Android_OkHttp简介
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一、Android网络通信
Android系统提供了两种HTTP通信类,HttpURLConnection和HttpClient。
关于HttpURLConnection和HttpClient的选择>>官方博客:http://android-developers.blogspot.com/2011/09/androids-http-clients.html
利用原生的这两种方式编写网络代码,需要自己考虑很多,网络加载获取数据或许可以,但是要将手机本地数据上传至网络,根据不同的web端接口,需要组织不同的数据内容上传,就会有很大的工作需要做。因此出现了很多开源的框架。
age:
android-async-http:https://github.com/loopj/android-async-http
它是专门针对Android在Apache的HttpClient基础上构建的异步的callback-based http client。所有的请求全在UI线程之外发生,而callback发生在创建它的线程中,应用了Android的Handler发送消息机制。你也可以把AsyncHttpClient应用在Service中或者后台线程中,库代码会自动识别出它所运行的context。
Http Request:https://github.com/kevinsawicki/http-request
HttpRequest就是一种简单粗暴,一个请求可以涵盖在一句代码当中,不给任何一点冗余的成分。不过它在2015年就停止更新了,因此现在基本很少使用!
okhttp:https://github.com/square/okhttp
okhttp更为强大,相对而言,使用方式稍显复杂,可是是目前最为流行的网络加载框架。而且这是著名公司Square的开源框架,出手不凡。
二、okhttp的简介
Google在大部分安卓版本中推荐使用HttpURLConnection,可是这个类相比HttpClient很难使用,OkHttp是一个相对成熟的解决方案,在Android4.4的源码中可以看到HttpURLConnection已经替换成OkHttp实现了。所以OkHttp还是很强大的
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。如果您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。
使用 OkHttp 无需重写您程序中的网络代码。OkHttp实现了几乎和java.net.HttpURLConnection一样的API。如果你用了 Apache HttpClient,则OkHttp也提供了一个对应的okhttp-apache 模块。
okhttp官方资料
官方介绍:http://square.github.io/okhttp/
github源码:https://github.com/square/okhttp
使用范围
OkHttp支持Android 2.3及其以上版本。
对于Java, JDK1.7以上。
jar包准备
使用OKHttp我们就需要OKHttp的jar包,同时由于OKHttp依赖于Okio,我们也需要下载Okio的jar包。官方的介绍界面中也有的下载:
OkHttp:http://download.csdn.net/detail/two_water/9631536
Okio:http://download.csdn.net/detail/two_water/9631637
三、okhttp的API
Http Get
OkHttpClient client = new OkHttpClient(); String run(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。
使用response.body()返回ResponseBody类,可以方便的获取string,当然也能获取到流的形式:
public final InputStream byteStream()
Http 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(); f (response.isSuccessful()) { return response.body().string(); } else { throw new IOException("Unexpected code " + response); }}
Http Post提交键值对的数据
OkHttpClient client = new OkHttpClient();String post(String url, String json) throws IOException { RequestBody formBody = new FormEncodingBuilder() .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); }}
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() ((response.body().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,可能会造成OOM,因此对于超过1MB的响应body,应使用流的方式来处理body
private final OkHttpClient client = new OkHttpClient(); public void run() 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());}
异步Get
在一个工作线程中下载文件,当响应可读时回调Callback接口。读取响应时会阻塞当前线程。OkHttp现阶段不提供异步api来接收响应体。
private final OkHttpClient client = new OkHttpClient(); public void run() throws Exception { Request request = new Request.Builder() .url("http://publicobject.com/helloworld.txt") .build(); client.newCall(request).enqueue(new Callback() { @Override public void onFailure(Request request, Throwable throwable) { throwable.printStackTrace(); } @Override public void onResponse(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()); } });}
提取响应头和给响应头添加多值
典型的HTTP头 像是一个 Map<String, String> :每个字段都有一个或没有值。但是一些头允许多个值,像Guava的Multimap。例如:HTTP响应里面提供的Vary响应头,就是多值的。OkHttp的api试图让这些情况都适用。
当写请求头的时候,使用header(name, value)可以设置唯一的name、value。如果已经有值,旧的将被移除,然后添加新的。使用addHeader(name, value)可以添加多值(添加,不移除已有的)。
当读取响应头时,使用header(name)返回最后出现的name、value。通常情况这也是唯一的name、value。如果没有值,那么header(name)将返回null。如果想读取字段对应的所有值,使用headers(name)会返回一个list。
为了获取所有的Header,Headers类支持按index访问。
private final OkHttpClient client = new OkHttpClient(); public void run() 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"));}
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 static final MediaType MEDIA_TYPE_MARKDOWN= MediaType.parse("text/x-markdown; charset=utf-8"); private final OkHttpClient client = new OkHttpClient(); 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());}
Post方式提交流
以流的方式POST提交请求体。请求体的内容由流写入产生。这个例子是流直接写入Okio的BufferedSink。你的程序可能会使用OutputStream,你可以使用BufferedSink.outputStream()来获取
public static final MediaType MEDIA_TYPE_MARKDOWN = MediaType.parse("text/x-markdown; charset=utf-8"); private final OkHttpClient client = new OkHttpClient(); public void run() throws Exception { RequestBody requestBody = new RequestBody() { @Override public MediaType contentType() { return MEDIA_TYPE_MARKDOWN; } @Override public void writeTo(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 factor(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());}
Post提交文件
public static final MediaType MEDIA_TYPE_MARKDOWN= MediaType.parse("text/x-markdown; charset=utf-8"); private final OkHttpClient client = new OkHttpClient(); public void run() 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());}
Post提交表单
使用FormEncodingBuilder来构建和HTML<form>标签相同效果的请求体。键值对将使用一种HTML兼容形式的URL编码来进行编码。
private final OkHttpClient client = new OkHttpClient(); public void run() 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());}
Post方式提交分块请求
MultipartBuilder可以构建复杂的请求体,与HTML文件上传形式兼容。多块请求体中每块请求都是一个请求体,可以定义自己的请求头。这些请求头可以用来描述这块请求,例如他的Content-Disposition。如果Content-Length和Content-Type可用的话,他们会被自动添加到请求头中。
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 run() throws Exception { // Use the imgur image upload API as documented at https://api.imgur.com/endpoints/image 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());}
取消一个Call
使用Call.cancel()可以立即停止掉一个正在执行的call。如果一个线程正在写请求或者读响应,将会引发IOException。当call没有必要的时候,使用这个api可以节约网络资源。例如当用户离开一个应用时。不管同步还是异步的call都可以取消。
你可以通过tags来同时取消多个请求。当你构建一请求时,使用RequestBuilder.tag(tag)来分配一个标签。之后你就可以用OkHttpClient.cancel(tag)来取消所有带有这个tag的call。
private final ScheduledExecutorService executor = Executors.newScheduledThreadPool(1);private final OkHttpClient client = new OkHttpClient(); public void run() throws Exception { Request request = new Request.Builder() .url("http://httpbin.org/delay/2") // This URL is served with a 2 second delay. .build(); final long startNanos = System.nanoTime(); final Call call = client.newCall(request); // Schedule a job to cancel the call in 1 second. executor.schedule(new Runnable() { @Override public void run() { 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); }}
超时
没有响应时使用超时结束call。没有响应的原因可能是客户点链接问题、服务器可用性问题或者这之间的其他东西。OkHttp支持连接,读取和写入超时。
private final OkHttpClient client; public ConfigureTimeouts() throws Exception { client = new OkHttpClient(); client.setConnectTimeout(10, TimeUnit.SECONDS); client.setWriteTimeout(10, TimeUnit.SECONDS); client.setReadTimeout(30, TimeUnit.SECONDS);} public void run() throws Exception { Request request = new Request.Builder() .url("http://httpbin.org/delay/2") // This URL is served with a 2 second delay. .build(); Response response = client.newCall(request).execute(); System.out.println("Response completed: " + response);}
每个Call的配置
使用OkHttpClient,所有的HTTP Client配置包括代理设置、超时设置、缓存设置。当你需要为单个call改变配置的时候,clone 一个 OkHttpClient。这个api将会返回一个浅拷贝(shallow copy),你可以用来单独自定义。下面的例子中,我们让一个请求是500ms的超时、另一个是3000ms的超时。
private final OkHttpClient client = new OkHttpClient(); public void run() throws Exception { Request request = new Request.Builder() .url("http://httpbin.org/delay/1") // This URL is served with a 1 second delay. .build(); try { Response response = client.clone() // Clone to make a customized OkHttp for this request. .setReadTimeout(500, TimeUnit.MILLISECONDS) .newCall(request) .execute(); System.out.println("Response 1 succeeded: " + response); } catch (IOException e) { System.out.println("Response 1 failed: " + e); } try { Response response = client.clone() // Clone to make a customized OkHttp for this request. .setReadTimeout(3000, TimeUnit.MILLISECONDS) .newCall(request) .execute(); System.out.println("Response 2 succeeded: " + response); } catch (IOException e) { System.out.println("Response 2 failed: " + e); }}
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