OkHttp 新手上路
原创
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1.概念
OKHttp 是一款高效的HTTP客户端,支持连接同一地址的链接共享同一个socket,通过连接池来减小响应延迟,还有透明的GZIP压缩,请求缓存等优势,其核心主要有路由、连接协议、拦截器、代理、安全性认证、连接池以及网络适配,拦截器主要是指添加,移除或者转换请求或者回应的头部信息
这个库也是square开源的一个网络请求库(okhttp内部依赖okio)。而且Google在(Android 4.4)版本里面删除了HttpClient相关API,现在是主流框架,很有必要研究
OkHttp 处理了很多网络疑难杂症:会从很多常用的连接问题中自动恢复。如果你的服务器配置了多个IP地址,当第一个IP连接失败的时候,OkHttp会自动尝试下一个IP。OkHttp还处理了代理服务器问题和SSL握手失败问题
这篇我将主要对 OKHttp 研究一下,下一篇再研究对它的封装
- 一般的get请求
- 一般的post请求
- 基于Http的文件上传
- 文件下载
- 加载图片
- 支持请求回调,直接返回对象、对象集合
- 支持session的保持
2. Http Get
new OkHttpClient();
private String get(String url) throws IOException {
Request request = new Request.Builder()
.url(url)
.build();
Response response = client.newCall(request).execute();
if (response.isSuccessful()) {
return response.body().string();
} else {
throw new IOException("Unexpected code " + response);
}
}
Request是OkHttp中访问的请求,Builder是辅助类。Response即OkHttp中的响应
2.1 Response类:
public boolean isSuccessful()
Returns true if the code is in [200..300),
which means the request was successfully received, understood, and
2.2 response.body()返回ResponseBody类
可以方便的获取string
public final String string() throws IOException
Returns the response as a string decoded with the charset of the Content-Type header. If that header is either absent or lacks a charset,
this will attempt to decode the response body as UTF-8.Throws:
IOException
当然也能获取到流的形式:
public final InputStream byteStream()
3. Http Post
3.1 Post 提交 Json 数据
public static final MediaType JSON = MediaType.parse("application/json; charset=utf-8");
OkHttpClient client = new OkHttpClient();
String post(String url, String json) throws IOException {
RequestBody body = RequestBody.create(JSON, json);
Request request = new Request.Builder()
.url(url)
.post(body)
.build();
Response response = client.newCall(request).execute();
if (response.isSuccessful()) {
return response.body().string();
} else {
throw new IOException("Unexpected code " + response);
}
}
使用Request的post方法来提交请求体RequestBody
3.2 POST提交键值对
很多时候我们会需要通过POST方式把键值对数据传送到服务器。 OkHttp提供了很方便的方式来做这件事情
OkHttpClient client = new OkHttpClient();
String post(String url, String json) throws IOException {
RequestBody formBody = FormBody.Builder()
.add("platform", "android")
.add("name", "bug")
.add("subject", "XXXXXXXXXXXXXXX")
.build();
Request request = new Request.Builder()
.url(url)
.post(body)
.build();
Response response = client.newCall(request).execute();
if (response.isSuccessful()) {
return response.body().string();
} else {
throw new IOException("Unexpected code " + response);
}
}
4. 新手须知
网络请求在子线程中进行
response = client.newCall(request).execute();
5. Synchronous Get(同步Get)
下载一个文件,打印他的响应头,以string形式打印响应体。
响应体的 string() 方法对于小文档来说十分方便、高效。但是如果响应体太大(超过1MB),应避免适应 string()方法 ,因为他会将把整个文档加载到内存中。对于超过1MB的响应body,应使用流的方式来处理body
private String get(String url) throws IOException {
Request request = new Request.Builder()
.url(url)
.build();
Response response = client.newCall(request).execute();
Headers responseHeaders = response.headers();
for (int i = 0; i < responseHeaders.size(); i++) {
Log.e(TAG, "get: "+responseHeaders.name(i) + ": " + responseHeaders.value(i));
}
return response.body().string();
}
6. Accessing Headers(提取响应头)
.Builder()
.url("https://api.github.com/repos/square/okhttp/issues")
.header("User-Agent", "OkHttp Headers.java")
.addHeader("Accept", "application/json; q=0.5")
.addHeader("Accept", "application/vnd.github.v3+json")
.build();
Response response = client.newCall(request).execute();
if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
System.out.println("Server: " + response.header("Server"));
System.out.println("Date: " + response.header("Date"));
System.out.println("Vary: " + response.headers("Vary"));
7. Posting a String(Post方式提交String)
使用HTTP POST提交请求到服务。这个例子提交了一个markdown文档到web服务,以HTML方式渲染markdown。因为整个请求体都在内存中,因此避免使用此api提交大文档(大于1MB)
public void run() throws Exception {
String postBody = ""
+ "Releases\n"
+ "--------\n"
+ "\n"
+ " * _1.0_ May 6, 2013\n"
+ " * _1.1_ June 15, 2013\n"
+ " * _1.2_ August 11, 2013\n";
Request request = new Request.Builder()
.url("https://api.github.com/markdown/raw")
.post(RequestBody.create(MEDIA_TYPE_MARKDOWN, postBody))
.build();
Response response = client.newCall(request).execute();
if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
System.out.println(response.body().string());
}
脖子疼,先不写了