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:执行会产生 NullPointerException
in方法 SnappyCodec.createCompressor
.
注意,我没有得到典型的 java.lang.UnsatisfiedLinkError
这可能是因为没有设置ld\u library\u path和java\u library\u path环境变量。snappy与cdh一起正确安装,通过运行 hadoop checknative
当我做手术的时候,快速减压很管用 hdfs dfs -text
在一个快速的文件上。
$ 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?
1条答案
按热度按时间gorkyyrv1#
好吧,问题是
CompressionCodec
需要适当的配置,如本回答中所指出的。配置snappy压缩机的简单方法如下:
生成的jar可以与原始问题中使用的命令行一起运行。