response實現文件的下載

@Controller  
public class FileController implements ServletContextAware{   
    //Spring這里是通過實現ServletContextAware接口來注入ServletContext對象   
    private ServletContext servletContext;   
  
  
    @RequestMapping("file/download")   
    public void fileDownload(HttpServletResponse response){   
        //獲取網站部署路徑(通過ServletContext對象)，用於確定下載文件位置，從而實現下載   
        String path = servletContext.getRealPath("/");   
  　　　　response.rset();         //清楚空格等操作
        //1.設置文件ContentType類型，這樣設置，會自動判斷下載文件類型   
        response.setContentType("multipart/form-data");   
        //2.設置文件頭：最后一個參數是設置下載文件名(假如我們叫a.pdf)   
        response.setHeader("Content-Disposition", "attachment;fileName="+"a.pdf");   
        ServletOutputStream out;   
        //通過文件路徑獲得File對象(假如此路徑中有一個download.pdf文件)   
        File file = new File(path + "download/" + "download.pdf");   
  
        try {   
            FileInputStream inputStream = new FileInputStream(file);   
  
            //3.通過response獲取ServletOutputStream對象(out)   
            out = response.getOutputStream();   
  
            int b = 0;   
            byte[] buffer = new byte[512];   
            while (b != -1){   
                b = inputStream.read(buffer);   
                //4.寫到輸出流(out)中   
                out.write(buffer,0,b);   
            }   
            inputStream.close();   
            out.close();   
            out.flush();   
  
        } catch (IOException e) {   
            e.printStackTrace();   
        }   
    }   
  
    @Override  
    public void setServletContext(ServletContext servletContext) {   
        this.servletContext = servletContext;   
    }   
}