为什么修改之后跳转显示页面没有显示 需要点一下商品分类才能显示

package com.imooc.web.action;

import java.io.IOException;
import java.util.List;
import java.util.Map;

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.imooc.dao.CategoryDao;
import com.imooc.dao.impl.CategoryDaoImpl;
import com.imooc.domain.Category;
import com.imooc.domain.Product;
import com.imooc.service.CategoryService;
import com.imooc.service.ProductService;
import com.imooc.service.impl.CategoryServiceImpl;
import com.imooc.service.impl.ProductServiceImpl;
import com.imooc.utils.UploadUtils;


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

	
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		//接受method参数
		String methodName = request.getParameter("method");
		if("findAll".equals(methodName)) {
			findAll(request,response);
		}else if("saveUI".equals(methodName)) {
			svaeUI(request,response);
		}else if("save".equals(methodName)) {
			save(request,response);
		}else if("updata".equals(methodName)) {
			updata(request,response);
		}else if("upDateok".equals(methodName)) {
			upDateok(request,response);
		}
	}
	
	/**
	 * 修改商品信息并跳转到显示页面的方法
	 * @param request
	 * @param response
	 * @throws IOException 
	 */
	private void upDateok(HttpServletRequest request, HttpServletResponse response) throws IOException {
		//文件上传
		Map<String,String> map = UploadUtils.uploadFile(request);
		//封装数据
		Integer pid = Integer.parseInt(request.getParameter("pid"));
		Product product = new Product();
		product.setPid(pid);
		product.setPname(map.get("pname"));
		product.setAuthor(map.get("author"));
		product.setPrice(Double.parseDouble(map.get("price")));
		product.setDescription(map.get("description"));
		product.setFilename(map.get("filename"));
		product.setPath(map.get("path"));
		product.getCategory().setCin(Integer.parseInt(map.get("cid")));
		System.out.println("修改后--" + product);
		//调用业务层处理数据
		ProductService productService = new ProductServiceImpl();
		productService.upDateok(product);
		//页面跳转
		response.sendRedirect(request.getContextPath() + "/admin/product_list.jsp?method=findAll");
		}

	/**
	 * 编辑商品信息的方法
	 * @param request
	 * @param response
	 * @throws IOException 
	 * @throws ServletException 
	 */
	private void updata(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		//获取参数
		Integer pid = Integer.parseInt(request.getParameter("pid"));
		//调用业务层处理
		ProductService proServive = new ProductServiceImpl();
		Product product = proServive.updata(pid);
		CategoryDao  categoryDao = new CategoryDaoImpl();
		List<Category> categoryList = categoryDao.findAll();
		//页面跳转
		request.setAttribute("categoryList", categoryList);
		request.setAttribute("product", product);
		request.getRequestDispatcher("/admin/product_update.jsp").forward(request, response);
			
	}


	/**
	 *后台 添加商品的方法
	 * @param request
	 * @param response
	 * @throws IOException 
	 */
	private void save(HttpServletRequest request, HttpServletResponse response) throws IOException {
		//文件上传
		Map<String, String> map = UploadUtils.uploadFile(request);
		//将数据进行分装
		Product product = new Product();
		product.setPname(map.get("pname"));
		product.setAuthor(map.get("author"));
		product.setPrice(Double.parseDouble(map.get("price")));
		product.setDescription(map.get("descirption"));
		System.out.println("MAP" + map.get("descirption"));
		product.setFilename(map.get("filename"));
		product.setPath(map.get("path"));
		product.getCategory().setCin(Integer.parseInt(map.get("cid")));
		//处理数据
		ProductService productService = new ProductServiceImpl();
		productService.save(product);
		//页面跳转
		response.sendRedirect(request.getContextPath() + "/admin/product_list.jsp?method=findAll");
	}



	/**
	 * 查询商品分类并跳转至添加页面
	 * @param request
	 * @param response
	 * @throws IOException 
	 * @throws ServletException 
	 */
	private void svaeUI(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		//查询所有分类的信息
		CategoryService categoryService = new CategoryServiceImpl();
		List<Category> categoryList = categoryService.findAll();
		
		//页面跳转
		request.setAttribute("categoryList", categoryList);
		request.getRequestDispatcher("/admin/product_add.jsp").forward(request, response);
	}
	
	/**
	 * 查询所有商品的方法
	 * @param request
	 * @param response
	 * @throws IOException 
	 * @throws ServletException 
	 */
	private void findAll(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		//调用业务层处理数据
		ProductService productService = new ProductServiceImpl();
		List<Product> productList = productService.findAll();
		//页面跳转
		request.setAttribute("productList", productList);	
		request.getRequestDispatcher("/admin/product_list.jsp").forward(request, response);
	}


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

}