从零教你如何获取hadoop2.X源码并使用eclipse关联hadoop2.X源码

问题导读：
1.如何通过官网src包，获取hadoop的全部代码
2.通过什么样的操作，可以查看hadoop某个函数或则类的实现？
3.maven的作用是什么？



前言
本文是以hadoop2.4为例，同样适用于其他hadoop2.x比如hadoop2.2,hadoop2.4,hadoop2.5,hadoop2.7,hadoop2.7.1等版本
这里是以win7为例，当然如果是Linux也是适用的，只不过路径有所不同


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我们如果想搞开发，研究源码对我们的帮助很大。不明白原理就如同黑盒子，遇到问题，我们也摸不着思路。所以这里交给大家
一.如何获取源码
二.如何关联源码

一.如何获取源码

1.下载hadoop的maven程序包

（1）官网下载
这里我们先从官网上下载maven包hadoop-2.4.0-src.tar.gz。
官网下载地址

对于不知道怎么去官网下载，可以查看：新手指导：hadoop官网介绍及如何下载hadoop（2.4）各个版本与查看hadoop API介绍

（2）网盘下载
也可以从网盘下载：
http://pan.baidu.com/s/1kToPuGB

2.通过maven获取源码
获取源码的方式有两种，一种是通过命令行的方式，一种是通过eclipse。这里主要讲通过命令的方式

通过命令的方式获取源码：
1.解压包




解压包的时候遇到了下面问题。不过不用管，我们继续往下走

[mw_shl_code=bash,true]1        : 无法创建文件：D:\hadoop2\hadoop-2.4.0-src\hadoop-yarn-project\hadoop-yarn\hadoop-yarn-server\hadoop-yarn-server-applicationhistoryservice\target\classes\org\apache\hadoop\yarn\server\applicationhistoryservice\ApplicationHistoryClientService$ApplicationHSClientProtocolHandler.class：
路径和文件名总长度不能超过260个字符
系统找不到指定的路径。        D:\hadoop2\hadoop-2.4.0-src.zip
2        : 无法创建文件：D:\hadoop2\hadoop-2.4.0-src\hadoop-yarn-project\hadoop-yarn\hadoop-yarn-server\hadoop-yarn-server-applicationhistoryservice\target\classes\org\apache\hadoop\yarn\server\applicationhistoryservice\timeline\LeveldbTimelineStore$LockMap$CountingReentrantLock.class：系统找不到指定的路径。        D:\hadoop2\hadoop-2.4.0-src.zip
3        : 无法创建文件：D:\hadoop2\hadoop-2.4.0-src\hadoop-yarn-project\hadoop-yarn\hadoop-yarn-server\hadoop-yarn-server-applicationhistoryservice\target\test-classes\org\apache\hadoop\yarn\server\applicationhistoryservice\webapp\TestAHSWebApp$MockApplicationHistoryManagerImpl.class：系统找不到指定的路径。        D:\hadoop2\hadoop-2.4.0-src.zip
4        : 无法创建文件：D:\hadoop2\hadoop-2.4.0-src\hadoop-yarn-project\hadoop-yarn\hadoop-yarn-server\hadoop-yarn-server-resourcemanager\target\test-classes\org\apache\hadoop\yarn\server\resourcemanager\monitor\capacity\TestProportionalCapacityPreemptionPolicy$IsPreemptionRequestFor.class：
路径和文件名总长度不能超过260个字符
系统找不到指定的路径。        D:\hadoop2\hadoop-2.4.0-src.zip
5        : 无法创建文件：D:\hadoop2\hadoop-2.4.0-src\hadoop-yarn-project\hadoop-yarn\hadoop-yarn-server\hadoop-yarn-server-resourcemanager\target\test-classes\org\apache\hadoop\yarn\server\resourcemanager\recovery\TestFSRMStateStore$TestFSRMStateStoreTester$TestFileSystemRMStore.class：系统找不到指定的路径。        D:\hadoop2\hadoop-2.4.0-src.zip
6        : 无法创建文件：D:\hadoop2\hadoop-2.4.0-src\hadoop-yarn-project\hadoop-yarn\hadoop-yarn-server\hadoop-yarn-server-resourcemanager\target\test-classes\org\apache\hadoop\yarn\server\resourcemanager\recovery\TestZKRMStateStore$TestZKRMStateStoreTester$TestZKRMStateStoreInternal.class：
路径和文件名总长度不能超过260个字符
系统找不到指定的路径。        D:\hadoop2\hadoop-2.4.0-src.zip
7        : 无法创建文件：D:\hadoop2\hadoop-2.4.0-src\hadoop-yarn-project\hadoop-yarn\hadoop-yarn-server\hadoop-yarn-server-resourcemanager\target\test-classes\org\apache\hadoop\yarn\server\resourcemanager\recovery\TestZKRMStateStoreZKClientConnections$TestZKClient$TestForwardingWatcher.class：
路径和文件名总长度不能超过260个字符
系统找不到指定的路径。        D:\hadoop2\hadoop-2.4.0-src.zip
8        : 无法创建文件：D:\hadoop2\hadoop-2.4.0-src\hadoop-yarn-project\hadoop-yarn\hadoop-yarn-server\hadoop-yarn-server-resourcemanager\target\test-classes\org\apache\hadoop\yarn\server\resourcemanager\recovery\TestZKRMStateStoreZKClientConnections$TestZKClient$TestZKRMStateStore.class：
路径和文件名总长度不能超过260个字符
系统找不到指定的路径。        D:\hadoop2\hadoop-2.4.0-src.zip
9        : 无法创建文件：D:\hadoop2\hadoop-2.4.0-src\hadoop-yarn-project\hadoop-yarn\hadoop-yarn-server\hadoop-yarn-server-resourcemanager\target\test-classes\org\apache\hadoop\yarn\server\resourcemanager\rmapp\attempt\TestRMAppAttemptTransitions$TestApplicationAttemptEventDispatcher.class：
路径和文件名总长度不能超过260个字符[/mw_shl_code]
系统找不到指定的路径。        D:\hadoop2\hadoop-2.4.0-src.zip

2.通过maven获取源码

这里需要说明的是，在使用maven的时候，需要先安装jdk，protoc ，如果没有安装可以参考win7如何安装maven、安装protoc

（1）进入hadoop-2.4.0-src\hadoop-maven-plugins，运行mvn install

[mw_shl_code=bash,true]D:\hadoop2\hadoop-2.4.0-src\hadoop-maven-plugins>mvn install[/mw_shl_code]

显示如下信息
[mw_shl_code=bash,true][INFO] Scanning for projects...
[WARNING]
[WARNING] Some problems were encountered while building the effective model for
org.apache.hadoop:hadoop-maven-plugins:maven-plugin:2.4.0
[WARNING] 'build.plugins.plugin.(groupId:artifactId)' must be unique but found d
uplicate declaration of plugin org.apache.maven.plugins:maven-enforcer-plugin @
org.apache.hadoop:hadoop-project:2.4.0, D:\hadoop2\hadoop-2.4.0-src\hadoop-proje
ct\pom.xml, line 1015, column 15
[WARNING]
[WARNING] It is highly recommended to fix these problems because they threaten t
he stability of your build.
[WARNING]
[WARNING] For this reason, future Maven versions might no longer support buildin
g such malformed projects.
[WARNING]
[INFO]
[INFO] Using the builder org.apache.maven.lifecycle.internal.builder.singlethrea
ded.SingleThreadedBuilder with a thread count of 1
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building Apache Hadoop Maven Plugins 2.4.0
[INFO] ------------------------------------------------------------------------
[INFO]
[INFO] --- maven-antrun-plugin:1.7:run (create-testdirs) @ hadoop-maven-plugins
---
[INFO] Executing tasks

main:
[INFO] Executed tasks
[INFO]
[INFO] --- maven-plugin-plugin:3.0:descriptor (default-descriptor) @ hadoop-mave
n-plugins ---
[INFO] Using 'UTF-8' encoding to read mojo metadata.
[INFO] Applying mojo extractor for language: java-annotations
[INFO] Mojo extractor for language: java-annotations found 2 mojo descriptors.
[INFO] Applying mojo extractor for language: java
[INFO] Mojo extractor for language: java found 0 mojo descriptors.
[INFO] Applying mojo extractor for language: bsh
[INFO] Mojo extractor for language: bsh found 0 mojo descriptors.
[INFO]
[INFO] --- maven-resources-plugin:2.2:resources (default-resources) @ hadoop-mav
en-plugins ---
[INFO] Using default encoding to copy filtered resources.
[INFO]
[INFO] --- maven-compiler-plugin:2.5.1:compile (default-compile) @ hadoop-maven-
plugins ---
[INFO] Nothing to compile - all classes are up to date
[INFO]
[INFO] --- maven-plugin-plugin:3.0:descriptor (mojo-descriptor) @ hadoop-maven-p
lugins ---
[INFO] Using 'UTF-8' encoding to read mojo metadata.
[INFO] Applying mojo extractor for language: java-annotations
[INFO] Mojo extractor for language: java-annotations found 2 mojo descriptors.
[INFO] Applying mojo extractor for language: java
[INFO] Mojo extractor for language: java found 0 mojo descriptors.
[INFO] Applying mojo extractor for language: bsh
[INFO] Mojo extractor for language: bsh found 0 mojo descriptors.
[INFO]
[INFO] --- maven-resources-plugin:2.2:testResources (default-testResources) @ ha
doop-maven-plugins ---
[INFO] Using default encoding to copy filtered resources.
[INFO]
[INFO] --- maven-compiler-plugin:2.5.1:testCompile (default-testCompile) @ hadoo
p-maven-plugins ---
[INFO] No sources to compile
[INFO]
[INFO] --- maven-surefire-plugin:2.16:test (default-test) @ hadoop-maven-plugins
---
[INFO] No tests to run.
[INFO]
[INFO] --- maven-jar-plugin:2.3.1:jar (default-jar) @ hadoop-maven-plugins ---
[INFO] Building jar: D:\hadoop2\hadoop-2.4.0-src\hadoop-maven-plugins\target\had
oop-maven-plugins-2.4.0.jar
[INFO]
[INFO] --- maven-plugin-plugin:3.0:addPluginArtifactMetadata (default-addPluginA
rtifactMetadata) @ hadoop-maven-plugins ---
[INFO]
[INFO] --- maven-site-plugin:3.3:attach-descriptor (attach-descriptor) @ hadoop-
maven-plugins ---
[INFO]
[INFO] --- maven-install-plugin:2.3.1:install (default-install) @ hadoop-maven-p
lugins ---
[INFO] Installing D:\hadoop2\hadoop-2.4.0-src\hadoop-maven-plugins\target\hadoop
-maven-plugins-2.4.0.jar to C:\Users\hyj\.m2\repository\org\apache\hadoop\hadoop
-maven-plugins\2.4.0\hadoop-maven-plugins-2.4.0.jar
[INFO] Installing D:\hadoop2\hadoop-2.4.0-src\hadoop-maven-plugins\pom.xml to C:
\Users\hyj\.m2\repository\org\apache\hadoop\hadoop-maven-plugins\2.4.0\hadoop-ma
ven-plugins-2.4.0.pom
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 4.891 s
[INFO] Finished at: 2014-06-23T14:47:33+08:00
[INFO] Final Memory: 21M/347M
[INFO] ------------------------------------------------------------------------[/mw_shl_code]

部分截图如下：








（2）运行


[mw_shl_code=bash,true]mvn eclipse:eclipse -DskipTests[/mw_shl_code]
这时候注意，我们进入的是hadoop_home,我这里是D:\hadoop2\hadoop-2.4.0-src

部分信息如下

[mw_shl_code=bash,true][INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Summary:
[INFO]
[INFO] Apache Hadoop Main ................................ SUCCESS [  0.684 s]
[INFO] Apache Hadoop Project POM ......................... SUCCESS [  0.720 s]
[INFO] Apache Hadoop Annotations ......................... SUCCESS [  0.276 s]
[INFO] Apache Hadoop Project Dist POM .................... SUCCESS [  0.179 s]
[INFO] Apache Hadoop Assemblies .......................... SUCCESS [  0.121 s]
[INFO] Apache Hadoop Maven Plugins ....................... SUCCESS [  1.680 s]
[INFO] Apache Hadoop MiniKDC ............................. SUCCESS [  1.802 s]
[INFO] Apache Hadoop Auth ................................ SUCCESS [  1.024 s]
[INFO] Apache Hadoop Auth Examples ....................... SUCCESS [  0.160 s]
[INFO] Apache Hadoop Common .............................. SUCCESS [  1.061 s]
[INFO] Apache Hadoop NFS ................................. SUCCESS [  0.489 s]
[INFO] Apache Hadoop Common Project ...................... SUCCESS [  0.056 s]
[INFO] Apache Hadoop HDFS ................................ SUCCESS [  2.770 s]
[INFO] Apache Hadoop HttpFS .............................. SUCCESS [  0.965 s]
[INFO] Apache Hadoop HDFS BookKeeper Journal ............. SUCCESS [  0.629 s]
[INFO] Apache Hadoop HDFS-NFS ............................ SUCCESS [  0.284 s]
[INFO] Apache Hadoop HDFS Project ........................ SUCCESS [  0.061 s]
[INFO] hadoop-yarn ....................................... SUCCESS [  0.052 s]
[INFO] hadoop-yarn-api ................................... SUCCESS [  0.842 s]
[INFO] hadoop-yarn-common ................................ SUCCESS [  0.322 s]
[INFO] hadoop-yarn-server ................................ SUCCESS [  0.065 s]
[INFO] hadoop-yarn-server-common ......................... SUCCESS [  0.972 s]
[INFO] hadoop-yarn-server-nodemanager .................... SUCCESS [  0.580 s]
[INFO] hadoop-yarn-server-web-proxy ...................... SUCCESS [  0.379 s]
[INFO] hadoop-yarn-server-applicationhistoryservice ...... SUCCESS [  0.281 s]
[INFO] hadoop-yarn-server-resourcemanager ................ SUCCESS [  0.378 s]
[INFO] hadoop-yarn-server-tests .......................... SUCCESS [  0.534 s]
[INFO] hadoop-yarn-client ................................ SUCCESS [  0.307 s]
[INFO] hadoop-yarn-applications .......................... SUCCESS [  0.050 s]
[INFO] hadoop-yarn-applications-distributedshell ......... SUCCESS [  0.202 s]
[INFO] hadoop-yarn-applications-unmanaged-am-launcher .... SUCCESS [  0.194 s]
[INFO] hadoop-yarn-site .................................. SUCCESS [  0.057 s]
[INFO] hadoop-yarn-project ............................... SUCCESS [  0.066 s]
[INFO] hadoop-mapreduce-client ........................... SUCCESS [  0.091 s]
[INFO] hadoop-mapreduce-client-core ...................... SUCCESS [  1.321 s]
[INFO] hadoop-mapreduce-client-common .................... SUCCESS [  0.786 s]
[INFO] hadoop-mapreduce-client-shuffle ................... SUCCESS [  0.456 s]
[INFO] hadoop-mapreduce-client-app ....................... SUCCESS [  0.508 s]
[INFO] hadoop-mapreduce-client-hs ........................ SUCCESS [  0.834 s]
[INFO] hadoop-mapreduce-client-jobclient ................. SUCCESS [  0.541 s]
[INFO] hadoop-mapreduce-client-hs-plugins ................ SUCCESS [  0.284 s]
[INFO] Apache Hadoop MapReduce Examples .................. SUCCESS [  0.851 s]
[INFO] hadoop-mapreduce .................................. SUCCESS [  0.099 s]
[INFO] Apache Hadoop MapReduce Streaming ................. SUCCESS [  0.742 s]
[INFO] Apache Hadoop Distributed Copy .................... SUCCESS [  0.335 s]
[INFO] Apache Hadoop Archives ............................ SUCCESS [  0.397 s]
[INFO] Apache Hadoop Rumen ............................... SUCCESS [  0.371 s]
[INFO] Apache Hadoop Gridmix ............................. SUCCESS [  0.230 s]
[INFO] Apache Hadoop Data Join ........................... SUCCESS [  0.184 s]
[INFO] Apache Hadoop Extras .............................. SUCCESS [  0.217 s]
[INFO] Apache Hadoop Pipes ............................... SUCCESS [  0.048 s]
[INFO] Apache Hadoop OpenStack support ................... SUCCESS [  0.244 s]
[INFO] Apache Hadoop Client .............................. SUCCESS [  0.590 s]
[INFO] Apache Hadoop Mini-Cluster ........................ SUCCESS [  0.230 s]
[INFO] Apache Hadoop Scheduler Load Simulator ............ SUCCESS [  0.650 s]
[INFO] Apache Hadoop Tools Dist .......................... SUCCESS [  0.334 s]
[INFO] Apache Hadoop Tools ............................... SUCCESS [  0.042 s]
[INFO] Apache Hadoop Distribution ........................ SUCCESS [  0.144 s]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 31.234 s
[INFO] Finished at: 2014-06-23T14:55:08+08:00
[INFO] Final Memory: 84M/759M
[INFO] ------------------------------------------------------------------------[/mw_shl_code]

这时候，我们已经把源码给下载下来了。这时候，我们会看到文件会明显增大。






3.关联eclipse源码

加入我们以下程序
hadoop2.2mapreduce例子.rar (1.14 MB, 下载次数: 215, 售价: 1 云币)
如下图示，对他们进行了打包


这两个文件， MaxTemperature.zip为mapreduce例子，mockito-core-1.8.5.jar为mapreduce例子所引用的包
（这里需要说明的是，mapreduce为2.2，但是不影响关联源码，只是交给大家该如何关联源码）
我们解压之后，导入eclipse
（对于导入项目不熟悉，参考零基础教你如何导入eclipse项目）




我们导入之后，看到很多的红线，这些其实都是没有引用包，下面我们开始解决这些语法问题。
一、解决导入jar包
（1）引入mockito-core-1.8.5.jar

（2）hadoop2.4编译包中的jar文件，这些文件的位置如下：

hadoop_home中share\hadoop文件夹下，具体我这的位置D:\hadoop2\hadoop-2.4.0\share\hadoop
找到里面的jar包，举例如下：lib文件中的jar包，以及下面的jar包都添加到buildpath中。
如果对于引用包，不知道该如何添加这些jar包，参考hadoop开发方式总结及操作指导。
（注意的是，我们这里是引入的是编译包，编译的下载hadoop--642.4.0.tar.gz
链接: http://pan.baidu.com/s/1c0vPjG0 密码:xj6l）

更多包下载可以参考hadoop家族、strom、spark、Linux、flume等jar包、安装包汇总下载








二、关联源码
1.我们导入jar包之后，就没有错误了，如下图所示



2.找不到源码

当我们想看一个类或则函数怎么实现的时候，通过Open Call Hierarchy，却找不到源文件。








3.Attach Source



上面三处，我们按照顺序添加即可，我们选定压缩包之后，单击确定，ok了，我们的工作已经完毕。

注意：对于hadoop-2.2.0-src.zip则是我们上面通过maven下载的源码，然后压缩的文件，记得一定是压缩文件zip的形式


4.验证关联后查看源码

我们再次执行上面操作，通过Open Call Hierarchy




看到下面内容






然后我们双击上图主类，即红字部分，我们看到下面内容：




问题：
细心的同学，这里面我们产生一个问题，因为我们看到的是.class文件，而不是.java文件。那么他会不会和我们所看到的.java文件不一样那。
其实是一样的，感兴趣的同学，可以验证一下。


下一篇：
如何通过eclipse查看、阅读hadoop2.4源码