OkHttp应该是目前最完善，也是相当流行的一个底层网络请求库。Google都在用，所以有必要深入了解一下，刚好最近在重构公司项目的网络层，就顺便梳理一下。
———–12.29————
最近暂时没有时间详细整理了。就简单过了一下官方文档。
以下取自官方文档。
网络请求
同步Get方法
以下样例代码下载一个文件，打印headers，打印字符串形式的 response body
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 | private final OkHttpClient client = new OkHttpClient();
public void () throws Exception {
Request request = new Request.Builder()
.url("http://publicobject.com/helloworld.txt")
.build();
Response response = client.newCall(request).execute();
if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
Headers responseHeaders = response.headers();
for (int i = 0; i < responseHeaders.size(); i++) {
System.out.println(responseHeaders.name(i) + ": " + responseHeaders.value(i));
}
System.out.println(response.body().string());
} |
string()方法对小文件是很方便高效的，但是当response body 大于1M时，避免用string()，因为它会加载整个文件到内存，此时应该把body用stream的形式来处理.异步Get方法
在工作线程下载一个文件，并且当response准备好了的时候回调Callback。 response headers 准备好了的时候，就走回调。读response body 也会阻塞线程，OkHttp暂时没有提供额外的异步
APIs来获得response body。
1 | private final OkHttpClient client = new OkHttpClient();
public void () throws Exception {
Request request = new Request.Builder()
.url("http://publicobject.com/helloworld.txt")
.build();
client.newCall(request).enqueue(new Callback() {
@Override public void (Request request, IOException throwable) {
throwable.printStackTrace();
}
@Override public void (Response response) throws IOException {
if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
Headers responseHeaders = response.headers();
for (int i = 0; i < responseHeaders.size(); i++) {
System.out.println(responseHeaders.name(i) + ": " + responseHeaders.value(i));
}
System.out.println(response.body().string());
}
});
} |
Accessing Headers
典型的HTTP请求头，像Map<String, String>那样工作，每个field有一个值或者没有，但是有的headers允许有多个值,就像Guava’s Multimap.比如，一个HTTP response 提供多个多样的headers是合法且普遍的。 OkHttp’s APIs 兼容这两种情况。
注意：当写request headers时，header(name, value) 设置唯一的键值对，这会覆盖已有的值。而用方法 addHeader(name, value) 来添加header时，不会移除已有的header。
相应的header(name)来获取最后的这个name的相应value，通常这也是唯一的，如果没有就返回null 。headers(name)用来read所有的field的值，已list的形式。
想要看所有的headers，使用支持通过索引访问的类Headers
1 | private final OkHttpClient client = new OkHttpClient();
public void () throws Exception {
Request request = new Request.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"));
} |
Posting a String
由于这个request body同时要完全加载到内存，所以避免用个API来posting大于1M的文件。
1 | public static final MediaType MEDIA_TYPE_MARKDOWN
= MediaType.parse("text/x-markdown; charset=utf-8");
private final OkHttpClient client = new OkHttpClient();
public void () 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());
} |
Post Streaming
一下示例代码使用到了Okio的buffered sink，你可能更喜欢使用OutputStream，你可以通过BufferedSink.outputStream()来获得。
1 | public static final MediaType MEDIA_TYPE_MARKDOWN
= MediaType.parse("text/x-markdown; charset=utf-8");
private final OkHttpClient client = new OkHttpClient();
public void () throws Exception {
RequestBody requestBody = new RequestBody() {
@Override public MediaType () {
return MEDIA_TYPE_MARKDOWN;
}
@Override public void (BufferedSink sink) throws IOException {
sink.writeUtf8("Numbers\n");
sink.writeUtf8("-------\n");
for (int i = 2; i <= 997; i++) {
sink.writeUtf8(String.format(" * %s = %s\n", i, factor(i)));
}
}
private String (int n) {
for (int i = 2; i < n; i++) {
int x = n / i;
if (x * i == n) return factor(x) + " × " + i;
}
return Integer.toString(n);
}
};
Request request = new Request.Builder()
.url("https://api.github.com/markdown/raw")
.post(requestBody)
.build();
Response response = client.newCall(request).execute();
if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
System.out.println(response.body().string());
} |
Posting文件
简单
1 | public static final MediaType MEDIA_TYPE_MARKDOWN
= MediaType.parse("text/x-markdown; charset=utf-8");
private final OkHttpClient client = new OkHttpClient();
public void () throws Exception {
File file = new File("README.md");
Request request = new Request.Builder()
.url("https://api.github.com/markdown/raw")
.post(RequestBody.create(MEDIA_TYPE_MARKDOWN, file))
.build();
Response response = client.newCall(request).execute();
if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
System.out.println(response.body().string());
} |
Posting form parameters(格式化参数)
用FormEncodingBuilder来构建一个request body，像HTML的
标签一样工作，键值对将以兼容HTML的URL编码方式被组织。
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 | private final OkHttpClient client = new OkHttpClient();
public void () throws Exception {
RequestBody formBody = new FormEncodingBuilder()
.add("search", "Jurassic Park")
.build();
Request request = new Request.Builder()
.url("https://en.wikipedia.org/w/index.php")
.post(formBody)
.build();
Response response = client.newCall(request).execute();
if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
System.out.println(response.body().string());
} |
Posting一个multipart request(复合请求)
MultipartBuilder可以构建复杂的request bodies，兼容html文件上传forms。复合请求的每个request body分别可以定义自己的headers，如果存在，这些headers分别描述相应的body，例如Content-Disposition。The Content-Length and Content-Type headers 会自动添加。
1 | private static final String IMGUR_CLIENT_ID = "...";
private static final MediaType MEDIA_TYPE_PNG = MediaType.parse("image/png");
private final OkHttpClient client = new OkHttpClient();
public void () throws Exception {
RequestBody requestBody = new MultipartBuilder()
.type(MultipartBuilder.FORM)
.addPart(
Headers.of("Content-Disposition", "form-data; name=\"title\""),
RequestBody.create(null, "Square Logo"))
.addPart(
Headers.of("Content-Disposition", "form-data; name=\"image\""),
RequestBody.create(MEDIA_TYPE_PNG, new File("website/static/logo-square.png")))
.build();
Request request = new Request.Builder()
.header("Authorization", "Client-ID " + IMGUR_CLIENT_ID)
.url("https://api.imgur.com/3/image")
.post(requestBody)
.build();
Response response = client.newCall(request).execute();
if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
System.out.println(response.body().string());
} |
用Gson解析JSON返回结果
Gson是一个便利的API用来转换JSON和java对象。
Note that ResponseBody.charStream() uses the Content-Type response header to select which charset to use when decoding the response body. It defaults to UTF-8 if no charset is specified.
注意ResponseBody.charStream()根据返回头的Content-Type来选择相应的编码方式，来解码response body。如果没有定义charset，默认是用UTF-8。
1 | private final OkHttpClient client = new OkHttpClient();
private final Gson gson = new Gson();
public void () throws Exception {
Request request = new Request.Builder()
.url("https://api.github.com/gists/c2a7c39532239ff261be")
.build();
Response response = client.newCall(request).execute();
if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
Gist gist = gson.fromJson(response.body().charStream(), Gist.class);
for (Map.Entry<String, GistFile> entry : gist.files.entrySet()) {
System.out.println(entry.getKey());
System.out.println(entry.getValue().content);
}
}
static class {
Map<String, GistFile> files;
}
static class {
String content;
} |
Response Caching
缓存请求结果，你需要一个你可以读写的限制大小的缓存目录，缓存目录应该是私有的，禁止未信任的程序随便读取。
Response caching uses HTTP headers for all configuration. You can add request headers like Cache-Control: max-stale=3600 and OkHttp’s cache will honor them. Your webserver configures how long responses are cached with its own response headers, like Cache-Control: max-age=9600. There are cache headers to force a cached response, force a network response, or force the network response to be validated with a conditional GET.
Response caching完全用HTTP headers来配置，你可以添加像这样的请求头：Cache-Control: max-stale=3600，你的web服务器可以这样的请求头Cache-Control: max-age=9600来配置请求结果缓存时间。可以设置相应的headers来强制缓存response，force a network response, or force the network response to be validated(经过验证的) with a conditional GET.
1 | private final OkHttpClient client;
public (File cacheDirectory) throws Exception {
int cacheSize = 10 * 1024 * 1024;
Cache cache = new Cache(cacheDirectory, cacheSize);
client = new OkHttpClient();
client.setCache(cache);
}
public void () throws Exception {
Request request = new Request.Builder()
.url("http://publicobject.com/helloworld.txt")
.build();
Response response1 = client.newCall(request).execute();
if (!response1.isSuccessful()) throw new IOException("Unexpected code " + response1);
String response1Body = response1.body().string();
System.out.println("Response 1 response: " + response1);
System.out.println("Response 1 cache response: " + response1.cacheResponse());
System.out.println("Response 1 network response: " + response1.networkResponse());
Response response2 = client.newCall(request).execute();
if (!response2.isSuccessful()) throw new IOException("Unexpected code " + response2);
String response2Body = response2.body().string();
System.out.println("Response 2 response: " + response2);
System.out.println("Response 2 cache response: " + response2.cacheResponse());
System.out.println("Response 2 network response: " + response2.networkResponse());
System.out.println("Response 2 equals Response 1? " + response1Body.equals(response2Body));
} |
阻止使用缓存的response，使用CacheControl.FORCE_NETWORK。阻止使用网络，使用 CacheControl.FORCE_CACHE。注意，如果你使用FORCE_CACHE而response需要网络支持的话，OkHttp 将返回一个 504 Unsatisfiable Request response.
取消一个call
用Call.cancel()会立刻停止一个进行中的请求，如果一个线程正在writing一个request，或者在reading一个response，将会抛IOException。
如果你的用户操作离开了app，所有的同步异步请求都应该取消。
你可以用tags来同时取消多个请求，用RequestBuilder.tag(tag)在创建请求的时候指定一个tag，用OkHttpClient.cancel(tag)取消所有有这个tag的请求。
1 | private final ScheduledExecutorService executor = Executors.newScheduledThreadPool(1);
private final OkHttpClient client = new OkHttpClient();
public void () throws Exception {
Request request = new Request.Builder()
.url("http://httpbin.org/delay/2")
.build();
final long startNanos = System.nanoTime();
final Call call = client.newCall(request);
executor.schedule(new Runnable() {
@Override public void () {
System.out.printf("%.2f Canceling call.%n", (System.nanoTime() - startNanos) / 1e9f);
call.cancel();
System.out.printf("%.2f Canceled call.%n", (System.nanoTime() - startNanos) / 1e9f);
}
}, 1, TimeUnit.SECONDS);
try {
System.out.printf("%.2f Executing call.%n", (System.nanoTime() - startNanos) / 1e9f);
Response response = call.execute();
System.out.printf("%.2f Call was expected to fail, but completed: %s%n",
(System.nanoTime() - startNanos) / 1e9f, response);
} catch (IOException e) {
System.out.printf("%.2f Call failed as expected: %s%n",
(System.nanoTime() - startNanos) / 1e9f, e);
}
} |
Timeouts
1 | private final OkHttpClient client;
public () throws Exception {
client = new OkHttpClient();
client.setConnectTimeout(10, TimeUnit.SECONDS);
client.setWriteTimeout(10, TimeUnit.SECONDS);
client.setReadTimeout(30, TimeUnit.SECONDS);
}
public void () throws Exception {
Request request = new Request.Builder()
.url("http://httpbin.org/delay/2")
.build();
Response response = client.newCall(request).execute();
System.out.println("Response completed: " + response);
} |
Per-call Configuration 某个请求特殊配置
所有的HTTP client配置都在OkHttpClient，包括代理，超时，缓存，你想为单个请求改变配置的话，clone the OkHttpClient，这个会返回一个浅(shallow)copy让你来单独定制，如下，你make了一个500ms超时的和3000ms超时的请求。
1 | private final OkHttpClient client = new OkHttpClient();
public void () throws Exception {
Request request = new Request.Builder()
.url("http://httpbin.org/delay/1")
.build();
try {
OkHttpClient cloned = client.clone();
cloned.setReadTimeout(500, TimeUnit.MILLISECONDS);
Response response = cloned.newCall(request).execute();
System.out.println("Response 1 succeeded: " + response);
} catch (IOException e) {
System.out.println("Response 1 failed: " + e);
}
try {
OkHttpClient cloned = client.clone();
cloned.setReadTimeout(3000, TimeUnit.MILLISECONDS);
Response response = cloned.newCall(request).execute();
System.out.println("Response 2 succeeded: " + response);
} catch (IOException e) {
System.out.println("Response 2 failed: " + e);
}
} |
新版3.0修改为如下：
1 | private final OkHttpClient client = new OkHttpClient();
public void () throws Exception {
Request request = new Request.Builder()
.url("http://httpbin.org/delay/1")
.build();
try {
OkHttpClient copy = client.newBuilder()
.readTimeout(500, TimeUnit.MILLISECONDS)
.build();
Response response = copy.newCall(request).execute();
System.out.println("Response 1 succeeded: " + response);
} catch (IOException e) {
System.out.println("Response 1 failed: " + e);
}
try {
OkHttpClient copy = client.newBuilder()
.readTimeout(3000, TimeUnit.MILLISECONDS)
.build();
Response response = copy.newCall(request).execute();
System.out.println("Response 2 succeeded: " + response);
} catch (IOException e) {
System.out.println("Response 2 failed: " + e);
}
} |
Handling authentication(身份验证)
OkHttp可以自动重操作没有验证通过的请求，当一个response是401 Not Authorized(未授权，未认可)，表示认证者需要你提供相应证书，实现是应该新建一个带有相应缺失证书的请求，如果获取不到证书，返回null跳过retry。
Use Response.challenges() to get the schemes and realms of any authentication challenges.
When fulfilling a Basic challenge, use Credentials.basic(username, password) to encode the request header.
1 | private final OkHttpClient client = new OkHttpClient();
public void () throws Exception {
client.setAuthenticator(new Authenticator() {
@Override public Request (Proxy proxy, Response response) {
System.out.println("Authenticating for response: " + response);
System.out.println("Challenges: " + response.challenges());
String credential = Credentials.basic("jesse", "password1");
return response.request().newBuilder()
.header("Authorization", credential)
.build();
}
@Override public Request (Proxy proxy, Response response) {
return null;
}
});
Request request = new Request.Builder()
.url("http://publicobject.com/secrets/hellosecret.txt")
.build();
Response response = client.newCall(request).execute();
if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
System.out.println(response.body().string());
} |
身份验证失效的时候就别多次retry了，return null放弃就好。
1 | if (credential.equals(response.request().header("Authorization"))) {
return null;
} |
You may also skip the retry when you’ve hit an application-defined attempt limit:
1 | if (responseCount(response) >= 3) {
return null;
}
private int (Response response) {
int result = 1;
while ((response = response.priorResponse()) != null) {
result++;
}
return result;
} |
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