下载文件到电脑本地

public void downloadSystemHelp(){
        DataInputStream in = null;
        OutputStream out= null;
        File f=null;
        try {
            
            f = new File(this.getClass().getResource("/").getPath());
            String path = f.getAbsolutePath();
            String newPath = path.replace('\', '/');
            if(newPath.contains("apache")){
                newPath = newPath.substring(0, newPath.indexOf("/apache"));
            }
            String dirName =newPath+"/SystemHelp/";      //获取自己创建的文件夹路径
            f = new File(dirName);
            if(!f.exists()){
                f.mkdirs();
            }
            String fileNames[] = f.list();   //获取文件夹下的文件
            String resultFileName="";
            System.out.println("文件 is "+fileNames);
            resultFileName = fileNames[0];
            response.setCharacterEncoding("UTF-8");  
            response.setHeader("Content-disposition", "attachment; filename=" +  URLEncoder.encode(resultFileName,"UTF-8"));// 设定输出文件头
            response.setContentType("multipart/form-data");// 定义输出类型
            //输入流：本地文件路径
            f=new File(dirName+resultFileName);
            in = new DataInputStream( new FileInputStream(f));  
            //输出流
            out = response.getOutputStream();
            //输出文件
            int bytes = 0;
            byte[] bufferOut = new byte[1024];  
            while ((bytes = in.read(bufferOut)) != -1) {  
                out.write(bufferOut, 0, bytes);  
            }  
            
        } catch (Exception e) {
            e.printStackTrace();    
        }finally{
            if(null != in) {
                try {
                    in.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if(null != out) {
                try {
                    out.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

//js代码
function download(){
        //后台方法、文件类型、文件名
        downloadTemplate('${pageContext.request.contextPath}/cardIssueVehicleInfo/exportVehicleInfo', 'filename', 'test');
    }

    /**
     * 用于下载导入模板时的影藏form表单的提交，采用post方式提交
     *
     */
    function downloadTemplate(action, type, value){
        var form = document.createElement('form');
        document.body.appendChild(form);
        form.style.display = "none";
        form.action = action;
        form.id = 'excel';
        form.method = 'post';
        
        var newElement = document.createElement("input");  
        newElement.setAttribute("type","hidden");  
        newElement.name = type;
        newElement.value = value;
        form.appendChild(newElement); 
        
        form.submit();
    }