hadoop 2.7.4：java.lang.UnsupportedClassVersionError: org/apache/hadoop/mapreduce/lib/output/Sequence

STARTUP_MSG:   java = 1.7.0_79************************************************************/17/10/02 15:32:29 INFO namenode.NameNode: registered UNIX signal handlers for [TERM, HUP, INT]17/10/02 15:32:29 INFO namenode.NameNode: createNameNode [-format]17/10/02 15:32:30 ERROR namenode.NameNode: Failed to start namenode.java.lang.UnsupportedClassVersionError: org/apache/hadoop/mapreduce/lib/output/SequenceFileAsBinaryOutputFormat : Unsupported major.minor version 52.0at java.lang.ClassLoader.defineClass1(Native Method)at java.lang.ClassLoader.defineClass(ClassLoader.java:800)at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)at java.net.URLClassLoader.access$100(URLClassLoader.java:71)at java.net.URLClassLoader$1.run(URLClassLoader.java:361)at java.net.URLClassLoader$1.run(URLClassLoader.java:355)at java.security.AccessController.doPrivileged(Native Method)at java.net.URLClassLoader.findClass(URLClassLoader.java:354)at java.lang.ClassLoader.loadClass(ClassLoader.java:425)at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)at java.lang.ClassLoader.loadClass(ClassLoader.java:358)at org.apache.hadoop.mapreduce.util.ConfigUtil.addDeprecatedKeys(ConfigUtil.java:54)at org.apache.hadoop.mapreduce.util.ConfigUtil.loadResources(ConfigUtil.java:42)at org.apache.hadoop.mapred.JobConf.<clinit>(JobConf.java:119)at java.lang.Class.forName0(Native Method)at java.lang.Class.forName(Class.java:274)at org.apache.hadoop.conf.Configuration.getClassByNameOrNull(Configuration.java:2134)at org.apache.hadoop.util.ReflectionUtils.setJobConf(ReflectionUtils.java:95)at org.apache.hadoop.util.ReflectionUtils.setConf(ReflectionUtils.java:78)at org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:136)at org.apache.hadoop.security.Groups.<init>(Groups.java:79)at org.apache.hadoop.security.Groups.<init>(Groups.java:74)at org.apache.hadoop.security.Groups.getUserToGroupsMappingService(Groups.java:303)at org.apache.hadoop.security.UserGroupInformation.initialize(UserGroupInformation.java:285)at org.apache.hadoop.security.UserGroupInformation.ensureInitialized(UserGroupInformation.java:262)at org.apache.hadoop.security.UserGroupInformation.isAuthenticationMethodEnabled(UserGroupInformation.java:339)at org.apache.hadoop.security.UserGroupInformation.isSecurityEnabled(UserGroupInformation.java:333)at org.apache.hadoop.hdfs.server.namenode.NameNode.format(NameNode.java:968)at org.apache.hadoop.hdfs.server.namenode.NameNode.createNameNode(NameNode.java:1441)at org.apache.hadoop.hdfs.server.namenode.NameNode.main(NameNode.java:1566)17/10/02 15:32:30 INFO util.ExitUtil: Exiting with status 117/10/02 15:32:30 INFO namenode.NameNode: SHUTDOWN_MSG: /************************************************************

hadoop 2.7.4  命令：hdfs namenode -format   //格式化文件系统

报错：java.lang.UnsupportedClassVersionError: org/apache/hadoop/mapreduce/lib/output/SequenceFileAsBinaryOutputFormat : Unsupported major.minor version 52.0

很明显，高版本的class文件，用在了低版本的jvm上，jdk7 的 version 是51，所以需要换成jdk8。

但根据官网的说法 jdk1.7 应该是支持 2.x.y 的。

有点坑。