mac 上運行cassandra出現的java.net.MalformedURLException: Local host name unknown: java.net.UnknownHostException: : : unknown error錯誤解決方法
運行： ./bin/cassandra
得到輸出結果：
objc[1881]: Class JavaLaunchHelper is implemented in both /Library/Java/JavaVirtualMachines/jdk1.8.0_25.jdk/Contents/Home/bin/java and /Library/Java/JavaVirtualMachines/jdk1.8.0_25.jdk/Contents/Home/jre/lib/libinstrument.dylib. One of the two will be used. Which one is undefined.
CompilerOracle: inline org/apache/cassandra/db/AbstractNativeCell.compareTo (Lorg/apache/cassandra/db/composites/Composite;)I
CompilerOracle: inline org/apache/cassandra/db/composites/AbstractSimpleCellNameType.compareUnsigned (Lorg/apache/cassandra/db/composites/Composite;Lorg/apache/cassandra/db/composites/Composite;)I
CompilerOracle: inline org/apache/cassandra/utils/ByteBufferUtil.compare (Ljava/nio/ByteBuffer;[B)I
CompilerOracle: inline org/apache/cassandra/utils/ByteBufferUtil.compare ([BLjava/nio/ByteBuffer;)I
CompilerOracle: inline org/apache/cassandra/utils/ByteBufferUtil.compareUnsigned (Ljava/nio/ByteBuffer;Ljava/nio/ByteBuffer;)I
CompilerOracle: inline org/apache/cassandra/utils/FastByteOperations$UnsafeOperations.compareTo (Ljava/lang/Object;JILjava/lang/Object;JI)I
CompilerOracle: inline org/apache/cassandra/utils/FastByteOperations$UnsafeOperations.compareTo (Ljava/lang/Object;JILjava/nio/ByteBuffer;)I
CompilerOracle: inline org/apache/cassandra/utils/FastByteOperations$UnsafeOperations.compareTo (Ljava/nio/ByteBuffer;Ljava/nio/ByteBuffer;)I
CompilerOracle: inline org/apache/cassandra/db/composites/AbstractSimpleCellNameType.compareUnsigned (Lorg/apache/cassandra/db/composites/Composite;Lorg/apache/cassandra/db/composites/Composite;)I
CompilerOracle: inline org/apache/cassandra/utils/ByteBufferUtil.compare (Ljava/nio/ByteBuffer;[B)I
CompilerOracle: inline org/apache/cassandra/utils/ByteBufferUtil.compare ([BLjava/nio/ByteBuffer;)I
CompilerOracle: inline org/apache/cassandra/utils/ByteBufferUtil.compareUnsigned (Ljava/nio/ByteBuffer;Ljava/nio/ByteBuffer;)I
CompilerOracle: inline org/apache/cassandra/utils/FastByteOperations$UnsafeOperations.compareTo (Ljava/lang/Object;JILjava/lang/Object;JI)I
CompilerOracle: inline org/apache/cassandra/utils/FastByteOperations$UnsafeOperations.compareTo (Ljava/lang/Object;JILjava/nio/ByteBuffer;)I
CompilerOracle: inline org/apache/cassandra/utils/FastByteOperations$UnsafeOperations.compareTo (Ljava/nio/ByteBuffer;Ljava/nio/ByteBuffer;)I
錯誤: 代理拋出異常錯誤: java.net.MalformedURLException: Local host name unknown: java.net.UnknownHostException: : : unknown error
初期總以為第一個錯誤導致的問題：
objc[1881]: Class JavaLaunchHelper is implemented in both /Library/Java/JavaVirtualMachines/jdk1.8.0_25.jdk/Contents/Home/bin/java and /Library/Java/JavaVirtualMachines/jdk1.8.0_25.jdk/Contents/Home/jre/lib/libinstrument.dylib. One of the two will be used. Which one is undefined.
然后搜尋stackoverflow， 說是mac上java7的一個漏洞，然后就更換了java8，統一了jre 和 jdk的版本到上面的1.8.0 update 25.
結果還是一樣。
然后，我只要把原因轉移到最后的MalformedURLException上，自己查看了hosts， 發現完全正常，實在無法子，今天又到另外的一台mac上安裝了相同版本的java，啟動cassandra，完全正常，唯獨就是我自己的mac 不行。
無意中發現了一個方法, 參見附錄一中的URL鏈接：
使用 scutils —get HostName 命令查看當前的hostname ， 盡然是空。
然后使用 scutils —set HostName localhost ， 之后重新啟動cassandra， 完全正常了。
參考：