Netty是一个NIO的客户端服务器框架,它使我们可以快速而简单地开发网络应用程序,比如协议服务器和客户端。它大大简化了网络编程,比如TCP和UDP socket服务器。
“快速而简单”并不意味着开发出来的应用可维护性或性能不好。Netty已经实现了大量的协议,比如FTP,SMTP,HTTP,以及各种基于二进制和文本的传统协议。可以说Netty已经找到了一种方法来实现简单的开发,高性能,稳定性,灵活性而不需要做妥协。
Netty的结构大体如下图这样:
就设计而言,Netty给不同的传输类型,不管是阻塞的还是非阻塞的,提供了统一的接口。它基于一个灵活的和可扩展的事件模型,这使得处理不同逻辑的部分可以有效的隔离开来。它具有高度可定制的线程模型 - 单线程,一个或多个线程池,比如SEDA。它还提供无连接的datagram socket支持。
如Netty这般,功能如此强大,性能如此优良的网络库,不用在Android上真是可惜了。这里我们就尝试将Netty用在Android上。
首先是下载Netty。 Netty的官网地址 ,我们可以在这里找到下载Netty的地址,当然还有许许多多的文档。这里使用了当前4.1.x最新版的Netty 4.1.4,下载地址:
http://dl.bintray.com/netty/downloads/netty-4.1.4.Final.tar.bz2
解压之后,为了省事,直接将netty-4.1.4.Final/jar/all-in-one/下的netty-all-4.1.4.Final.jar拷贝进了工程下app module的libs目录下。
不出意外,直接通过编译。接着我们就参考 netty/example/src/main/java/io/netty/example/http/snoop
中client部分的代码,将Netty用起来,这主要有如下几个类:
package io.netty.example.http.snoop; import java.net.URI; import java.net.URISyntaxException; import javax.net.ssl.SSLException; import io.netty.bootstrap.Bootstrap; import io.netty.channel.Channel; import io.netty.channel.EventLoopGroup; import io.netty.channel.nio.NioEventLoopGroup; import io.netty.channel.socket.nio.NioSocketChannel; import io.netty.handler.codec.http.DefaultFullHttpRequest; import io.netty.handler.codec.http.HttpHeaderNames; import io.netty.handler.codec.http.HttpHeaderValues; import io.netty.handler.codec.http.HttpMethod; import io.netty.handler.codec.http.HttpVersion; import io.netty.handler.ssl.SslContext; import io.netty.handler.ssl.SslContextBuilder; import io.netty.handler.ssl.util.InsecureTrustManagerFactory; public classHttpClient{ public static final String TAG = "NettyClient"; public static voidgetResponse(finalString url){ new Thread() { @Override public voidrun(){ try { URI uri = new URI(url); String scheme = uri.getScheme() == null ? "http" : uri.getScheme(); String host = uri.getHost(); int port = uri.getPort(); if (port == -1) { if ("http".equalsIgnoreCase(scheme)) { port = 80; } else if ("https".equalsIgnoreCase(scheme)) { port = 443; } } if (!"http".equalsIgnoreCase(scheme) && !"https".equalsIgnoreCase(scheme)) { System.err.println("Only HTTP(S) is supported."); return; } final boolean ssl = "https".equalsIgnoreCase(scheme); final SslContext sslCtx; if (ssl) { sslCtx = SslContextBuilder.forClient().trustManager(InsecureTrustManagerFactory.INSTANCE).build(); } else { sslCtx = null; } EventLoopGroup group = new NioEventLoopGroup(); try { Bootstrap bootstrap = new Bootstrap(); bootstrap.group(group).channel(NioSocketChannel.class) .handler(new HttpClientInitializer(sslCtx)); // Make the connection attempt. Channel channel = bootstrap.connect(host, port).sync().channel(); // Prepare the HTTP request. DefaultFullHttpRequest request = new DefaultFullHttpRequest(HttpVersion.HTTP_1_1, HttpMethod.GET, url); request.headers().set(HttpHeaderNames.HOST, host); request.headers().set(HttpHeaderNames.CONNECTION, HttpHeaderNames.KEEP_ALIVE); request.headers().set(HttpHeaderNames.ACCEPT_ENCODING, HttpHeaderValues.GZIP); // Send the HTTP request. channel.writeAndFlush(request); // Wait for the server to close the connection. channel.closeFuture().sync(); } finally { group.shutdownGracefully(); } } catch (URISyntaxException e) { } catch (SSLException e) { } catch (InterruptedException e) { } } }.start(); } }
这个class提供给外部调用的接口。使用者可以传入URL,将借由这个类,通过Netty来访问网络并获取响应。然后来看HttpClientInitializer:
package io.netty.example.http.snoop; import io.netty.channel.ChannelInitializer; import io.netty.channel.ChannelPipeline; import io.netty.channel.socket.SocketChannel; import io.netty.handler.codec.http.HttpClientCodec; import io.netty.handler.codec.http.HttpContentDecompressor; import io.netty.handler.ssl.SslContext; public classHttpClientInitializerextendsChannelInitializer<SocketChannel>{ private final SslContext sslCtx; public HttpClientInitializer(SslContext sslCtx) { this.sslCtx = sslCtx; } @Override public void initChannel(SocketChannel ch) { ChannelPipeline p = ch.pipeline(); // Enable HTTPS if necessary. if (sslCtx != null) { p.addLast(sslCtx.newHandler(ch.alloc())); } p.addLast(new HttpClientCodec()); // Remove the following line if you don't want automatic content decompression. p.addLast(new HttpContentDecompressor()); // Uncomment the following line if you don't want to handle HttpContents. //p.addLast(new HttpObjectAggregator(1048576)); p.addLast(new HttpClientHandler()); } }
这个class负责对Channel的Pipeline进行初始化,这其中最关键的是HttpClientHandler:
package io.netty.example.http.snoop; import android.util.Log; import io.netty.channel.ChannelHandlerContext; import io.netty.channel.SimpleChannelInboundHandler; import io.netty.handler.codec.http.HttpContent; import io.netty.handler.codec.http.HttpObject; import io.netty.handler.codec.http.HttpResponse; import io.netty.handler.codec.http.LastHttpContent; import io.netty.util.CharsetUtil; public classHttpClientHandlerextendsSimpleChannelInboundHandler<HttpObject>{ @Override public voidchannelRead0(ChannelHandlerContext ctx, HttpObject msg){ if (msg instanceof HttpResponse) { HttpResponse response = (HttpResponse) msg; Log.i(HttpClient.TAG, "STATUS: " + response.status()); Log.i(HttpClient.TAG, "VERSION: " + response.protocolVersion()); if (!response.headers().isEmpty()) { for (CharSequence name: response.headers().names()) { for (CharSequence value: response.headers().getAll(name)) { Log.i(HttpClient.TAG, "HEADER: " + name + " = " + value); } } } } if (msg instanceof HttpContent) { HttpContent content = (HttpContent) msg; String responseContent = content.content().toString(CharsetUtil.UTF_8); Log.i(HttpClient.TAG, responseContent); if (content instanceof LastHttpContent) { ctx.close(); } } } @Override public voidexceptionCaught(ChannelHandlerContext ctx, Throwable cause){ cause.printStackTrace(); ctx.close(); } }
我们正是通过实现HttpClientHandler,而获取到Netty返回给我们的响应的。
在我们的Android应用代码中调用 HttpClient
来通过Netty从网络获取响应:
package io.netty.example.http.snoop; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.util.Log; import android.view.View; import android.widget.Button; import android.widget.TextView; public classMainActivityextendsAppCompatActivity{ private static final String TAG = "MainActivity"; private TextView mTextScreen; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); Button btnGetIpInfo = (Button) findViewById(R.id.btn_get_ip_info_with_netty); btnGetIpInfo.setOnClickListener(mBtnClickListener); mTextScreen = (TextView) findViewById(R.id.text_screen); } View.OnClickListener mBtnClickListener = new View.OnClickListener() { @Override public void onClick(View v) { String url = "http://ip.taobao.com/service/getIpInfo.php?ip=123.58.191.68"; mTextScreen.setText("To access " + url); Log.i(TAG, "To access " + url); if (R.id.btn_get_ip_info_with_netty == v.getId()) { HttpClient.getResponse(url); } } }; }
当然不能忘记了在AndroidManifest.xml中添加对INTERNET权限的请求:
<uses-permission android:name="android.permission.INTERNET"/>
做完了所有这些之后,Netty基本上就可以跑起来了。不过意外还是发生了:
08-10 10:13:33.670 17720-17720/io.netty.example.http.snoop6.myapplication I/MainActivity: To access http://ip.taobao.com/service/getIpInfo.php?ip=123.58.191.68 08-10 10:13:33.818 17720-18708/io.netty.example.http.snoop6.myapplication W/System.err: java.lang.NoClassDefFoundError: com.jcraft.jzlib.Inflater 08-10 10:13:33.818 17720-18708/io.netty.example.http.snoop6.myapplication W/System.err: at io.netty.handler.codec.compression.JZlibDecoder.<init>(JZlibDecoder.java:27) 08-10 10:13:33.826 17720-18708/io.netty.example.http.snoop6.myapplication W/System.err: at io.netty.handler.codec.compression.ZlibCodecFactory.newZlibDecoder(ZlibCodecFactory.java:122) 08-10 10:13:33.826 17720-18708/io.netty.example.http.snoop6.myapplication W/System.err: at io.netty.handler.codec.http.HttpContentDecompressor.newContentDecoder(HttpContentDecompressor.java:57) 08-10 10:13:33.826 17720-18708/io.netty.example.http.snoop6.myapplication W/System.err: at io.netty.handler.codec.http.HttpContentDecoder.decode(HttpContentDecoder.java:87) 08-10 10:13:33.826 17720-18708/io.netty.example.http.snoop6.myapplication W/System.err: at io.netty.handler.codec.http.HttpContentDecoder.decode(HttpContentDecoder.java:46) 08-10 10:13:33.826 17720-18708/io.netty.example.http.snoop6.myapplication W/System.err: at io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:88) 08-10 10:13:33.826 17720-18708/io.netty.example.http.snoop6.myapplication W/System.err: at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:372) 08-10 10:13:33.826 17720-18708/io.netty.example.http.snoop6.myapplication W/System.err: at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:358) 08-10 10:13:33.826 17720-18708/io.netty.example.http.snoop6.myapplication W/System.err: at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:350) 08-10 10:13:33.826 17720-18708/io.netty.example.http.snoop6.myapplication W/System.err: at io.netty.channel.CombinedChannelDuplexHandler$DelegatingChannelHandlerContext.fireChannelRead(CombinedChannelDuplexHandler.java:435) 08-10 10:13:33.826 17720-18708/io.netty.example.http.snoop6.myapplication W/System.err: at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:293) 08-10 10:13:33.826 17720-18708/io.netty.example.http.snoop6.myapplication W/System.err: at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:280) 08-10 10:13:33.826 17720-18708/io.netty.example.http.snoop6.myapplication W/System.err: at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:396) 08-10 10:13:33.826 17720-18708/io.netty.example.http.snoop6.myapplication W/System.err: at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:248) 08-10 10:13:33.826 17720-18708/io.netty.example.http.snoop6.myapplication W/System.err: at io.netty.channel.CombinedChannelDuplexHandler.channelRead(CombinedChannelDuplexHandler.java:250) 08-10 10:13:33.834 17720-18708/io.netty.example.http.snoop6.myapplication W/System.err: at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:372) 08-10 10:13:33.834 17720-18708/io.netty.example.http.snoop6.myapplication W/System.err: at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:358) 08-10 10:13:33.834 17720-18708/io.netty.example.http.snoop6.myapplication W/System.err: at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:350) 08-10 10:13:33.834 17720-18708/io.netty.example.http.snoop6.myapplication W/System.err: at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1334) 08-10 10:13:33.834 17720-18708/io.netty.example.http.snoop6.myapplication W/System.err: at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:372) 08-10 10:13:33.834 17720-18708/io.netty.example.http.snoop6.myapplication W/System.err: at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:358) 08-10 10:13:33.834 17720-18708/io.netty.example.http.snoop6.myapplication W/System.err: at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:926) 08-10 10:13:33.834 17720-18708/io.netty.example.http.snoop6.myapplication W/System.err: at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:129) 08-10 10:13:33.834 17720-18708/io.netty.example.http.snoop6.myapplication W/System.err: at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:571) 08-10 10:13:33.834 17720-18708/io.netty.example.http.snoop6.myapplication W/System.err: at io.netty.channel.nio.NioEventLoop.processSelectedKeysPlain(NioEventLoop.java:474) 08-10 10:13:33.834 17720-18708/io.netty.example.http.snoop6.myapplication W/System.err: at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:428) 08-10 10:13:33.834 17720-18708/io.netty.example.http.snoop6.myapplication W/System.err: at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:398) 08-10 10:13:33.834 17720-18708/io.netty.example.http.snoop6.myapplication W/System.err: at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:877) 08-10 10:13:33.841 17720-18708/io.netty.example.http.snoop6.myapplication W/System.err: at io.netty.util.concurrent.DefaultThreadFactory$DefaultRunnableDecorator.run(DefaultThreadFactory.java:144) 08-10 10:13:33.841 17720-18708/io.netty.example.http.snoop6.myapplication W/System.err: at java.lang.Thread.run(Thread.java:841) 08-10 10:13:33.841 17720-18708/io.netty.example.http.snoop6.myapplication I/NettyClient: --------- beginning of /dev/log/system 08-10 10:35:02.162 17720-17720/io.netty.example.http.snoop6.myapplication I/Timeline: Timeline: Activity_idle id: android.os.BinderProxy@41c10f28 time:1282964865
有一个class com.jcraft.jzlib.Inflater
找不到。这还需要添加对jzlib的依赖:
compile 'com.jcraft:jzlib:1.1.2'
至此顺利地将Netty跑起来:
{ "code":0, "data":{ "country":"中国", "country_id":"CN", "area":"华东", "area_id":"300000", "region":"浙江省", "region_id":"330000", "city":"杭州市", "city_id":"330100", "county":"", "county_id":"-1", "isp":"网易网络", "isp_id":"1000119", "ip":"123.58.191.68" } }
Netty很强大,all-in-one jar用起来很方便,这很不错。但all-in-one jar有点大,其中包含的一些诸如对memcache,redis,stomp,sctp和udt等的支持,我们在移动端并不会用掉。因而需要对它做一点裁剪。
既然不能用all-in-one包,那就把需要的几个jar文件单独copy进我们的工程好了。对于android而言,目测netty-4.1.4.Final/jar/下我们需要拷贝的jar文件主要有下面这些:
netty-codec-4.1.4.Final.jar netty-codec-http-4.1.4.Final.jar netty-codec-http2-4.1.4.Final.jar netty-codec-socks-4.1.4.Final.jar netty-common-4.1.4.Final.jar netty-handler-4.1.4.Final.jar netty-transport-4.1.4.Final.jar
用这些文件来替换之前的netty-all-4.1.4.Final.jar。遇到了编译错误:
:app:compileDebugJavaWithJavac Full recompilation is required because at least one of the classes of removed jar 'netty-all-4.1.4.Final.jar' requires it. Analysis took 0.364 secs. /media/data/MyProjects/MyApplication/app/src/main/java/io/netty/example/http/snoop/myapplication/HttpClient.java:67: 错误: 无法访问ByteBufHolder request.headers().set(HttpHeaderNames.HOST, host); ^ 找不到io.netty.buffer.ByteBufHolder的类文件 /media/data/MyProjects/MyApplication/app/src/main/java/io/netty/example/http/snoop/myapplication/HttpClientInitializer.java:39: 错误: 无法访问ByteBufAllocator p.addLast(sslCtx.newHandler(ch.alloc())); ^ 找不到io.netty.buffer.ByteBufAllocator的类文件 /media/data/MyProjects/MyApplication/app/src/main/java/io/netty/example/http/snoop/myapplication/HttpClientHandler.java:48: 错误: 找不到符号 String responseContent = content.content().toString(CharsetUtil.UTF_8); ^ 符号: 方法 content() 位置: 类型为HttpContent的变量 content 注: /media/data/MyProjects/MyApplication/app/src/main/java/io/netty/example/http/snoop/myapplication/HttpClient.java使用或覆盖了已过时的 API。 注: 有关详细信息, 请使用 -Xlint:deprecation 重新编译。 3 个错误 :app:compileDebugJavaWithJavac FAILED FAILURE: Build failed with an exception. * What went wrong: Execution failed for task ':app:compileDebugJavaWithJavac'. > Compilation failed; see the compiler error output for details. * Try: Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. BUILD FAILED
看来是少了一些东西了, ByteBufHolder
。那就把 netty-buffer-4.1.4.Final.jar
也加进工程里。再次编译,继续出错,这是在产生APK时遇到了麻烦:
:app:transformResourcesWithMergeJavaResForDebug FAILED FAILURE: Build failed with an exception. * What went wrong: Execution failed for task ':app:transformResourcesWithMergeJavaResForDebug'. > com.android.build.api.transform.TransformException: com.android.builder.packaging.DuplicateFileException: Duplicate files copied in APK META-INF/INDEX.LIST File1: /media/data/MyProjects/MyApplication/app/libs/netty-codec-4.1.4.Final.jar File2: /media/data/MyProjects/MyApplication/app/libs/netty-transport-4.1.4.Final.jar File3: /media/data/MyProjects/MyApplication/app/libs/netty-buffer-4.1.4.Final.jar File4: /media/data/MyProjects/MyApplication/app/libs/netty-codec-socks-4.1.4.Final.jar File5: /media/data/MyProjects/MyApplication/app/libs/netty-handler-4.1.4.Final.jar File6: /media/data/MyProjects/MyApplication/app/libs/netty-codec-http2-4.1.4.Final.jar File7: /media/data/MyProjects/MyApplication/app/libs/netty-codec-http-4.1.4.Final.jar * Try: Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. BUILD FAILED Total time: 15.352 secs Duplicate files copied in APK META-INF/INDEX.LIST File1: /media/data/MyProjects/MyApplication/app/libs/netty-codec-4.1.4.Final.jar File2: /media/data/MyProjects/MyApplication/app/libs/netty-transport-4.1.4.Final.jar File3: /media/data/MyProjects/MyApplication/app/libs/netty-buffer-4.1.4.Final.jar File4: /media/data/MyProjects/MyApplication/app/libs/netty-codec-socks-4.1.4.Final.jar File5: /media/data/MyProjects/MyApplication/app/libs/netty-handler-4.1.4.Final.jar File6: /media/data/MyProjects/MyApplication/app/libs/netty-codec-http2-4.1.4.Final.jar File7: /media/data/MyProjects/MyApplication/app/libs/netty-codec-http-4.1.4.Final.jar 11:03:39: External task execution finished 'assembleDebug'.
总是报 Duplicate files copied in APK META-INF/INDEX.LIST
的错误。这主要是因为这些jar文件里,不同的jar文件中的 META-INF/INDEX.LIST
包含了相同的内容所致。这需要在 build.gradle
中的android元素里添加如下的配置:
packagingOptions { exclude 'META-INF/INDEX.LIST' }
再次编译,这次则是包 Duplicate files copied in APK META-INF/io.netty.versions.properties
。这证明了前面的方法是行之有效的,于是把 META-INF/io.netty.versions.properties
也加进 packagingOptions
的exclude列表:
packagingOptions { exclude 'META-INF/INDEX.LIST' exclude 'META-INF/io.netty.versions.properties' }
再次编译,编译通过。但是在运行的时候遇到了一点小麻烦:
11:29:59.685 9005-9050/com.example.hanpfei0306.myapplication W/dalvikvm: threadid=11: thread exiting with uncaught exception (group=0x41959ce0) 08-11 11:29:59.685 9005-9050/com.example.hanpfei0306.myapplication E/AndroidRuntime: FATAL EXCEPTION: Thread-1197 Process: com.example.hanpfei0306.myapplication, PID: 9005 java.lang.NoClassDefFoundError: io.netty.resolver.DefaultAddressResolverGroup at io.netty.bootstrap.Bootstrap.<clinit>(Bootstrap.java:53) at com.example.hanpfei0306.myapplication.HttpClient$1.run(HttpClient.java:57)
提示找不到class io.netty.resolver.DefaultAddressResolverGroup,看来我们的jar文件是加少了,把 netty-resolver-4.1.4.Final.jar
也加进来。终于,我们前面编写的HttpClient能够正常地跑起来了。经过一番裁剪,Netty的大小大概从3.4MB减小到2.9MB。
总结一下,若不用体型巨大的 netty-all
jar文件,则我们需要导入如下的这些jar文件以编译和运行Netty:
netty-buffer-4.1.4.Final.jar netty-codec-4.1.4.Final.jar netty-codec-http-4.1.4.Final.jar netty-codec-http2-4.1.4.Final.jar netty-codec-socks-4.1.4.Final.jar netty-common-4.1.4.Final.jar netty-handler-4.1.4.Final.jar netty-resolver-4.1.4.Final.jar netty-transport-4.1.4.Final.jar
Netty的诸多抽象,比如Bootstrap,Channel,EventLoopGroup,Handler,codec,Buffer等诸多高级特性,以及它的NIO接口,这里都没有涉及,线程模型也没有仔细厘清。这里只是最最简单的一个使用范例,要把Netty很好地应用在实际的项目中,还需要对Netty本身更深入的研究。
同时,对Netty的裁剪可能也过于粗糙,或许还有更多的东西可以裁剪掉,以减小最终的APP的大小。
要使用Netty来支持HTTP/2也还需要做更多的事情。
但窥探到Netty的灵活强大,还是让我们对这个库充满期待。