文件上传后端 随堂代码1208

package servlet;

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

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

@WebServlet("/upload")
public class Upload extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("解决乱码问题");
        req.setCharacterEncoding("utf8");

        System.out.println("已进入post请求");

        System.out.println("确认这个表单是不是multipart表单");
        boolean multipartContent = ServletFileUpload.isMultipartContent(req);
        System.out.println(multipartContent);

        System.out.println("期望上传的文件都保存在一个名叫uploads目录中");
        System.out.println("获取该目录的路径");
        String uploadsPath = req.getServletContext().getRealPath("uploads");
        System.out.println(uploadsPath);

        System.out.println("判断这个路径是否存在");
        File uploadFile = new File(uploadsPath);
        boolean exists = uploadFile.exists();

        if (!exists) {
            System.out.println("文件夹不存在，我们就创建");
            boolean mkdir = uploadFile.mkdir();
            System.out.println("创建目录的结果");
            System.out.println(mkdir);
        }

        System.out.println("代码来到此处，一定就存在上传资源的存放目录了");
        System.out.println(uploadsPath);


        System.out.println("主要的保存文件操作===========");

        if (multipartContent) {
            // 工厂
            FileItemFactory diskFileItemFactory = new DiskFileItemFactory();
            // 规则
            ServletFileUpload servletFileUpload = new ServletFileUpload(diskFileItemFactory);
            // 利用规则解析请求
            List<FileItem> list = null;
            try {
                list = servletFileUpload.parseRequest(req);
            } catch (FileUploadException e) {
                e.printStackTrace();
            }
            // 【item1，itemn】

            // 遍历集合
            for (FileItem item :
                    list) {
                // 判断成员是否是普通的字段控件
                boolean formField = item.isFormField();

                // 如果是普通控件
                if (formField) {
                    // 当前item是一个普通的控件
                    // 取值
                    String value = item.getString("utf8");
                    String name = item.getName();
                    System.out.println("当前控件的name是" + name);
                    System.out.println("当前控件的值是" + value);
                }
                // 如果不是普通控件
                else {
                    // 当前item一定是文件上传控件
                    // 获取文件名
                    String name = item.getName();
                    // 拼一个保存的路径
                    File file = new File(uploadsPath, name);
                    // 保存数据
                    try {
                        item.write(file);
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }

            }

        } else {
            String name = req.getParameter("name");
        }

    }
}