java调用API操作HDFS

java调用API操作HDFS

本文介绍Java调用API从hdfs读取数据

package mongodb;import java.io.BufferedReader;import java.io.IOException;import java.io.InputStreamReader;import java.net.URI;import java.util.Arrays;import org.apache.commons.lang.StringUtils;import org.apache.hadoop.conf.Configuration;import org.apache.hadoop.fs.FSDataInputStream;import org.apache.hadoop.fs.FileStatus;import org.apache.hadoop.fs.FileSystem;import org.apache.hadoop.fs.Path;import org.apache.hadoop.io.compress.CompressionCodec;import org.apache.hadoop.io.compress.CompressionCodecFactory;import org.apache.hadoop.io.compress.CompressionInputStream;import org.apache.hadoop.util.ReflectionUtils;class Item implements Comparable{String value;double weight;public Item(String v){value=v;weight = Double.parseDouble(value.split(":")[1]);}public int compareTo(Object o){          return this.weight == ((Item) o).weight ? 0 :             (this.weight  > ((Item) o).weight ? -1 : 1);    } }public class BatchUpdateSim {public static String parse(String str){//String str="9000320718001:1.0,2077635:1.0,2053809:1.0";String[] fields=str.split("\t");String[] valueArray= fields[1].split(",");Item[] items = new Item[valueArray.length];for(int i=0;i<items.length;i++){items[i]=new Item(valueArray[i]);}Arrays.sort(items);for(int i=0;i<valueArray.length;i++){valueArray[i] = "{"+items[i].value+"}";}String valueStr = StringUtils.join(valueArray,",");return  "{\"key\":"+fields[0]+",\"values\":["+valueStr+"]}";}public static void main(String[] args) throws IOException, ClassNotFoundException {// TODO Auto-generated method stubConfiguration  conf = new Configuration ();    conf.addResource("/usr/local/hadoop/conf/core-site.xml");  conf.addResource("/usr/local/hadoop/conf/hdfs-site.xml");   conf.addResource("/usr/local/hadoop/conf/mapred-site.xml");//String HDFS="hdfs://webdm-cluster";//String HDFS="hdfs://localhost:9000";    String HDFS=args[0];FileSystem hdfs = FileSystem.get(URI.create(HDFS),conf); String filePath=args[1];FSDataInputStream fin = hdfs.open(new Path(filePath));//CompressionCodecFactory factory = new CompressionCodecFactory(conf);  //CompressionCodec codec = factory.getCodec(new Path(filePath)); //根据hdfs文件的后缀类型自动识别//Class<?> codecClass = Class.forName("com.hadoop.compression.lzo.LzoCodec");//CompressionCodec codec = (CompressionCodec)ReflectionUtils.newInstance(codecClass, conf);        BufferedReader reader = null;String line;int count=0;RecsysDb db = RecsysDb.getInstance();String itemSimName=args[2];try {// if (codec == null)// {          reader = new BufferedReader(new InputStreamReader(fin)); // in = new BufferedReader(new InputStreamReader(fin, "UTF-8"));    // }        /* else  {      System.out.println("识别出压缩类型");        CompressionInputStream comInputStream = codec.createInputStream(fin);          reader = new BufferedReader(new InputStreamReader(comInputStream));    } */ while ((line = reader.readLine()) != null) {//if(count==0) System.out.println(line);String strJson=parse(line);db.updateItemSim(itemSimName, strJson);count++;if(count%1000==0)System.out.println("count:"+count);}} finally {if (reader != null) {reader.close();}System.out.println(count);}}}

下面是一个shell脚本，用Java命令执行上面的程序的话，需要加载各种Hadoop相关的jar包。

（PS：后来发现有种更好的方法，就是用Hadoop命令执行，因为用Hadoop命令执行，Hadoop自己会加载一些jar包，无需自己再手动加载）

hd_core="/usr/local/hadoop/hadoop-core-1.1.2.jar";s4j="/usr/local/hadoop/lib/slf4j-log4j12-1.6.1.jar";s4japi="/usr/local/hadoop/lib/slf4j-api-1.6.1.jar";log4j="/usr/local/hadoop/lib/log4j-1.2.17.jar";guva="/usr/local/hadoop/lib/guava-11.0.2.jar";clog="/usr/local/hadoop/lib/commons-logging-1.1.1.jar";cconf="/usr/local/hadoop/lib/commons-configuration-1.6.jar";cl="/usr/local/hadoop/lib/commons-lang-2.5.jar";ccli="/usr/local/hadoop/lib/commons-cli-1.2.jar";protobuf="/usr/local/hadoop/lib/protobuf-java-2.4.0a.jar";hdfs="/usr/local/hadoop/lib/hadoop-hdfs-1.1.2.jar";mongodb="/data/home/liulian/linger/jars/mongo-java-driver-2.12.4.jar";libs=($hd_core$s4j$s4japi$log4j$guva$clog$cconf$cl$ccli$protobuf$hdfs$mongodb)libstr=""for jarlib in ${libs[@]};do    libstr=${jarlib}":"${libstr}doneecho $libstr;java -Xbootclasspath/a:${libstr}  -jar ../jars/updateSim.jar hdfs://10.200.91.164:9000 tv_sim/result/000000_0 tvItemsimColl

本文链接：http://blog.csdn.net/lingerlanlan/article/details/42178675

本文作者：linger