protobuf实现js与java间的http通信

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前端js与后端java之间的http通信我们一般采用json这种文本格式，实现非常简单，也非常容易被人抓包。protobuf协议起源于google，采用类似TLV(tag，length，value)的编码方式，输出一段字节数组，是一种二进制格式的协议。相比json格式，protobuf编码出来的内容更少，效率更高，传输过程中因为是二进制被人抓包也就更难。protobuf官方给出了很多后端语言(java，C++，python)基于protobuf的交互。前端js与后端的交互例子比较少，因为本身js在处理http请求方面也比较弱。下面提供简单demo：

proto协议文件:

message Req {    required string text = 1;}message Resp {    required string code = 1;}

前端代码:

<!DOCTYPE html><html><head><script src="./long.js"></script>   <script src="./bytebuffer.js"></script><script src="./protobuf.js"></script><script>if (typeof dcodeIO === 'undefined' || !dcodeIO.ProtoBuf) {    throw(new Error("ProtoBuf.js is not present. Please see www/index.html for manual setup instructions."));}var ProtoBuf = dcodeIO.ProtoBuf;var proto = ProtoBuf.loadProtoFile("./example.proto");var Req   = proto.build("Req");var Resp  = proto.build("Resp");var req = new Req();req.text="1";var  body = new Uint8Array(req.toArrayBuffer());var xhr = new XMLHttpRequest();xhr.open('POST', 'http://localhost:8089/xxxxx_getProtoBufReq.action', true);xhr.responseType = 'arraybuffer';xhr.onload = function(e) {if (this.status == 200) {var resp=Resp.decode(this.response);alert(resp.code);}};xhr.send(body);</script></head><body></body></html>

上面的html需要引入long.js，bytebuffer.js，protobuf.js三个文件，都可以在https://github.com/dcodeIO 的网站上找到。

参考资料:

http://mozilla.com.cn/thread-34886-1-1.html

http://web.jobbole.com/83701/

后端java代码:

public String getProtoBuf() {return "protoBuf";}public void getProtoBufReq()  {HttpServletRequest request = ServletActionContext.getRequest();InputStream input=null;ByteArrayOutputStream out=null;ServletOutputStream output=null;try {input = request.getInputStream();out = new ByteArrayOutputStream();byte by[] = new byte[1024];int len = 0;while ((len = input.read(by)) != -1) {out.write(by, 0, len);}Example.Req req=Example.Req.parseFrom(out.toByteArray());System.out.println(req.getText());Example.Resp.Builder resp=Example.Resp.newBuilder();resp.setCode("300");HttpServletResponse response = ServletActionContext.getResponse();output=response.getOutputStream();output.write(resp.build().toByteArray());} catch (Exception e) {e.printStackTrace();}finally{IOUtils.closeQuietly(output);IOUtils.closeQuietly(out);IOUtils.closeQuietly(input);}}

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