这篇文章将为大家详细讲解有关如何将nutch2.3的bin/crawl脚本改写为java类，小编觉得挺实用的，因此分享给大家做个参考，希望大家阅读完这篇文章后可以有所收获。
nutch2.8以后，以前的主控代码org.apache.nutch.crawl.Crawl类没了，只剩下对应的控制脚本bin/crawl，感觉在IDEA里面调试不方便，所以我了解了下shell脚本,根据nutch3.3的bin/crawl和bin/nutch脚本，把bin/crawl翻译成了java的Crawl类以便在IDEA里面调试
我参考了nutch2.7的crawl类，nutch3.3的bin/crawl和bin/nutch,尽量按照shell脚本的原组织结构和逻辑进行翻译，有些地方不能直接使用的，就稍作了修改。
主要的业务逻辑在public int run(String[] args)方法里
程序主入口是main，调用ToolRunner.run(NutchConfiguration.create(), new Crawl(), args);执行上面的run方法
public void binNutch5j(String jobName,String commandLine,String options)相当于bin/crawl脚本里函数__bin_nutch的功能
public int runJob(String jobName,String commandLine,String options)相当于脚本bin/nutch的功能，这里没有像脚本中那样用if-else，也没有使用switch-case,而是采用反射创建相应的job
public void preConfig(Configuration conf,String options)用于根据带-D参数 commonOptions等指令设置每个Job的配置项
CLASS_MAP是静态(static)属性，一个记录JobName和对应的类名的映射关系的哈希表(HashMap)
我之前是在每个job是按照脚本使用batchId参数的，遇到了下面这个问题:
Gora MongoDb Exception, can't serialize Utf8
貌似是序列化问题，好像gora-0.6版本解决了这个BUG,但我的nutch代码是gora-0.5的，不会升级，所以就简单的把-batchId参数去掉，使用-all参数就行了，这点在代码里可以看到。
关于升级到gora-0.6,有空再研究好了。
通过这个脚本的改写，我了解了脚本的基本使用，同时对之前看的java反射等知识进行了实践，并对nutch的完整爬取流程、主要控制逻辑有了深刻的印象。主要是前面那个gora的BUG卡了我几天，我还以为自己翻译的有问题，看来调试能力还需要加强。
这段代码是翻译nutch3.3的bin/crawl和bin/nutch脚本
Crawl类加到在org.apache.nutch.crawl包下，源码如下：
package org.apache.nutch.crawl;
/**
* Created by brianway on 2016/1/19.
* @author brianway
* @site brianway.github.io
* org.apache.nutch.crawl.Crawl;
*/
import org.apache.commons.lang.StringUtils;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;
import org.apache.nutch.fetcher.FetcherJob;
import org.apache.nutch.util.NutchConfiguration;
import org.apache.nutch.util.NutchTool;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.lang.reflect.Constructor;
import java.util.HashMap;
import java.util.Map;
import java.util.Random;
// Commons Logging imports
//import org.apache.hadoop.fs.*;
//import org.apache.hadoop.mapred.*;
//import org.apache.nutch.util.HadoopFSUtil;
//import org.apache.nutch.util.NutchJob;
//import org.apache.nutch.crawl.InjectorJob;
//import org.apache.nutch.crawl.GeneratorJob;
//import org.apache.nutch.fetcher.FetcherJob;
//import org.apache.nutch.parse.ParserJob;
//import org.apache.nutch.crawl.DbUpdaterJob;
//import org.apache.nutch.indexer.IndexingJob;
//import org.apache.nutch.indexer.solr.SolrDeleteDuplicates;
public class Crawl extends NutchTool implements Tool{
public static final Logger LOG = LoggerFactory.getLogger(Crawl.class);
/* Perform complete crawling and indexing (to Solr) given a set of root urls and the -solr
parameter respectively. More information and Usage parameters can be found below. */
public static void main(String args[]) throws Exception {
int res = ToolRunner.run(NutchConfiguration.create(), new Crawl(), args);
System.exit(res);
}
//为了编译过
@Override
public Map<String, Object> run(Map<String, Object> args) throws Exception {
return null;
}
@Override
public int run(String[] args) throws Exception {
if (args.length < 1) {
System.out.println
("Usage: Crawl -urls <urlDir> -crawlId <crawlID> -solr <solrURL> [-threads n] [-depth i] [-topN N]");
// ("Usage: crawl <seedDir> <crawlID> [<solrUrl>] <numberOfRounds>");
return -1;
}
// ------------check args---------
/*
//！！由脚本直译的，感觉少参数,所以注释掉，换下面的方式
String seedDir = args[1];
String crawlID = args[2];
String solrUrl=null;
int limit=1;
if(args.length-1 == 3){
limit = Integer.parseInt(args[3]);
}else if(args.length-1 == 4){
solrUrl = args[3];
limit = Integer.parseInt(args[4]);
}else{
System.out.println("Unknown # of arguments "+(args.length-1));
System.out.println
("Usage: crawl <seedDir> <crawlID> [<solrUrl>] <numberOfRounds>");
return -1;
//"Usage: Crawl <urlDir> -solr <solrURL> [-dir d] [-threads n] [-depth i] [-topN N]"
//"Usage: crawl <seedDir> <crawlID> [<solrUrl>] <numberOfRounds>";
}
*/
String seedDir = null;
String crawlID = null;
String solrUrl=null;
int limit = 0;
long topN = Long.MAX_VALUE;
int threads = getConf().getInt("fetcher.threads.fetch", 10);
//parameter-format in crawl class is
// like nutch2.7 "Usage: Crawl <urlDir> -solr <solrURL> [-dir d] [-threads n] [-depth i] [-topN N]"
//not like nutch3.3 "Usage: crawl <seedDir> <crawlID> [<solrUrl>] <numberOfRounds>";
for (int i = 0; i < args.length; i++) {
if ("-urls".equals(args[i])) {
seedDir = args[++i];
} else if ("-crawlId".equals(args[i])) {
crawlID = args[++i];
} else if ("-threads".equals(args[i])) {
threads = Integer.parseInt(args[++i]);
} else if ("-depth".equals(args[i])) {
limit = Integer.parseInt(args[++i]);
} else if ("-topN".equals(args[i])) {
topN = Long.parseLong(args[++i]);
} else if ("-solr".equals(args[i])) {
solrUrl = args[++i];
i++;
} else {
System.err.println("Unrecognized arg " + args[i]);
return -1;
}
}
if(StringUtils.isEmpty(seedDir)){
System.out.println("Missing seedDir : crawl <seedDir> <crawlID> [<solrURL>] <numberOfRounds>");
return -1;
}
if(StringUtils.isEmpty(crawlID)){
System.out.println("Missing crawlID : crawl <seedDir> <crawlID> [<solrURL>] <numberOfRounds>");
return -1;
}
if(StringUtils.isEmpty(solrUrl)){
System.out.println("No SOLRURL specified. Skipping indexing.");
}
if(limit == 0) {
System.out.println("Missing numberOfRounds : crawl <seedDir> <crawlID> [<solrURL>] <numberOfRounds>");
return -1;
}
/**
* MODIFY THE PARAMETERS BELOW TO YOUR NEEDS
*/
//set the number of slaves nodes
int numSlaves = 1;
//and the total number of available tasks
// sets Hadoop parameter "mapred.reduce.tasks"
int numTasks = numSlaves<<1;
// number of urls to fetch in one iteration
// 250K per task?
//!!这里使用topN
long sizeFetchlist = topN;//numSlaves *5;
// time limit for feching
int timeLimitFetch=180;
//Adds <days> to the current time to facilitate
//crawling urls already fetched sooner then
//db.default.fetch.interval.
int addDays=0;
// note that some of the options listed here could be set in the
// corresponding hadoop site xml param file
String commonOptions="-D mapred.reduce.tasks="+numTasks+" -D mapred.child.java.opts=-Xmx1000m -D mapred.reduce.tasks.speculative.execution=false -D mapred.map.tasks.speculative.execution=false -D mapred.compress.map.output=true ";
preConfig(getConf(),commonOptions);
//initial injection
System.out.println("Injecting seed URLs");
String inject_args = seedDir+" -crawlId "+crawlID;
binNutch5j("inject",inject_args,commonOptions);
for(int a=1;a<=limit;a++){
//-----------generating-------------
System.out.println("Generating batchId");
String batchId = System.currentTimeMillis()+"-"+new Random().nextInt(32767);
System.out.println("Generating a new fetchlist");
String generate_args = "-topN "+ sizeFetchlist +" -noNorm -noFilter -adddays "+addDays+" -crawlId "+crawlID+" -batchId "+batchId;
//String generate_options = commonOptions;
int res = runJob("generate",generate_args,commonOptions);
System.out.println("binNutch5j generate "+generate_args);
if(res==0){
}else if(res == 1){
System.out.println("Generate returned 1 (no new segments created)");
System.out.println("Escaping loop: no more URLs to fetch now");
break;
}else{
System.out.println("Error running:");
System.out.println("binNutch5j generate "+generate_args);
System.out.println("Failed with exit value "+res);
return res;
}
//--------fetching-----------
System.out.println("Fetching : ");
//String fetch_args = batchId+" -crawlId "+crawlID+" -threads "+threads;
String fetch_args = "-all"+" -crawlId "+crawlID+" -threads "+threads;
String fetch_options = commonOptions+" -D fetcher.timelimit.mins="+timeLimitFetch;
//10 threads
binNutch5j("fetch",fetch_args,fetch_options);
//----------parsing--------------
// parsing the batch
//
if(!getConf().getBoolean(FetcherJob.PARSE_KEY, false)){
System.out.println("Parsing : ");
//enable the skipping of records for the parsing so that a dodgy document
// so that it does not fail the full task
//String parse_args = batchId+" -crawlId "+crawlID;
String parse_args = "-all"+" -crawlId "+crawlID;
String skipRecordsOptions=" -D mapred.skip.attempts.to.start.skipping=2 -D mapred.skip.map.max.skip.records=1";
binNutch5j("parse",parse_args,commonOptions+skipRecordsOptions);
}
//----------updatedb------------
// updatedb with this batch
System.out.println("CrawlDB update for "+crawlID);
// String updatedb_args = batchId+" -crawlId "+crawlID;
String updatedb_args = "-all"+" -crawlId "+crawlID;
binNutch5j("updatedb",updatedb_args,commonOptions);
if(!StringUtils.isEmpty(solrUrl)){
System.out.println("Indexing "+ crawlID+ " on SOLR index -> " +solrUrl);
String index_args = batchId+" -all -crawlId "+crawlID;
String index_options = commonOptions+" -D solr.server.url="+solrUrl;
binNutch5j("index",index_args,index_options);
System.out.println("SOLR dedup -> "+solrUrl);
binNutch5j("solrdedup",solrUrl,commonOptions);
}else{
System.out.println("Skipping indexing tasks: no SOLR url provided.");
}
}
return 0;
}
/**
* 相当于bin/crawl的函数__bin_nutch的功能
* @param jobName job
* @param commandLine
*/
public void binNutch5j(String jobName,String commandLine,String options)throws Exception{
int res = runJob(jobName,commandLine,options);
if(res!=0) {
System.out.println("Error running:");
System.out.println(jobName + " " + commandLine);
System.out.println("Error running:");
System.exit(res);
}
}
/**
* 相当于脚本bin/nutch的功能
*
* @param jobName
* @param commandLine
* @return
*/
public int runJob(String jobName,String commandLine,String options)throws Exception{
//这里为了方便，没有像脚本那样用多个if-elif语句，也没有用switch-case,直接用了反射来完成
Configuration conf = NutchConfiguration.create();
if(!StringUtils.isEmpty(options)){
preConfig(conf,options);
}
String[] args = commandLine.split("\\s+");
String className = CLASS_MAP.get(jobName);
Class<?> jobClass = Class.forName(className);
Constructor c = jobClass.getConstructor();
Tool job =(Tool) c.newInstance();
System.out.println("---------------runJob: "+jobClass.getName()+"----------------------");
return ToolRunner.run(conf, job, args);
}
/**
* 设置每个job的配置
* @param conf
* @param options
*/
public void preConfig(Configuration conf,String options){
String [] equations = options.split("\\s*-D\\s+");
System.out.println("options:"+options);
// i start from 1 not 0, skip the empty string ""
for (int i=1;i<equations.length;i++) {
String equation = equations[i];
String [] pair = equation.split("=");
//System.out.println(pair[0]+":"+pair[1]);
conf.set(pair[0],pair[1]);
//System.out.println("conf print: "+pair[0]+" "+conf.get(pair[0]));
}
}
/**
* the map to store the mapping relations jobName->ClassName
*/
public static HashMap<String,String> CLASS_MAP = new HashMap<String,String>();
/**
* init the CLASS_MAP，refer to "bin/nutch"
*/
static {
CLASS_MAP.put("inject","org.apache.nutch.crawl.InjectorJob");
CLASS_MAP.put("generate","org.apache.nutch.crawl.GeneratorJob");
CLASS_MAP.put("fetch","org.apache.nutch.fetcher.FetcherJob");
CLASS_MAP.put("parse","org.apache.nutch.parse.ParserJob");
CLASS_MAP.put("updatedb","org.apache.nutch.crawl.DbUpdaterJob");
CLASS_MAP.put("readdb","org.apache.nutch.crawl.WebTableReader");
CLASS_MAP.put("elasticindex","org.apache.nutch.indexer.elastic.ElasticIndexerJob");
CLASS_MAP.put("index","org.apache.nutch.indexer.IndexingJob");
CLASS_MAP.put("solrdedup","org.apache.nutch.indexer.solr.SolrDeleteDuplicates");
}
}关于“如何将nutch2.3的bin/crawl脚本改写为java类”这篇文章就分享到这里了，希望以上内容可以对大家有一定的帮助，使各位可以学到更多知识，如果觉得文章不错，请把它分享出去让更多的人看到。
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