BaseBackServlet.java

package tmall.servlet;


import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import tmall.dao.*;
import tmall.util.Page;

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.InputStream;
import java.lang.reflect.Method;
import java.nio.charset.StandardCharsets;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

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();

    @Override
    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);


            String method = (String) request.getAttribute("method"); //假设method = list，Servlet = CategoryServlet
            /**
             * 借助反射，调用对应的方法利用反射，调用对应业务类的方法，注意此处的 this 并不是指本类的对象，
             * 而是具体的业务类，如 CategoryServlet 对象，为什么呢？
             * 因为上面的 Filter 跳转目的地是 CategoryServlet
             * 只是CategoryServlet 调用了父类 BaseBackServlet 的 service 方法而已
             */
            Method m = this.getClass().getMethod(method, javax.servlet.http.HttpServletRequest.class,
                    javax.servlet.http.HttpServletResponse.class, Page.class); // CategoryServlet.list(..)
            String redirect = m.invoke(this, request, response, page).toString(); // redirect = "admin/listCategory.jsp";

            /*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)); // 客户端跳转，即重定向，原 request 会失效
            else if (redirect.startsWith("%"))
                response.getWriter().print(redirect.substring(1)); // 输出字符串
            else
                request.getRequestDispatcher(redirect).forward(request, response); //服务端跳转

        } 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()) {
                    System.out.println("上传文件：进入获取输入流。！item.isFormField为true");
                    // item.getInputStream() 获取上传文件的输入流
                    is = item.getInputStream();
                } else {
                    System.out.println("上传文件：未进入获取输入流。！item.isFormField为false");

                    String paramName = item.getFieldName();
                    String paramValue = item.getString();
                    System.out.println(paramName + ":" + paramValue);
                    paramValue = new String(paramValue.getBytes(StandardCharsets.ISO_8859_1), StandardCharsets.UTF_8);
                    params.put(paramName, paramValue);
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return is;
    }


}