本教程能帮助用户快速搭建一个基于 bos 的文件直传 图片处理的手机 app，主要基于 sts 临时授权、android sdk 和图片处理 api 三个模块实现。
移动互联时代手机上传数据的场景随处可见，为了方便开发者聚焦于产品的业务逻辑，用户可以直接将文件存储到 bos 上。 bos 产品基于 sts 授权方式为用户提供了安全的上传和下载方式，bos 还支持图片处理服务。bos 具有成本低、支持海量存储和弹性扩展的特性，能帮助开发者更方便实现移动 app 业务的开发。手机美图 app 的整体搭建逻辑如下：
手机美图示例 app 下载地址：
下载完 app 并安装完成后可以直接通过应用服务器地址访问 bos ，并进行图片处理。应用服务器地址是指搭建移动应用的后台服务器，默认开启的端口为8080。关于 bos 的区域和 bucket 设置都需要在应用服务器进行配置。
该 app 支持用户上传、下载和下载缩放图三个功能。
搭建美图 app 包含以下几个步骤：
从 github 上下载的代码包，代码包主要包含 “bos_meitu_app” 和 “bos_meitu_app_server” 两部分，其中 “bos_meitu_app” 主要用于定义app界面及相关动作，“bos_meitu_app_server” 为应用服务器相关配置。
修改 “bos_meitu_app_server” 中的 “meituappserverhandler.java” 文件，其中定义了 ak/sk、bos 服务器对应的 endpoint 和 bucket 名称等信息。 ``` public string getbosinfo(string bosrequesttype) { //配置ak、sk string bosak = "开发者的ak"; string bossk = "开发者的sk"; //百度智能云提供的stsendpoint string stsendpoint = "";
bcecredentials credentials = new defaultbcecredentials(bosak, bossk);
bceclientconfiguration clientconfig = new bceclientconfiguration();
clientconfig.setcredentials(credentials);
clientconfig.setendpoint(stsendpoint);
stsclient stsclient = new stsclient(clientconfig);
getsessiontokenrequest stsreq = new getsessiontokenrequest();
// request expiration time
stsreq.setdurationseconds(1800);
getsessiontokenresponse ststoken = stsclient.getsessiontoken(stsreq);
string ststokenak = ststoken.getcredentials().getaccesskeyid();
string ststokensk = ststoken.getcredentials().getsecretaccesskey();
string ststokensessiontoken = ststoken.getcredentials().getsessiontoken();
// bos服务的endpoint地址，及bucket名称。
string bosendpoint = "http://bj.bcebos.com";
string bucketname = "bucket名称";
if (bosrequesttype.equalsignorecase("download-processed")) {
// the binded image processing domain set by app developer on bce console
bosendpoint = "http://" bucketname ".bj.bcebos.com";
}
// prefix is the bucket name, and does not specify the object name
bosinfo bosinfo = new bosinfo(ststokenak, ststokensk, ststokensessiontoken, bosendpoint,
bucketname, "", bucketname);
string res = "";
objectmapper mapper = new objectmapper();
try {
res = mapper.writerwithdefaultprettyprinter().writevalueasstring(bosinfo);
} catch (jsonprocessingexception e) {
// todo auto-generated catch block
e.printstacktrace();
res = "";
}
system.out.println(res);
try {
res = new string(res.getbytes(), "utf8");
} catch (unsupportedencodingexception e) {
// todo auto-generated catch block
e.printstacktrace();
res = "";
}
return res;
}```
将修改完成的服务器代码重新编译打包为 bos_meitu_app_server.jar，将 jar 包上传到应用服务器上并执行命令 java -jar bos_meitu_app_server.jar。
上传图片到 bos 过程中 app、app server 和 bos 的交互过程如下图所示：
从 bos 下载图片过程中 app、app server 和 bos 的交互过程如下图所示：
从 bos 下载缩放图过程中 app、app server 和 bos 的交互过程如下图所示：
从 bos 下载缩放图和从 bos 上下载图片交互过程基本类似，只是在从 bos 下载缩放图时需要携带 app 上设定的图片处理参数，如图片宽、高和旋转角度等。
示例代码以 java 语言为例讲解美图 app 的实现，代码分为 app 客户端和应用服务器端两部分。
app 端代码主要包括 bosclient 初始化、从 app server 端获取 bos 信息、及上传文件到 bos 三个功能模块。
public class bos {
private string ak = null;
private string sk = null;
private string endpoint = null;
private string ststoken = null;
private bosclient client = null;
public bos(string ak, string sk, string endpoint, string ststoken) {
this.ak = ak;
this.sk = sk;
this.endpoint = endpoint;
this.ststoken = ststoken;
client = createclient();
}
public bosclient createclient() {
bosclientconfiguration config = new bosclientconfiguration();
bcecredentials credentials = null;
if (ststoken != null && !ststoken.equalsignorecase("")) {
credentials = new defaultbcesessioncredentials(ak, sk, ststoken);
} else {
credentials = new defaultbcecredentials(ak, sk);
}
config.setendpoint(endpoint);
config.setcredentials(credentials);
return new bosclient(config);
}
public void uploadfile(string bucket, string object, file file) {
client.putobject(bucket, object, file);
}
public void uploadfile(string bucket, string object, inputstream inputstream) {
client.putobject(bucket, object, inputstream);
}
public void uploadfile(string bucket, string object, byte[] data) {
client.putobject(bucket, object, data);
}
public byte[] downloadfilecontent(string bucket, string object) {
return client.getobjectcontent(bucket, object);
}
}public void uploadpictobos() {
// 1. get pic params from ui: file name, file location uri etc
// 2. send params to app server and get sts, bucket name and region
// 3. upload selected pic to bos with sts etc, which bos client needs
edittext et = (edittext) findviewbyid(r.id.app_server_addr_edittext);
final string appserveraddr = et.gettext().tostring();
new thread(new runnable() {
@override
public void run() {
map bosinfo = appserver.getbosinfofromappserver(appserveraddr, "user-demo",
appserver.bosoperationtype.upload);
if (bosinfo == null) {
return;
}
showtoast(bosinfo.tostring(), toast.length_long);
string ak = (string) bosinfo.get("ak");
string sk = (string) bosinfo.get("sk");
string ststoken = (string) bosinfo.get("ststoken");
string endpoint = (string) bosinfo.get("endpoint");
string bucketname = (string) bosinfo.get("bucketname");
string objectname = (string) bosinfo.get("objectname");
string prefix = (string) bosinfo.get("prefix");
log.i("uploadfiletobos", bosinfo.tostring());
// specify a object name if the app server does not specify one
if (objectname == null || objectname.equalsignorecase("")) {
objectname = ((edittext) findviewbyid(r.id.bos_object_name_edittext)).gettext().tostring();
if (prefix != null && !prefix.equalsignorecase("")) {
objectname = prefix "/" objectname;
}
}
bos bos = new bos(ak, sk, endpoint, ststoken);
try {
byte[] data = utils.readallfromstream(mainactivity.this.getcontentresolver().openinputstream(selectedpicuri));
bos.uploadfile(bucketname, objectname, data);
} catch (throwable e) {
log.e("mainactivity/upload", "failed to upload file to bos: " e.getmessage());
showtoast("failed to upload file: " e.getmessage());
return;
}
// finished uploading file, send a message to inform ui
handler.sendemptymessage(upload_file_finished);
}
}).start();
} public class appserver {
/**
* get info from app server for the file to upload to or download from bos
*
* @param appserverendpoint app server
* @param username the app user's name, registered in app server
* @param bosoperationtype download? upload? or?
* @return sts, and bos endpoint, bucketname, prefix, path, object name etc
*/
public static map getbosinfofromappserver(string appserverendpoint, string username, bosoperationtype bosoperationtype) {
string type = "";
switch (bosoperationtype) {
// to simplify
case upload: {
type = "upload";
break;
}
case download: {
type = "download";
break;
}
case download_processed: {
type = "download-processed";
break;
}
default:{
break;
}
}
// todo: this url should be url encoded
string appserverurl = appserverendpoint "/?" "username=" username "&command=ststoken&type=" type;
// create a http client to contact app server to get sts
httpparams httpparameters = new basichttpparams();
httpclient httpclient = new defaulthttpclient(httpparameters);
httpget httpget = new httpget(appserverurl);
httpget.addheader("user-agent", "bos-meitu-app/demo");
httpget.setheader("accept", "*/*");
try {
httpget.setheader("host", new .gethost());
} catch (malformedurlexception e) {
e.printstacktrace();
}
httpget.setheader("accept-encoding", "identity");
map bosinfo = new hashmap();
try {
httpresponse response = httpclient.execute(httpget);
if (response.getstatusline().getstatuscode() != 200) {
return null;
}
httpentity entity = response.getentity();
long len = entity.getcontentlength();
inputstream is = entity.getcontent();
int off = 0;
byte[] b = new byte[(int) len];
while (true) {
int readcount = is.read(b, off, (int) len);
if (readcount < 0) {
break;
}
off = readcount;
}
log.d("appserver", new string(b, "utf8"));
jsonobject jsonobject = new jsonobject(new string(b, "utf8"));
iterator keys = jsonobject.keys();
while (keys.hasnext()) {
string key = keys.next();
bosinfo.put(key, jsonobject.get(key));
}
} catch (ioexception e) {
e.printstacktrace();
return null;
} catch (jsonexception e) {
e.printstacktrace();
return null;
}
return bosinfo;
}
public enum bosoperationtype {
upload,
download,
download_processed,
}
} app server 端基于 jetty 框架，接口主要处理 android app 获取 bos 信息的请求。app server 端会返回临时 ak、sk、session token、bucket 名称、资源路径和资源请求的 endpoint 等参数。以下为 jetty 处理的代码示例。
@override
public void handle(string target, request baserequest, httpservletrequest request, httpservletresponse response)
throws ioexception, servletexception {
// inform jetty that this request has now been handled
baserequest.sethandled(true);
if (!request.getmethod().equalsignorecase("get")) {
response.setstatus(httpservletresponse.sc_not_implemented);
return;
}
// expected url example: localhost:8080/?command=ststoken&type=download
map parammap = request.getparametermap();
if (parammap.get("command") == null || parammap.get("type") == null) {
// invalid request
response.setstatus(httpservletresponse.sc_bad_request);
return;
}
if (!parammap.get("command")[0].equalsignorecase("ststoken")) {
response.setstatus(httpservletresponse.sc_not_implemented);
return;
}
string responsebody = "";
responsebody = getbosinfo(parammap.get("type")[0]);
// declare response encoding and types
response.setcontenttype("application/json; charset=utf-8");
// declare response status code
response.setstatus(httpservletresponse.sc_ok);
// write back response, utf8 encoded
response.getwriter().println(responsebody);
}
/**
* generates bos info needed by app according to requset type(upload, download etc)
* this is the key part for uploading file to bos with sts token
* @param bosrequesttype
* @return utf8 encoded json string
*/
public string getbosinfo(string bosrequesttype) {
// configuration for getting ststoken
// bce bos credentials ak sk
string bosak = "your_bos_ak";
string bossk = "your_bos_sk";
// bce sts service endpoint
string stsendpoint = "http://sts.bj.baidubce.com";
bcecredentials credentials = new defaultbcecredentials(bosak, bossk);
bceclientconfiguration clientconfig = new bceclientconfiguration();
clientconfig.setcredentials(credentials);
clientconfig.setendpoint(stsendpoint);
stsclient stsclient = new stsclient(clientconfig);
getsessiontokenrequest stsreq = new getsessiontokenrequest();
// request expiration time
stsreq.setdurationseconds(1800);
getsessiontokenresponse ststoken = stsclient.getsessiontoken(stsreq);
string ststokenak = ststoken.getcredentials().getaccesskeyid();
string ststokensk = ststoken.getcredentials().getsecretaccesskey();
string ststokensessiontoken = ststoken.getcredentials().getsessiontoken();
// **to simplify this demo there is no difference between "download" and "upload"**
// parts of bos info
string bosendpoint = "http://bj.bcebos.com";
string bucketname = "bos-android-sdk-app";
if (bosrequesttype.equalsignorecase("download-processed")) {
// the binded image processing domain set by app developer on bce console
bosendpoint = "http://" bucketname ".bj.bcebos.com";
}
// prefix is the bucket name, and does not specify the object name
bosinfo bosinfo = new bosinfo(ststokenak, ststokensk, ststokensessiontoken, bosendpoint,
bucketname, "", bucketname);
string res = "";
objectmapper mapper = new objectmapper();
try {
res = mapper.writerwithdefaultprettyprinter().writevalueasstring(bosinfo);
} catch (jsonprocessingexception e) {
e.printstacktrace();
res = "";
}
try {
res = new string(res.getbytes(), "utf8");
} catch (unsupportedencodingexception e) {
// todo auto-generated catch block
e.printstacktrace();
res = "";
}
return res;
}