Java判断上传图片格式的实例代码

由于客户上传图片将png的图片的后缀名改为jpg,所以通过后缀名判断不行,用下面这个方法可以

   //判断是否是JPG格式
   log.info("-1----进入JPG格式判断.....");
   ImageInputStream iis = ImageIO.createImageInputStream(file.getInputStream());
   Iterator<ImageReader> iter = ImageIO.getImageReaders(iis);
   if (!iter.hasNext()) {
     throw new RuntimeException("No readers found!");
   }
   ImageReader reader = iter.next();
   
   log.info("Format1: " + reader.getFormatName()); //这里会打印出图片的格式
   if(!"JPEG".equals(reader.getFormatName())){
     return new ResponseBean(ResponseBean.FAIL, "不支持修改后缀名为jpg的图片");
   }
   iis.close();

PS:Java使用文件头的类型判断上传的文件是否为图片类型

web判断文件的格式的时候,我们一般都是通过扩展名来判断,这个有点不太靠谱和安全,例如,修改文件名的后缀即可绕过判断。一般要判断是利用头文件来判断。下面是利用头文件来判断的代码:

package com.metro.crm.util;
import java.io.FileInputStream;
public class FileType{
  public static String bytesToHexString(byte[] src) {
    StringBuilder stringBuilder = new StringBuilder();
    if (src == null || src.length <= 0) {
      return null;
    }
    for (int i = 0; i < src.length; i++) {
      int v = src[i] & 0xFF;
      String hv = Integer.toHexString(v);
      if (hv.length() < 2) {
        stringBuilder.append(0);
      }
      stringBuilder.append(hv);
    }
    return stringBuilder.toString();
  }
  /**
   * @param args
   */
  public static void main(String[] args) throws Exception {
    FileInputStream is = new FileInputStream("F:\aaa.jpg");
    byte[] b = new byte[3];
    is.read(b, 0, b.length);
    String photo = bytesToHexString(b);
    photo = photo.toUpperCase();
    System.out.println("头文件是:" + photo);
    String ooo = TypeDict.checkType(photo);
    System.out.println("后缀名是:" + ooo);
  }
}

package com.metro.crm.util;
public class TypeDict {
  /**
   常用文件的文件头如下:(以前六位为准)
   JPEG (jpg),文件头:FFD8FF
   PNG (png),文件头:89504E47
   GIF (gif),文件头:47494638
   TIFF (tif),文件头:49492A00
   Windows Bitmap (bmp),文件头:424D
   CAD (dwg),文件头:41433130
   Adobe Photoshop (psd),文件头:38425053
   Rich Text Format (rtf),文件头:7B5C727466
   XML (xml),文件头:3C3F786D6C
   HTML (html),文件头:68746D6C3E
   Email [thorough only] (eml),文件头:44656C69766572792D646174653A
   Outlook Express (dbx),文件头:CFAD12FEC5FD746F
   Outlook (pst),文件头:2142444E
   MS Word/Excel (xls.or.doc),文件头:D0CF11E0
   MS Access (mdb),文件头:5374616E64617264204A
   WordPerfect (wpd),文件头:FF575043
   Postscript (eps.or.ps),文件头:252150532D41646F6265
   Adobe Acrobat (pdf),文件头:255044462D312E
   Quicken (qdf),文件头:AC9EBD8F
   Windows Password (pwl),文件头:E3828596
   ZIP Archive (zip),文件头:504B0304
   RAR Archive (rar),文件头:52617221
   Wave (wav),文件头:57415645
   AVI (avi),文件头:41564920
   Real Audio (ram),文件头:2E7261FD
   Real Media (rm),文件头:2E524D46
   MPEG (mpg),文件头:000001BA
   MPEG (mpg),文件头:000001B3
   Quicktime (mov),文件头:6D6F6F76
   Windows Media (asf),文件头:3026B2758E66CF11
   MIDI (mid),文件头:4D546864
   */
  public static String checkType(String fileType) {
    switch (fileType) {
      case "FFD8FF": return "jpg";
      case "89504E": return "png";
      case "474946": return "jif";
      default: return "0000";
    }
  }
}

 

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