```java

@Override

public void doHandle(HttpRequest request, HttpResponse response) throws IOException {

String fileName = request.getRequestURI();

String method = request.getMethod();

if (StringUtils.isEmpty(fileName)) {

fileName += "/";

}

if (StringUtils.endsWith(fileName, "/")) {

fileName += "index.html";

}

LOGGER.info("请求URL:{}", fileName);

File file = new File(baseDir, fileName);

//404

if (!file.isFile()) {

LOGGER.warn("file:{} not found!", request.getRequestURI());

response.setHttpStatus(HttpStatus.NOT_FOUND);

response.setHeader(HttpHeaderConstant.Names.CONTENT_TYPE, "text/html; charset=utf-8");

if (!HttpMethodEnum.HEAD.getMethod().equals(method)) {

response.write(URL_404.getBytes());

}

return;

}

//304

Date lastModifyDate = new Date(file.lastModified());

try {

String requestModified = request.getHeader(HttpHeaderConstant.Names.IF_MODIFIED_SINCE);

if (StringUtils.isNotBlank(requestModified) && lastModifyDate.getTime() <= sdf.get().parse(requestModified).getTime()) {

response.setHttpStatus(HttpStatus.NOT_MODIFIED);

return;

}

} catch (Exception e) {

LOGGER.error("exception", e);

}

response.setHeader(HttpHeaderConstant.Names.LAST_MODIFIED, sdf.get().format(lastModifyDate));

//************ start:此处为我这边修改的内容 *****************

response.setHeader(HttpHeaderConstant.Names.CONTENT_LENGTH, file.length()+"");

//************ end:此处为我这边修改的内容 *****************

String contentType = Mimetypes.getInstance().getMimetype(file);

response.setHeader(HttpHeaderConstant.Names.CONTENT_TYPE, contentType + "; charset=utf-8");

//HEAD不输出内容

if (HttpMethodEnum.HEAD.getMethod().equals(method)) {

return;

}

FileInputStream fis = new FileInputStream(file);

FileChannel fileChannel = fis.getChannel();

long fileSize = fileChannel.size();

long readPos = 0;

while (readPos < fileSize) {

MappedByteBuffer mappedByteBuffer = fileChannel.map(FileChannel.MapMode.READ_ONLY, readPos, fileSize - readPos > READ_BUFFER ? READ_BUFFER : fileSize - readPos);

readPos += mappedByteBuffer.remaining();

byte[] data = new byte[mappedByteBuffer.remaining()];

mappedByteBuffer.get(data);

response.write(data);

}

fis.close();

}

```

对于兼容性不好的浏览器，如果不返回长度会导致在下载大文件时失败或者不显示下载进度

```java

response.setHeader(HttpHeaderConstant.Names.CONTENT_TYPE, contentType + "; charset=utf-8");

```

String fileName = request.getRequestURI();

String method = request.getMethod();

if (StringUtils.isEmpty(fileName)) {

fileName += "/";

}

if (StringUtils.endsWith(fileName, "/")) {

fileName += "index.html";

}

LOGGER.info("请求URL:{}", fileName);

File file = new File(baseDir, fileName);

//404

if (!file.isFile()) {

LOGGER.warn("file:{} not found!", request.getRequestURI());

response.setHttpStatus(HttpStatus.NOT_FOUND);

response.setHeader(HttpHeaderConstant.Names.CONTENT_TYPE, "text/html; charset=utf-8");

if (!HttpMethodEnum.HEAD.getMethod().equals(method)) {

response.write(URL_404.getBytes());

}

return;

}

//304

Date lastModifyDate = new Date(file.lastModified());

try {

String requestModified = request.getHeader(HttpHeaderConstant.Names.IF_MODIFIED_SINCE);

if (StringUtils.isNotBlank(requestModified) && lastModifyDate.getTime() <= sdf.get().parse(requestModified).getTime()) {

response.setHttpStatus(HttpStatus.NOT_MODIFIED);

return;

}

} catch (Exception e) {

LOGGER.error("exception", e);

}

response.setHeader(HttpHeaderConstant.Names.LAST_MODIFIED, sdf.get().format(lastModifyDate));

//************ start:此处为我这边修改的内容 *****************

response.setHeader(HttpHeaderConstant.Names.CONTENT_LENGTH, file.length()+"");

//************ end:此处为我这边修改的内容 *****************

String contentType = Mimetypes.getInstance().getMimetype(file);

response.setHeader(HttpHeaderConstant.Names.CONTENT_TYPE, contentType + "; charset=utf-8");

//HEAD不输出内容

if (HttpMethodEnum.HEAD.getMethod().equals(method)) {

return;

}

FileInputStream fis = new FileInputStream(file);

FileChannel fileChannel = fis.getChannel();

long fileSize = fileChannel.size();

long readPos = 0;

while (readPos < fileSize) {

MappedByteBuffer mappedByteBuffer = fileChannel.map(FileChannel.MapMode.READ_ONLY, readPos, fileSize - readPos > READ_BUFFER ? READ_BUFFER : fileSize - readPos);

readPos += mappedByteBuffer.remaining();

byte[] data = new byte[mappedByteBuffer.remaining()];

mappedByteBuffer.get(data);

response.write(data);

}

fis.close();

}

```

对于兼容性不好的浏览器，如果不返回长度会导致在下载大文件时失败或者不显示下载进度

```java

response.setHeader(HttpHeaderConstant.Names.CONTENT_LENGTH, file.length()+"");

```