表单的输入
 * @author wangzheng
 *
 */
public class ProductForm {
	private String name;
	private String description;
	private String price;

	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getDescription() {
		return description;
	}
	public void setDescription(String description) {
		this.description = description;
	}
	public String getPrice() {
		return price;
	}
	public void setPrice(String price) {
		this.price = price;
	}

}

　　Controller

package com.mstf.controller;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public interface Controller {

	String handleRequest(HttpServletRequest req,HttpServletResponse resp);
}

　　InputProductController

package com.mstf.controller;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class InputProductController implements Controller {

	@Override
	public String handleRequest(HttpServletRequest req,HttpServletResponse resp) {
		return "/WEB-INF/jsp/ProductForm.jsp";
	}
}

　　SaveProductController

package com.mstf.controller;

import java.util.List;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.mstf.bean.Product;
import com.mstf.bean.form.ProductForm;
import com.mstf.validator.ProductValidator;

public class SaveProductController implements Controller {

	@Override
	public String handleRequest(HttpServletRequest req,HttpServletResponse resp) {
		// 构建一个ProductForm表单对象
        ProductForm productForm = new ProductForm();
        // 写入表单对象
        productForm.setName(req.getParameter("name"));
        productForm.setDescription(req.getParameter("description"));
        productForm.setPrice(req.getParameter("price"));

        //引入校验器
        ProductValidator productValidator=new ProductValidator();
        List<String> errors=productValidator.validate(productForm);
        if(errors.isEmpty()) {
        	// 创建模型
        	Product product = new Product();
            product.setName(productForm.getName());
            product.setDescription(productForm.getDescription());
            product.setPrice(Float.parseFloat(productForm.getPrice()));
            req.setAttribute("product", product);
            return "/WEB-INF/jsp/ProductDetails.jsp";
        } else {
        	req.setAttribute("errors", errors);
        	req.setAttribute("form", productForm);
        	return "/WEB-INF/jsp/ProductForm.jsp";
        }
	}
}

　　DispatcherServlet

package com.mstf.servlet;

import java.io.IOException;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.mstf.controller.InputProductController;
import com.mstf.controller.SaveProductController;

public class DispatcherServlet extends HttpServlet {

	private static final long serialVersionUID = 1L;

	@Override
	public void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		process(req, resp);
	}

	@Override
	public void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		process(req, resp);
	}
	/**
	 * 这个方法用来处理所有输入请求
	 * @param req
	 * @param resp
	 * @throws IOException
	 * @throws ServletException
	 */
	private void process(HttpServletRequest req,HttpServletResponse resp) throws IOException,ServletException {
		req.setCharacterEncoding("UTF-8"); //转码
		resp.setCharacterEncoding("UTF-8");
		String uri=req.getRequestURI(); // 获取请求URI
		int lastIndex=uri.lastIndexOf("/");
		String action=uri.substring(lastIndex+1); // 获取action名称
		String dispatchUrl=null;
		// 执行方法
		if(action.equals("product_input.action")) {
			InputProductController controller=new InputProductController();
			dispatchUrl=controller.handleRequest(req, resp);
		} else if (action.equals("product_save.action")) {
			SaveProductController controller=new SaveProductController();
			dispatchUrl=controller.handleRequest(req, resp);
		}
		if(dispatchUrl!=null) {
			RequestDispatcher rd=req.getRequestDispatcher(dispatchUrl);
			rd.forward(req, resp);
		}
	}
}

　ProductValidator

package com.mstf.validator;

import java.util.ArrayList;
import java.util.List;

import com.mstf.bean.form.ProductForm;
/**
 * 校验器
 * @author wangzheng
 *
 */
public class ProductValidator {

	public List<String> validate(ProductForm productForm) {
		List<String> errors = new ArrayList<String>();
		String name = productForm.getName();
		if (name == null || name.trim().isEmpty()) {
			errors.add("必须输入名称！");
		}
		String price = productForm.getPrice();
		if (price == null || price.trim().isEmpty()) {
			errors.add("必须输入价格！");
		} else {
			try {
				Float.parseFloat(price);
			} catch (NumberFormatException e) {
				errors.add("输入的价格无效！");
			}
		}
		return errors;
	}
}

　　ProductDetails.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>详情</title>
<style type="text/css">@IMPORT url("css/main.css");</style>
</head>
<body>
	<div id="global">
    <h4>产品已保存</h4>
    <p>
        <h5>详细列表:</h5>
        	名称: ${product.name}<br>
        	简介: ${product.description}<br>
        	价格: ￥${product.price}
    </p>
</div>
</body>
</html>

　　ProductForm.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>添加</title>
<style type="text/css">@IMPORT url("css/main.css");</style>
</head>
<body>
	<div id="global">
	<c:if test="${requestScope.errors != null }">
		<p id="errors">
			操作出错！
			<ul>
				<c:forEach var="error" items="${requestScope.errors }">
					<li>
						${error }
					</li>
				</c:forEach>
			</ul>
		</p>
	</c:if>
		<form action="product_save.action" method="post">
			<fieldset>
				<legend>添加：</legend>
					<p>
					    <label for="name">名称: </label>
						<input type="text" id="name" name="name" tabindex="1">
		            </p>
		            <p>
					    <label for="description">简介: </label>
						<input type="text" id="description" name="description" tabindex="2">
					</p>
		            <p>
		    			<label for="price">价格: </label>
						<input type="text" id="price" name="price" tabindex="3">
					</p>
					<p id="buttons">
						<input id="reset" type="reset" tabindex="4">
						<input id="submit" type="submit" tabindex="5" value="添加">
					</p>
			</fieldset>
		</form>
	</div>
</body>
</html>