java操作之HDFS-创建-删除目录-读写文件-追加写文件

Hadoop文件操作之HDFS，创建。删除目录，读写文件，追加写文件

package hadoop.hadoop_demo;

import java.io.InputStream;
import java.io.OutputStream;
import java.net.URI;

import org.apache.commons.io.IOUtils;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;

/**
 * <dependency>
    <groupId>org.apache.hadoop</groupId>
    <artifactId>hadoop-common</artifactId>
    <version>2.7.2</version>
</dependency>
   
    <dependency>
    <groupId>org.apache.hadoop</groupId>
    <artifactId>hadoop-hdfs</artifactId>
    <version>2.7.2</version>
</dependency>
 *
 */
public class App {
    public static void main(String[] args) throws Exception {
        System.out.println("Hello World!");
        String hdfs = "hdfs://192.168.1.111:9000";

        // mkdir(hdfs,"gaojs");

        // touchFile(hdfs,"gjs/1.log");

         rmdir(hdfs, "zookeeper_server.pid");

        appendFile(hdfs, "gjs/1.log");

        // readFile(hdfs);
    }

    /**
     * 追加文件，新版本才支持
     * @param hdfs
     * @param fullNasme
     * @throws Exception
     */
    private static void appendFile(String hdfs, String fullNasme)
            throws Exception {
        FileSystem fileSystem = getFileSystem();

        OutputStream out = fileSystem.append(new Path(hdfs + "/" + fullNasme));
        out.write(("I am gaojs, who are you" + System.currentTimeMillis() + "\r\n")
                .getBytes("UTF-8"));
        out.flush();
        out.close();
    }

    /**
     * 取得FileSystem
     * @return
     * @throws Exception
     */
    public static final FileSystem getFileSystem() throws Exception {
        String hdfs = "hdfs://192.168.1.111:9000";
        Configuration conf = new Configuration();
        conf.set("dfs.client.block.write.replace-datanode-on-failure.policy","NEVER");
        conf.set("dfs.client.block.write.replace-datanode-on-failure.enable","true");
        FileSystem fileSystem = FileSystem.get(URI.create(hdfs), conf);
        System.out.println(fileSystem);
        return fileSystem;
    }

    /**
     * 读文件
     * @param hdfs
     * @throws Exception
     */
    private static void readFile(String hdfs) throws Exception {
        FileSystem fileSystem = getFileSystem();
        InputStream in = fileSystem.open(new Path(hdfs + "/"
                + "zookeeper_server.pid"));
        IOUtils.copy(in, System.out);
        fileSystem.close();
    }

    /**
     * 创建空文件
     * @param hdfs
     * @param fullNasme
     * @throws Exception
     */
    private static void touchFile(String hdfs, String fullNasme)
            throws Exception {
        FileSystem fileSystem = getFileSystem();
        boolean res = fileSystem
                .createNewFile(new Path(hdfs + "/" + fullNasme));
        if (res) {
            System.out.println("-------create File Success------" + fullNasme);
        } else {
            System.out.println("-------create File Fail------" + fullNasme);
        }
        fileSystem.close();
    }

    /**
     * 删除文件或者目录
     * @param hdfs
     * @param fullNasme
     * @throws Exception
     */
    private static void rmdir(String hdfs, String fullNasme) throws Exception {
        FileSystem fileSystem = getFileSystem();
        boolean res = fileSystem.delete(new Path(hdfs + "/" + fullNasme));
        if (res) {
            System.out.println("------rmdir Success------" + fullNasme);
        } else {
            System.out.println("------rmdir Fail------" + fullNasme);
        }
        fileSystem.close();
    }

    /**
     * 创建目录
     * @param hdfs
     * @param fullNasme
     * @throws Exception
     */
    private static void mkdir(String hdfs, String fullNasme) throws Exception {
        FileSystem fileSystem = getFileSystem();
        boolean res = fileSystem.mkdirs(new Path(hdfs + "/" + fullNasme));
        if (res) {
            System.out.println("-------mkdir Success------" + fullNasme);
        } else {
            System.out.println("-------mkdir Fail------" + fullNasme);
        }
    }

}

错误解决方案：

log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
DFS[DFSClient[clientName=DFSClient_NONMAPREDUCE_242718953_1, ugi=Administrator (auth:SIMPLE)]]
Exception in thread "main" java.io.IOException: Failed to replace a bad datanode on the existing pipeline due to no more good datanodes being available to try. (Nodes: current=[DatanodeInfoWithStorage[192.168.1.111:50010,DS-c7e4fa47-633d-4d8b-aa09-c50b1e6a411a,DISK]], original=[DatanodeInfoWithStorage[192.168.1.111:50010,DS-c7e4fa47-633d-4d8b-aa09-c50b1e6a411a,DISK]]). The current failed datanode replacement policy is DEFAULT, and a client may configure this via 'dfs.client.block.write.replace-datanode-on-failure.policy' in its configuration.
    at org.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.findNewDatanode(DFSOutputStream.java:929)
    at org.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.addDatanode2ExistingPipeline(DFSOutputStream.java:992)
    at org.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.setupPipelineForAppendOrRecovery(DFSOutputStream.java:1160)
    at org.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.run(DFSOutputStream.java:455)

解决方案：

conf.set("dfs.client.block.write.replace-datanode-on-failure.policy","NEVER");
 conf.set("dfs.client.block.write.replace-datanode-on-failure.enable","true");