Java下载文件的四种方式详细代码

1.以流的方式下载

public httpservletresponse download(string path, httpservletresponse response) {
        try {
            // path是指欲下载的文件的路径。
            file file = new file(path);
            // 取得文件名。
            string filename = file.getname();
            // 取得文件的后缀名。
            string ext = filename.substring(filename.lastindexof(".") + 1).touppercase();
 
            // 以流的形式下载文件。
            inputstream fis = new bufferedinputstream(new fileinputstream(path));
            byte[] buffer = new byte[fis.available()];
            fis.read(buffer);
            fis.close();
            // 清空response
            response.reset();
            // 设置response的header
            response.addheader("content-disposition", "attachment;filename=" + new string(filename.getbytes()));
            response.addheader("content-length", "" + file.length());
            outputstream toclient = new bufferedoutputstream(response.getoutputstream());
            response.setcontenttype("application/octet-stream");
            toclient.write(buffer);
            toclient.flush();
            toclient.close();
        } catch (ioexception ex) {
            ex.printstacktrace();
        }
        return response;
    }

2.下载本地文件

public void downloadlocal(httpservletresponse response) throws filenotfoundexception {
        // 下载本地文件
        string filename = "operator.doc".tostring(); // 文件的默认保存名
        // 读到流中
        inputstream instream = new fileinputstream("c:/operator.doc");// 文件的存放路径
        // 设置输出的格式
        response.reset();
        response.setcontenttype("bin");
        response.addheader("content-disposition", "attachment; filename=\"" + filename + "\"");
        // 循环取出流中的数据
        byte[] b = new byte[100];
        int len;
        try {
            while ((len = instream.read(b)) > 0)
                response.getoutputstream().write(b, 0, len);
            instream.close();
        } catch (ioexception e) {
            e.printstacktrace();
        }
    }

3.下载网络文件

public void downloadnet(httpservletresponse response) throws malformedurlexception {
        // 下载网络文件
        int bytesum = 0;
        int byteread = 0;
 
        url url = new url("windine.blogdriver.com/logo.gif");
 
        try {
            urlconnection conn = url.openconnection();
            inputstream instream = conn.getinputstream();
            fileoutputstream fs = new fileoutputstream("c:/abc.gif");
 
            byte[] buffer = new byte[1204];
            int length;
            while ((byteread = instream.read(buffer)) != -1) {
                bytesum += byteread;
                system.out.println(bytesum);
                fs.write(buffer, 0, byteread);
            }
        } catch (filenotfoundexception e) {
            e.printstacktrace();
        } catch (ioexception e) {
            e.printstacktrace();
        }
    }

4.支持在线打开的方式

public void download(string filepath, httpservletresponse response, boolean isonline) throws exception {
        file f = new file(filepath);
        if (!f.exists()) {
            response.senderror(404, "file not found!");
            return;
        }
        bufferedinputstream br = new bufferedinputstream(new fileinputstream(f));
        byte[] buf = new byte[1024];
        int len = 0;
 
        response.reset(); // 非常重要
        if (isonline) { // 在线打开方式
            url u = new url("file:///" + filepath);
            response.setcontenttype(u.openconnection().getcontenttype());
            response.setheader("content-disposition", "inline; filename=" + f.getname());
            // 文件名应该编码成utf-8
        } else { // 纯下载方式
            response.setcontenttype("application/x-msdownload");
            response.setheader("content-disposition", "attachment; filename=" + f.getname());
        }
        outputstream out = response.getoutputstream();
        while ((len = br.read(buf)) > 0)
            out.write(buf, 0, len);
        br.close();
        out.close();
    }

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