package tmall.filter;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.lang.StringUtils;

public class BackServletFilter implements Filter {

	public void destroy() {
		
	}

	@Override
	public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)
			throws IOException, ServletException {
		HttpServletRequest request = (HttpServletRequest) req;
		HttpServletResponse response = (HttpServletResponse) res;
		
		String contextPath=request.getServletContext().getContextPath();
		String uri = request.getRequestURI();
		uri =StringUtils.remove(uri, contextPath);
		if(uri.startsWith("/admin_")){		
			String servletPath = StringUtils.substringBetween(uri,"_", "_") + "Servlet";
			String method = StringUtils.substringAfterLast(uri,"_" );
			request.setAttribute("method", method);
			req.getRequestDispatcher("/" + servletPath).forward(request, response);
			return;
		}
		
		chain.doFilter(request, response);
	}

	public void init(FilterConfig arg0) throws ServletException {
	
	}
}

    <filter>
        <filter-name>BackServletFilter</filter-name>
        <filter-class>tmall.filter.BackServletFilter</filter-class>
    </filter>
 
    <filter-mapping>
        <filter-name>BackServletFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

package tmall.servlet;

import java.awt.image.BufferedImage;	
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

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

import tmall.bean.Category;
import tmall.util.ImageUtil;
import tmall.util.Page;

public class CategoryServlet extends BaseBackServlet {
	
	public String add(HttpServletRequest request, HttpServletResponse response, Page page) {
		Map<String,String> params = new HashMap<>();
		InputStream is = super.parseUpload(request, params);
		
		String name= params.get("name");
		Category c = new Category();
		c.setName(name);
		categoryDAO.add(c);
		
		File  imageFolder= new File(request.getSession().getServletContext().getRealPath("img/category"));
		File file = new File(imageFolder,c.getId()+".jpg");
		
		try {
			if(null!=is && 0!=is.available()){
			    try(FileOutputStream fos = new FileOutputStream(file)){
			        byte b[] = new byte[1024 * 1024];
			        int length = 0;
			        while (-1 != (length = is.read(b))) {
			            fos.write(b, 0, length);
			        }
			        fos.flush();
			        //通过如下代码，把文件保存为jpg格式
			        BufferedImage img = ImageUtil.change2jpg(file);
			        ImageIO.write(img, "jpg", file);		
			    }
			    catch(Exception e){
			    	e.printStackTrace();
			    }
			}
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}	
		return "@admin_category_list";
	}

	public String delete(HttpServletRequest request, HttpServletResponse response, Page page) {
		int id = Integer.parseInt(request.getParameter("id"));
		categoryDAO.delete(id);
		return "@admin_category_list";
	}

	public String edit(HttpServletRequest request, HttpServletResponse response, Page page) {
		int id = Integer.parseInt(request.getParameter("id"));
		Category c = categoryDAO.get(id);
		request.setAttribute("c", c);
		return "admin/editCategory.jsp";		
	}

	public String update(HttpServletRequest request, HttpServletResponse response, Page page) {
		Map<String,String> params = new HashMap<>();
		InputStream is = super.parseUpload(request, params);
		
		System.out.println(params);
		String name= params.get("name");
		int id = Integer.parseInt(params.get("id"));

		Category c = new Category();
		c.setId(id);
		c.setName(name);
		categoryDAO.update(c);
		
		File  imageFolder= new File(request.getSession().getServletContext().getRealPath("img/category"));
		File file = new File(imageFolder,c.getId()+".jpg");
		file.getParentFile().mkdirs();
		
		try {
			if(null!=is && 0!=is.available()){
			    try(FileOutputStream fos = new FileOutputStream(file)){
			        byte b[] = new byte[1024 * 1024];
			        int length = 0;
			        while (-1 != (length = is.read(b))) {
			            fos.write(b, 0, length);
			        }
			        fos.flush();
			        //通过如下代码，把文件保存为jpg格式
			        BufferedImage img = ImageUtil.change2jpg(file);
			        ImageIO.write(img, "jpg", file);		
			    }
			    catch(Exception e){
			    	e.printStackTrace();
			    }
			}
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return "@admin_category_list";

	}

	public String list(HttpServletRequest request, HttpServletResponse response, Page page) {
		List<Category> cs = categoryDAO.list(page.getStart(),page.getCount());
		int total = categoryDAO.getTotal();
		page.setTotal(total);
		
		request.setAttribute("thecs", cs);
		request.setAttribute("page", page);
		
		return "admin/listCategory.jsp";
	}
}

package tmall.servlet;

import java.io.InputStream;

import java.lang.reflect.Method;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

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

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

import tmall.dao.CategoryDAO;
import tmall.dao.OrderDAO;
import tmall.dao.OrderItemDAO;
import tmall.dao.ProductDAO;
import tmall.dao.ProductImageDAO;
import tmall.dao.PropertyDAO;
import tmall.dao.PropertyValueDAO;
import tmall.dao.ReviewDAO;
import tmall.dao.UserDAO;
import tmall.util.Page;

public abstract class BaseBackServlet extends HttpServlet {

	public abstract String add(HttpServletRequest request, HttpServletResponse response, Page page) ;
	public abstract String delete(HttpServletRequest request, HttpServletResponse response, Page page) ;
	public abstract String edit(HttpServletRequest request, HttpServletResponse response, Page page) ;
	public abstract String update(HttpServletRequest request, HttpServletResponse response, Page page) ;
	public abstract String list(HttpServletRequest request, HttpServletResponse response, Page page) ;
	
	protected CategoryDAO categoryDAO = new CategoryDAO();
	protected OrderDAO orderDAO = new OrderDAO();
	protected OrderItemDAO orderItemDAO = new OrderItemDAO();
	protected ProductDAO productDAO = new ProductDAO();
	protected ProductImageDAO productImageDAO = new ProductImageDAO();
	protected PropertyDAO propertyDAO = new PropertyDAO();
	protected PropertyValueDAO propertyValueDAO = new PropertyValueDAO();
	protected ReviewDAO reviewDAO = new ReviewDAO();
	protected UserDAO userDAO = new UserDAO();

	public void service(HttpServletRequest request, HttpServletResponse response) {
		try {
			
			/*获取分页信息*/
			int start= 0;
			int count = 5;
			try {
				start = Integer.parseInt(request.getParameter("page.start"));
			} catch (Exception e) {
				
			}
			try {
				count = Integer.parseInt(request.getParameter("page.count"));
			} catch (Exception e) {
			}
			Page page = new Page(start,count);
			
			/*借助反射，调用对应的方法*/
			String method = (String) request.getAttribute("method");
			Method m = this.getClass().getMethod(method, javax.servlet.http.HttpServletRequest.class,
					javax.servlet.http.HttpServletResponse.class,Page.class);
			String redirect = m.invoke(this,request, response,page).toString();
			
			/*根据方法的返回值，进行相应的客户端跳转，服务端跳转，或者仅仅是输出字符串*/
			
			if(redirect.startsWith("@"))
				response.sendRedirect(redirect.substring(1));
			else if(redirect.startsWith("%"))
				response.getWriter().print(redirect.substring(1));
			else
				request.getRequestDispatcher(redirect).forward(request, response);
			
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
			throw new RuntimeException(e);
		}
	}
	public InputStream parseUpload(HttpServletRequest request, Map<String, String> params) {
			InputStream is =null;
			try {
	            DiskFileItemFactory factory = new DiskFileItemFactory();
	            ServletFileUpload upload = new ServletFileUpload(factory);
	            // 设置上传文件的大小限制为10M
	            factory.setSizeThreshold(1024 * 10240);
	             
	            List items = upload.parseRequest(request);
	            Iterator iter = items.iterator();
	            while (iter.hasNext()) {
	                FileItem item = (FileItem) iter.next();
	                if (!item.isFormField()) {
	                    // item.getInputStream() 获取上传文件的输入流
	                    is = item.getInputStream();
	                } else {
	                	String paramName = item.getFieldName();
	                	String paramValue = item.getString();
	                	paramValue = new String(paramValue.getBytes("ISO-8859-1"), "UTF-8");
	                	params.put(paramName, paramValue);
	                }
	            }
	             
	        } catch (Exception e) {
	            e.printStackTrace();
	        }
			return is;
		}
}

    <servlet>
        <servlet-name>CategoryServlet</servlet-name>
        <servlet-class>tmall.servlet.CategoryServlet</servlet-class>
    </servlet>
 
    <servlet-mapping>
        <servlet-name>CategoryServlet</servlet-name>
        <url-pattern>/categoryServlet</url-pattern>
    </servlet-mapping>