java实现文件上传、下载（包含下载网络图片上传到服务器上）

拿去直接用就好：
1、文件上传

package com.myproject.aiplatform.core.utils;

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;

import org.apache.commons.io.FileUtils;
import org.springframework.web.multipart.MultipartFile;

/**
 * 上传文件
 * @version
 */
public class FileUpload {

    /**上传文件
     * @param file          //文件对象
     * @param filePath      //上传路径
     * @param fileName      //文件名
     * @return  文件名
     */
    public static String fileUp(MultipartFile file, String filePath, String fileName){
        String extName = ""; // 扩展名格式：
        try {
            if (file.getOriginalFilename().lastIndexOf(".") >= 0){
                extName = file.getOriginalFilename().substring(file.getOriginalFilename().lastIndexOf("."));
            }
            copyFile(file.getInputStream(), filePath, fileName+extName).replaceAll("-", "");
        } catch (IOException e) {
            System.out.println(e);
        }
        return fileName+extName;
    }

    /**
     * 写文件到当前目录的upload目录中
     * @param in
     * @param fileName
     * @throws IOException
     */
    public static String copyFile(InputStream in, String dir, String realName)
            throws IOException {
        File file = mkdirsmy(dir,realName);
        FileUtils.copyInputStreamToFile(in, file);
        in.close();
        return realName;
    }


    /**判断路径是否存在，否：创建此路径
     * @param dir  文件路径
     * @param realName  文件名
     * @throws IOException 
     */
    public static File mkdirsmy(String dir, String realName) throws IOException{
        File file = new File(dir, realName);
        if (!file.exists()) {
            if (!file.getParentFile().exists()) {
                file.getParentFile().mkdirs();
            }
            file.createNewFile();
        }
        return file;
    }


    /**下载网络图片上传到服务器上
     * @param httpUrl 图片网络地址
     * @param filePath  图片保存路径
     * @param myFileName  图片文件名(null时用网络图片原名)
     * @return  返回图片名称
     */
    public static String getHtmlPicture(String httpUrl, String filePath , String myFileName) {

        URL url;                        //定义URL对象url
        BufferedInputStream in;         //定义输入字节缓冲流对象in
        FileOutputStream file;          //定义文件输出流对象file
        try {
            String fileName = null == myFileName?httpUrl.substring(httpUrl.lastIndexOf("/")).replace("/", ""):myFileName; //图片文件名(null时用网络图片原名)
            url = new URL(httpUrl);     //初始化url对象
            in = new BufferedInputStream(url.openStream());                                 //初始化in对象，也就是获得url字节流
            //file = new FileOutputStream(new File(filePath +"\\"+ fileName));
            file = new FileOutputStream(mkdirsmy(filePath,fileName));
            int t;
            while ((t = in.read()) != -1) {
                file.write(t);
            }
            file.close();
            in.close();
            return fileName;
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;

    }
}

2、文件下载

package com.myproject.aiplatform.core.utils;

import java.io.BufferedOutputStream;
import java.io.OutputStream;
import java.net.URLEncoder;

import javax.servlet.http.HttpServletResponse;

/**
 * 下载文件
 * @version
 */
public class FileDownload {

    /**
     * @param response 
     * @param filePath      //文件完整路径(包括文件名和扩展名)
     * @param fileName      //下载后看到的文件名
     * @return  文件名
     */
    public static void fileDownload(final HttpServletResponse response, String filePath, String fileName) throws Exception{  
        byte[] data = FileUtil.toByteArray2(filePath);  
        fileName = URLEncoder.encode(fileName, "UTF-8");  
        response.reset();  
        response.setHeader("Content-Disposition", "attachment; filename=" + fileName );  
        response.addHeader("Content-Length", "" + data.length);  
        response.setContentType("application/octet-stream;charset=UTF-8");  
        OutputStream outputStream = new BufferedOutputStream(response.getOutputStream());  
        outputStream.write(data);  
        outputStream.flush();  
        outputStream.close();
        response.flushBuffer();
    } 

}