下载PDF文件为什么成了网页？

String fileName = fullPath.substring(fullPath.lastIndexOf("\\") + 1);
FileInputStream file = new FileInputStream(fullPath);
ServletOutputStream out = response.getOutputStream();

//response.setContentType("application/octet-stream");

response.setContentType("application/x-msdownload");
response.setHeader("Content-Disposition", "attachment;filename="+ fileName);

byte buffer[] = new byte[1024];
int size;
while ((size = file.read(buffer)) != -1) {
	out.println(new String(buffer));
	out.write(buffer, 0, size);
//控制台打印出的内容与文件内容一致
System.out.println(new String(buffer));
}
file.close();
out.close();

页面通过一个按钮链接到以上代码，但保存下来的文件内容是按钮所在的页面的代码？？？