开门见山,直奔主题~
目录
OkHttp3简介
OkHttp3用法
1、GET请求
---- 同步
---- 异步
---- GET请求下载文件
2、POST请求:
---- 提交String请求
---- 提交数据流请求
---- 提交文件请求
---- 提交表单请求
---- 提交multipart请求
3、取消调用
4、配置相关
---- 处理响应缓存
---- 处理响应超时
---- 处理单独配置请求参数
---- 处理身份验证
5、拦截器OkHttp3源码分析(待续)
OkHttp3封装应用(待续)
OkHttp3简介
1、链接:
官网:https://square.github.io/okhttp/
GitHub:https://github.com/square/okhttp
2、简介:
官方:An HTTP & HTTP/2 client for Android and Java applications
OKHttp是一个处理网络请求的开源项目,Android 当前最火热网络框架之一,由移动支付Square公司贡献,用于替代HttpUrlConnection和Apache HttpClient(Android6.0 API 23里已移除HttpClient)。
3、特征:
OkHttp是一个默认有效的HTTP客户端:
· 支持http2,对一台机器的所有请求共享同一个socket。
· 连接池减少了请求延迟(如果HTTP/2 不可用)。
· 透明的GZIP压缩减少响应数据的大小。
· 缓存响应数据,避免了重复的网络请求。
~自动恢复一般的连接问题
~ 若你的服务器配有多个IP地址,请求失败时自动重试主机的其他IP,自动重定向
~ OkHttp使用现代TLS技术(SNI1.3,ALPN)初始化新的连接。
~OkHttp的API很友好,请求和响应采用建造者模式可进行链式调用
~支持阻塞式的同步调用,和回调式的异步调用。
注意:
OkHttp最新版本(3.14.0)支持Android 5.0+(API级别21+)和Java 8+。
如果考虑到版本限制的问题,可以使用低版本(3.12.0)
本文参考版本为3.12.0
OkHttp3用法
1、引入下载
//这里未使用最新的,是因为3.14.0版本需要在Android5.0+和Java8+版本以上
implementation("com.squareup.okhttp3:okhttp:3.12.0")
你也可能需要引入Okio(用于OkHttp,对于I/O操作和缓冲区大小都做了更好的处理):
//没用最新的2.xx.xx版本是因为Kotlin的原因
compile 'com.squareup.okio:okio:1.17.3'
若需要看最新版本,请移步官方GitHub地址,见上。
添加权限:
//可能用到
2、使用:
使用前先了解OkHttp核心的几个类:
· OkHttpClient:HTTP客户端对象,应当作为单例被共享。
· Request:访问请求类,对HTTP请求的相关参数的封装。
· RequestBody:请求体类,对HTTP请求体的封装,用于Post请求中。
· MediaType:请求的数据类型,指明请求数据的格式(json/image/file...)
· Response:响应结果类,即网络请求的响应结果。
· execute():同步的请求方法,会阻塞线程,需要在工作线程中调用。
· enqueue(Callback callBack):异步的请求方法,可直接调用。
··· 而Callback中的回调方法是执行在子线程中的,因此不能在其中进行UI更新操作。
2.1、GET请求
同步:
/**
* 同步Get请求
* @param url 请求地址
*/
private void callGetSynchronous(String url) {
final OkHttpClient client = new OkHttpClient();
final Request request = new Request.Builder()
.get() //此处可以省略不写,默认就是Get请求
.url(url)
.build();
//同步调用会阻塞主线程,因此需要在子线程进行
//这里只是演示,实际开发中最好使用线程池等相关技术处理
new Thread(new Runnable() {
@Override
public void run() {
try {
Response response = client.newCall(request).execute();
if (!response.isSuccessful()) {
throw new IOException("Unexpected code " + response);
}
Log.e(TAG, "body==>" + response.body().string());
} catch (IOException e) {
e.printStackTrace();
}
}
}).start();
}
异步:
/**
* 异步GE请求
* @param url 请求地址
*/
private void callGetAsynchronous(String url) {
OkHttpClient client = new OkHttpClient();
Request request = new Request.Builder()
.get()
.url(url)
.build();
Call call = client.newCall(request);
call.enqueue(new Callback() {
@Override
public void onFailure(@NonNull Call call, @NonNull IOException e) {
Log.e(TAG, "onFailure::Thread==>" + Thread.currentThread().getName());
}
@Override
public void onResponse(@NonNull Call call, @NonNull Response response) throws IOException {
if (!response.isSuccessful()) {
throw new IOException("Unexpected code " + response);
}
//Thread[OkHttp https://api.github.com/...,5,main]
Log.e(TAG, "onResponse::Thread==>" + Thread.currentThread());
//isUIThread==>false
Log.e(TAG, "isUIThread==>" + (Looper.getMainLooper().getThread()==Thread.currentThread()));
Log.e(TAG, "onResponse::body==>" + response.body().string());
}
});
}
GET请求下载文件:
/**
* 异步GET下载文件
*/
private void callDownloadFile() {
String fileUrl = "https://publicobject.com/helloworld.txt";
OkHttpClient client = new OkHttpClient();
final Request request = new Request.Builder()
.url(fileUrl)
.get()
.build();
Call call = client.newCall(request);
call.enqueue(new Callback() {
@Override
public void onFailure(@NonNull Call call, @NonNull IOException e) {
Log.d(TAG, "onFailure::" + e.getMessage());
}
@Override
public void onResponse(@NonNull Call call, @NonNull final Response response) throws IOException {
//Thread[OkHttp https://publicobject.com/...,5,main]
Log.e(TAG, "onResponse::Thread==>" + Thread.currentThread());
//isUIThread==>false
Log.e(TAG, "isUIThread==>" + (Looper.getMainLooper().getThread()==Thread.currentThread()));
if (!response.isSuccessful()) {
throw new IOException("Unexpected code " + response);
}
//保存文件,此处省略
saveFile(response.body().byteStream());
}
});
}
·说明:
1、同步Get请求中Response
的相关方法(至少body()方法)会阻塞线程,不能在主线程(UI线程)中进行调用,否则会报错:android.os.NetworkOnMainThreadException
。
2、从打印结果来看,异步Get请求的回调方法是在子线程(OkHttp自定义的线程名称)中的,所以不可以在回调方法中进行UI的更新。
3、在异步Get请求的回调方法中response.body().string()
只能有效的调用一次,否则会报错:java.lang.IllegalStateException: closed
。
2.2、POST请求
POST请求在构造时,需要传入一个RequestBody对象,用它来携带我们要提交的数据。
备注:
官方测试数据:
url:https://api.github.com/markdown/raw
MediaType:text/x-markdown; charset=utf-8
提交String请求:
/**
* 异步POST请求字符串
*/
private void callPostString() {
String url = "https://api.github.com/markdown/raw";
String postString = "This is POST RequestBody";
MediaType MEDIA_TYPE_MARKDOWN = MediaType.parse("text/x-markdown; charset=utf-8");
OkHttpClient client = new OkHttpClient();
RequestBody body = RequestBody.create(MEDIA_TYPE_MARKDOWN, postString);
Request request = new Request.Builder()
.post(body)
.url(url)
.build();
client.newCall(request).enqueue(new Callback() {
@Override
public void onFailure(@NonNull Call call, @NonNull IOException e) {
Log.d(TAG, "onFailure::" + e.getMessage());
}
@Override
public void onResponse(@NonNull Call call, @NonNull Response response) throws IOException {
//Thread[OkHttp https://api.github.com/...,5,main]
Log.e(TAG, "onResponse::Thread==>" + Thread.currentThread());
//isUIThread==>false
Log.e(TAG, "isUIThread==>" + (Looper.getMainLooper().getThread()==Thread.currentThread()));
if (!response.isSuccessful()) {
throw new IOException("Unexpected code " + response);
}
Log.e(TAG, response.protocol() //http协议
+ "," + response.code() //响应码
+ "," + response.message()); //响应状态
Headers headers = response.headers(); //响应头
for (int i = 0; i < headers.size(); i++) {
Log.e(TAG, headers.name(i) + ":" + headers.value(i));
}
Log.d(TAG, "onResponse::" + response.body().string()); //响应内容
}
});
}
提交数据流请求:
/**
* 异步POST请求提交数据流
*/
private void callPostStream() {
String url = "https://api.github.com/markdown/raw";
OkHttpClient client = new OkHttpClient();
RequestBody requestBody = new RequestBody() {
@Override
public MediaType contentType() {
return MediaType.parse("text/x-markdown; charset=utf-8");
}
@Override
public void writeTo(@NonNull BufferedSink sink) throws IOException {
sink.writeUtf8("POST STREAM REQUESTBODY");
}
};
Request request = new Request.Builder()
.post(requestBody)
.url(url)
.build();
Call call = client.newCall(request);
call.enqueue(new Callback() {
@Override
public void onFailure(@NonNull Call call, @NonNull IOException e) {
Log.d(TAG, "onFailure::" + e.getMessage());
}
@Override
public void onResponse(@NonNull Call call, @NonNull Response response) throws IOException {
//Thread[OkHttp https://api.github.com/...,5,main]
Log.e(TAG, "onResponse::Thread==>" + Thread.currentThread());
//isUIThread==>false
Log.e(TAG, "isUIThread==>" + (Looper.getMainLooper().getThread()==Thread.currentThread()));
if (!response.isSuccessful()) {
throw new IOException("Unexpected code " + response);
}
Log.e(TAG, response.protocol() //http协议
+ "," + response.code() //响应码
+ "," + response.message()); //响应状态
Headers headers = response.headers(); //响应头
for (int i = 0; i < headers.size(); i++) {
Log.e(TAG, headers.name(i) + ":" + headers.value(i));
}
Log.d(TAG, "onResponse::" + response.body().string()); //响应内容
}
});
}
提交文件请求:
/**
* 异步POST提交文件
*/
private void callPostFile() {
String url = "https://api.github.com/markdown/raw";
MediaType MEDIA_TYPE_MARKDOWN = MediaType.parse("text/x-markdown; charset=utf-8");
File file = new File("POST_FILE.md");
OkHttpClient client = new OkHttpClient();
RequestBody requestBody = RequestBody.create(MEDIA_TYPE_MARKDOWN, file);
Request request = new Request.Builder()
.url(url)
.post(requestBody)
.build();
Call call = client.newCall(request);
call.enqueue(new Callback() {
@Override
public void onFailure(@NonNull Call call, @NonNull IOException e) {
Log.d(TAG, "onFailure::" + e.getMessage());
}
@Override
public void onResponse(@NonNull Call call, @NonNull Response response) throws IOException {
//Thread[OkHttp https://api.github.com/...,5,main]
Log.e(TAG, "onResponse::Thread==>" + Thread.currentThread());
//isUIThread==>false
Log.e(TAG, "isUIThread==>" + (Looper.getMainLooper().getThread()==Thread.currentThread()));
if (!response.isSuccessful()) {
throw new IOException("Unexpected code " + response);
}
Log.d(TAG, "onResponse::" + response.body().string());
}
});
}
提交表单请求:
在提交表单请求时,需要使用RequestBody
的子类FormBody
来构造表单数据,name
和value
将使用HTML兼容的表单URL编码进行编码。
通过查看源码,其中name
和value
分别存储在如下的集合中:
private final List encodedNames;
private final List encodedValues;
/**
* 异步POST提交表单
*/
private void callPostForm() {
String url = "https://en.wikipedia.org/w/index.php";
FormBody formBody = new FormBody.Builder()
.add("formKey", "formValue")
.add("search", "Jurassic Park")
.build();
OkHttpClient client = new OkHttpClient();
Request request = new Request.Builder()
.url(url)
.post(formBody)
.build();
Call call = client.newCall(request);
call.enqueue(new Callback() {
@Override
public void onFailure(@NonNull Call call, @NonNull IOException e) {
Log.d(TAG, "onFailure::" + e.getMessage());
}
@Override
public void onResponse(@NonNull Call call, @NonNull Response response) throws IOException {
//Thread[OkHttp https://api.github.com/...,5,main]
Log.e(TAG, "onResponse::Thread==>" + Thread.currentThread());
//isUIThread==>false
Log.e(TAG, "isUIThread==>" + (Looper.getMainLooper().getThread()==Thread.currentThread()));
if (!response.isSuccessful()) {
throw new IOException("Unexpected code " + response);
}
Log.d(TAG, "onResponse::" + response.body().string());
}
});
}
提交multipart请求:
MultipartBody.Builder
可以构建与HTML文件上传表单兼容的复杂的请求体。multipart请求体中的每部分请求都是一个请求体,并可以自定义请求头。如果可用的话,这些请求头应当用来描述这一部分的请求,例如这部分的 Content-Disposition
。如果 Content-Length
和 Content-Type
可用的话,它们将会被自动添加到请求头中。(注:翻译自官方例子,如有错误,请指正。)
multipart请求就是将多个请求体封装到一起,进行数据请求。
/**
* 异步POST提交multipart请求
*/
private void callPostMultipart() {
String IMGUR_CLIENT_ID = "..."; //请自定义id
String url = "https://api.imgur.com/3/image";
MediaType MEDIA_TYPE_PNG = MediaType.parse("image/png");
RequestBody requestBody = new MultipartBody.Builder()
.setType(MultipartBody.FORM) //multipart/form-data
.addFormDataPart("title", "Square Logo")
.addFormDataPart("image", "logo-square.png",
RequestBody.create(MEDIA_TYPE_PNG, new File("website/static/logo-square.png")))
.build();
OkHttpClient client = new OkHttpClient();
Request request = new Request.Builder()
.header("Authorization", "Client-ID " + IMGUR_CLIENT_ID)
.url(url)
.post(requestBody)
.build();
Call call = client.newCall(request);
call.enqueue(new Callback() {
@Override
public void onFailure(@NonNull Call call, @NonNull IOException e) {
Log.d(TAG, "onFailure::" + e.getMessage());
}
@Override
public void onResponse(@NonNull Call call, @NonNull Response response) throws IOException {
//Thread[OkHttp https://api.github.com/...,5,main]
Log.e(TAG, "onResponse::Thread==>" + Thread.currentThread());
//isUIThread==>false
Log.e(TAG, "isUIThread==>" + (Looper.getMainLooper().getThread()==Thread.currentThread()));
if (!response.isSuccessful()) {
throw new IOException("Unexpected code " + response);
}
Log.d(TAG, "onResponse::" + response.body().string());
}
});
}
·说明:
1、如果响应正文是超过1Mb的,要避免使用string()
方法,因为此方法将会把整个内容加载到内存中;作为替代方式,最好可以用stream来处理响应正文。
But if the response body is large (greater than 1 MiB), avoid string() because it will load the entire document into memory. In that case, prefer to process the body as a stream.
2.3、取消调用:
调用Call.cancel()
会立即停止正在进行的调用。如果某个线程当前正在写入或读取一个响应的话,它将会受到一个IOException
异常。比如说,当您的用户离开了应用的时候,是不在需要进行调用请求或响应的了,便可以用此方法来节省网络开销。同步和异步调用都可以取消。
/**
* 取消调用
*/
private void callCancel() {
ScheduledExecutorService executor = Executors.newScheduledThreadPool(1);
OkHttpClient client = new OkHttpClient();
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 run() {
//1.00 Canceling call.
Log.e(TAG, String.format("%.2f Canceling call.%n", (System.nanoTime() - startNanos) / 1e9f));
call.cancel();
//1.01 Canceled call.
Log.e(TAG, String.format("%.2f Canceled call.%n", (System.nanoTime() - startNanos) / 1e9f));
}
}, 1, TimeUnit.SECONDS);
Log.e(TAG, String.format("%.2f Executing call.%n", (System.nanoTime() - startNanos) / 1e9f));
new Thread(new Runnable() {
@Override
public void run() {
try {
Response response = call.execute();
Log.e(TAG, String.format("%.2f Call was expected to fail, but completed: %s%n",
(System.nanoTime() - startNanos) / 1e9f, response));
} catch (IOException e) {
//1.02 Call failed as expected: java.io.IOException: Canceled
Log.e(TAG, String.format("%.2f Call failed as expected: %s%n",
(System.nanoTime() - startNanos) / 1e9f, e));
e.printStackTrace();
}
}
}).start();
}
2.4、配置相关
处理响应缓存:
如果需要缓存响应结果,您需要一个可以读写的并限制缓存大小的缓存目录,此目录必须是私有的,不能被非信任的应用程序读取缓存内容。
让多个缓存同时访问同一缓存目录是错误的。大多数应用程序应该只调用一次new OkHttpClient()
,使用缓存配置它,并在任何地方使用同一实例。否则,两个缓存实例将相互影响,破坏响应缓存,并可能导致程序崩溃。
响应缓存使用HTTP请求头进行所有配置。您可以添加类似的请求标头如Cache-Control: max-stale=3600
,OkHttp的缓存将依照它们设置。您的服务器配置使用自身的响应头缓存响应时间,例如Cache-Control: max-age=9600
。这些缓存缓存的响应头可强制使用缓存数据,强制使用网络数据,或强制使用GET条件验证的网络数据。
要避免使用缓存,请使用CacheControl.FORCE_NETWORK,要避免使用网络数据,请使用CacheControl.FORCE_CACHE。
·警告:如果您使用FORCE_CACHE
并且还要请求网络数据,OkHttp将返回504 Unsatisfiable Request
响应。
/**
* 响应缓存
*/
private void callCache() {
String url = "http://publicobject.com/helloworld.txt";
File cacheDir = FileUtil.getExternalCacheDirectory(mContext, "cache_okhttp");
// File cacheDir = new File(FileUtil."cache_okhttp");
int cacheSize = 10 * 1024 * 1024; // 10 MiB
Cache cache = new Cache(cacheDir, cacheSize);
final OkHttpClient client = new OkHttpClient.Builder()
.cache(cache)
.build();
final Request request = new Request.Builder()
.url(url)
.get()
.build();
new Thread(new Runnable() {
@Override
public void run() {
String response1Body = null;
try {
Response response1 = client.newCall(request).execute();
if (!response1.isSuccessful()) {
throw new IOException("Unexpected code " + response1);
}
response1Body = response1.body().string();
//Response 1 response: Response{protocol=http/1.1, code=200, message=OK, url=https://publicobject.com/helloworld.txt}
Log.e(TAG, "Response 1 response: " + response1);
//Response 1 cache response: null
Log.e(TAG, "Response 1 cache response: " + response1.cacheResponse());
//Response 1 network response: Response{protocol=http/1.1, code=200, message=OK, url=https://publicobject.com/helloworld.txt}
Log.e(TAG, "Response 1 network response: " + response1.networkResponse());
} catch (IOException e) {
e.printStackTrace();
}
String response2Body = null;
try {
Response response2 = client.newCall(request).execute();
if (!response2.isSuccessful()) {
throw new IOException("Unexpected code " + response2);
}
response2Body = response2.body().string();
//Response 2 response: Response{protocol=http/1.1, code=200, message=OK, url=https://publicobject.com/helloworld.txt}
Log.e(TAG, "Response 2 response: " + response2);
//Response 2 cache response: Response{protocol=http/1.1, code=200, message=OK, url=https://publicobject.com/helloworld.txt}
Log.e(TAG, "Response 2 cache response: " + response2.cacheResponse());
//Response 2 network response: null
Log.e(TAG, "Response 2 network response: " + response2.networkResponse());
} catch (IOException e) {
e.printStackTrace();
}
//Response 2 equals Response 1? true
Log.e(TAG, "Response 2 equals Response 1? " + response1Body.equals(response2Body));
}
}).start();
}
处理响应超时:
当连接不可用或失败时,可以通过超时来响应一个失败结果,网络连接断开可能是由于客户端的连接问题,服务器有效性的问题,或者其他问题导致的。OkHttp支持连接超时、读取超时和写入超时等。
/**
* 超时
*/
private void callTimeouts() {
OkHttpClient client = new OkHttpClient.Builder()
.connectTimeout(10, TimeUnit.SECONDS)
.writeTimeout(10, TimeUnit.SECONDS)
.readTimeout(30, TimeUnit.SECONDS)
.build();
Request request = new Request.Builder()
.url("http://httpbin.org/delay/2")
.get()
.build();
final Call call = client.newCall(request);
new Thread(new Runnable() {
@Override
public void run() {
try {
Response response = call.execute();
//Response completed: Response{protocol=http/1.1, code=200, message=OK, url=http://httpbin.org/delay/2}
Log.e(TAG, "Response completed: " + response);
} catch (IOException e) {
e.printStackTrace();
}
}
}).start();
}
处理单独配置请求参数:
全部的客户端配置都会在OkHttpClient
中生效,包括代理设置,超时,已经缓存等。当你需要修改单独请求的配置时,可以调用OkHttpClient.newBuilder()
。这将返回与原始客户端共享的相同连接池、调度器和配置的构造器中。
/**
* 个性化配置
*/
private void callPercallConfiguration() {
OkHttpClient client = new OkHttpClient();
final Request request = new Request.Builder()
.url("http://httpbin.org/delay/1")
.get()
.build();
final OkHttpClient client1 = client.newBuilder()
.readTimeout(500, TimeUnit.MILLISECONDS)
.build();
final OkHttpClient client2 = client.newBuilder()
.readTimeout(3000, TimeUnit.MILLISECONDS)
.build();
new Thread(new Runnable() {
@Override
public void run() {
try {
Response response1 = client1.newCall(request).execute();
Log.e(TAG, "Response 1 succeeded: " + response1);
} catch (IOException e) {
//Response 1 failed: java.net.SocketTimeoutException: timeout
Log.e(TAG, "Response 1 failed: " + e);
e.printStackTrace();
}
try {
Response response2 = client2.newCall(request).execute();
//Response 2 succeeded: Response{protocol=http/1.1, code=200, message=OK, url=http://httpbin.org/delay/1}
Log.e(TAG, "Response 2 succeeded: " + response2);
} catch (IOException e) {
Log.e(TAG, "Response 2 failed: " + e);
e.printStackTrace();
}
//readTime1==>500,,readTime2==>3000
Log.e(TAG, "readTime1==>" + client1.readTimeoutMillis() + ",," +
"readTime2==>" + client2.readTimeoutMillis());
}
}).start();
}
处理身份验证:
OkHttp可以自动重试未经身份验证的请求。当响应结果为401 Not Authorized
时,一个名为Authenticator
的类会要求提供凭据。实现应该构建一个包含丢失凭据的新请求。如果没有可用的凭据,则返回null以跳过重试。
使用Response.challenges()
会得到任意的身份验证挑战计划和领域。在完成Basic挑战时,使用Credentials.basic(username, password)
进行编码请求头。
/**
* 身份验证
*/
private void callAuthenticate() {
OkHttpClient client = new OkHttpClient.Builder()
.authenticator(new Authenticator() {
@Nullable
@Override
public Request authenticate(@Nullable Route route, @NonNull Response response) throws IOException {
if (response.request().header("Authorization") != null) {
return null; // 放弃验证,已经得到了一个身份验证
}
//Authenticating for response: Response{protocol=http/1.1, code=401, message=Unauthorized, url=https://publicobject.com/secrets/hellosecret.txt}
Log.e(TAG, "Authenticating for response: " + response);
//Challenges: [Basic authParams={realm=OkHttp Secrets}]
Log.e(TAG, "Challenges: " + response.challenges());
String credential = Credentials.basic("jesse", "password1");
return response.request().newBuilder()
.header("Authorization", credential)
.build();
}
})
.build();
Request request = new Request.Builder()
.url("http://publicobject.com/secrets/hellosecret.txt")
.get()
.build();
final Call call = client.newCall(request);
new Thread(new Runnable() {
@Override
public void run() {
try {
Response response = call.execute();
if (!response.isSuccessful()) {
throw new IOException("Unexpected code " + response);
}
//Response:: 此处省略好多字......
Log.e(TAG, "Response::" + response.body().string());
} catch (IOException e) {
e.printStackTrace();
}
}
}).start();
}
您可以通过以下两种方式在身份验证不起作用时来跳过重试请求:
- 当已经有验证身份的时候:
if (credential.equals(response.request().header("Authorization"))) {
return null; // If we already failed with these credentials, don't retry.
}
- 当达到程序限制的时候:
if (responseCount(response) >= 3) {
return null; // If we've failed 3 times, give up.
}
以上代码依赖于此responseCount()
方法:
private int responseCount(Response response) {
int result = 1;
while ((response = response.priorResponse()) != null) {
result++;
}
return result;
}
2.5、拦截器(interceptor)
拦截器是一种强大的机制,可以进行监视,重写和重试调用。
使用拦截器,要实现Interceptor
接口,并实现其中的方法intercept(Interceptor.Chain chain)
,在实现此方法中,调用chain.proceed(request)
是每个拦截器实现的关键部分。因为它是所有HTTP执行的地方,并产生满足请求的响应结果。
您可以同时加入多个拦截器,拦截器会链接在一起,因为OkHttp会用一个列表进行跟踪每一个拦截器,并按顺序调用拦截器。下图是拦截器的示意图:
从示意图中可以看出,拦截器有两种:Application Interceptors
和 Network Interceptors
。
示例:
- 日志拦截器
/**
* 日志拦截器
*/
class LoggingInterceptor implements Interceptor {
@NonNull
@Override
public Response intercept(@NonNull Interceptor.Chain chain) throws IOException {
Request request = chain.request();
long t1 = System.nanoTime();
Log.e(TAG, String.format("Sending request %s on %s%n%s",
request.url(), chain.connection(), request.headers()));
Response response = chain.proceed(request);
long t2 = System.nanoTime();
Log.e(TAG, String.format("Received response for %s in %.1fms%n%s",
response.request().url(), (t2 - t1) / 1e6d, response.headers()));
return response;
}
}
- 注册Application Interceptors
/**
* Application Interceptors
*/
private void callApplicationInterceptors() {
final OkHttpClient client = new OkHttpClient.Builder()
.addInterceptor(new LoggingInterceptor())
.build();
final Request request = new Request.Builder()
.url("http://www.publicobject.com/helloworld.txt")
.header("User-Agent", "OkHttp Example")
.build();
new Thread(new Runnable() {
@Override
public void run() {
try {
Response response = client.newCall(request).execute();
response.body().close();
} catch (IOException e) {
e.printStackTrace();
}
}
}).start();
}
/*
打印结果:(一次)
(打印的是:request.url())
Sending request http://www.publicobject.com/helloworld.txt on null
User-Agent: OkHttp Example
(打印的是:response.request().url())
Received response for https://publicobject.com/helloworld.txt in 4683.0ms
Server: nginx/1.10.0 (Ubuntu)
Date: Mon, 25 Mar 2019 14:34:52 GMT
Content-Type: text/plain
Content-Length: 1759
Last-Modified: Tue, 27 May 2014 02:35:47 GMT
Connection: keep-alive
ETag: "5383fa03-6df"
Accept-Ranges: bytes
*/
- 注册Network Interceptors
/**
* Network Interceptors
*/
private void callNetInterceptors() {
final OkHttpClient client = new OkHttpClient.Builder()
.addNetworkInterceptor(new LoggingInterceptor())
.build();
final Request request = new Request.Builder()
.url("http://www.publicobject.com/helloworld.txt")
.header("User-Agent", "OkHttp Example")
.build();
new Thread(new Runnable() {
@Override
public void run() {
try {
Response response = client.newCall(request).execute();
response.body().close();
} catch (IOException e) {
e.printStackTrace();
}
}
}).start();
}
/*
打印结果:
(第一次)
(初始化请求)
Sending request http://www.publicobject.com/helloworld.txt on Connection{www.publicobject.com:80, proxy=DIRECT hostAddress=www.publicobject.com/54.187.32.157:80 cipherSuite=none protocol=http/1.1}
User-Agent: OkHttp Example
Host: www.publicobject.com
Connection: Keep-Alive
Accept-Encoding: gzip
Received response for http://www.publicobject.com/helloworld.txt in 398.1ms
Server: nginx/1.10.0 (Ubuntu)
Date: Mon, 25 Mar 2019 14:41:14 GMT
Content-Type: text/html
Content-Length: 194
Connection: keep-alive
Location: https://publicobject.com/helloworld.txt
(第二次)
(重定向)
Sending request https://publicobject.com/helloworld.txt on Connection{publicobject.com:443, proxy=DIRECT hostAddress=publicobject.com/54.187.32.157:443 cipherSuite=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 protocol=http/1.1}
User-Agent: OkHttp Example
Host: publicobject.com
Connection: Keep-Alive
Accept-Encoding: gzip
Received response for https://publicobject.com/helloworld.txt in 1498.7ms
Server: nginx/1.10.0 (Ubuntu)
Date: Mon, 25 Mar 2019 14:41:16 GMT
Content-Type: text/plain
Content-Length: 1759
Last-Modified: Tue, 27 May 2014 02:35:47 GMT
Connection: keep-alive
ETag: "5383fa03-6df"
Accept-Ranges: bytes
*/
从上面的示例来比较两者区别:
- 注册的调用方式不同:
//Application Interceptors
OkHttpClient client = new OkHttpClient.Builder()
.addInterceptor(自定义的应用拦截器);
//Network Interceptors
OkHttpClient client = new OkHttpClient.Builder()
.addNetworkInterceptor(自定义的网络拦截器);
- 调用次数不同:
Application Interceptors
调用了一次,在返回响应内容时调用了一次
Network Interceptors
调用了两次,一次在初始请求时,一次用于重定向 - 网络请求还包含更多数据,例如通过OkHttp添加的请求头
Accept-Encoding: gzip
,用于告知对响应压缩的支持。网络拦截器Chain
具有非空值Connection
,可用于询问用于连接到Web服务器的IP地址和TLS配置。
每种拦截器的有点:
应用拦截器
- 不需要担心重定向和重试等中间响应。
- 即使从缓存提供HTTP响应,也始终调用一次。
- 观察应用程序的原始意图。没有关注OkHttp注入的请求头
If-None-Match
。 - 允许绕过且不调用
Chain.proceed()
。 - 允许重试并进行多次调用
Chain.proceed()
。
网络拦截器
- 能够对重定向和重试等中间响应进行操作。
- 不调用网络而使用缓存响应。
- 观察数据,就像它将通过网络传输一样。
- 访问
Connection
请求。