OkHttp超时时间设置

OkHttp3中设置超时的方法

    public WebApi(){client = new OkHttpClient.Builder().connectTimeout(10, TimeUnit.SECONDS).readTimeout(20, TimeUnit.SECONDS).build();}

捕获OkHttp3超时

然后捕获异常，加以处理。

    public void GetServersList(IServersListEvent serversListEvent) {this.serversListEvent = serversListEvent;serversLoadTimes = 0;Request request = new Request.Builder().url(serversListUrl).build();client.newCall(request).enqueue(new Callback() {@Overridepublic void onFailure(Call call, IOException e) {if(e.getCause().equals(SocketTimeoutException.class) && serversLoadTimes<maxLoadTimes)//如果超时并未超过指定次数，则重新连接{serversLoadTimes++;client.newCall(call.request()).enqueue(this);}else {e.printStackTrace();WebApi.this.serversListEvent.getServers(null);}}@Overridepublic void onResponse(Call call, Response response) throws IOException {String html = new String(response.body().bytes(), "big5");Matcher m = serversListPattern.matcher(html);ServersList serverList = new ServersList();while (m.find()){serverList.add(new ServerInfo(m.group(1), m.group(2)));}Matcher mc1 = selectServerCodePattern.matcher(html);Matcher mc2 = selectCityCodePattern.matcher(html);if(mc1.find())serverList.selectServerCode=mc1.group(1);if(mc2.find())serverList.selectCityCode=mc2.group(1);WebApi.this.serversListEvent.getServers(serverList);}});}

解析dns超时时间

问题
使用OkHttp，设备切换路由后，访问网络出现长时间无响应，很久以后才抛出UnknownHostException，这明显不是我们想要的，我们设置的connectTimeout属性似乎对dns的解析不起作用。

如何解决
我们先看看OkHttpClient有没有关于Dns的相关设置，发现OkHttpClient的Builder类存在dns()方法可以设置一个Dns类型参数。
Dns类源码如下：

package okhttp3;import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.Arrays;
import java.util.List;/*** A domain name service that resolves IP addresses for host names. Most applications will use the* {@linkplain #SYSTEM system DNS service}, which is the default. Some applications may provide* their own implementation to use a different DNS server, to prefer IPv6 addresses, to prefer IPv4* addresses, or to force a specific known IP address.** <p>Implementations of this interface must be safe for concurrent use.*/
public interface Dns {/*** A DNS that uses {@link InetAddress#getAllByName} to ask the underlying operating system to* lookup IP addresses. Most custom {@link Dns} implementations should delegate to this instance.*/Dns SYSTEM = new Dns() {@Override public List<InetAddress> lookup(String hostname) throws UnknownHostException {if (hostname == null) throw new UnknownHostException("hostname == null");try {return Arrays.asList(InetAddress.getAllByName(hostname));} catch (NullPointerException e) {UnknownHostException unknownHostException =new UnknownHostException("Broken system behaviour for dns lookup of " + hostname);unknownHostException.initCause(e);throw unknownHostException;}}};/*** Returns the IP addresses of {@code hostname}, in the order they will be attempted by OkHttp. If* a connection to an address fails, OkHttp will retry the connection with the next address until* either a connection is made, the set of IP addresses is exhausted, or a limit is exceeded.*/List<InetAddress> lookup(String hostname) throws UnknownHostException;
}

这是一个抽象类，并且其中已经写好了默认实现并赋值给了SYSTEM对象。
透过代码我们可以看出，解析dns主要是靠这行代码：

InetAddress.getAllByName(hostname)

Ok，我们已经知道如何解析dns并设置给OkHttpClient了，现在我们只需要重新实现这个过程，插入超时控制，并让OKHttp调用新的Dns解析就好了。

实现
实现抽象类Dns

package com.x.http;import okhttp3.Dns;import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.Arrays;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.FutureTask;
import java.util.concurrent.TimeUnit;public class XDns implements Dns {private long timeout;public XDns(long timeout) {this.timeout = timeout;}@Overridepublic List<InetAddress> lookup(final String hostname) throws UnknownHostException {if (hostname == null) {throw new UnknownHostException("hostname == null");} else {try {FutureTask<List<InetAddress>> task = new FutureTask<>(new Callable<List<InetAddress>>() {@Overridepublic List<InetAddress> call() throws Exception {return Arrays.asList(InetAddress.getAllByName(hostname));}});new Thread(task).start();return task.get(timeout, TimeUnit.MILLISECONDS);} catch (Exception var4) {UnknownHostException unknownHostException =new UnknownHostException("Broken system behaviour for dns lookup of " + hostname);unknownHostException.initCause(var4);throw unknownHostException;}}}
}

上面的实现主要依赖了FutureTask可以设置任务执行时间的特性，不明白的同学可以自行学习一下。
然后把新的dns解析类设置给OkHttpClient

public static OkHttpClient createClient(long timeout, long writeTimeout,long readTimeout, boolean bRetry) {OkHttpClient.Builder builder = new OkHttpClient.Builder().connectTimeout(timeout, TimeUnit.MILLISECONDS).dns(new XDns(timeout)).retryOnConnectionFailure(bRetry);if (writeTimeout > 0)builder.writeTimeout(writeTimeout, TimeUnit.MILLISECONDS);if (readTimeout > 0)builder.readTimeout(readTimeout, TimeUnit.MILLISECONDS);OkHttpClient client = builder.build();client.dispatcher().setMaxRequestsPerHost(10);client.dispatcher().setMaxRequests(30);return client;}

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作者：猿小二
来源：CSDN
原文：https://blog.csdn.net/quwei3930921/article/details/85336552
版权声明：本文为博主原创文章，转载请附上博文链接！

 new Thread(task).start();

这个地方应该改用线程池，DNS解析应该是比较频繁的操作，直接开新线程不合适