Netty源码阅读之调试环境搭建
1、依赖工具
- Maven
- Git
- JDK
- IntelliJ IDEA
2、源码拉取
从官方仓库 https://github.com/netty/netty Fork 出属于自己的仓库。为什么要 Fork ？既然开始阅读、调试源码，我们可能会写一些注释，有了自己的仓库，可以进行*的提交。
使用 IntelliJ IDEA 从 Fork 出来的仓库拉取代码。
本文使用的 Netty 版本为 4.1.58.Final-SNAPSHOT 。
3、编译Netty
3.1 重要步骤（必看）
前提条件
1、JDK 1.8
2、maven 3.1以上
重要步骤
注意第一步不要直接idea编译使用控制台患者cmd执行命令如下
mvn install -DskipTests
-DskipTests代表跳过测试用例步骤，因为跑测试用例时间有点长，当然你也可以直接mvn install。
当出现入下提示时 就代表编译完成
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Summary for Netty 4.1.58.Final:
[INFO]
[INFO] Netty/Dev-Tools .................................... SUCCESS [ 1.063 s]
[INFO] Netty .............................................. SUCCESS [ 6.490 s]
[INFO] Netty/Common ....................................... SUCCESS [ 18.608 s]
[INFO] Netty/Buffer ....................................... SUCCESS [ 9.118 s]
[INFO] Netty/Resolver ..................................... SUCCESS [ 2.809 s]
[INFO] Netty/Transport .................................... SUCCESS [ 14.347 s]
[INFO] Netty/Codec ........................................ SUCCESS [ 7.712 s]
[INFO] Netty/Codec/DNS .................................... SUCCESS [ 3.861 s]
[INFO] Netty/Codec/HAProxy ................................ SUCCESS [ 3.181 s]
[INFO] Netty/Handler ...................................... SUCCESS [ 13.156 s]
[INFO] Netty/Codec/HTTP ................................... SUCCESS [ 10.510 s]
[INFO] Netty/Codec/HTTP2 .................................. SUCCESS [ 10.533 s]
[INFO] Netty/Codec/Memcache ............................... SUCCESS [ 3.281 s]
[INFO] Netty/Codec/MQTT ................................... SUCCESS [ 3.791 s]
[INFO] Netty/Codec/Redis .................................. SUCCESS [ 3.009 s]
[INFO] Netty/Codec/SMTP ................................... SUCCESS [ 2.652 s]
[INFO] Netty/Codec/Socks .................................. SUCCESS [ 3.744 s]
[INFO] Netty/Codec/Stomp .................................. SUCCESS [ 2.903 s]
[INFO] Netty/Codec/XML .................................... SUCCESS [ 2.736 s]
[INFO] Netty/Handler/Proxy ................................ SUCCESS [ 3.212 s]
[INFO] Netty/Resolver/DNS ................................. SUCCESS [ 5.204 s]
[INFO] Netty/Transport/RXTX ............................... SUCCESS [ 1.848 s]
[INFO] Netty/Transport/SCTP ............................... SUCCESS [ 2.356 s]
[INFO] Netty/Transport/UDT ................................ SUCCESS [ 3.311 s]
[INFO] Netty/Example ...................................... SUCCESS [ 6.374 s]
[INFO] Netty/Transport/Native/Unix/Common ................. SUCCESS [ 8.725 s]
[INFO] Netty/Testsuite .................................... SUCCESS [ 4.922 s]
[INFO] Netty/Transport/Native/Unix/Common/Tests ........... SUCCESS [ 2.376 s]
[INFO] Netty/Transport/Native/KQueue ...................... SUCCESS [ 27.796 s]
[INFO] Netty/Resolver/DNS/MacOS ........................... SUCCESS [ 18.286 s]
[INFO] Netty/Transport/Native/Epoll ....................... SUCCESS [ 5.117 s]
[INFO] Netty/All-in-One ................................... SUCCESS [ 6.035 s]
[INFO] Netty/Tarball ...................................... SUCCESS [ 0.384 s]
[INFO] Netty/Testsuite/Autobahn ........................... SUCCESS [ 1.623 s]
[INFO] Netty/Testsuite/Http2 .............................. SUCCESS [ 1.750 s]
[INFO] Netty/Testsuite/OSGI ............................... SUCCESS [ 1.734 s]
[INFO] Netty/Testsuite/Shading ............................ SUCCESS [ 6.056 s]
[INFO] Netty/Testsuite/NativeImage ........................ SUCCESS [ 1.627 s]
[INFO] Netty/Testsuite/NativeImage/Client ................. SUCCESS [ 1.420 s]
[INFO] Netty/Testsuite/NativeImage/ClientRuntimeInit ...... SUCCESS [ 1.152 s]
[INFO] Netty/Transport/BlockHound/Tests ................... SUCCESS [ 2.260 s]
[INFO] Netty/Microbench ................................... SUCCESS [ 22.396 s]
[INFO] Netty/BOM .......................................... SUCCESS [ 0.003 s]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 04:20 min
[INFO] Finished at: 2021-01-19T13:16:00+08:00
[INFO] ------------------------------------------------------------------------
3.2 直接导入idea
操作如下
如果出现如下内容表示编译成功
[INFO] Reactor Summary for Netty 4.1.58.Final:
[INFO]
[INFO] Netty/Dev-Tools .................................... SUCCESS [ 1.563 s]
[INFO] Netty .............................................. SUCCESS [ 9.045 s]
[INFO] Netty/Common ....................................... SUCCESS [ 11.077 s]
[INFO] Netty/Buffer ....................................... SUCCESS [ 3.646 s]
[INFO] Netty/Resolver ..................................... SUCCESS [ 1.974 s]
[INFO] Netty/Transport .................................... SUCCESS [ 4.865 s]
[INFO] Netty/Codec ........................................ SUCCESS [ 5.682 s]
[INFO] Netty/Codec/DNS .................................... SUCCESS [ 3.259 s]
[INFO] Netty/Codec/HAProxy ................................ SUCCESS [ 2.300 s]
[INFO] Netty/Handler ...................................... SUCCESS [ 6.015 s]
[INFO] Netty/Codec/HTTP ................................... SUCCESS [ 4.828 s]
[INFO] Netty/Codec/HTTP2 .................................. SUCCESS [ 3.827 s]
[INFO] Netty/Codec/Memcache ............................... SUCCESS [ 1.701 s]
[INFO] Netty/Codec/MQTT ................................... SUCCESS [ 2.107 s]
[INFO] Netty/Codec/Redis .................................. SUCCESS [ 1.758 s]
[INFO] Netty/Codec/SMTP ................................... SUCCESS [ 1.588 s]
[INFO] Netty/Codec/Socks .................................. SUCCESS [ 2.754 s]
[INFO] Netty/Codec/Stomp .................................. SUCCESS [ 1.930 s]
[INFO] Netty/Codec/XML .................................... SUCCESS [ 1.910 s]
[INFO] Netty/Handler/Proxy ................................ SUCCESS [ 2.107 s]
[INFO] Netty/Resolver/DNS ................................. SUCCESS [ 3.646 s]
[INFO] Netty/Transport/RXTX ............................... SUCCESS [ 1.772 s]
[INFO] Netty/Transport/SCTP ............................... SUCCESS [ 2.256 s]
[INFO] Netty/Transport/UDT ................................ SUCCESS [ 3.782 s]
[INFO] Netty/Example ...................................... SUCCESS [ 4.813 s]
[INFO] Netty/Transport/Native/Unix/Common ................. SUCCESS [ 2.153 s]
[INFO] Netty/Testsuite .................................... SUCCESS [ 3.897 s]
[INFO] Netty/Transport/Native/Unix/Common/Tests ........... SUCCESS [ 1.789 s]
[INFO] Netty/Transport/Native/KQueue ...................... SUCCESS [ 4.482 s]
[INFO] Netty/Resolver/DNS/MacOS ........................... SUCCESS [ 2.740 s]
[INFO] Netty/Transport/Native/Epoll ....................... SUCCESS [ 2.473 s]
[INFO] Netty/All-in-One ................................... SUCCESS [ 6.780 s]
[INFO] Netty/Tarball ...................................... SUCCESS [ 0.882 s]
[INFO] Netty/Testsuite/Autobahn ........................... SUCCESS [ 1.594 s]
[INFO] Netty/Testsuite/Http2 .............................. SUCCESS [ 1.878 s]
[INFO] Netty/Testsuite/OSGI ............................... SUCCESS [ 3.380 s]
[INFO] Netty/Testsuite/Shading ............................ SUCCESS [ 8.570 s]
[INFO] Netty/Testsuite/NativeImage ........................ SUCCESS [ 1.764 s]
[INFO] Netty/Testsuite/NativeImage/Client ................. SUCCESS [ 1.622 s]
[INFO] Netty/Testsuite/NativeImage/ClientRuntimeInit ...... SUCCESS [ 1.355 s]
[INFO] Netty/Transport/BlockHound/Tests ................... SUCCESS [ 2.400 s]
[INFO] Netty/Microbench ................................... SUCCESS [ 26.080 s]
[INFO] Netty/BOM .......................................... SUCCESS [ 0.017 s]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 02:44 min
[INFO] Finished at: 2021-01-19T13:20:26+08:00
[INFO] ------------------------------------------------------------------------
jar包文件在all-->target目录下
5、可能出现的错误
错误一
mac 需要安装
brew install autoconf automake libtool
如果找不到brew命令请安装
/bin/zsh -c "$(curl -fsSL https://gitee.com/cunkai/HomebrewCN/raw/master/Homebrew.sh)"
6、example 模块
在 example 模块里，官网提供了多个 Netty 的使用示例。
本文以 echo 包下来作为示例。哈哈哈，因为最简单。
6.1 EchoServer
执行 io.netty.example.echo.EchoServer 的 #main(args) 方法，启动服务端。输出日志如下：
13:34:37.536 [nioEventLoopGroup-2-1] INFO i.n.handler.logging.LoggingHandler - [id: 0x801be9e5] REGISTERED
13:34:37.541 [nioEventLoopGroup-2-1] INFO i.n.handler.logging.LoggingHandler - [id: 0x801be9e5] BIND: 0.0.0.0/0.0.0.0:8007
13:34:37.545 [nioEventLoopGroup-2-1] INFO i.n.handler.logging.LoggingHandler - [id: 0x801be9e5, L:/0:0:0:0:0:0:0:0:8007] ACTIVE
6.2 EchoClient
执行 io.netty.example.echo.EchoClientr 的 #main(args) 方法，启动客户端。不输出任何日志。
但是，EchoServer 会新输出如下日志：
13:35:05.715 [nioEventLoopGroup-2-1] INFO i.n.handler.logging.LoggingHandler - [id: 0x801be9e5, L:/0:0:0:0:0:0:0:0:8007] READ: [id: 0x22709165, L:/127.0.0.1:8007 - R:/127.0.0.1:53844]
13:35:05.717 [nioEventLoopGroup-2-1] INFO i.n.handler.logging.LoggingHandler - [id: 0x801be9e5, L:/0:0:0:0:0:0:0:0:8007] READ COMPLETE
7. 结尾
如此，我们就可以愉快的进行 Netty 调试啦。读源码，一定要多多调试源码。非常重要！！！
8、为什么使用 Netty
Netty底层基于 JDK的 NIO ，我们为什么不直接基于 JDK的 NIO 或者其他 NIO 框架？下面是我总结出来的原因
- 使用 JDK 自带的 NIO 需要了解太多的概念，编程复杂
- Netty底层 IO 模型随意切换，而这一切只需要做微小的改动
- Netty自带的拆包解包，异常检测等机制让你从NIO的繁重细节中脱离出来，让你只需要关心业务逻辑
- Netty解决了 JDK的很多包括空轮训在内的 bug
- Netty底层对线程，selector 做了很多细小的优化，精心设计的 reactor 线程做到非常高效的并发处理
- 自带各种协议栈让你处理任何一种通用协议都几乎不用亲自动手
- Netty社区活跃，遇到问题随时邮件列表或者 issue
- Netty已经历各大rpc框架，消息中间件，分布式通信中间件线上的广泛验证，健壮性无比强大