1. 今天想做一个hdfs的java工具类，但是在连接hdfs的时候，报如下错误：

Exception in thread "main" org.apache.hadoop.ipc.RemoteException: Server IPC version 9 cannot communicate with client version 4

at org.apache.hadoop.ipc.Client.call(Client.java:1113)

at org.apache.hadoop.ipc.RPC$Invoker.invoke(RPC.java:229)

at com.sun.proxy.$Proxy1.getProtocolVersion(Unknown Source)

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.io.retry.RetryInvocationHandler.invokeMethod(RetryInvocationHandler.java:85)

at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke(RetryInvocationHandler.java:62)

at com.sun.proxy.$Proxy1.getProtocolVersion(Unknown Source)

at org.apache.hadoop.ipc.RPC.checkVersion(RPC.java:422)

at org.apache.hadoop.hdfs.DFSClient.createNamenode(DFSClient.java:183)

at org.apache.hadoop.hdfs.DFSClient.<init>(DFSClient.java:281)

at org.apache.hadoop.hdfs.DFSClient.<init>(DFSClient.java:245)

at org.apache.hadoop.hdfs.DistributedFileSystem.initialize(DistributedFileSystem.java:100)

at org.apache.hadoop.fs.FileSystem.createFileSystem(FileSystem.java:1446)

at org.apache.hadoop.fs.FileSystem.access$200(FileSystem.java:67)

at org.apache.hadoop.fs.FileSystem$Cache.get(FileSystem.java:1464)

at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:263)

at com.dk.hdfs.HdfsDAO.ls(HdfsDAO.java:53)

at com.dk.hdfs.HdfsDAO.main(HdfsDAO.java:24)

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 com.intellij.rt.execution.application.AppMain.main(AppMain.java:140)

找了半天，也没有找到怎么回事，我的hadoop 2.6.0. mav 的配置库都是依赖2.6.0的。可是就是出错

在statckoverflow上也没有给出答案：

最后一个个jar包测验。发现at org.apache.hadoop.ipc.Client.call(Client.java:1113)  这个地方有2个jar包可选

猜测引用jar包有问题.我发现

hadoop –core这个是唯一不是2.6.0.的估计就是它的问题。然后我就在pom文件中加入如下代码：

<dependency>

            <groupId>org.apache.hadoop</groupId>

            <artifactId>hadoop-client</artifactId>

            <version>2.6.0</version>

        </dependency>

        <dependency>

            <groupId>org.apache.hadoop</groupId>

            <artifactId>hadoop-core</artifactId>

            <version>1.2.0</version>

        </dependency>

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问题解决。

2.思考

具体不知道什么原因，如果阁下直到原因，请发邮件通知。十分感谢。chaoren399@126.com .

.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }