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;ibytes.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;ibytes.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;ib.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;ib.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：
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;ij;i++){
bufferedOutputStream.write(b[i]^9527);
}
}
