servlet 中通过response下载文件

public class ResponseDemo3 extends HttpServlet {
private static final long serialVersionUID = -5232952995715123473L;

public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// ServletOutputStream outputStream = response.getOutputStream();
// outputStream.write("hello,download!".getBytes());
String realPath = this.getServletContext().getRealPath("/download/日本妞.jpg");
String filename = realPath.substring(realPath.lastIndexOf("\\") + 1);
//如果下载文件是中文文件,则文件名需要经过url编码
response.setHeader("content-disposition", "attachment;filename="+URLEncoder.encode(filename,"utf-8"));
InputStream in = null;
OutputStream out = null;
try{
in = new FileInputStream(realPath);
int len = 0;
byte buffer[] = new byte[1024];
out = response.getOutputStream();
while((len=in.read(buffer))>0){
out.write(buffer,0,len);
}

}finally{
if(in!=null){
try{
in.close();
}catch(Exception e){
e.printStackTrace();
}
}
}

}

public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}

}