问题场景
按照官网http://wiki.apache.org/hadoop/EclipseEnvironment指导，要把Hadoop下载到本地，并构建Eclipse开发环境，只需要三条指令：
$ git clone git://git.apache.org/hadoop-common.git$ mvn install -DskipTests$ mvn eclipse:eclipse -DdownloadSources=true -DdownloadJavadocs=true
即可，但当我在本地执行完第二条后，报出如下错误日志信息：
[INFO] [INFO] --- maven-antrun-plugin:1.6:run (compile-proto) @ hadoop-common ---[INFO] Executing tasksmain: [exec] target/compile-proto.sh: line 17: protoc: command not found [exec] target/compile-proto.sh: line 17: protoc: command not found[INFO] ------------------------------------[INFO] Reactor Summary:[INFO] [INFO] Apache Hadoop Main ................................ SUCCESS [2.389s][INFO] Apache Hadoop Project POM ......................... SUCCESS [0.698s][INFO] Apache Hadoop Annotations ......................... SUCCESS [1.761s][INFO] Apache Hadoop Project Dist POM .................... SUCCESS [0.729s][INFO] Apache Hadoop Assemblies .......................... SUCCESS [0.353s][INFO] Apache Hadoop Auth ................................ SUCCESS [1.998s][INFO] Apache Hadoop Auth Examples ....................... SUCCESS [1.227s][INFO] Apache Hadoop Common .............................. FAILURE [1.132s][INFO] Apache Hadoop Common Project ...................... SKIPPED[INFO] Apache Hadoop HDFS ................................ SKIPPED[INFO] Apache Hadoop HttpFS .............................. SKIPPED[INFO] Apache Hadoop HDFS BookKeeper Journal ............. SKIPPED[INFO] Apache Hadoop HDFS Project ........................ SKIPPED[INFO] hadoop-yarn ....................................... SKIPPED[INFO] hadoop-yarn-api ................................... SKIPPED[INFO] hadoop-yarn-common ................................ SKIPPED[INFO] hadoop-yarn-server ................................ SKIPPED[INFO] hadoop-yarn-server-common ......................... SKIPPED[INFO] hadoop-yarn-server-nodemanager .................... SKIPPED[INFO] hadoop-yarn-server-web-proxy ...................... SKIPPED[INFO] hadoop-yarn-server-resourcemanager ................ SKIPPED[INFO] hadoop-yarn-server-tests .......................... SKIPPED[INFO] hadoop-mapreduce-client ........................... SKIPPED[INFO] hadoop-mapreduce-client-core ...................... SKIPPED[INFO] hadoop-yarn-applications .......................... SKIPPED[INFO] hadoop-yarn-applications-distributedshell ......... SKIPPED[INFO] hadoop-yarn-site .................................. SKIPPED[INFO] hadoop-mapreduce-client-common .................... SKIPPED[INFO] hadoop-mapreduce-client-shuffle ................... SKIPPED[INFO] hadoop-mapreduce-client-app ....................... SKIPPED[INFO] hadoop-mapreduce-client-hs ........................ SKIPPED[INFO] hadoop-mapreduce-client-jobclient ................. SKIPPED[INFO] Apache Hadoop MapReduce Examples .................. SKIPPED[INFO] hadoop-mapreduce .................................. SKIPPED[INFO] Apache Hadoop MapReduce Streaming ................. SKIPPED[INFO] Apache Hadoop Distributed Copy .................... SKIPPED[INFO] Apache Hadoop Archives ............................ SKIPPED[INFO] Apache Hadoop Rumen ............................... SKIPPED[INFO] Apache Hadoop Extras .............................. SKIPPED[INFO] Apache Hadoop Tools Dist .......................... SKIPPED[INFO] Apache Hadoop Tools ............................... SKIPPED[INFO] Apache Hadoop Distribution ........................ SKIPPED[INFO] ------------------------------------[INFO] BUILD FAILURE[INFO] ------------------------------------[INFO] Total time: 12.483s[INFO] Finished at: Mon Jan 30 22:57:23 GMT+08:00 2012[INFO] Final Memory: 24M/81M[INFO] ------------------------------------[ERROR] Failed to execute goal org.apache.maven.plugins:maven-antrun-plugin:1.6:run (compile-proto) on project hadoop-common: An Ant BuildException has occured: exec returned: 127 -> [Help 1][ERROR] [ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.[ERROR] Re-run Maven using the -X switch to enable full debug logging.[ERROR] [ERROR] For more information about the errors and possible solutions, please read the following articles:[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoExecutionException[ERROR] [ERROR] After correcting the problems, you can resume the build with the command[ERROR] mvn <goals> -rf :hadoop-common
此问题我暂时还未分析具体原因和解决方案，暂时记录下。
展开分析
通过再此使用命令打出错误信息：
$ mvn install -DskipTests -e
得到详细错误信息为：
[INFO] ------------------------------------[INFO] BUILD FAILURE[INFO] ------------------------------------[INFO] Total time: 9.387s[INFO] Finished at: Mon Jan 30 23:11:07 GMT+08:00 2012[INFO] Final Memory: 19M/81M[INFO] ------------------------------------[ERROR] Failed to execute goal org.apache.maven.plugins:maven-antrun-plugin:1.6:run (compile-proto) on project hadoop-common: An Ant BuildException has occured: exec returned: 127 -> [Help 1]org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.apache.maven.plugins:maven-antrun-plugin:1.6:run (compile-proto) on project hadoop-common: An Ant BuildException has occured: exec returned: 127 at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:217) at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153) at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145) at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:84) at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:59) at org.apache.maven.lifecycle.internal.LifecycleStarter.singleThreadedBuild(LifecycleStarter.java:183) at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:161) at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:319) at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:156) at org.apache.maven.cli.MavenCli.execute(MavenCli.java:537) at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:196) at org.apache.maven.cli.MavenCli.main(MavenCli.java:141) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:290) at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:230) at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:409) at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:352)Caused by: org.apache.maven.plugin.MojoExecutionException: An Ant BuildException has occured: exec returned: 127 at org.apache.maven.plugin.antrun.AntRunMojo.execute(AntRunMojo.java:283) at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:101) at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:209) ... 19 moreCaused by: /Users/apple/Documents/Hadoop-common-dev/hadoop-common/hadoop-common-project/hadoop-common/target/antrun/build-main.xml:23: exec returned: 127 at org.apache.tools.ant.taskdefs.ExecTask.runExecute(ExecTask.java:650) at org.apache.tools.ant.taskdefs.ExecTask.runExec(ExecTask.java:676) at org.apache.tools.ant.taskdefs.ExecTask.execute(ExecTask.java:502) at org.apache.tools.ant.UnknownElement.execute(UnknownElement.java:291) at sun.reflect.GeneratedMethodAccessor16.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.apache.tools.ant.dispatch.DispatchUtils.execute(DispatchUtils.java:106) at org.apache.tools.ant.Task.perform(Task.java:348) at org.apache.tools.ant.Target.execute(Target.java:390) at org.apache.tools.ant.Target.performTasks(Target.java:411) at org.apache.tools.ant.Project.executeSortedTargets(Project.java:1397) at org.apache.tools.ant.Project.executeTarget(Project.java:1366) at org.apache.maven.plugin.antrun.AntRunMojo.execute(AntRunMojo.java:270) ... 21 more[ERROR] [ERROR] Re-run Maven using the -X switch to enable full debug logging.[ERROR] [ERROR] For more information about the errors and possible solutions, please read the following articles:[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoExecutionException[ERROR]
通过上面错误信息，真方便找到解决方案。
根据上面的提示，访问https://cwiki.apache.org/confluence/display/MAVEN/MojoExecutionException
得到如下提示信息：
Unlike many other errors, this exception is not generated by the Maven core itself but by a plugin. As a rule of thumb, plugins use this error to signal a problem in their configuration or the information they retrieved from the POM.
这里说的意思是：
这个错误不是Maven本身的错误，根据经验，可能是Maven使用的插件通过这个异常来标识它们没有从POM中获得相关的配置信息。
接下来进一步分析，通过Maven构建Hadoop过程中是否使用了插件。
从错误日志分析，编译过程使用了插件：maven-antrun-plugin。由于编译Hadoop-common过程中出错，所以进一步定位到hadoop-common工程下的POM.xml，可到看到下面信息：
<plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-antrun-plugin</artifactId> <executions> <execution> <id>compile-proto</id> <phase>generate-sources</phase> <goals> <goal>run</goal> </goals> <configuration> <target> <echo file="target/compile-proto.sh"> PROTO_DIR=src/main/proto JAVA_DIR=target/generated-sources/java which cygpath 2> /dev/null if [ $? = 1 ]; then IS_WIN=false else IS_WIN=true WIN_PROTO_DIR=`cygpath --windows $PROTO_DIR` WIN_JAVA_DIR=`cygpath --windows $JAVA_DIR` fi mkdir -p $JAVA_DIR 2> /dev/null for PROTO_FILE in `ls $PROTO_DIR/*.proto 2> /dev/null` do if [ "$IS_WIN" = "true" ]; then protoc -I$WIN_PROTO_DIR --java_out=$WIN_JAVA_DIR $PROTO_FILE else protoc -I$PROTO_DIR --java_out=$JAVA_DIR $PROTO_FILE fi done </echo> <exec executable="sh" dir="${basedir}" failonerror="true"> <arg line="target/compile-proto.sh"/> </exec> </target> </configuration> </execution> <execution> <id>compile-test-proto</id> <phase>generate-test-sources</phase> <goals> <goal>run</goal> </goals> <configuration> <target> <echo file="target/compile-test-proto.sh"> PROTO_DIR=src/test/proto JAVA_DIR=target/generated-test-sources/java which cygpath 2> /dev/null if [ $? = 1 ]; then IS_WIN=false else IS_WIN=true WIN_PROTO_DIR=`cygpath --windows $PROTO_DIR` WIN_JAVA_DIR=`cygpath --windows $JAVA_DIR` fi mkdir -p $JAVA_DIR 2> /dev/null for PROTO_FILE in `ls $PROTO_DIR/*.proto 2> /dev/null` do if [ "$IS_WIN" = "true" ]; then protoc -I$WIN_PROTO_DIR --java_out=$WIN_JAVA_DIR $PROTO_FILE else protoc -I$PROTO_DIR --java_out=$JAVA_DIR $PROTO_FILE fi done </echo> <exec executable="sh" dir="${basedir}" failonerror="true"> <arg line="target/compile-test-proto.sh"/> </exec> </target> </configuration> </execution> <execution> <id>save-version</id> <phase>generate-sources</phase> <goals> <goal>run</goal> </goals> <configuration> <target> <mkdir dir="${project.build.directory}/generated-sources/java"/> <exec executable="sh"> <arg line="${basedir}/dev-support/saveVersion.sh ${project.version} ${project.build.directory}/generated-sources/java"/> </exec> </target> </configuration> </execution> <execution> <id>generate-test-sources</id> <phase>generate-test-sources</phase> <goals> <goal>run</goal> </goals> <configuration> <target> <mkdir dir="${project.build.directory}/generated-test-sources/java"/> <taskdef name="recordcc" classname="org.apache.hadoop.record.compiler.ant.RccTask"> <classpath refid="maven.compile.classpath"/> </taskdef> <recordcc destdir="${project.build.directory}/generated-test-sources/java"> <fileset dir="${basedir}/src/test/ddl" includes="**/*.jr"/> </recordcc> </target> </configuration> </execution> <execution> <id>create-log-dir</id> <phase>process-test-resources</phase> <goals> <goal>run</goal> </goals> <configuration> <target> <!-- TODO: there are tests (TestLocalFileSystem#testCopy) that fail if data TODO: from a previous run is present --> <delete dir="${test.build.data}"/> <mkdir dir="${test.build.data}"/> <mkdir dir="${hadoop.log.dir}"/> <copy toDir="${project.build.directory}/test-classes"> <fileset dir="${basedir}/src/main/conf"/> </copy> </target> </configuration> </execution> <execution> <phase>pre-site</phase> <goals> <goal>run</goal> </goals> <configuration> <tasks> <copy file="src/main/resources/core-default.xml" todir="src/site/resources"/> <copy file="src/main/xsl/configuration.xsl" todir="src/site/resources"/> </tasks> </configuration> </execution> </executions> </plugin>上面是在Pom.xml文件中使用Maven下使用Ant插件，里面有一行：
<echo file="target/compile-proto.sh">
看着让人不解，联系到HowToContribueToHadoop的文章http://wiki.apache.org/hadoop/HowToContribute可以推知，有可能由于本地没有安装ProtocolBuffers引起的，因为文章内部特别说明了：
引用
Hadoop 0.23+ must have Google's ProtocolBuffers for compilation to work.
接下来打算在本地重新安装ProtocolBuffers后再编译部署。如预期，在本地安装好了Protoc Buffer后，后面两条指令顺利执行完整，剩下的就依据官网把目录下的工程导入Eclipse后，就可以在Eclipse下学习调试源码。