文件上传 后端代码 1208

package servlet;

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileItemFactory;
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 doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("in");
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("in post");

        System.out.println("是不是multipart：");
        boolean multipartContent = ServletFileUpload.isMultipartContent(req);
        System.out.println(multipartContent);

        System.out.println("上传目录");
        String upload = req.getServletContext().getRealPath("upload");
        System.out.println(upload);

        System.out.println("目录是否存在：");
        File file = new File(upload);
        boolean exists = file.exists();
        System.out.println(exists);

        if (!exists) {
            System.out.println("目录不存在就创建一个：");
            boolean mkdir = file.mkdir();
            System.out.println("创建的结果");
            System.out.println(mkdir);
        }


        if (multipartContent) {
            System.out.println("如果是multipart");

            FileItemFactory fileItemFactory = new DiskFileItemFactory();
            ServletFileUpload servletFileUpload = new ServletFileUpload(fileItemFactory);
            List<FileItem> list = servletFileUpload.parseRequest(req);

            for (FileItem item :
                    list) {
                // 是否普通字段
                boolean formField = item.isFormField();


                if (formField) {
                    // 普通字段拿数据
                    String value = item.getString("utf8");
                    System.out.println("控件的值是：");
                    System.out.println(value);
                } else {
                    String name = item.getName();
                    File myFile = new File(upload, name);
                    item.write(myFile);
                }
            }
        }
        
    }
}

加上异常

然后调一调后

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 doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("in");
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        req.setCharacterEncoding("utf8");
        System.out.println("in post");

        System.out.println("是不是multipart：");
        boolean multipartContent = ServletFileUpload.isMultipartContent(req);
        System.out.println(multipartContent);

        System.out.println("上传目录");
        String upload = req.getServletContext().getRealPath("upload");
        System.out.println(upload);

        System.out.println("目录是否存在：");
        File file = new File(upload);
        boolean exists = file.exists();
        System.out.println(exists);

        if (!exists) {
            System.out.println("目录不存在就创建一个：");
            boolean mkdir = file.mkdir();
            System.out.println("创建的结果");
            System.out.println(mkdir);
        }


        if (multipartContent) {
            System.out.println("如果是multipart");

            FileItemFactory fileItemFactory = new DiskFileItemFactory();
            ServletFileUpload servletFileUpload = new ServletFileUpload(fileItemFactory);
            List<FileItem> list = null;
            try {
                list = servletFileUpload.parseRequest(req);
            } catch (FileUploadException e) {
                e.printStackTrace();
            }

            for (FileItem item :
                    list) {
                // 是否普通字段
                boolean formField = item.isFormField();


                if (formField) {
                    // 普通字段拿数据
                    String value = item.getString("utf8");
                    System.out.println("控件的值是：");
                    System.out.println(value);
                } else {
                    String name = item.getName();
                    File myFile = new File(upload, name);
                    try {
                        item.write(myFile);
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            }
        }

    }
}