SpringMVC实现文件下载的两种方式

1.常规方法

@RequestMapping("/download")
public String download( String fileName ,String filePath, HttpServletRequest request, HttpServletResponse response){

response.setContentType("text/html;charset=utf-8");
try {
request.setCharacterEncoding("UTF-8");
} catch (UnsupportedEncodingException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}

java.io.BufferedInputStream bis = null;
java.io.BufferedOutputStream bos = null;

String downLoadPath = filePath; //注意不同系统的分隔符
// String downLoadPath =filePath.replaceAll("/", "\\\\\\\\"); //replace replaceAll区别 *****
System.out.println(downLoadPath);

try {
long fileLength = new File(downLoadPath).length();
response.setContentType("application/x-msdownload;");
response.setHeader("Content-disposition", "attachment; filename=" + new String(fileName.getBytes("utf-8"), "ISO8859-1"));
response.setHeader("Content-Length", String.valueOf(fileLength));
bis = new BufferedInputStream(new FileInputStream(downLoadPath));
bos = new BufferedOutputStream(response.getOutputStream());
byte[] buff = new byte[2048];
int bytesRead;
while (-1 != (bytesRead = bis.read(buff, 0, buff.length))) {
bos.write(buff, 0, bytesRead);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
if (bis != null)
try {
bis.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
if (bos != null)
try {
bos.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return null;
}

2.利用springmvc提供的ResponseEntity类型,使用它可以很方便地定义返回的HttpHeaders和HttpStatus。

RequestMapping("/download")
public ResponseEntity<byte[]> export(String fileName,String filePath) throws IOException {

HttpHeaders headers = new HttpHeaders();
File file = new File(filePath);

headers.setContentType(MediaType.APPLICATION_OCTET_STREAM);
headers.setContentDispositionFormData("attachment", fileName);

return new ResponseEntity<byte[]>(FileUtils.readFileToByteArray(file),
headers, HttpStatus.CREATED);
}

另外需要注意的一点
ajax请求无法响应下载功能因为response原因，一般请求浏览器是会处理服务器输出的response，例如生成png、文件下载等,然而ajax请求只是个“字符型”的请求，即请求的内容是以文本类型存放的。文件的下载是以二进制形式进行的，虽然可以读取到返回的response，但只是读取而已，是无法执行的，说白点就是js无法调用到浏览器的下载处理机制和程序。

推荐使用这种方式 自己构建表单进行提交

var form = $("<form>");
form.attr("style","display:none");
form.attr("target","");
form.attr("method","post");
form.attr("action",rootPath + "T_academic_essay/DownloadZipFile.do");
var input1 = $("<input>");
input1.attr("type","hidden");
input1.attr("name","strZipPath");
input1.attr("value",strZipPath);
$("body").append(form);
form.append(input1);
form.submit();
form.remove();