HDFS的java访问接口——FileSystem

• 写文件 create
• 读取文件 open
• 删除文件 delete
• 创建目录 mkdirs
• 删除文件或目录 delete
• 列出目录的内容 listStatus
• 显示文件系统的目录和文件的元数据信息 getFileStatus

//打开 FileSystem
FileSystem getFileSystem(){
    URI uri=new URI(“hdfs://192.168.111.129:9000/”);
    FileSystem fileSystem = FileSystem.get(uri,new Configuration());
    Return fileSystem ;
}

//读取文件
private static void readFile() throws Exception {
    FileSystem fileSystem = getFileSystem();
    FSDataInputStream openStream = fileSystem.open(new Path("hdfs://hadoop0:9000/aaa"));
    IOUtils.copyBytes(openStream, System.out, 1024, false);
    IOUtils.closeStream(openStream);
}

//创建目录
private static void mkdir() throws Exception {
    FileSystem fileSystem = getFileSystem();
    fileSystem.mkdirs(new Path("hdfs://hadoop0:9000/bbb"));
}

//删除目录
private static void rmdir() throws Exception {
    FileSystem fileSystem = getFileSystem();
    fileSystem.delete(new Path("hdfs://hadoop0:9000/bbb"));
}

//遍历目录
private static void list() throws Exception{
    FileSystem fileSystem = getFileSystem();
    FileStatus[] listStatus = fileSystem.listStatus(new Path("hdfs://hadoop0:9000/"));
    for (FileStatus fileStatus : listStatus) {
        String isDir = fileStatus.isDir()?"目录":"文件";
        String name = fileStatus.getPath().toString();
        System.out.println(isDir+"  "+name);
    }
}