1. Description

该篇方法适合于小文件的上传，大文件的上传需要编写TCP进行上传
客户端把一个本地文件（图片，视频，音频）上传到服务器并保存在服务器

2. Front-end and back-end requirements

1. Front-end requirements

1、必须使用表单元素
	<input type="file">
2、form表单提交方式必须为post请求
3、form表单中必须修改默认的enctype值
	enctype="multipart/form-data"

2. Backend requirements

需要借助第三方jar包来获取文件，这里使用Apache提供的jar包

insert image description here

3. Commons-fileupload usage steps

fileitem相当于表单中的一项，即一个input

1、导入依赖
	将上面的两个jar包放入WEB-INF/lib下
	
2、创建一个工厂类DiskFileItemFactory
	DiskFileItemFactory diskFileItemFactory = new DiskFileItemFactory();
	
3、创建解析request的解析器
	ServletFileUpload servletFileUpload = new ServletFileUpload(diskFileItemFactory);
	
4、解析request得到集合
	List<FileItem> fileItems = servletFileUpload.parseRequest(request);
	
5、遍历fileItems依次拿到fileItem
   5.1 调用fileItems的isFormField()方法判断fileItems，如果结果为true则表
   	   示该项为普通字段，为false则表示该项为文件字段
   	   if (fileItem.isFormField()) 
   	   
   5.2 为true则使用fileItems的getFieldName()方法获得input中的name属性名，
   	   然后再使用getString()方法获得input表单中的value属性值
   
   5.3、为false则先指定一个专门存放客户端传入的图片的文件夹的，并通过fileItem的
   	   getName()方法得到传入的图片的名称，由于多个用户可能有多个图片名字一致所以
   	   需要将其换一个重复率低的名称再存入文件夹
   	   // 文件夹路径
       String uploadFilePath = "E:\\JavaCode\\JavaWeb\\user\\web\\img";
       // 得到图片文件名
       String fileName = fileItem.getName();
       String newFileName = FileUploadUitl.randomFilename() + FileUploadUitl.getSuffix(fileName);
       // 将图片写入文件夹中
       fileItem.write(new File(uploadFilePath,newFileName));

Four, pay attention

It is impossible to access pictures through the browser by only writing the above code, and some configuration is required at this time
insert image description here

After the ectype is modified on the front-end page, the value passed from the front-end to the back-end will be garbled, and relevant configurations are required at this time
1. Directly set the encoding of the parser to utf-8. If it still does not work, then modify step 2.
insert image description here
2. Modify the encoding when obtaining the value

In the file acquisition method, the getParameter() method of the request will be invalid, so the above code uses getFileName(), getName() and other methods to obtain

5. Code

package com.ww.web.web;

import com.ww.web.util.FileUploadUitl;
import org.apache.commons.fileupload.FileItem;
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(name = "TestServlet" ,value = "/TestServlet")
public class TestServlet extends HttpServlet {
    
    
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
    
        request.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;chartset=UTF-8");

        // 1、创建工厂
        DiskFileItemFactory diskFileItemFactory = new DiskFileItemFactory();
        // 2、创建解析request的解析器
        ServletFileUpload servletFileUpload = new ServletFileUpload(diskFileItemFactory);

        try {
    
    
            // 3、解析request
            List<FileItem> fileItems = servletFileUpload.parseRequest(request);
            // 4、判断是否是文件对象
            for (FileItem fileItem : fileItems) {
    
    
                if (fileItem.isFormField()){
    
    
                    // 普通表

                    //1、拿到表单项的name
                    String name = fileItem.getFieldName();
                    //2、因为该方法中默认编码是ISO..需要设置编码为UTF-8并拿到值
                    String value = fileItem.getString("UTF-8");
                    System.out.println(name+"---"+value);
                }else {
    
    
                    // 文件

                    //1、获得图片保存的路径
                    String path = "E:\\JavaCode\\JavaWeb\\user\\web\\img";
                    //2、得到图片的文件名
                    String uploadFileName = fileItem.getName();
                    //3、使用工具类将图片名称创建为唯一的
                    String saveFile= FileUploadUitl.randomFilename()+FileUploadUitl.getSuffix(uploadFileName);
                    //4、存入文件夹中
                    fileItem.write(new File(path,saveFile));

                }
            }
        } catch (FileUploadException e) {
    
    
            e.printStackTrace();
        } catch (Exception e) {
    
    
            e.printStackTrace();
        }
    }

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

    }
}

JavaWeb-File upload

Article directory