Hadoop学习：Map/Reduce初探与小Demo实现
Posted
tags:
篇首语：本文由小常识网(cha138.com)小编为大家整理，主要介绍了Hadoop学习：Map/Reduce初探与小Demo实现相关的知识，希望对你有一定的参考价值。
一、 概念知识介绍
Hadoop MapReduce是一个用于处理海量数据的分布式计算框架。这个框架攻克了诸如数据分布式存储、作业调度、容错、机器间通信等复杂问题，能够使没有并行 处理或者分布式计算经验的project师，也能非常轻松地写出结构简单的、应用于成百上千台机器处理大规模数据的并行分布式程序。
Hadoop MapReduce基于“分而治之”的思想，将计算任务抽象成map和reduce两个计算过程，能够简单理解为“分散运算—归并结果”的过程。一个 MapReduce程序首先会把输入数据切割成不相关的若干键/值对（key1/value1）集合。这些键/值对会由多个map任务来并行地处理。 MapReduce会对map的输出（一些中间键/值对key2/value2集合）依照key2进行排序，排序是用memcmp的方式对key在内存中 字节数组比較后进行升序排序。并将属于同一个key2的全部value2组合在一起作为reduce任务的输入，由reduce任务计算出终于结果并输出 key3/value3。作为一个优化。同一个计算节点上的key2/value2会通过combine在本地归并。基本流程例如以下：
Hadoop和单机程序计算流程对照：
常计算任务的输入和输出都是存放在文件中的，而且这些文件被存放在Hadoop分布式文件系统HDFS（Hadoop Distributed File System）中，系统会尽量调度计算任务到数据所在的节点上执行，而不是尽量将数据移动到计算节点上。降低大量数据在网络中传输，尽量节省带宽消耗。
应用程序开发者普通情况下须要关心的是图中灰色的部分，单机程序须要处理数据读取和写入、数据处理；Hadoop程序须要实现map和 reduce。而数据读取和写入、map和reduce之间的传输数据、容错处理等由Hadoop MapReduce和HDFS自己主动完毕。
二、 开发环境搭建
Map/Reduce程序依赖Hadoop集群，另外Eclipse须要安装依赖的hadoop包。
Hadoop集群搭建：參考Hadoop 2.2.0集群搭建
1. 安装、配置Eclipse
在官网下载合适的Eclipse，将hadoop开发所依赖的插件jar包复制到eclipse的安装目录plugins下。下载地址參考：hadoop2.2.0开发依赖的jar包，当然也能够自己编译。
启动eclipse，选择Window—>Prefrances，若出现例如以下Hadoop Map/Reduce说明插件成功安装
2. 配置DFS，主要是数据文件的输入输出管理。
Window—>Open Perspective—>other—>Map/Reduce，显示Map/Reduce视图。点击Map/Reduce Locations 的小象图标。新建Hadoop Location，输入例如以下：
项目视图会出现DFS Location。用来管理输入、输出数据文件。
须要配置hadoop安装目录：新建Map/Reduceproject单击Configure Hadoop install direction。输入hadoop的安装路径。
右键单击DFS Location下的空目录上传一个文本文件，然后刷新，若文件出现了则说明环境配置成功。
三、 编程模型
MapReduce编程模型的原理是：利用一个输入key/value pair集合来产生一个输出的key/value pair集合。
MapReduce库的用户用两个函数表达这个计算：Map和Reduce。
用户自己定义的Map函数接受一个输入的key/value pair值，然后产生一个中间key/value pair值的集合。
MapReduce库把全部具有同样中间key值I的中间value值集合在一起后传递给reduce函数。
用户自己定义的Reduce函数接受一个中间key的值I和相关的一个value值的集合。Reduce函数合并这些value值，形成一个较小的 value值的集合。一般的。每次Reduce函数调用仅仅产生0或1个输出value值。
通常我们通过一个迭代器把中间value值提供给Reduce函 数，这样我们就能够处理无法所有放入内存中的大量的value值的集合。
四、 小样例
1. 数据准备
以Tomcat日志为例。日志格式例如以下：
127.0.0.1,-,-,[08/May/2014:13:42:40 +0800],GET / HTTP/1.1,200,11444 127.0.0.1,-,-,[08/May/2014:13:42:42 +0800],GET /jygl/jaxrs/teachingManage/ClassBatchPlanService/getCurrentClassPlanVO HTTP/1.1,204,- 127.0.0.1,-,-,[08/May/2014:13:42:42 +0800],GET /jygl/jaxrs/teachingManage/ClassBatchPlanService/getCurClassPlanVO HTTP/1.1,204,- 127.0.0.1,-,-,[08/May/2014:13:42:47 +0800],GET /jygl/jaxrs/right/isValidUserByType/1-admin-superadmin HTTP/1.1,200,20 127.0.0.1,-,-,[08/May/2014:13:42:47 +0800],GET /jygl/jaxrs/right/getUserByLoginName/admin HTTP/1.1,200,198 0:0:0:0:0:0:0:1,-,-,[08/May/2014:13:42:47 +0800],GET /jyglFront/right_login2home?loginName=admin&password=superadmin&type=1 HTTP/1.1,200,2525 0:0:0:0:0:0:0:1,-,-,[08/May/2014:13:42:47 +0800],GET /jyglFront/mainView/navigate/style/style.css HTTP/1.1,304,- 0:0:0:0:0:0:0:1,-,-,[08/May/2014:13:42:47 +0800],GET /jyglFront/mainView/navigate/js/tree.js HTTP/1.1,304,- 0:0:0:0:0:0:0:1,-,-,[08/May/2014:13:42:47 +0800],GET /jyglFront/mainView/navigate/js/jquery.js HTTP/1.1,304,- 0:0:0:0:0:0:0:1,-,-,[08/May/2014:13:42:47 +0800],GET /jyglFront/mainView/navigate/js/frame.js HTTP/1.1,304,- 0:0:0:0:0:0:0:1,-,-,[08/May/2014:13:42:47 +0800],GET /jyglFront/mainView/navigate/images/logo.png HTTP/1.1,304,- 0:0:0:0:0:0:0:1,-,-,[08/May/2014:13:42:47 +0800],GET /jyglFront/mainView/navigate/images/leftmenu_bg.gif HTTP/1.1,404,1105 0:0:0:0:0:0:0:1,-,-,[08/May/2014:13:42:47 +0800],GET /jyglFront/mainView/navigate/menuList.jsp HTTP/1.1,200,47603 0:0:0:0:0:0:0:1,-,-,[08/May/2014:13:42:47 +0800],GET /jyglFront/mainView/navigate/style/images/header_bg.jpg HTTP/1.1,304,- 0:0:0:0:0:0:0:1,-,-,[08/May/2014:13:42:47 +0800],GET /jyglFront/mainView/navigate/images/allmenu.gif HTTP/1.1,404,1093 0:0:0:0:0:0:0:1,-,-,[08/May/2014:13:42:47 +0800],GET /jyglFront/mainView/navigate/images/toggle_menu.gif HTTP/1.1,404,1105 127.0.0.1,-,-,[08/May/2014:13:42:48 +0800],GET /jygl/jaxrs/article/getArticleList/10-1 HTTP/1.1,200,20913 127.0.0.1,-,-,[08/May/2014:13:42:48 +0800],GET /jygl/jaxrs/article/getTotalArticleRecords HTTP/1.1,200,22 0:0:0:0:0:0:0:1,-,-,[08/May/2014:13:42:48 +0800],GET /jyglFront/baseInfo_articleList?flag=1 HTTP/1.1,200,8989 0:0:0:0:0:0:0:1,-,-,[08/May/2014:13:42:48 +0800],GET /jyglFront/mainView/studentView/style/images/nav_10.png HTTP/1.1,404,1117 127.0.0.1,-,-,[08/May/2014:13:43:21 +0800],GET /jygl/jaxrs/right/isValidUserByType/1-admin-superadmin HTTP/1.1,200,20 127.0.0.1,-,-,[08/May/2014:13:43:21 +0800],GET /jygl/jaxrs/right/getUserByLoginName/admin HTTP/1.1,200,198 0:0:0:0:0:0:0:1,-,-,[08/May/2014:13:43:21 +0800],GET /jyglFront/right_login2home?loginName=admin&password=superadmin&type=1 HTTP/1.1,200,2525 0:0:0:0:0:0:0:1,-,-,[08/May/2014:13:43:21 +0800],GET /jyglFront/mainView/navigate/js/tree.js HTTP/1.1,304,- 0:0:0:0:0:0:0:1,-,-,[08/May/2014:13:43:21 +0800],GET /jyglFront/mainView/navigate/js/jquery.js HTTP/1.1,304,- 0:0:0:0:0:0:0:1,-,-,[08/May/2014:13:43:21 +0800],GET /jyglFront/mainView/navigate/js/frame.js HTTP/1.1,304,- 0:0:0:0:0:0:0:1,-,-,[08/May/2014:13:43:21 +0800],GET /jyglFront/mainView/navigate/style/style.css HTTP/1.1,304,- 0:0:0:0:0:0:0:1,-,-,[08/May/2014:13:43:21 +0800],GET /jyglFront/mainView/navigate/menuList.jsp HTTP/1.1,200,47603 0:0:0:0:0:0:0:1,-,-,[08/May/2014:13:43:21 +0800],GET /jyglFront/mainView/navigate/images/logo.png HTTP/1.1,304,- 0:0:0:0:0:0:0:1,-,-,[08/May/2014:13:43:21 +0800],GET /jyglFront/mainView/navigate/images/leftmenu_bg.gif HTTP/1.1,404,1105 0:0:0:0:0:0:0:1,-,-,[08/May/2014:13:43:21 +0800],GET /jyglFront/mainView/navigate/images/toggle_menu.gif HTTP/1.1,404,1105 0:0:0:0:0:0:0:1,-,-,[08/May/2014:13:43:21 +0800],GET /jyglFront/mainView/navigate/style/images/header_bg.jpg HTTP/1.1,304,- 127.0.0.1,-,-,[08/May/2014:13:43:21 +0800],GET /jygl/jaxrs/article/getArticleList/10-1 HTTP/1.1,200,20913 0:0:0:0:0:0:0:1,-,-,[08/May/2014:13:43:21 +0800],GET /jyglFront/mainView/navigate/images/allmenu.gif HTTP/1.1,404,1093 127.0.0.1,-,-,[08/May/2014:13:43:21 +0800],GET /jygl/jaxrs/article/getTotalArticleRecords HTTP/1.1,200,22 0:0:0:0:0:0:0:1,-,-,[08/May/2014:13:43:21 +0800],GET /jyglFront/baseInfo_articleList?
flag=1 HTTP/1.1,200,8989 0:0:0:0:0:0:0:1,-,-,[08/May/2014:13:43:21 +0800],GET /jyglFront/mainView/studentView/style/images/nav_10.png HTTP/1.1,404,1117 127.0.0.1,-,-,[08/May/2014:13:43:25 +0800],GET /jygl/jaxrs/graduate/graduateBatchService/getGraduateBatchByConditions?
graduateBatchName=&pageSize=10&pageNo=1 HTTP/1.1,200,597 127.0.0.1,-,-,[08/May/2014:13:43:25 +0800],GET /jygl/jaxrs/graduate/graduateBatchService/getTotalGraduateBatchByCondition?
graduateBatchName= HTTP/1.1,200,21 0:0:0:0:0:0:0:1,-,-,[08/May/2014:13:43:26 +0800],GET /jyglFront/graduate_initGraduateBatch HTTP/1.1,200,8766 127.0.0.1,-,-,[08/May/2014:13:43:27 +0800],GET /jygl/jaxrs/exam/examParameterService/getAllStudyCenters HTTP/1.1,200,29089 127.0.0.1,-,-,[08/May/2014:13:43:27 +0800],GET /jygl/jaxrs/exam/examParameterService/getAllGradeInfo HTTP/1.1,200,3785 127.0.0.1,-,-,[08/May/2014:13:43:27 +0800],GET /jygl/jaxrs/enroll/educationLevelService/allEducationLevels HTTP/1.1,200,227 0:0:0:0:0:0:0:1,-,-,[08/May/2014:13:43:28 +0800],GET /jyglFront/graduate_initGraduateQulifyCheck HTTP/1.1,200,26397 127.0.0.1,-,-,[08/May/2014:13:43:29 +0800],GET /jygl/jaxrs/exam/examParameterService/getAllStudyCenters HTTP/1.1,200,29089 127.0.0.1,-,-,[08/May/2014:13:43:29 +0800],GET /jygl/jaxrs/exam/examParameterService/getAllGradeInfo HTTP/1.1,200,3785 127.0.0.1,-,-,[08/May/2014:13:43:29 +0800],GET /jygl/jaxrs/enroll/educationLevelService/allEducationLevels HTTP/1.1,200,227 0:0:0:0:0:0:0:1,-,-,[08/May/2014:13:43:29 +0800],GET /jyglFront/graduate_initLeaveSchoolInfo HTTP/1.1,200,20125 127.0.0.1,-,-,[08/May/2014:13:43:30 +0800],GET /jygl/jaxrs/exam/examParameterService/getAllStudyCenters HTTP/1.1,200,29089 127.0.0.1,-,-,[08/May/2014:13:43:31 +0800],GET /jygl/jaxrs/exam/examParameterService/getAllGradeInfo HTTP/1.1,200,3785 127.0.0.1,-,-,[08/May/2014:13:43:31 +0800],GET /jygl/jaxrs/enroll/educationLevelService/allEducationLevels HTTP/1.1,200,227 127.0.0.1,-,-,[08/May/2014:13:43:31 +0800],GET /jygl/jaxrs/graduate/graduateBatchService/getAllGraduateBatch HTTP/1.1,200,597 0:0:0:0:0:0:0:1,-,-,[08/May/2014:13:43:31 +0800],GET /jyglFront/graduate_initGraduateInfo HTTP/1.1,200,28464 127.0.0.1,-,-,[08/May/2014:14:27:10 +0800],GET / HTTP/1.1,200,11444 127.0.0.1,-,-,[08/May/2014:14:27:12 +0800],GET /jygl/jaxrs/teachingManage/ClassBatchPlanService/getCurrentClassPlanVO HTTP/1.1,204,- 127.0.0.1,-,-,[08/May/2014:14:27:12 +0800],GET /jygl/jaxrs/teachingManage/ClassBatchPlanService/getCurClassPlanVO HTTP/1.1,204,- 127.0.0.1,-,-,[08/May/2014:14:27:34 +0800],GET /jygl/jaxrs/exam/examArrangeService/getExamBatchIdByLatest HTTP/1.1,200,43 127.0.0.1,-,-,[08/May/2014:14:27:34 +0800],GET /jygl/jaxrs/exam/examArrangeService/getExamBatchNameByEBId/4af2a0424323412e014327739b1702bd HTTP/1.1,200,16 127.0.0.1,-,-,[08/May/2014:14:27:35 +0800],GET /jygl/jaxrs/exam/examSubscribeService/getUtilObjectThirExamBatchsByEBNN/201403 HTTP/1.1,200,653 0:0:0:0:0:0:0:1,-,-,[08/May/2014:14:27:35 +0800],GET /jyglFront/exam_initgroupsubscribestatistic HTTP/1.1,200,13551 0:0:0:0:0:0:0:1,-,-,[08/May/2014:14:27:37 +0800],GET /jyglFront/exam_initsubstudentsubscribe HTTP/1.1,500,3900 0:0:0:0:0:0:0:1,-,-,[08/May/2014:14:27:41 +0800],GET /jyglFront/supervisor/intoInitAssignmentDetail HTTP/1.1,200,1808 127.0.0.1,-,-,[08/May/2014:14:27:42 +0800],GET /jygl/jaxrs/right/isValidUserByType/1-admin-superadmin HTTP/1.1,200,20 127.0.0.1,-,-,[08/May/2014:14:27:42 +0800],GET /jygl/jaxrs/right/getUserByLoginName/admin HTTP/1.1,200,198 0:0:0:0:0:0:0:1,-,-,[08/May/2014:14:27:42 +0800],GET /jyglFront/right_login2home?loginName=admin&password=superadmin&type=1 HTTP/1.1,200,2525 0:0:0:0:0:0:0:1,-,-,[08/May/2014:14:27:42 +0800],GET /jyglFront/mainView/navigate/js/tree.js HTTP/1.1,304,- 0:0:0:0:0:0:0:1,-,-,[08/May/2014:14:27:42 +0800],GET /jyglFront/mainView/navigate/style/style.css HTTP/1.1,304,- 0:0:0:0:0:0:0:1,-,-,[08/May/2014:14:27:42 +0800],GET /jyglFront/mainView/navigate/js/frame.js HTTP/1.1,304,- 0:0:0:0:0:0:0:1,-,-,[08/May/2014:14:27:42 +0800],GET /jyglFront/mainView/navigate/js/jquery.js HTTP/1.1,304,- 0:0:0:0:0:0:0:1,-,-,[08/May/2014:14:27:42 +0800],GET /jyglFront/mainView/navigate/menuList.jsp HTTP/1.1,200,47603 0:0:0:0:0:0:0:1,-,-,[08/May/2014:14:27:42 +0800],GET /jyglFront/mainView/navigate/images/leftmenu_bg.gif HTTP/1.1,404,1105 0:0:0:0:0:0:0:1,-,-,[08/May/2014:14:27:42 +0800],GET /jyglFront/mainView/navigate/images/allmenu.gif HTTP/1.1,404,1093 0:0:0:0:0:0:0:1,-,-,[08/May/2014:14:27:42 +0800],GET /jyglFront/mainView/navigate/images/logo.png HTTP/1.1,304,- 0:0:0:0:0:0:0:1,-,-,[08/May/2014:14:27:42 +0800],GET /jyglFront/mainView/navigate/style/images/header_bg.jpg HTTP/1.1,304,- 0:0:0:0:0:0:0:1,-,-,[08/May/2014:14:27:42 +0800],GET /jyglFront/mainView/navigate/images/toggle_menu.gif HTTP/1.1,404,1105 127.0.0.1,-,-,[08/May/2014:14:27:42 +0800],GET /jygl/jaxrs/article/getArticleList/10-1 HTTP/1.1,200,20913 127.0.0.1,-,-,[08/May/2014:14:27:42 +0800],GET /jygl/jaxrs/article/getTotalArticleRecords HTTP/1.1,200,22 0:0:0:0:0:0:0:1,-,-,[08/May/2014:14:27:42 +0800],GET /jyglFront/baseInfo_articleList?flag=1 HTTP/1.1,200,8989 0:0:0:0:0:0:0:1,-,-,[08/May/2014:14:27:43 +0800],GET /jyglFront/mainView/studentView/style/images/nav_10.png HTTP/1.1,404,1117 127.0.0.1,-,-,[08/May/2014:14:27:44 +0800],GET /jygl/jaxrs/nationInfo/getAllNationInPage?
pageSize=10&pageNo=1 HTTP/1.1,200,374 127.0.0.1,-,-,[08/May/2014:14:27:44 +0800],GET /jygl/jaxrs/nationInfo/getTotalNations HTTP/1.1,200,22 0:0:0:0:0:0:0:1,-,-,[08/May/2014:14:27:44 +0800],GET /jyglFront/baseInfo_nationInfoList HTTP/1.1,200,7471 0:0:0:0:0:0:0:1,-,-,[08/May/2014:14:27:44 +0800],GET /jyglFront/common/css/menuStyle2.css HTTP/1.1,404,1060 0:0:0:0:0:0:0:1,-,-,[08/May/2014:14:27:44 +0800],GET /jyglFront/common/css/basic.css HTTP/1.1,200,1476 0:0:0:0:0:0:0:1,-,-,[08/May/2014:14:27:45 +0800],GET /jyglFront/common/css/_images/botton2.gif HTTP/1.1,404,1075 127.0.0.1,-,-,[08/May/2014:14:27:47 +0800],GET /jygl/jaxrs/enroll/educationLevelService/allEducationLevels HTTP/1.1,200,227 127.0.0.1,-,-,[08/May/2014:14:27:47 +0800],GET /jygl/jaxrs/enroll/gradeInfoService/allGradeInfos HTTP/1.1,200,3785 127.0.0.1,-,-,[08/May/2014:14:27:47 +0800],GET /jygl/jaxrs/teaching/teachingPlanService/getSpeicalListByTwo?gradeID=&educationLevelID= HTTP/1.1,200,12061 127.0.0.1,-,-,[08/May/2014:14:27:47 +0800],GET /jygl/jaxrs/enroll/studyCenterService/allStudyCentersByUtilObject HTTP/1.1,200,6006 0:0:0:0:0:0:0:1,-,-,[08/May/2014:14:27:48 +0800],GET /jyglFront/teaching/openReplaceChooseCourse HTTP/1.1,200,26455 127.0.0.1,-,-,[08/May/2014:14:27:49 +0800],GET /jygl/jaxrs/teachingManage/ClassBatchPlanService/getCurClassBatchPlanVOList?
newClassBatchName=&gradeName=&term=-1 HTTP/1.1,204,- 127.0.0.1,-,-,[08/May/2014:14:27:49 +0800],GET /jygl/jaxrs/teachingManage/ClassBatchPlanService/getCurClassBatchPlanVOList?newClassBatchName=&gradeName=&term=-1 HTTP/1.1,204,- 0:0:0:0:0:0:0:1,-,-,[08/May/2014:14:27:49 +0800],GET /jyglFront/teaching/openChooseCourse HTTP/1.1,200,1611 127.0.0.1,-,-,[08/May/2014:14:27:51 +0800],GET /jygl/jaxrs/enroll/gradeInfoService/currentGradeInfo HTTP/1.1,200,473 127.0.0.1,-,-,[08/May/2014:14:27:51 +0800],GET /jygl/jaxrs/enroll/educationLevelService/allEducationLevels HTTP/1.1,200,227 127.0.0.1,-,-,[08/May/2014:14:27:51 +0800],GET /jygl/jaxrs/enroll/gradeInfoService/allGradeInfos HTTP/1.1,200,3785 127.0.0.1,-,-,[08/May/2014:14:27:51 +0800],GET /jygl/jaxrs/teaching/teachingPlanService/hasTeachingPlanInGrade?
gradeId=4af2a042437c2c0801437ed1cdea0017 HTTP/1.1,200,20 127.0.0.1,-,-,[08/May/2014:14:27:51 +0800],GET /jygl/jaxrs/teaching/teachingPlanService/hasTeachingPlanInGrade?gradeId=4af2a0423f41d66d013f5a1f766c00ce HTTP/1.1,200,20 127.0.0.1,-,-,[08/May/2014:14:27:51 +0800],GET /jygl/jaxrs/teaching/teachingPlanService/teachingPlanListByEducationLevelAndGradeId?
grade=4af2a042437c2c0801437ed1cdea0017&educationLevel= HTTP/1.1,200,4849 0:0:0:0:0:0:0:1,-,-,[08/May/2014:14:27:52 +0800],GET /jyglFront/teaching/teachingPlanList HTTP/1.1,200,22794 0:0:0:0:0:0:0:1,-,-,[08/May/2014:14:27:52 +0800],GET /jyglFront/js/jquery.form.js HTTP/1.1,200,30330 127.0.0.1,-,-,[08/May/2014:14:28:02 +0800],GET /jygl/jaxrs/exam/examArrangeService/getExamBatchIdByLatest HTTP/1.1,200,43 127.0.0.1,-,-,[08/May/2014:14:28:02 +0800],GET /jygl/jaxrs/exam/examArrangeService/getExamBatchNameByEBId/4af2a0424323412e014327739b1702bd HTTP/1.1,200,16 127.0.0.1,-,-,[08/May/2014:14:28:02 +0800],GET /jygl/jaxrs/exam/examSubscribeService/getUtilObjectThirExamBatchsByEBNN/201403 HTTP/1.1,200,653 0:0:0:0:0:0:0:1,-,-,[08/May/2014:14:28:02 +0800],GET /jyglFront/exam_initgroupsubscribestatistic HTTP/1.1,200,13551 127.0.0.1,-,-,[08/May/2014:14:28:19 +0800],POST /jygl/jaxrs/right/addUserLog HTTP/1.1,200,- 127.0.0.1,-,-,[08/May/2014:14:31:42 +0800],GET /jygl/jaxrs/exam/examSubscribeService/groupSubscribe/201403/0/0/201309/1 HTTP/1.1,200,-
2. 要解决的问题：统计资源（URL）被訪问的次数。
3. 编程实现
想法：解析Tomcat日志，map的工作是将每一行日志中的URL截取作为key值，value为1表示1次，reduce的工作是将同样key值的行合并。value为总次数。
代码例如以下：
package org.ly.ccnu;
import java.io.IOException;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;
public class SecondTest extends Configured implements Tool{
enum Counter{
LINESKIP,
}
public static class Map extends Mapper<LongWritable,Text,Text,IntWritable>{
private static final IntWritable one = new IntWritable(1);
public void map(LongWritable key,Text value,Context context) throws IOException, InterruptedException{
String line = value.toString();
try{
String[] lineSplit = line.split(",");
String requestUrl = lineSplit[4];
requestUrl = requestUrl.substring(requestUrl.indexOf(‘ ‘)+1, requestUrl.lastIndexOf(‘ ‘));
Text out = new Text(requestUrl);
context.write(out,one);
}catch(java.lang.ArrayIndexOutOfBoundsException e){
context.getCounter(Counter.LINESKIP).increment(1);
}
}
}
public static class Reduce extends Reducer<Text,IntWritable,Text,IntWritable>{
public void reduce(Text key, Iterable<IntWritable> values,Context context)throws IOException{
int count = 0;
for(IntWritable v : values){
count = count + 1;
}
try {
context.write(key, new IntWritable(count));
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
@Override
public int run(String[] args) throws Exception {
Configuration conf = getConf();
Job job = new Job(conf, "logAnalysis");
job.setJarByClass(SecondTest.class);
FileInputFormat.addInputPath(job, new Path(args[0]));
FileOutputFormat.setOutputPath(job, new Path(args[1]));
job.setMapperClass(Map.class);
job.setReducerClass(Reduce.class);
job.setOutputFormatClass(TextOutputFormat.class);
//keep the same format with the output of Map and Reduce
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(IntWritable.class);
job.waitForCompletion(true);
return job.isSuccessful()?0:1;
}
public static void main(String[] args)throws Exception{
int res = ToolRunner.run(new Configuration(), new SecondTest(),args);
System.exit(res);
}
}
4. 处理结果
/ 2 /jygl/jaxrs/article/getArticleList/10-1 3 /jygl/jaxrs/article/getTotalArticleRecords 3 /jygl/jaxrs/enroll/educationLevelService/allEducationLevels 5 /jygl/jaxrs/enroll/gradeInfoService/allGradeInfos 2 /jygl/jaxrs/enroll/gradeInfoService/currentGradeInfo 1 /jygl/jaxrs/enroll/studyCenterService/allStudyCentersByUtilObject 1 /jygl/jaxrs/exam/examArrangeService/getExamBatchIdByLatest 2 /jygl/jaxrs/exam/examArrangeService/getExamBatchNameByEBId/4af2a0424323412e014327739b1702bd 2 /jygl/jaxrs/exam/examParameterService/getAllGradeInfo 3 /jygl/jaxrs/exam/examParameterService/getAllStudyCenters 3 /jygl/jaxrs/exam/examSubscribeService/getUtilObjectThirExamBatchsByEBNN/201403 2 /jygl/jaxrs/exam/examSubscribeService/groupSubscribe/201403/0/0/201309/1 1 /jygl/jaxrs/graduate/graduateBatchService/getAllGraduateBatch 1 /jygl/jaxrs/graduate/graduateBatchService/getGraduateBatchByConditions?graduateBatchName=&pageSize=10&pageNo=1 1 /jygl/jaxrs/graduate/graduateBatchService/getTotalGraduateBatchByCondition?graduateBatchName= 1 /jygl/jaxrs/nationInfo/getAllNationInPage?pageSize=10&pageNo=1 1 /jygl/jaxrs/nationInfo/getTotalNations 1 /jygl/jaxrs/right/addUserLog 1 /jygl/jaxrs/right/getUserByLoginName/admin 3 /jygl/jaxrs/right/isValidUserByType/1-admin-superadmin 3 /jygl/jaxrs/teaching/teachingPlanService/getSpeicalListByTwo?gradeID=&educationLevelID= 1 /jygl/jaxrs/teaching/teachingPlanService/hasTeachingPlanInGrade?
gradeId=4af2a0423f41d66d013f5a1f766c00ce 1 /jygl/jaxrs/teaching/teachingPlanService/hasTeachingPlanInGrade?
gradeId=4af2a042437c2c0801437ed1cdea0017 1 /jygl/jaxrs/teaching/teachingPlanService/teachingPlanListByEducationLevelAndGradeId?grade=4af2a042437c2c0801437ed1cdea0017&educationLevel= 1 /jygl/jaxrs/teachingManage/ClassBatchPlanService/getCurClassBatchPlanVOList?newClassBatchName=&gradeName=&term=-1 2 /jygl/jaxrs/teachingManage/ClassBatchPlanService/getCurClassPlanVO 2 /jygl/jaxrs/teachingManage/ClassBatchPlanService/getCurrentClassPlanVO 2 /jyglFront/baseInfo_articleList?flag=1 3 /jyglFront/baseInfo_nationInfoList 1 /jyglFront/common/css/_images/botton2.gif 1 /jyglFront/common/css/basic.css 1 /jyglFront/common/css/menuStyle2.css 1 /jyglFront/exam_initgroupsubscribestatistic 2 /jyglFront/exam_initsubstudentsubscribe 1 /jyglFront/graduate_initGraduateBatch 1 /jyglFront/graduate_initGraduateInfo 1 /jyglFront/graduate_initGraduateQulifyCheck 1 /jyglFront/graduate_initLeaveSchoolInfo 1 /jyglFront/js/jquery.form.js 1 /jyglFront/mainView/navigate/images/allmenu.gif 3 /jyglFront/mainView/navigate/images/leftmenu_bg.gif 3 /jyglFront/mainView/navigate/images/logo.png 3 /jyglFront/mainView/navigate/images/toggle_menu.gif 3 /jyglFront/mainView/navigate/js/frame.js 3 /jyglFront/mainView/navigate/js/jquery.js 3 /jyglFront/mainView/navigate/js/tree.js 3 /jyglFront/mainView/navigate/menuList.jsp 3 /jyglFront/mainView/navigate/style/images/header_bg.jpg 3 /jyglFront/mainView/navigate/style/style.css 3 /jyglFront/mainView/studentView/style/images/nav_10.png 3 /jyglFront/right_login2home?
loginName=admin&password=superadmin&type=1 3 /jyglFront/supervisor/intoInitAssignmentDetail 1 /jyglFront/teaching/openChooseCourse 1 /jyglFront/teaching/openReplaceChooseCourse 1 /jyglFront/teaching/teachingPlanList 1
以上是关于Hadoop学习：Map/Reduce初探与小Demo实现的主要内容，如果未能解决你的问题，请参考以下文章
第九篇：Map/Reduce 工作机制分析 - 作业的执行流程