idea中使用maven运行wordcount代码
1.创建maven项目
pom文件：
<?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>hadoop01</groupId> <artifactId>hadoop01</artifactId> <version>1.0-SNAPSHOT</version> <dependencies> <dependency> <groupId>org.apache.hadoop</groupId> <artifactId>hadoop-common</artifactId> <version>2.7.1</version> </dependency> <dependency> <groupId>org.apache.hadoop</groupId> <artifactId>hadoop-hdfs</artifactId> <version>2.7.1</version> </dependency> <dependency> <groupId>org.apache.hadoop</groupId> <artifactId>hadoop-client</artifactId> <version>2.7.1</version> </dependency> </dependencies> <build> <plugins> <plugin> <artifactId>maven-dependency-plugin</artifactId> <configuration> <excludeTransitive>false</excludeTransitive> <stripVersion>true</stripVersion> <outputDirectory>./lib</outputDirectory> </configuration> </plugin> </plugins> </build> </project>
2.编写wordcound
import java.io.IOException; import java.util.StringTokenizer; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.fs.Path; import org.apache.hadoop.io.IntWritable; import org.apache.hadoop.io.Text; import org.apache.hadoop.mapreduce.Job; import org.apache.hadoop.mapreduce.Mapper; import org.apache.hadoop.mapreduce.Reducer; import org.apache.hadoop.mapreduce.lib.input.FileInputFormat; import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat; public class WordCount { public static class TokenizerMapper extends Mapper<Object, Text, Text, IntWritable> { private final static IntWritable one = new IntWritable(1); private Text word = new Text(); public void map(Object key, Text value, Context context ) throws IOException, InterruptedException { StringTokenizer itr = new StringTokenizer(value.toString()); while (itr.hasMoreTokens()) { word.set(itr.nextToken()); context.write(word, one); } } } public static class IntSumReducer extends Reducer<Text, IntWritable, Text, IntWritable> { private IntWritable result = new IntWritable(); public void reduce(Text key, Iterable<IntWritable> values, Context context ) throws IOException, InterruptedException { int sum = 0; for (IntWritable val : values) { sum += val.get(); } result.set(sum); context.write(key, result); } } public static void main(String[] args) throws Exception { Configuration conf = new Configuration(); Job job = Job.getInstance(conf, "word count"); job.setJarByClass(WordCount.class); job.setMapperClass(TokenizerMapper.class); job.setCombinerClass(IntSumReducer.class); job.setReducerClass(IntSumReducer.class); job.setOutputKeyClass(Text.class); job.setOutputValueClass(IntWritable.class); FileInputFormat.addInputPath(job, new Path(args[0])); FileOutputFormat.setOutputPath(job, new Path(args[1])); System.exit(job.waitForCompletion(true) ? 0 : 1); } }
3.在src下面创建NativeIO
创建package：org.apache.hadoop.io.nativeio
创建类：NativeIO
/** * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF licenses this file * to you under the Apache License, Version 2.0 (the * "License"); you may not use this file except in compliance * with the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.apache.hadoop.io.nativeio; import java.io.File; import java.io.FileDescriptor; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; import java.io.RandomAccessFile; import java.lang.reflect.Field; import java.nio.ByteBuffer; import java.nio.MappedByteBuffer; import java.util.Map; import java.util.concurrent.ConcurrentHashMap; import org.apache.hadoop.classification.InterfaceAudience; import org.apache.hadoop.classification.InterfaceStability; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.fs.CommonConfigurationKeys; import org.apache.hadoop.io.SecureIOUtils.AlreadyExistsException; import org.apache.hadoop.util.NativeCodeLoader; import org.apache.hadoop.util.Shell; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import sun.misc.Unsafe; import com.google.common.annotations.VisibleForTesting; /** * JNI wrappers for various native IO-related calls not available in Java. * These functions should generally be used alongside a fallback to another * more portable mechanism. */ @InterfaceAudience.Private @InterfaceStability.Unstable public class NativeIO { public static class POSIX { // Flags for open() call from bits/fcntl.h public static final int O_RDONLY = 00; public static final int O_WRONLY = 01; public static final int O_RDWR = 02; public static final int O_CREAT = 0100; public static final int O_EXCL = 0200; public static final int O_NOCTTY = 0400; public static final int O_TRUNC = 01000; public static final int O_APPEND = 02000; public static final int O_NONBLOCK = 04000; public static final int O_SYNC = 010000; public static final int O_ASYNC = 020000; public static final int O_FSYNC = O_SYNC; public static final int O_NDELAY = O_NONBLOCK; // Flags for posix_fadvise() from bits/fcntl.h /* No further special treatment. */ public static final int POSIX_FADV_NORMAL = 0; /* Expect random page references. */ public static final int POSIX_FADV_RANDOM = 1; /* Expect sequential page references. */ public static final int POSIX_FADV_SEQUENTIAL = 2; /* Will need these pages. */ public static final int POSIX_FADV_WILLNEED = 3; /* Don't need these pages. */ public static final int POSIX_FADV_DONTNEED = 4; /* Data will be accessed once. */ public static final int POSIX_FADV_NOREUSE = 5; /* Wait upon writeout of all pages in the range before performing the write. */ public static final int SYNC_FILE_RANGE_WAIT_BEFORE = 1; /* Initiate writeout of all those dirty pages in the range which are not presently under writeback. */ public static final int SYNC_FILE_RANGE_WRITE = 2; /* Wait upon writeout of all pages in the range after performing the write. */ public static final int SYNC_FILE_RANGE_WAIT_AFTER = 4; private static final Log LOG = LogFactory.getLog(NativeIO.class); private static boolean nativeLoaded = false; private static boolean fadvisePossible = true; private static boolean syncFileRangePossible = true; static final String WORKAROUND_NON_THREADSAFE_CALLS_KEY = "hadoop.workaround.non.threadsafe.getpwuid"; static final boolean WORKAROUND_NON_THREADSAFE_CALLS_DEFAULT = true; private static long cacheTimeout = -1; private static CacheManipulator cacheManipulator = new CacheManipulator(); public static CacheManipulator getCacheManipulator() { return cacheManipulator; } public static void setCacheManipulator(CacheManipulator cacheManipulator) { POSIX.cacheManipulator = cacheManipulator; } /** * Used to manipulate the operating system cache. */ @VisibleForTesting public static class CacheManipulator { public void mlock(String identifier, ByteBuffer buffer, long len) throws IOException { POSIX.mlock(buffer, len); } public long getMemlockLimit() { return NativeIO.getMemlockLimit(); } public long getOperatingSystemPageSize() { return NativeIO.getOperatingSystemPageSize(); } public void posixFadviseIfPossible(String identifier, FileDescriptor fd, long offset, long len, int flags) throws NativeIOException { POSIX.posixFadviseIfPossible(identifier, fd, offset, len, flags); } public boolean verifyCanMlock() { return NativeIO.isAvailable(); } } /** * A CacheManipulator used for testing which does not actually call mlock. * This allows many tests to be run even when the operating system does not * allow mlock, or only allows limited mlocking. */ @VisibleForTesting public static class NoMlockCacheManipulator extends CacheManipulator { public void mlock(String identifier, ByteBuffer buffer, long len) throws IOException { LOG.info("mlocking " + identifier); } public long getMemlockLimit() { return 1125899906842624L; } public long getOperatingSystemPageSize() { return 4096; } public boolean verifyCanMlock() { return true; } } static { if (NativeCodeLoader.isNativeCodeLoaded()) { try { Configuration conf = new Configuration(); workaroundNonThreadSafePasswdCalls = conf.getBoolean( WORKAROUND_NON_THREADSAFE_CALLS_KEY, WORKAROUND_NON_THREADSAFE_CALLS_DEFAULT); initNative(); nativeLoaded = true; cacheTimeout = conf.getLong( CommonConfigurationKeys.HADOOP_SECURITY_UID_NAME_CACHE_TIMEOUT_KEY, CommonConfigurationKeys.HADOOP_SECURITY_UID_NAME_CACHE_TIMEOUT_DEFAULT) * 1000; LOG.debug("Initialized cache for IDs to User/Group mapping with a " + " cache timeout of " + cacheTimeout/1000 + " seconds."); } catch (Throwable t) { // This can happen if the user has an older version of libhadoop.so // installed - in this case we can continue without native IO // after warning LOG.error("Unable to initialize NativeIO libraries", t); } } } /** * Return true if the JNI-based native IO extensions are available. */ public static boolean isAvailable() { return NativeCodeLoader.isNativeCodeLoaded() && nativeLoaded; } private static void assertCodeLoaded() throws IOException { if (!isAvailable()) { throw new IOException("NativeIO was not loaded"); } } /** Wrapper around open(2) */ public static native FileDescriptor open(String path, int flags, int mode) throws IOException; /** Wrapper around fstat(2) */ private static native Stat fstat(FileDescriptor fd) throws IOException; /** Native chmod implementation. On UNIX, it is a wrapper around chmod(2) */ private static native void chmodImpl(String path, int mode) throws IOException; public static void chmod(String path, int mode) throws IOException { if (!Shell.WINDOWS) { chmodImpl(path, mode); } else { try { chmodImpl(path, mode); } catch (NativeIOException nioe) { if (nioe.getErrorCode() == 3) { throw new NativeIOException("No such file or directory", Errno.ENOENT); } else { LOG.warn(String.format("NativeIO.chmod error (%d): %s", nioe.getErrorCode(), nioe.getMessage())); throw new NativeIOException("Unknown error", Errno.UNKNOWN); } } } } /** Wrapper around posix_fadvise(2) */ static native void posix_fadvise( FileDescriptor fd, long offset, long len, int flags) throws NativeIOException; /** Wrapper around sync_file_range(2) */ static native void sync_file_range( FileDescriptor fd, long offset, long nbytes, int flags) throws NativeIOException; /** * Call posix_fadvise on the given file descriptor. See the manpage * for this syscall for more information. On systems where this * call is not available, does nothing. * * @throws NativeIOException if there is an error with the syscall */ static void posixFadviseIfPossible(String identifier, FileDescriptor fd, long offset, long len, int flags) throws NativeIOException { if (nativeLoaded && fadvisePossible) { try { posix_fadvise(fd, offset, len, flags); } catch (UnsupportedOperationException uoe) { fadvisePossible = false; } catch (UnsatisfiedLinkError ule) { fadvisePossible = false; } } } /** * Call sync_file_range on the given file descriptor. See the manpage * for this syscall for more information. On systems where this * call is not available, does nothing. * * @throws NativeIOException if there is an error with the syscall */ public static void syncFileRangeIfPossible( FileDescriptor fd, long offset, long nbytes, int flags) throws NativeIOException { if (nativeLoaded && syncFileRangePossible) { try { sync_file_range(fd, offset, nbytes, flags); } catch (UnsupportedOperationException uoe) { syncFileRangePossible = false; } catch (UnsatisfiedLinkError ule) { syncFileRangePossible = false; } } } static native void mlock_native( ByteBuffer buffer, long len) throws NativeIOException; static native void munlock_native( ByteBuffer buffer, long len) throws NativeIOException; /** * Locks the provided direct ByteBuffer into memory, preventing it from * swapping out. After a buffer is locked, future accesses will not incur * a page fault. * * See the mlock(2) man page for more information. * * @throws NativeIOException */ static void mlock(ByteBuffer buffer, long len) throws IOException { assertCodeLoaded(); if (!buffer.isDirect()) { throw new IOException("Cannot mlock a non-direct ByteBuffer"); } mlock_native(buffer, len); } /** * Unlocks a locked direct ByteBuffer, allowing it to swap out of memory. * This is a no-op if the ByteBuffer was not previously locked. * * See the munlock(2) man page for more information. * * @throws NativeIOException */ public static void munlock(ByteBuffer buffer, long len) throws IOException { assertCodeLoaded(); if (!buffer.isDirect()) { throw new IOException("Cannot munlock a non-direct ByteBuffer"); } munlock_native(buffer, len); } /** * Unmaps the block from memory. See munmap(2). * * There isn't any portable way to unmap a memory region in Java. * So we use the sun.nio method here. * Note that unmapping a memory region could cause crashes if code * continues to reference the unmapped code. However, if we don't * manually unmap the memory, we are dependent on the finalizer to * do it, and we have no idea when the finalizer will run. * * @param buffer The buffer to unmap. */ public static void munmap(MappedByteBuffer buffer) { if (buffer instanceof sun.nio.ch.DirectBuffer) { sun.misc.Cleaner cleaner = ((sun.nio.ch.DirectBuffer)buffer).cleaner(); cleaner.clean(); } } /** Linux only methods used for getOwner() implementation */ private static native long getUIDforFDOwnerforOwner(FileDescriptor fd) throws IOException; private static native String getUserName(long uid) throws IOException; /** * Result type of the fstat call */ public static class Stat { private int ownerId, groupId; private String owner, group; private int mode; // Mode constants public static final int S_IFMT = 0170000; /* type of file */ public static final int S_IFIFO = 0010000; /* named pipe (fifo) */ public static final int S_IFCHR = 0020000; /* character special */ public static final int S_IFDIR = 0040000; /* directory */ public static final int S_IFBLK = 0060000; /* block special */ public static final int S_IFREG = 0100000; /* regular */ public static final int S_IFLNK = 0120000; /* symbolic link */ public static final int S_IFSOCK = 0140000; /* socket */ public static final int S_IFWHT = 0160000; /* whiteout */ public static final int S_ISUID = 0004000; /* set user id on execution */ public static final int S_ISGID = 0002000; /* set group id on execution */ public static final int S_ISVTX = 0001000; /* save swapped text even after use */ public static final int S_IRUSR = 0000400; /* read permission, owner */ public static final int S_IWUSR = 0000200; /* write permission, owner */ public static final int S_IXUSR = 0000100; /* execute/search permission, owner */ Stat(int ownerId, int groupId, int mode) { this.ownerId = ownerId; this.groupId = groupId; this.mode = mode; } Stat(String owner, String group, int mode) { if (!Shell.WINDOWS) { this.owner = owner; } else { this.owner = stripDomain(owner); } if (!Shell.WINDOWS) { this.group = group; } else { this.group = stripDomain(group); } this.mode = mode; } @Override public String toString() { return "Stat(owner='" + owner + "', group='" + group + "'" + ", mode=" + mode + ")"; } public String getOwner() { return owner; } public String getGroup() { return group; } public int getMode() { return mode; } } /** * Returns the file stat for a file descriptor. * * @param fd file descriptor. * @return the file descriptor file stat. * @throws IOException thrown if there was an IO error while obtaining the file stat. */ public static Stat getFstat(FileDescriptor fd) throws IOException { Stat stat = null; if (!Shell.WINDOWS) { stat = fstat(fd); stat.owner = getName(IdCache.USER, stat.ownerId); stat.group = getName(IdCache.GROUP, stat.groupId); } else { try { stat = fstat(fd); } catch (NativeIOException nioe) { if (nioe.getErrorCode() == 6) { throw new NativeIOException("The handle is invalid.", Errno.EBADF); } else { LOG.warn(String.format("NativeIO.getFstat error (%d): %s", nioe.getErrorCode(), nioe.getMessage())); throw new NativeIOException("Unknown error", Errno.UNKNOWN); } } } return stat; } private static String getName(IdCache domain, int id) throws IOException { Map<Integer, CachedName> idNameCache = (domain == IdCache.USER) ? USER_ID_NAME_CACHE : GROUP_ID_NAME_CACHE; String name; CachedName cachedName = idNameCache.get(id); long now = System.currentTimeMillis(); if (cachedName != null && (cachedName.timestamp + cacheTimeout) > now) { name = cachedName.name; } else { name = (domain == IdCache.USER) ? getUserName(id) : getGroupName(id); if (LOG.isDebugEnabled()) { String type = (domain == IdCache.USER) ? "UserName" : "GroupName"; LOG.debug("Got " + type + " " + name + " for ID " + id + " from the native implementation"); } cachedName = new CachedName(name, now); idNameCache.put(id, cachedName); } return name; } static native String getUserName(int uid) throws IOException; static native String getGroupName(int uid) throws IOException; private static class CachedName { final long timestamp; final String name; public CachedName(String name, long timestamp) { this.name = name; this.timestamp = timestamp; } } private static final Map<Integer, CachedName> USER_ID_NAME_CACHE = new ConcurrentHashMap<Integer, CachedName>(); private static final Map<Integer, CachedName> GROUP_ID_NAME_CACHE = new ConcurrentHashMap<Integer, CachedName>(); private enum IdCache { USER, GROUP } public final static int MMAP_PROT_READ = 0x1; public final static int MMAP_PROT_WRITE = 0x2; public final static int MMAP_PROT_EXEC = 0x4; public static native long mmap(FileDescriptor fd, int prot, boolean shared, long length) throws IOException; public static native void munmap(long addr, long length) throws IOException; } private static boolean workaroundNonThreadSafePasswdCalls = false; public static class Windows { // Flags for CreateFile() call on Windows public static final long GENERIC_READ = 0x80000000L; public static final long GENERIC_WRITE = 0x40000000L; public static final long FILE_SHARE_READ = 0x00000001L; public static final long FILE_SHARE_WRITE = 0x00000002L; public static final long FILE_SHARE_DELETE = 0x00000004L; public static final long CREATE_NEW = 1; public static final long CREATE_ALWAYS = 2; public static final long OPEN_EXISTING = 3; public static final long OPEN_ALWAYS = 4; public static final long TRUNCATE_EXISTING = 5; public static final long FILE_BEGIN = 0; public static final long FILE_CURRENT = 1; public static final long FILE_END = 2; /** Wrapper around CreateFile() on Windows */ public static native FileDescriptor createFile(String path, long desiredAccess, long shareMode, long creationDisposition) throws IOException; /** Wrapper around SetFilePointer() on Windows */ public static native long setFilePointer(FileDescriptor fd, long distanceToMove, long moveMethod) throws IOException; /** Windows only methods used for getOwner() implementation */ private static native String getOwner(FileDescriptor fd) throws IOException; /** Supported list of Windows access right flags */ public static enum AccessRight { ACCESS_READ (0x0001), // FILE_READ_DATA ACCESS_WRITE (0x0002), // FILE_WRITE_DATA ACCESS_EXECUTE (0x0020); // FILE_EXECUTE private final int accessRight; AccessRight(int access) { accessRight = access; } public int accessRight() { return accessRight; } }; /** Windows only method used to check if the current process has requested * access rights on the given path. */ private static native boolean access0(String path, int requestedAccess); /** * Checks whether the current process has desired access rights on * the given path. * * Longer term this native function can be substituted with JDK7 * function Files#isReadable, isWritable, isExecutable. * * @param path input path * @param desiredAccess ACCESS_READ, ACCESS_WRITE or ACCESS_EXECUTE * @return true if access is allowed * @throws IOException I/O exception on error */ public static boolean access(String path, AccessRight desiredAccess) throws IOException { return true; //return access0(path, desiredAccess.accessRight()); } static { if (NativeCodeLoader.isNativeCodeLoaded()) { try { initNative(); nativeLoaded = true; } catch (Throwable t) { // This can happen if the user has an older version of libhadoop.so // installed - in this case we can continue without native IO // after warning LOG.error("Unable to initialize NativeIO libraries", t); } } } } private static final Log LOG = LogFactory.getLog(NativeIO.class); private static boolean nativeLoaded = false; static { if (NativeCodeLoader.isNativeCodeLoaded()) { try { initNative(); nativeLoaded = true; } catch (Throwable t) { // This can happen if the user has an older version of libhadoop.so // installed - in this case we can continue without native IO // after warning LOG.error("Unable to initialize NativeIO libraries", t); } } } /** * Return true if the JNI-based native IO extensions are available. */ public static boolean isAvailable() { return NativeCodeLoader.isNativeCodeLoaded() && nativeLoaded; } /** Initialize the JNI method ID and class ID cache */ private static native void initNative(); /** * Get the maximum number of bytes that can be locked into memory at any * given point. * * @return 0 if no bytes can be locked into memory; * Long.MAX_VALUE if there is no limit; * The number of bytes that can be locked into memory otherwise. */ static long getMemlockLimit() { return isAvailable() ? getMemlockLimit0() : 0; } private static native long getMemlockLimit0(); /** * @return the operating system's page size. */ static long getOperatingSystemPageSize() { try { Field f = Unsafe.class.getDeclaredField("theUnsafe"); f.setAccessible(true); Unsafe unsafe = (Unsafe)f.get(null); return unsafe.pageSize(); } catch (Throwable e) { LOG.warn("Unable to get operating system page size. Guessing 4096.", e); return 4096; } } private static class CachedUid { final long timestamp; final String username; public CachedUid(String username, long timestamp) { this.timestamp = timestamp; this.username = username; } } private static final Map<Long, CachedUid> uidCache = new ConcurrentHashMap<Long, CachedUid>(); private static long cacheTimeout; private static boolean initialized = false; /** * The Windows logon name has two part, NetBIOS domain name and * user account name, of the format DOMAIN\UserName. This method * will remove the domain part of the full logon name. * * @param the full principal name containing the domain * @return name with domain removed */ private static String stripDomain(String name) { int i = name.indexOf('\\'); if (i != -1) name = name.substring(i + 1); return name; } public static String getOwner(FileDescriptor fd) throws IOException { ensureInitialized(); if (Shell.WINDOWS) { String owner = Windows.getOwner(fd); owner = stripDomain(owner); return owner; } else { long uid = POSIX.getUIDforFDOwnerforOwner(fd); CachedUid cUid = uidCache.get(uid); long now = System.currentTimeMillis(); if (cUid != null && (cUid.timestamp + cacheTimeout) > now) { return cUid.username; } String user = POSIX.getUserName(uid); LOG.info("Got UserName " + user + " for UID " + uid + " from the native implementation"); cUid = new CachedUid(user, now); uidCache.put(uid, cUid); return user; } } /** * Create a FileInputStream that shares delete permission on the * file opened, i.e. other process can delete the file the * FileInputStream is reading. Only Windows implementation uses * the native interface. */ public static FileInputStream getShareDeleteFileInputStream(File f) throws IOException { if (!Shell.WINDOWS) { // On Linux the default FileInputStream shares delete permission // on the file opened. // return new FileInputStream(f); } else { // Use Windows native interface to create a FileInputStream that // shares delete permission on the file opened. // FileDescriptor fd = Windows.createFile( f.getAbsolutePath(), Windows.GENERIC_READ, Windows.FILE_SHARE_READ | Windows.FILE_SHARE_WRITE | Windows.FILE_SHARE_DELETE, Windows.OPEN_EXISTING); return new FileInputStream(fd); } } /** * Create a FileInputStream that shares delete permission on the * file opened at a given offset, i.e. other process can delete * the file the FileInputStream is reading. Only Windows implementation * uses the native interface. */ public static FileInputStream getShareDeleteFileInputStream(File f, long seekOffset) throws IOException { if (!Shell.WINDOWS) { RandomAccessFile rf = new RandomAccessFile(f, "r"); if (seekOffset > 0) { rf.seek(seekOffset); } return new FileInputStream(rf.getFD()); } else { // Use Windows native interface to create a FileInputStream that // shares delete permission on the file opened, and set it to the // given offset. // FileDescriptor fd = Windows.createFile( f.getAbsolutePath(), Windows.GENERIC_READ, Windows.FILE_SHARE_READ | Windows.FILE_SHARE_WRITE | Windows.FILE_SHARE_DELETE, Windows.OPEN_EXISTING); if (seekOffset > 0) Windows.setFilePointer(fd, seekOffset, Windows.FILE_BEGIN); return new FileInputStream(fd); } } /** * Create the specified File for write access, ensuring that it does not exist. * @param f the file that we want to create * @param permissions we want to have on the file (if security is enabled) * * @throws AlreadyExistsException if the file already exists * @throws IOException if any other error occurred */ public static FileOutputStream getCreateForWriteFileOutputStream(File f, int permissions) throws IOException { if (!Shell.WINDOWS) { // Use the native wrapper around open(2) try { FileDescriptor fd = POSIX.open(f.getAbsolutePath(), POSIX.O_WRONLY | POSIX.O_CREAT | POSIX.O_EXCL, permissions); return new FileOutputStream(fd); } catch (NativeIOException nioe) { if (nioe.getErrno() == Errno.EEXIST) { throw new AlreadyExistsException(nioe); } throw nioe; } } else { // Use the Windows native APIs to create equivalent FileOutputStream try { FileDescriptor fd = Windows.createFile(f.getCanonicalPath(), Windows.GENERIC_WRITE, Windows.FILE_SHARE_DELETE | Windows.FILE_SHARE_READ | Windows.FILE_SHARE_WRITE, Windows.CREATE_NEW); POSIX.chmod(f.getCanonicalPath(), permissions); return new FileOutputStream(fd); } catch (NativeIOException nioe) { if (nioe.getErrorCode() == 80) { // ERROR_FILE_EXISTS // 80 (0x50) // The file exists throw new AlreadyExistsException(nioe); } throw nioe; } } } private synchronized static void ensureInitialized() { if (!initialized) { cacheTimeout = new Configuration().getLong("hadoop.security.uid.cache.secs", 4*60*60) * 1000; LOG.info("Initialized cache for UID to User mapping with a cache" + " timeout of " + cacheTimeout/1000 + " seconds."); initialized = true; } } /** * A version of renameTo that throws a descriptive exception when it fails. * * @param src The source path * @param dst The destination path * * @throws NativeIOException On failure. */ public static void renameTo(File src, File dst) throws IOException { if (!nativeLoaded) { if (!src.renameTo(dst)) { throw new IOException("renameTo(src=" + src + ", dst=" + dst + ") failed."); } } else { renameTo0(src.getAbsolutePath(), dst.getAbsolutePath()); } } /** * A version of renameTo that throws a descriptive exception when it fails. * * @param src The source path * @param dst The destination path * * @throws NativeIOException On failure. */ private static native void renameTo0(String src, String dst) throws NativeIOException; }
4.确保hadoop运行正常，将文件上传到hdfs上
hadoop fs -mkdir -p /user/root/input
随便创建一个文件，比如：/root/a.txt,在里面输入点内容。wordcount是按照行进行分割统计的。
hadoop fs -put /root/a.txt /user/root/input
5.配置application
在idea右上角点击红框标记的地方，在之后的页面中的加号中添加一个applicaiton，将下图的三个地方配置好，第二个是代码指定的输入路径和输出路径
6.运行如果没有报错就表示成功。
可以在浏览器访问 http://192.168.21.101:50070/explorer.html#/ 查看hdfs上的数据（ip换成自己的）
2017-07-24 23:52:25
