FileSystem是Hadoop提供的一个通用的文件系统API, Hadoop文件系统中通过Hadoop Path 对象(而非java.io.File 对象，因为它的语义与本地文件系统联系太紧密)来代表文件。可以将路径视为一个Hadoop 文件系统URI,如hdfs://localhost/user/ tom/ quangle. txt。下面就用最简单的方法来举例java 读取，删除，写入文件到hdfs。

先贴一下maven依赖

		<dependency>
			<groupId>org.apache.hadoop</groupId>
			<artifactId>hadoop-common</artifactId>
			<version>2.7.7</version>
		</dependency>
		<dependency>
			<groupId>org.apache.hadoop</groupId>
			<artifactId>hadoop-hdfs</artifactId>
			<version>2.7.7</version>
		</dependency>
		<dependency>
			<groupId>org.apache.hadoop</groupId>
			<artifactId>hadoop-client</artifactId>
			<version>2.7.7</version>
		</dependency>

1.java hdfs 创建文件夹

FileSystem fs = null;
try {
	Configuration config = new Configuration();
	fs = FileSystem.get(URI.create("hdfs://hadoopMaster:9000"), config);
	Path path = new Path("/tmp");
	if (!fs.exists(path)) {
		fs.mkdirs(path);
	}
	
	fs.close();
} catch (Throwable e) {
	logger.error("出现异常", e);
}

2.java hdfs写入文件

FileSystem fs = null;
FSDataOutputStream fsDataOutputStream = null;
try {

	fs = FileSystem.get(URI.create("hdfs://hadoopMaster:9000"), config);
	Path path = new Path("/tmp");
	if (!fs.exists(path)) {
		fs.mkdirs(path);
	}
	fsDataOutputStream = fs.create(new Path("/tmp/itxw.txt"));

	byte[] buff = "哈哈IT学问网".getBytes("UTF-8");
	fsDataOutputStream.write(buff);
	fsDataOutputStream.flush();
	fsDataOutputStream.close();
	fs.close();

} catch (Throwable e) {
	logger.error("出现异常", e);
}

3.java hdfs删除文件

FileSystem fs = null;
FSDataOutputStream fsDataOutputStream = null;
try {

	fs = FileSystem.get(URI.create("hdfs://hadoopMaster:9000"), config);
	fs.delete(new Path("/tmp/itxw.txw"),false);//第二个参数表示是否递归删除
	fs.close();

} catch (Throwable e) {
	logger.error("出现异常", e);
}

4.java hdfs 读取文件

FileSystem fs = null;
FSDataInputStream fsDataInputStream = null;
try {

	fs = FileSystem.get(URI.create("hdfs://hadoopMaster:9000"), config);
	
	fsDataInputStream =fs.open(new Path("/tmp/itxw.txw"));
	String content=IOUtils.toString(fsDataInputStream, "utf-8");
	System.out.println(content);
	
	fsDataInputStream.flush();
	fsDataInputStream.close();
	fs.close();

} catch (Throwable e) {
	logger.error("出现异常", e);
}