代码是转载的，但是我找不到来源了，都是在网上找的，积累了一段时间的，如果有知道可以在评论里回复我。
工具类有两种方式上传，一种是base64，常用于客户端上传图片；另一种是一文件形式上传，常用于网页端上传文件。
import java.awt.Graphics;import java.awt.image.BufferedImage;import java.io.ByteArrayInputStream;import java.io.DataInputStream;import java.io.DataOutputStream;import java.io.File;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;import .HttpURLConnection;import .URL;import java.util.UUID;import javax.imageio.ImageIO;import javax.servlet.http.HttpServletRequest;import sun.misc.BASE64Decoder;public class FileTool {//上传图片路径public final static String PATH = "/upload";private final static int xhdpi = 660;private final static int mhdpi = 1280;/*** 上传图片，以文件的形式上传，对图片进行压缩，会生成多个分辨率的图片* @param file文件数据* @param filePath文件的存储路径* @param fileName生成的文件名* @throws Exception*/public static void uploadFile(byte[] file, String filePath, String fileName) throws Exception { String fileType = fileName.substring(fileName.length()-3, fileName.length());File targetFile = new File(filePath); if(!targetFile.exists()){ targetFile.mkdirs(); } FileOutputStream out = new FileOutputStream(filePath+PATH + "/"+fileName);out.write(file);out.close();System.out.println(filePath+PATH + "/"+fileName);String upNameXhdpi = "xhdpi-" + fileName;String upNameMhdpi = "mhdpi-" + fileName;FileOutputStream outXhdpi = new FileOutputStream(filePath+"/"+PATH+ "/" +upNameXhdpi);FileOutputStream outMhdpi = new FileOutputStream(filePath+"/"+PATH+ "/" +upNameMhdpi);resizeImageFile(file, outXhdpi, xhdpi, fileType);resizeImageFile(file, outMhdpi, mhdpi, fileType);}/*** 上传文件，以文件的形式，不会对图片进行压缩* @param file要上传的文件* @param filename文件名* @return 上传成功后的文件名*/public static String upload(HttpServletRequest request,File file, String fileFileName) throws Exception {String dir = request.getSession().getServletContext().getRealPath("/");File fileLocation = new File(dir);if(!fileLocation.exists()) {boolean isCreated = fileLocation.mkdir();if(!isCreated) {//目标上传目录创建失败,可做其他处理,例如抛出自定义异常等,一般应该不会出现这种情况。return null;}}//fileFileName = UUID.randomUUID().toString()+System.currentTimeMillis()+fileFileName;fileFileName = fileFileName;InputStream is = new FileInputStream(file);OutputStream os = new FileOutputStream(dir+"/"+fileFileName);// 因为file是存放在临时文件夹的文件，我们可以将其文件名和文件路径打印出来，看和之前的fileFileName是否相同byte[] buffer = new byte[500];int length = 0;while(-1 != (length = is.read(buffer, 0, buffer.length))){os.write(buffer);}os.close();is.close();return fileFileName;}/*** 将网络资源的图片下载到本地，比如说将微信用户头像下载到本地* @param request* @param fileUrl 网络资源的路径* @return*/public static String uploadQianURL(HttpServletRequest request,String fileUrl) {//获取文件名，文件名实际上在URL中可以找到String fileName = UUID.randomUUID().toString()+System.currentTimeMillis() + ".jpg";//这里服务器上要将此图保存的路径String savePath = request.getServletContext().getRealPath(PATH);System.out.println();try {URL url = new URL(fileUrl);/*将网络资源地址传给,即赋值给url*//*此为联系获得网络资源的固定格式用法，以便后面的in变量获得url截取网络资源的输入流*/HttpURLConnection connection = (HttpURLConnection)url.openConnection();DataInputStream in = new DataInputStream(connection.getInputStream());/*此处也可用BufferedInputStream与BufferedOutputStream*/DataOutputStream out = new DataOutputStream(new FileOutputStream(savePath+"\\"+fileName));/*将参数savePath，即将截取的图片的存储在本地地址赋值给out输出流所指定的地址*/byte[] buffer = new byte[4096];int count = 0;/*将输入流以字节的形式读取并写入buffer中*/while ((count = in.read(buffer)) > 0) {out.write(buffer, 0, count);}out.close();/*后面三行为关闭输入输出流以及网络资源的固定格式*/in.close();connection.disconnect();//返回内容是文件名return fileName;/*网络资源截取并存储本地成功返回true*/} catch (Exception e) {System.out.println(e + fileUrl + savePath);return null;}}/*** 上传图片，以base64的形式* @param base64 图片编码后的字符串* @return 上传成功后的文件名*/public static String upload(HttpServletRequest request,String base64) {String dir = request.getServletContext().getRealPath(PATH);File fileLocation = new File(dir);if(!fileLocation.exists()) {boolean isCreated = fileLocation.mkdir();if(!isCreated) {//目标上传目录创建失败,可做其他处理,例如抛出自定义异常等,一般应该不会出现这种情况。return null;}}if(base64.indexOf("jpeg") != -1) {//存在jpeg文件的情况base64 = base64.replaceFirst("jpeg", "jpg");}String upName = UUID.randomUUID().toString()+System.currentTimeMillis()+"."+base64.substring(11, 14);FileOutputStream out;String iconBase64 = base64.substring(22);try {byte[] buffer = new BASE64Decoder().decodeBuffer(iconBase64);out = new FileOutputStream(dir+"/"+upName);out.write(buffer);out.close();return upName;} catch (FileNotFoundException e) {// TODO Auto-generated catch blocke.printStackTrace();return null;} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();return null;}}/*** 上传图片，会生成多个分辨率的图片* @param base64 图片编码后的字符串* @return 上传成功后的文件名*/public static String uploadResize(HttpServletRequest request,String base64) {String dir = request.getServletContext().getRealPath(PATH);if(base64.indexOf("jpeg") != -1) {//存在jpeg文件的情况base64 = base64.replaceFirst("jpeg", "jpg");}File fileLocation = new File(dir);String fileType = base64.substring(11, 14);if(!fileLocation.exists()) {boolean isCreated = fileLocation.mkdir();if(!isCreated) {//目标上传目录创建失败,可做其他处理,例如抛出自定义异常等,一般应该不会出现这种情况。return null;}}String tempStr = UUID.randomUUID().toString()+System.currentTimeMillis();String upName = tempStr+"."+fileType;FileOutputStream out;String iconBase64 = base64.substring(22);try {byte[] buffer = new BASE64Decoder().decodeBuffer(iconBase64);out = new FileOutputStream(dir+"/"+upName);out.write(buffer);out.close();String upNameXhdpi = "xhdpi-" + upName;String upNameMhdpi = "mhdpi-"+upName;FileOutputStream outXhdpi = new FileOutputStream(dir+"/"+upNameXhdpi);FileOutputStream outMhdpi = new FileOutputStream(dir+"/"+upNameMhdpi);resizeImage(iconBase64, outXhdpi, xhdpi, fileType);resizeImage(iconBase64, outMhdpi, mhdpi, fileType);return upName;} catch (FileNotFoundException e) {// TODO Auto-generated catch blocke.printStackTrace();return null;} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();return null;}}/*** 改变图片的大小到宽为size，然后高随着宽等比例变化* @param is 上传的图片的输入流* @param os 改变了图片的大小后，把图片的流输出到目标OutputStream* @param size 新图片的宽* @param format 新图片的格式* @throws IOException*/public static void resizeImage(String is, OutputStream os, int size, String format) throws IOException {ByteArrayInputStream in = new ByteArrayInputStream(new BASE64Decoder().decodeBuffer(is));ByteArrayInputStream in2 = new ByteArrayInputStream(new BASE64Decoder().decodeBuffer(is));StringBuffer out = new StringBuffer(); byte[] b = new byte[4096]; for(int n; (n = in2.read(b)) != -1;) { out.append(new String(b, 0, n)); }System.out.println(out.length());BufferedImage prevImage = ImageIO.read(in); double width = prevImage.getWidth();double height = prevImage.getHeight();double percent = size/width;int newWidth = (int)(width * percent);int newHeight = (int)(height * percent);BufferedImage image = new BufferedImage(newWidth, newHeight, BufferedImage.TYPE_INT_BGR);Graphics graphics = image.createGraphics();graphics.drawImage(prevImage, 0, 0, newWidth, newHeight, null);ImageIO.write(image, format, os);os.flush();in.close();os.close();}/*** 改变图片的大小到宽为size，然后高随着宽等比例变化* @param is 上传的图片的输入流* @param os 改变了图片的大小后，把图片的流输出到目标OutputStream* @param size 新图片的宽* @param format 新图片的格式* @throws IOException*/public static void resizeImageFile(byte[] file, OutputStream os, int size, String format) throws IOException {ByteArrayInputStream in = new ByteArrayInputStream(file);ByteArrayInputStream in2 = new ByteArrayInputStream(file);StringBuffer out = new StringBuffer(); byte[] b = new byte[4096]; for(int n; (n = in2.read(b)) != -1;) { out.append(new String(b, 0, n)); }System.out.println(out.length());BufferedImage prevImage = ImageIO.read(in); double width = prevImage.getWidth();double height = prevImage.getHeight();double percent = size/width;int newWidth = (int)(width * percent);int newHeight = (int)(height * percent);BufferedImage image = new BufferedImage(newWidth, newHeight, BufferedImage.TYPE_INT_BGR);Graphics graphics = image.createGraphics();graphics.drawImage(prevImage, 0, 0, newWidth, newHeight, null);ImageIO.write(image, format, os);os.flush();in.close();os.close();}}
使用举例
//上传图片@PostMapping("/img")public Msg img(HttpServletRequest request, @RequestParam String base64) {String fileName = FileTool.uploadResize(request, base64);if(fileName != null) {msg.set("上传成功", CodeConstant.SUCCESS, fileName);} else {msg.set("上传失败", CodeConstant.ERROR, null);}return msg;}//upload上传文件，以文件的格式@PostMapping("/upload")public String upload(@RequestParam MultipartFile file, HttpServletRequest request) {String fileName = UUID.randomUUID().toString()+System.currentTimeMillis()+file.getOriginalFilename();/*System.out.println("fileName-->" + fileName);System.out.println("getContentType-->" + contentType);*/String filePath = request.getSession().getServletContext().getRealPath("/");try {FileTool.uploadFile(file.getBytes(), filePath, fileName);return fileName;} catch (Exception e) {// TODO: handle exceptionreturn "上传失败";}}
