http网络请求框架
github
关于什么是okhttp3我就不介绍了，我们直入主题
1. okhttp API介绍
- Request.Builder 请求构造者
- url(String url)：请求的url
- post()：默认是Get方式
- post(RequestBody body)：Post带参数
- build()：构造请求
请求参数有三种： - RequestBody：普通的请求参数
- FormBody.Builder：以表单的方式传递键值对的请求参数
- MultipartBody.Builder：以表单的方式上传文件的请求参数
执行方法：
Call - enqueue(Callback callback)：异步请求
- execute()：同步请求
2. 用法
2.1 创建一个OkHttpClient实例
基本配置
OkHttpClient.Builder builder = new OkHttpClient.Builder();
builder.connectTimeout(DEFAULT_TIME_OUT, TimeUnit.SECONDS);//连接超时时间
builder.writeTimeout(DEFAULT_WRITE_OUT, TimeUnit.SECONDS);//写操作 超时时间
builder.readTimeout(DEFAULT_READ_TIME_OUT, TimeUnit.SECONDS);//读操作超时时间
其它配置
这些配置在这篇文章就不详细说明了，会放在单独的文章解析
builder.sslSocketFactory() //添加https证书信任
builder.addInterceptor() //添加拦截器，可调用多次
builder.cache() //添加缓存配置
builder.cookieJar() //添加cookie
build出OkHttpClient实例
mClient.newBuilder().build();
2.2 调用接口方法封装
get方法
public void httpGet(String url, Object tag, Map<String, String> params, final StringCallback callback) {
Request request = new Request.Builder().url(url).tag(tag).build();
Call call = this.mClient.newCall(request);
call.enqueue(new Callback() {
public void onResponse(Call call, final Response response) throws IOException {
final String res = response.body().string();
OkhttpUtils.this.mDelivery.post(new Runnable() {
public void run() {
if (response.isSuccessful()) {
callback.OnSuccess(res);
} else {
callback.OnError(String.valueOf(response.code()));
}
}
});
}
public void onFailure(Call call, final IOException e) {
OkhttpUtils.this.mDelivery.post(new Runnable() {
public void run() {
if (e != null && e.getMessage() != null) {
callback.OnError(e.getMessage());
} else {
callback.OnError("服务器通讯异常，请重试");
}
}
});
}
});
}
post表单
public void httpPost(String url, Object tag, Map<String, String> params, final StringCallback callback) {
FormBody.Builder fbuilder = new FormBody.Builder();
for (String key : params.keySet()) {
builder.add(key, params.get(key));
}
Request request = new Request.Builder().url(url).tag(tag).post(fBuilder.build()).build();
Call call = this.mClient.newCall(request);
call.enqueue(new Callback() {
public void onResponse(Call call, final Response response) throws IOException {
final String res = response.body().string();
OkhttpUtils.this.mDelivery.post(new Runnable() {
public void run() {
if (response.isSuccessful()) {
callback.OnSuccess(res);
} else {
callback.OnError(String.valueOf(response.code()));
}
}
});
}
public void onFailure(Call call, final IOException e) {
OkhttpUtils.this.mDelivery.post(new Runnable() {
public void run() {
if (e != null && e.getMessage() != null) {
callback.OnError(e.getMessage());
} else {
callback.OnError("服务器通讯异常，请重试");
}
}
});
}
});
}
post提交json格式参数
public void httpPostJson(String url, Object tag, Map<String, String> params, final StringCallback callback) {
MediaType JSON = MediaType.parse("application/json");
JSONObject json = new JSONObject();
Iterator var9 = params.entrySet().iterator();
while(var9.hasNext()) {
Entry<String, String> entry = (Entry)var9.next();
String key = (String)entry.getKey();
String value = (String)entry.getValue();
json.put(key, value);
}
RequestBody requestBody = RequestBody.create(JSON, json.toString());
Request request = new Request.Builder().url(url).tag(tag).post(requestBody).build();
Call call = this.mClient.newCall(request);
call.enqueue(new Callback() {
public void onResponse(Call call, final Response response) throws IOException {
final String res = response.body().string();
OkhttpUtils.this.mDelivery.post(new Runnable() {
public void run() {
if (response.isSuccessful()) {
callback.OnSuccess(res);
} else {
callback.OnError(String.valueOf(response.code()));
}
}
});
}
public void onFailure(Call call, final IOException e) {
OkhttpUtils.this.mDelivery.post(new Runnable() {
public void run() {
if (e != null && e.getMessage() != null) {
callback.OnError(e.getMessage());
} else {
callback.OnError("服务器通讯异常，请重试");
}
}
});
}
});
}
okhttp的基本使用到这已经结束了
3. 核心类解析
我们从一个标准的okhttp发送请求的代码开始
OkHttpClient client = new OkHttpClient.Builder().build();
Request request = new Request.Builder()
.url("http://www.baidu.com").get().build();
client.newCall(request).enqueue(new Callback() {
@Override public void onFailure(Call call, IOException e) {
}
@Override public void onResponse(Call call, Response response) throws IOException {
}
});
用到的类OkHttpClient，Request，Call，Response
OkHttpClient
参数配置类，举例说明一下
CookieJar Cookie配置
Cache 缓存配置
SSLSocketFactory https配置
HostnameVerifier 验证主机
interceptors 拦截器，如日志拦截器。
Request
请求类，包含了与请求相关的参数
final HttpUrl url; //请求地址
final String method; //请求方法get,post等等
final Headers headers; //请求头
final RequestBody body; //请求体
final Object tag; //标记
Call
public Call newCall(Request request) {
return new RealCall(this, request, false /* for web socket */);
}
这是一个接口，里面有两个关键方法
execute()和enqueue(Callback paramCallback)
真正的实现放在了RealCall这个实现类里面
execute 是同步任务
enqueue是异步任务
public void enqueue(Callback responseCallback) {
synchronized (this) {
if (executed) throw new IllegalStateException("Already Executed");
executed = true;
}
captureCallStackTrace();
client.dispatcher().enqueue(new AsyncCall(responseCallback));
}
根据上述代码，我们知道调用的是dispatcher的入队方法
Dispatcher
synchronized void enqueue(AsyncCall call) {
if (runningAsyncCalls.size() < maxRequests && runningCallsForHost(call) < maxRequestsPerHost) {
runningAsyncCalls.add(call);
executorService().execute(call);
} else {
readyAsyncCalls.add(call);
}
}
其中runningAsyncCalls是可执行的异步任务队列，runningCallsForHost表示同一个主机正在接受的请求数
从源码中可看出maxRequests=64，maxRequestsPerHost=5。
当满足if条件，则将新增加的请求添加到异步任务队列，并且立刻执行任务，否咋就将异步任务添加到预备队列
从 executorService().execute(call)这句代码，我们知道AsyncCall是一个线程，在从源码中可以看出，这句代码最终会调用AsyncCall的execute方法
AsyncCall
protected void execute() {
boolean signalledCallback = false;
try {
Response response = getResponseWithInterceptorChain();
if (retryAndFollowUpInterceptor.isCanceled()) {
signalledCallback = true;
responseCallback.onFailure(RealCall.this, new IOException("Canceled"));
} else {
signalledCallback = true;
responseCallback.onResponse(RealCall.this, response);
}
} catch (IOException e) {
if (signalledCallback) {
// Do not signal the callback twice!
Platform.get().log(INFO, "Callback failure for " + toLoggableString(), e);
} else {
responseCallback.onFailure(RealCall.this, e);
}
} finally {
client.dispatcher().finished(this);
}
}
从这里就很可以很容易看出，请求被发出去了，并将Response返了回去，并且在finally中调用了Dispatcher的finished方法
private <T> void finished(Deque<T> calls, T call, boolean promoteCalls) {
int runningCallsCount;
Runnable idleCallback;
synchronized (this) {
if (!calls.remove(call)) throw new AssertionError("Call wasn't in-flight!");
if (promoteCalls) promoteCalls();
runningCallsCount = runningCallsCount();
idleCallback = this.idleCallback;
}
if (runningCallsCount == 0 && idleCallback != null) {
idleCallback.run();
}
}
从上述代码可以看出，在这里面会移除刚才执行过的任务，并调用了promoteCalls()方法
private void promoteCalls() {
if (runningAsyncCalls.size() >= maxRequests) return; // Already running max capacity.
if (readyAsyncCalls.isEmpty()) return; // No ready calls to promote.
for (Iterator<AsyncCall> i = readyAsyncCalls.iterator(); i.hasNext(); ) {
AsyncCall call = i.next();
if (runningCallsForHost(call) < maxRequestsPerHost) {
i.remove();
runningAsyncCalls.add(call);
executorService().execute(call);
}
if (runningAsyncCalls.size() >= maxRequests) return; // Reached max capacity.
}
}
上述代码做的操作主要是
循环遍历预备队列
将预备队列的异步任务移除，并放进执行队列中
调用execute方法执行异步任务
Response
final Request request; //请求类
final Protocol protocol; //协议http1.0,http1.1和http2.0
final int code; //返回码
final String message;
final Handshake handshake; //TLS(SSL后续版本),https加密
final Headers headers; //响应头
final ResponseBody body; //响应内容
final Response networkResponse;
final Response cacheResponse;
final Response priorResponse;
final long sentRequestAtMillis;
final long receivedResponseAtMillis;
其他用到的技术
ConnectionPool
连接池
我们知道http在传输层用的协议是tcp，而tcp在通信时，每次都需要三次握手来创建连接，四次挥手来释放连接，这必然会增加通信的时间，连接池的出现则解决了这个问题，连接池的实现方式类似于java的垃圾回收机制。每次创建的连接都会保存在连接池中，并不会马上释放，而那些空闲的连接会在合适的时机被释放掉
由于不用每次都三次握手，四次挥手，明显缩短了通信的时间。
Connection:keep-alive //保持长连接 1.0默认关闭，1.1默认开启
Connection:close //关闭长连接
4.总结
这篇文章主要是介绍如何快速使用okhttp
注意okhttp的回调在子线程，需要自己切回主线程
接下来会持续更新okhttp的高级使用，即前面所讲的okhttp的配置的详细解析
