java实现文件加密解密

一、对于文件流读写取的方式对比:

inputStream.read()与OutputStream.write() 单字节读取,效率低下
inputStream.read(new byte[80*1024])与OutputStream.write(new byte[80*1024]) 固定数组读取,经测试数组增加到80k左右性能最佳
nputStream.read(inputStream.available()) 与OutputStream.write(inputStream.available()) 按文件大小一次性读取,如文件过大有内存溢出风险
BufferedInputStream.read()与BufferedOutputStream.write() 默认有一个8K的缓存数组

二、循环每个字节加解密(此方法效率最低):

1.通过inputStream.read()单字节加密,inputStream.read()返回的是一个字节的内容(0-255之间的数字),可直接异或加密:

    @PostMapping("/swlUpload")
    public void swlUpload(MultipartFile file) throws IOException {
        String originalFilename = file.getOriginalFilename();
        InputStream inputStream = file.getInputStream();
        //FileInputStream inputStream = new FileInputStream((File) file);
        byte[] b = new byte[1024];
        FileOutputStream fileOutputStream = new FileOutputStream(new File("D:\\"+originalFilename));
        BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(fileOutputStream);
        int  swl = 0;
        while((swl=inputStream.read())!=-1){
            //System.out.println(b);
            bufferedOutputStream.write(swl^9527);
        }
        //6.2用来刷新缓冲区,刷新后可以再次写出
        bufferedOutputStream.flush();
        inputStream.close();
        bufferedOutputStream.close();
    }

2.通过inputStream.read()单字节解密:

    @PostMapping("/swlDownload")
    public void swlDownload(HttpServletResponse response) throws IOException {
        File f2= new File("D:\\108B计划.xlsx");
        boolean exists = f2.exists();
        FileInputStream inputStream = new FileInputStream(f2);
        //byte[] b = new byte[1024];

        String filePath = "108B计划.xlsx";
        //6.1清除buffer缓存
        response.reset();
        response.setContentType("application/octet-stream;charset=UTF-8");
        //response.setHeader("Content-Disposition", "inline; filename="+ new String(filePath.getBytes("UTF-8"), "ISO-8859-1"));// 定义文件名
        //response.setHeader("Content-Disposition", "attachment; filename="+ new String(filePath.getBytes("UTF-8"), "ISO-8859-1"));// 定义文件名
        response.setHeader("Content-Disposition", "attachment; filename=" + java.net.URLEncoder.encode(filePath, "UTF-8"));
        response.setHeader("Pragma", "no-cache");
        response.setHeader("Cache-Control", "no-cache");
        response.setHeader("Expires", " 0");
        ServletOutputStream outputStream = response.getOutputStream();
        BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(outputStream);
        int swl = 0;
        while((swl = inputStream.read())!=-1){
            bufferedOutputStream.write(swl^9527);
        }
        //6.2用来刷新缓冲区,刷新后可以再次写出
        bufferedOutputStream.flush();
        inputStream.close();
        bufferedOutputStream.close();
    }

三、加载整个文件加解密(效率快,有内存溢出风险):

1.通过inputStream.read(bytes) 加载整个文件,inputStream.read(bytes)返回bytes大小的字节,放入bytes数组中,循环异或加密:

    @PostMapping("/swlUpload")
    public void swlUpload(MultipartFile file) throws IOException {
        String originalFilename = file.getOriginalFilename();
        InputStream inputStream = file.getInputStream();
        //FileInputStream inputStream = new FileInputStream((File) file);
        byte[] b = new byte[8*1024];
        
        FileOutputStream fileOutputStream = new FileOutputStream(new File("D:\\"+originalFilename));
        BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(fileOutputStream);

        //一、整体io读取、循环加密
        long l = System.currentTimeMillis();
        log.info(String.valueOf(System.currentTimeMillis()));
        int  swl = 0;
        byte[] bytes = new byte[inputStream.available()];
        while((inputStream.read(bytes))!=-1){
            //System.out.println(b);
            for(int i=0;i<bytes.length;i++){
                bufferedOutputStream.write(bytes[i]^9527);
            }
        }
        //6.2用来刷新缓冲区,刷新后可以再次写出
        bufferedOutputStream.flush();
        inputStream.close();
        bufferedOutputStream.close();
        log.info(String.valueOf(System.currentTimeMillis()));
        log.info(String.valueOf(System.currentTimeMillis()-l));

    }

2.通过inputStream.read(bytes) 加载整个文件解密:

    @PostMapping("/swlDownloadAll")
    public void swlDownloadAll(HttpServletResponse response) throws IOException {
        File f2= new File("D:\\84333c1377d99d970a0984049db926ae.mp4");
        boolean exists = f2.exists();
        FileInputStream inputStream = new FileInputStream(f2);
        //byte[] b = new byte[1024];

        String filePath = "84333c1377d99d970a0984049db926ae.mp4";
        //6.1清除buffer缓存
        response.reset();
        response.setContentType("application/octet-stream;charset=UTF-8");
        //response.setHeader("Content-Disposition", "inline; filename="+ new String(filePath.getBytes("UTF-8"), "ISO-8859-1"));// 定义文件名
        //response.setHeader("Content-Disposition", "attachment; filename="+ new String(filePath.getBytes("UTF-8"), "ISO-8859-1"));// 定义文件名
        response.setHeader("Content-Disposition", "attachment; filename=" + java.net.URLEncoder.encode(filePath, "UTF-8"));
        response.setHeader("Pragma", "no-cache");
        response.setHeader("Cache-Control", "no-cache");
        response.setHeader("Expires", " 0");
        ServletOutputStream outputStream = response.getOutputStream();
        BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(outputStream);

        long l = System.currentTimeMillis();
        log.info(String.valueOf(System.currentTimeMillis()));
        int swl = 0;
        byte[] bytes = new byte[inputStream.available()];
        while((inputStream.read(bytes))!=-1){
            for(int i=0;i<bytes.length;i++){
                bufferedOutputStream.write(bytes[i]^9527);
            }
        }
        //6.2用来刷新缓冲区,刷新后可以再次写出
        bufferedOutputStream.flush();
        inputStream.close();
        bufferedOutputStream.close();
        log.info(String.valueOf(System.currentTimeMillis()));
        log.info(String.valueOf(System.currentTimeMillis()-l));
    }

四、小数组加载文件加解密(效率快,无内存溢出风险)【推荐】:

1.通过inputStream.read(b) 加载整个文件,inputStream.read(b)返回b大小的字节,放入b数组中,循环异或加密:

    @PostMapping("/swlUploadArray")
    public void swlUploadArray(MultipartFile file) throws IOException {
        String originalFilename = file.getOriginalFilename();
        InputStream inputStream = file.getInputStream();
        //FileInputStream inputStream = new FileInputStream((File) file);
        byte[] b = new byte[8*1024];
        FileOutputStream fileOutputStream = new FileOutputStream(new File("D:\\"+originalFilename));
        BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(fileOutputStream);

        //三、小数组循环io读取、循环加密
        long l = System.currentTimeMillis();
        log.info(String.valueOf(System.currentTimeMillis()));
        while((inputStream.read(b))!=-1){
            //System.out.println(b);
            for(int i=0;i<b.length;i++){
                bufferedOutputStream.write(b[i]^9527);
            }
        }
        //6.2用来刷新缓冲区,刷新后可以再次写出
        bufferedOutputStream.flush();
        inputStream.close();
        bufferedOutputStream.close();
        log.info(String.valueOf(System.currentTimeMillis()));
        log.info(String.valueOf(System.currentTimeMillis()-l));

    }

2.通过inputStream.read(b) 加载整个文件解密:

    @PostMapping("/swlDownloadArray")
    public void swlDownloadArray(HttpServletResponse response) throws IOException {
        File f2= new File("D:\\84333c1377d99d970a0984049db926ae.mp4");
        boolean exists = f2.exists();
        FileInputStream inputStream = new FileInputStream(f2);
        byte[] b = new byte[8*1024];

        String filePath = "84333c1377d99d970a0984049db926ae.mp4";
        //6.1清除buffer缓存
        response.reset();
        response.setContentType("application/octet-stream;charset=UTF-8");
        //response.setHeader("Content-Disposition", "inline; filename="+ new String(filePath.getBytes("UTF-8"), "ISO-8859-1"));// 定义文件名
        //response.setHeader("Content-Disposition", "attachment; filename="+ new String(filePath.getBytes("UTF-8"), "ISO-8859-1"));// 定义文件名
        response.setHeader("Content-Disposition", "attachment; filename=" + java.net.URLEncoder.encode(filePath, "UTF-8"));
        response.setHeader("Pragma", "no-cache");
        response.setHeader("Cache-Control", "no-cache");
        response.setHeader("Expires", " 0");
        ServletOutputStream outputStream = response.getOutputStream();
        BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(outputStream);
        long l = System.currentTimeMillis();
        log.info(String.valueOf(System.currentTimeMillis()));
        int swl = 0;
        while((inputStream.read(b))!=-1){
            for(int i=0;i<b.length;i++){
                bufferedOutputStream.write(b[i]^9527);
            }
        }
        //6.2用来刷新缓冲区,刷新后可以再次写出
        bufferedOutputStream.flush();
        inputStream.close();
        bufferedOutputStream.close();
        log.info(String.valueOf(System.currentTimeMillis()));
        log.info(String.valueOf(System.currentTimeMillis()-l));
    }

五、解决小数组读取文件流后,office文档打开异常的问题:

注意看下面的代码:
java实现文件加密解密_第1张图片

原因:这是文档最后一次读取文件,剩余的文件流不足b.length造成的,不足时会在数组中补0,造成上传后的文件与原文件有出入。
解决方案1:采用byte[] bytes = new byte[inputStream.available()];
解决方案2(推荐):

        int j;
        while((j=(inputStream.read(b)))!=-1){
            for(int i=0;i<j;i++){
                bufferedOutputStream.write(b[i]^9527);
            }
        }

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