Java 无法将SnappyCodec与hadoop jar:NullPointerException一起使用
我试图在一个简单的java程序中使用Hadoop的压缩库。但是,我无法使用Snappy编解码器:在方法Java 无法将SnappyCodec与hadoop jar:NullPointerException一起使用,java,hadoop,snappy,Java,Hadoop,Snappy,我试图在一个简单的java程序中使用Hadoop的压缩库。但是,我无法使用Snappy编解码器:在方法SnappyCodec.createCompressor中执行会产生NullPointerException 注意我没有得到典型的java.lang.UnsatifiedLinkError,这是由于没有设置LD\u LIBRARY\u PATH和java\u LIBRARY\u PATH环境变量而导致的。Snappy与CDH一起正确安装,通过运行hadoop checknative报告可用,当我
SnappyCodec.createCompressor
中执行会产生NullPointerException
注意我没有得到典型的java.lang.UnsatifiedLinkError
,这是由于没有设置LD\u LIBRARY\u PATH和java\u LIBRARY\u PATH环境变量而导致的。Snappy与CDH一起正确安装,通过运行hadoop checknative
报告可用,当我对Snappy文件执行hdfs dfs-text
时,Snappy解压工作
$ hadoop jar SnappyTool-0.0.1-SNAPSHOT.jar com.mycorp.SnappyCompressor
Exception in thread "main" java.lang.NullPointerException
at org.apache.hadoop.io.compress.SnappyCodec.createCompressor(SnappyCodec.java:145)
at org.apache.hadoop.io.compress.CodecPool.getCompressor(CodecPool.java:152)
at org.apache.hadoop.io.compress.CodecPool.getCompressor(CodecPool.java:165)
at com.mycorp.SnappyCompressor.main(SnappyCompressor.java:19)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.hadoop.util.RunJar.run(RunJar.java:221)
at org.apache.hadoop.util.RunJar.main(RunJar.java:136)
$
$ hadoop checknative | grep snappy 2>/dev/null
$ snappy: true /opt/cloudera/parcels/CDH-5.5.1-1.cdh5.5.1.p0.11/lib/hadoop/lib/native/libsnappy.so.1
$ ls /opt/cloudera/parcels/CDH-5.5.1-1.cdh5.5.1.p0.11/lib/hadoop/lib/native/
libhadoop.a libhadoop.so.1.0.0 libnativetask.a libsnappy.so
libhadooppipes.a libhadooputils.a libnativetask.so libsnappy.so.1
libhadoop.so libhdfs.a libnativetask.so.1.0.0
libsnappy.so.1.1.4
$ export LD_LIBRARY_PATH=/opt/cloudera/parcels/CDH-5.5.1-1.cdh5.5.1.p0.11/lib/hadoop/lib/native/
$ java -Djava.library.path=/opt/cloudera/parcels/CDH-5.5.1-1.cdh5.5.1.p0.11/lib/hadoop/lib/native/ -cp `hadoop classpath`:SnappyTool-0.0.1-SNAPSHOT.jar com.mycorp.SnappyCompressor
Exception in thread "main" java.lang.NullPointerException
at org.apache.hadoop.io.compress.SnappyCodec.createCompressor(SnappyCodec.java:145)
at org.apache.hadoop.io.compress.CodecPool.getCompressor(CodecPool.java:152)
at org.apache.hadoop.io.compress.CodecPool.getCompressor(CodecPool.java:165)
at com.mycorp.SnappyCompressor.main(SnappyCompressor.java:19)
Java代码如下所示,最后一行是罪魁祸首:
SnappyCodec.checkNativeCodeLoaded();
CompressionCodec codec = new SnappyCodec();
Compressor comp = CodecPool.getCompressor(codec);
我错过了什么?好吧,问题是,
压缩编解码器
需要正确的配置,如中所述
配置Snappy压缩器的简单方法如下:
Configuration conf = new Configuration();
CompressionCodecFactory ccf = new CompressionCodecFactory(conf);
CompressionCodec codec = ccf.getCodecByClassName(SnappyCodec.class.getName());
Compressor comp = codec.createCompressor();
生成的jar可以使用原始问题中使用的命令行运行