如何动态改变Retrofit的base url和rest版本详解

概述

随着google对httpclient 摒弃,和volley的逐渐没落,okhttp开始异军突起,而retrofit则对okhttp进行了强制依赖。

retrofit是由square公司出品的针对于android和java的类型安全的http客户端，

如果看源码会发现其实质上就是对okhttp的封装，使用面向接口的方式进行网络请求，利用动态生成的代理类封装了网络接口请求的底层,

其将请求返回javabean，对网络认证 rest api进行了很好对支持此，使用retrofit将会极大的提高我们应用的网络体验。

rest

既然是restful架构,那么我们就来看一下什么是rest吧。

rest(representational state transfer)是一组架构约束条件和原则。

restful架构都满足以下规则：

（1）每一个uri代表一种资源；

（2）客户端和服务器之间，传递这种资源的某种表现层；

（3）客户端通过四个http动词，对服务器端资源进行操作，实现”表现层状态转化”。

下面话不多说了，来开始本文的正文吧

1. 需求与前提

base url

默认base url: https://cloud.devwiki.net

测试版 url : https://dev.devwiki.net

私有云版本url: https://private.devwiki.net

rest 版本

• /rest/v1/
• /rest/v2/
• /rest/v3/

需求点

• 大部分接口使用 cloud host, 部分接口使用 private host
• 大部分接口使用 rest/v3 版本, 部分接口使用 v2, v1版本.
• 每个host 都有可能存在 rest v1, v2, v3的接口

2. 实现思路

okhttp 可以添加拦截器, 可在发起访问前进行拦截, 通常我们会在 拦截器中统一添加 header, 比如:

class headerinterceptor implements interceptor {
 
 private static final string encoding_gzip = "gzip";
 private static final string content_type_json = "application/json;charset=utf-8";
 private static final string header_content_type = "content-type";
 private static final string header_accept_type = "application/json";
 private static final string header_content_encoding = "content-encoding";
 private final static string charset = "utf-8";
 
 @override
 public response intercept(chain chain) throws ioexception {
  request originrequest = chain.request();
  request.builder newbuilder = originrequest.newbuilder();
  newbuilder.addheader("accept", header_accept_type);
  newbuilder.addheader("accept-charset", charset);
  newbuilder.addheader("accept-encoding", encoding_gzip);
  newbuilder.addheader("accept-language", locale.getdefault().tostring().replace("_", "-"));
  newbuilder.addheader(header_content_type, content_type_json);
  return chain.proceed(newbuilder.build());
 }
}

同理我们也可以在所有请求中添加统一的uuid 或者 key 进行防劫持或者认证. 比如:

request originrequest = chain.request();
if (paramsmap != null) {
 httpurl originurl = originrequest.url();
 httpurl.builder newbuilder = originurl.newbuilder();
 for (string key : paramsmap.keyset()) {
  newbuilder.addencodedqueryparameter(key, paramsmap.get(key));
 }
 httpurl newurl = newbuilder.build();
 request newrequest = originrequest.newbuilder().url(newurl).build();
 return chain.proceed(newrequest);
}
return chain.proceed(originrequest);

那么, 同样我们可以再拦截器中进行host 和 path的替换, 那么怎么替换呢?

3. 实现过程

3.1 定义host 类型和 rest 版本

host类型:

interface hostname {
 string cloud = "cloud";
 string private = "private";
 string dev = "dev";
}
 
interface hostvalue {
 string cloud = "https://www.baidu.com";
 string private = "https://private.bidu.com";
 string dev = "https://dev.baidu.com";
}

rest 版本:

interface restversioncode {
 string empty = "empty";
 string v1 = "v1";
 string v2 = "v2";
 string private = "private";
}
 
/**
 * path 前缀值
 */
interface restversionvalue {
 string empty = "";
 string v1 = "rest/v1";
 string v2 = "rest/v2";
 string private = "rest/private";
}

设置一个默认的 host 和 rest 版本, 然后在需要更改host和rest 版本的请求接口处添header, 根据header设置来变更.

interface baiduapiservice {
 
 @get("s")
 observable<response<object>> search(@query("wd")string wd);
 
 @get("s")
 @headers({urlconstants.header.rest_version_v1})
 observable<response<object>> searchchangepath(@query("wd")string wd);
 
 @get("s")
 @headers({urlconstants.header.host_dev})
 observable<response<object>> searchchangehost(@query("wd")string wd);
 
 @headers({urlconstants.header.host_private, urlconstants.header.rest_version_private})
 @get("s")
 observable<response<object>> searchchangehostpath(@query("wd")string wd);
}

header 的可选值:

interface header {
 string split_colon = ":";
 string host = "hostname";
 string host_cloud = host + split_colon + hostname.cloud;
 string host_private = host + split_colon + hostname.private;
 string host_dev = host + split_colon + hostname.dev;
 string rest_version = "restversion";
 string rest_version_v1 = rest_version + split_colon + restversioncode.v1;
 string rest_version_v2 = rest_version + split_colon + restversioncode.v2;
 string rest_version_private = rest_version + split_colon + restversioncode.private;
 string rest_version_empty = rest_version + split_colon + restversioncode.empty;
}

然后是解析:

class requestinterceptor implements interceptor {
 
 @override
 public response intercept(chain chain) throws ioexception {
  request originrequest = chain.request();
  httpurl originurl = originrequest.url();
  httpurl.builder newbuilder;
 
  string hosttype = originrequest.header(urlconstants.header.host);
  system.out.println("hosttype:" + hosttype);
  if (hosttype != null && hosttype.length() > 0) {
   string hostvalue = urlmanager.getinstance().gethost(hosttype);
   httpurl temp = httpurl.parse(hostvalue);
   if (temp == null) {
    throw new illegalargumentexception(hosttype + "对应的host地址不合法:" + hostvalue);
   }
   newbuilder = temp.newbuilder();
  } else {
   newbuilder = new httpurl.builder()
     .scheme(originurl.scheme())
     .host(originurl.host())
     .port(originurl.port());
  }
  string restversion = originrequest.header(urlconstants.header.rest_version);
  system.out.println("restversion:" + restversion);
  if (restversion == null) {
   restversion = urlconstants.restversioncode.v2;
  }
  string restvalue = urlmanager.getinstance().getrest(restversion);
  if (restvalue.contains("/")) {
   string[] paths = restvalue.split("/");
   for (string path : paths) {
    newbuilder.addencodedpathsegment(path);
   }
  } else {
   newbuilder.addencodedpathsegment(restvalue);
  }
  for (int i = 0; i < originurl.pathsegments().size(); i++) {
   newbuilder.addencodedpathsegment(originurl.encodedpathsegments().get(i));
  }
 
  newbuilder.encodedpassword(originurl.encodedpassword())
    .encodedusername(originurl.encodedusername())
    .encodedquery(originurl.encodedquery())
    .encodedfragment(originurl.encodedfragment());
 
  httpurl newurl = newbuilder.build();
  system.out.println("newurl:" + newurl.tostring());
  request newrequest = originrequest.newbuilder().url(newurl).build();
  return chain.proceed(newrequest);
 }
}

为了能动态设置host, 我们需要一个map来存储host 类型和值.

private map<string, string> hostmap;
private map<string, string> restmap;
 
private urlmanager() {
 hostmap = new hashmap<>(16);
 for (urlconstants.host host : urlconstants.host.values()) {
  hostmap.put(host.getname(), host.getvalue());
 }
 restmap = new hashmap<>();
 for (urlconstants.rest rest : urlconstants.rest.values()) {
  restmap.put(rest.getversion(), rest.getvalue());
 }
}
 
//更新host 的值
public void sethost(string name, string value) {
 if (hostmap.containskey(name)) {
  httpurl httpurl = httpurl.parse(value);
  if (httpurl == null) {
   throw new illegalargumentexception("要存入的host " + name + "对应的value:"
     + value + "不合法!");
  }
  hostmap.put(name, value);
 } else {
  throw new nosuchelementexception("没有找到已经定义的host名称:" + name + ",请先在" +
    "net.devwiki.manager.urlconstants.host中定义!");
 }
}
 
//根据host 获取值
public string gethost(string name) {
 if (!hostmap.containskey(name)) {
  throw new nosuchelementexception("没有找到已经定义的host名称:" + name + ",请先在" +
    "net.devwiki.manager.urlconstants.host中定义!");
 }
 return hostmap.get(name);
}

这样就可以动态替换host 和 rest版本了.

4.测试运行

测试代码:

private static void testrequest() {
 baidurest rest = new baidurest();
 
 testdefault(rest);
 
 testchangehost(rest);
 
 testchangepath(rest);
 
 testchangehostpath(rest);
}

测试运行结果:

osttype:null
restversion:null
newurl:https://www.baidu.com/rest/v2/s?wd=123
九月 07, 2018 11:36:58 上午 okhttp3.internal.platform.platform log
信息: --> get http/1.1
九月 07, 2018 11:36:58 上午 okhttp3.internal.platform.platform log
信息: <-- 302 found (83ms, 154-byte body)
九月 07, 2018 11:36:58 上午 okhttp3.internal.platform.platform log
信息: --> get http://www.baidu.com/s?wd=123&tn=se_psstatistics_p1d9m0nf http/1.1
九月 07, 2018 11:36:58 上午 okhttp3.internal.platform.platform log
信息: <-- 200 ok http://www.baidu.com/s?wd=123&tn=se_psstatistics_p1d9m0nf (46ms, unknown-length body)
hosttype:dev
restversion:null
newurl:https://dev.baidu.com/rest/v2/s?wd=123
九月 07, 2018 11:36:58 上午 okhttp3.internal.platform.platform log
信息: --> get http/1.1
九月 07, 2018 11:36:59 上午 okhttp3.internal.platform.platform log
信息: <-- 302 found (154ms, 154-byte body)
九月 07, 2018 11:36:59 上午 okhttp3.internal.platform.platform log
信息: --> get http/1.1
九月 07, 2018 11:36:59 上午 okhttp3.internal.platform.platform log
信息: <-- 301 moved permanently (18ms, 73-byte body)
九月 07, 2018 11:36:59 上午 okhttp3.internal.platform.platform log
信息: --> get http/1.1
hosttype:null
restversion:v1
newurl:https://www.baidu.com/rest/v1/s?wd=123
九月 07, 2018 11:36:59 上午 okhttp3.internal.platform.platform log
信息: <-- 200 ok (157ms, unknown-length body)
九月 07, 2018 11:36:59 上午 okhttp3.internal.platform.platform log
信息: --> get http/1.1
九月 07, 2018 11:36:59 上午 okhttp3.internal.platform.platform log
信息: <-- 302 found (46ms, 154-byte body)
九月 07, 2018 11:36:59 上午 okhttp3.internal.platform.platform log
信息: --> get http://www.baidu.com/s?wd=123&tn=se_psstatistics_p1d9m0nf http/1.1
九月 07, 2018 11:36:59 上午 okhttp3.internal.platform.platform log
信息: <-- 200 ok http://www.baidu.com/s?wd=123&tn=se_psstatistics_p1d9m0nf (54ms, unknown-length body)
hosttype:private
restversion:private
newurl:https://private.bidu.com/rest/private/s?wd=123

结果按照设置进行了host 和 rest 的变更.

5. 项目代码

项目代码地址: dev-wiki/okhttpdemo （本地下载）

总结

以上就是这篇文章的全部内容了，希望本文的内容对大家的学习或者工作具有一定的参考学习价值，如果有疑问大家可以留言交流，谢谢大家对的支持。