接着之前继续API操作的学习
CopyFromLocalFile: 顾名思义，从本地文件拷贝
/**
* 使用Java API操作HDFS文件系统
* 关键点:
* 1)create Configuration
* 2)get FileSystem
* 3)...It's your HDFS API operation.
*/
public class HDFSApp { public static final String HDFS_PATH = "hdfs://hadoop000:8020";
FileSystem fileSystem = null;
Configuration configuration = null; @Before
public void setUp() throws Exception{
System.out.println("setUp-----------");
configuration = new Configuration();
configuration.set("dfs.replication","1"); /*
* 构造一个访问制定HDFS系统的客户端对象
* 第一个参数：HDFS的URI
* 第二个参数：客户端制定的配置参数
* 第三个参数：客户端的身份，说白了就是用户名
*/
fileSystem = FileSystem.get(new URI(HDFS_PATH),configuration,"hadoop");
} /*
* 拷贝本地文件到HDFS文件系统
*/
@Test
public void copyFromLocalFile() throws Exception{
Path src = new Path("/home/hadoop/t.txt");
Path dst = new Path("/hdfsapi/test/");
fileSystem.copyFromLocalFile(src,dst);
}
@After
public void tearDown(){
configuration = null;
fileSystem = null;
System.out.println("----------tearDown------");
}
}
方法怎么用？还是那句 哪里不会Ctrl点哪里。
点进CopyFromLocalFile方法源码得知方法需要两个参数：本地文件的Path，和目标文件的Path，无返回值。
我们运行该测试类后进入终端使用-ls查看/hdfsapi/test目录下包含了刚刚copy进来的t.txt文件，测试成功。
[hadoop@hadoop000 ~]$ hadoop fs -ls /hdfsapi/test
Found 3 items
-rw-r--r-- 3 hadoop supergroup 14 2019-04-19 16:31 /hdfsapi/test/a.txt
-rw-r--r-- 1 hadoop supergroup 28 2019-04-19 16:50 /hdfsapi/test/c.txt
-rw-r--r-- 1 hadoop supergroup 2732 2019-04-20 19:51 /hdfsapi/test/t.txt
如果我们需要从本地拷贝一个大文件，文件越大需要等待的时间自然越长，这么漫长的等待且毫无显示严重影响用户体验。
所以在上传大文件的时候可以添加上传进度条，在fileSystem下有个create方法带有进度条的功能：
/**
* Create an FSDataOutputStream at the indicated Path with write-progress
* reporting.
* Files are overwritten by default.
* @param f the file to create
* @param progress to report progress
*在具有写入进度的指定路径上创建fsdataoutputstream。
*默认情况下会覆盖文件。
*@参数 f 要创建的文件
*@参数 progress 报告进度
*/
public FSDataOutputStream create(Path f, Progressable progress)
throws IOException {
return create(f, true,
getConf().getInt("io.file.buffer.size", 4096),
getDefaultReplication(f),
getDefaultBlockSize(f), progress);
}
运行测试类，能看到打印显示，虽然全是点看起来比较抽象，但是比什么都没有到怀疑死机还是要好点儿。
setUp-----------
log4j:WARN No appenders could be found for logger (org.apache.hadoop.metrics2.lib.MutableMetricsFactory).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
...................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................----------tearDown------ Process finished with exit code 0
........................
我们打开终端-ls查看，上传成功。
[hadoop@hadoop000 software]$ hadoop fs -ls /hdfsapi/test
Found 4 items
-rw-r--r-- 3 hadoop supergroup 14 2019-04-19 16:31 /hdfsapi/test/a.txt
-rw-r--r-- 1 hadoop supergroup 28 2019-04-19 16:50 /hdfsapi/test/c.txt
-rw-r--r-- 1 hadoop supergroup 181367942 2019-04-20 20:10 /hdfsapi/test/jdk.zip
-rw-r--r-- 1 hadoop supergroup 2732 2019-04-20 19:51 /hdfsapi/test/t.txt
能上传那就自然会问：怎么下载？直接上代码，和上面类似就不多介绍了。
/**
* 拷贝HDFS文件到本地：下载
* @throws Exception
*/
@Test
public void copyToLocalFile() throws Exception{
Path src = new Path("/hdfsapi/test/t.txt");
Path dst = new Path("/home/hadoop/app");
fileSystem.copyToLocalFile(src,dst);
}