org.apache.hadoop.fs

列挙型 CreateFlag

java.lang.Object

java.lang.Enum<CreateFlag>

org.apache.hadoop.fs.CreateFlag

すべての実装されたインタフェース:

Serializable, Comparable<CreateFlag>

@InterfaceAudience.Public
 @InterfaceStability.Evolving
public enum CreateFlag
extends Enum<CreateFlag>

CreateFlag specifies the file create semantic. Users can combine flags like:
EnumSet.of(CreateFlag.CREATE, CreateFlag.APPEND)

Use the CreateFlag as follows:

1. CREATE - to create a file if it does not exist, else throw FileAlreadyExists.
2. APPEND - to append to a file if it exists, else throw FileNotFoundException.
3. OVERWRITE - to truncate a file if it exists, else throw FileNotFoundException.
4. CREATE|APPEND - to create a file if it does not exist, else append to an existing file.
5. CREATE|OVERWRITE - to create a file if it does not exist, else overwrite an existing file.
6. SYNC_BLOCK - to force closed blocks to the disk device. In addition Syncable.hsync() should be called after each write, if true synchronous behavior is required.
7. LAZY_PERSIST - Create the block on transient storage (RAM) if available.
8. APPEND_NEWBLOCK - Append data to a new block instead of end of the last partial block.

Following combinations are not valid and will result in HadoopIllegalArgumentException:

1. APPEND|OVERWRITE
2. CREATE|APPEND|OVERWRITE

列挙型定数のサマリー

列挙型定数

列挙型定数と説明
APPEND Append to a file.
CREATE Create a file.
LAZY_PERSIST Create the block on transient storage (RAM) if available.
NEW_BLOCK Append data to a new block instead of the end of the last partial block.
NO_LOCAL_WRITE Advise that a block replica NOT be written to the local DataNode where 'local' means the same host as the client is being run on.
OVERWRITE Truncate/overwrite a file.
SYNC_BLOCK Force closed blocks to disk.

メソッドのサマリー

修飾子とタイプ	メソッドと説明
static void	validate(EnumSet<CreateFlag> flag) Validate the CreateFlag and throw exception if it is invalid
static void	validate(Object path, boolean pathExists, EnumSet<CreateFlag> flag) Validate the CreateFlag for create operation
static void	validateForAppend(EnumSet<CreateFlag> flag) Validate the CreateFlag for the append operation.
static CreateFlag	valueOf(String name) 指定した名前を持つこの型の列挙型定数を返します。
static CreateFlag[]	values() この列挙型の定数を含む配列を宣言されている順序で返します。

クラスから継承されたメソッド java.lang.Enum

clone, compareTo, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf

クラスから継承されたメソッド java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

列挙型定数の詳細

CREATE

public static final CreateFlag CREATE

Create a file. See javadoc for more description already exists

OVERWRITE

public static final CreateFlag OVERWRITE

Truncate/overwrite a file. Same as POSIX O_TRUNC. See javadoc for description.

APPEND

public static final CreateFlag APPEND

Append to a file. See javadoc for more description.

SYNC_BLOCK

public static final CreateFlag SYNC_BLOCK

Force closed blocks to disk. Similar to POSIX O_SYNC. See javadoc for description.

LAZY_PERSIST

public static final CreateFlag LAZY_PERSIST

Create the block on transient storage (RAM) if available. If transient storage is unavailable then the block will be created on disk. HDFS will make a best effort to lazily write these files to persistent storage, however file contents may be lost at any time due to process/ node restarts, hence there is no guarantee of data durability. This flag must only be used for intermediate data whose loss can be tolerated by the application.

NEW_BLOCK

public static final CreateFlag NEW_BLOCK

Append data to a new block instead of the end of the last partial block. This is only useful for APPEND.

NO_LOCAL_WRITE

@InterfaceAudience.LimitedPrivate(value="HBase")
public static final CreateFlag NO_LOCAL_WRITE

Advise that a block replica NOT be written to the local DataNode where 'local' means the same host as the client is being run on.

メソッドの詳細

values

public static CreateFlag[] values()

この列挙型の定数を含む配列を宣言されている順序で返します。 このメソッドは次のようにして定数を反復するために 使用できます:

for(CreateFlag c: CreateFlag.values())
  System.out.println(c);

戻り値:

この列挙型の定数を含む、宣言されている順序での配列

valueOf

public static CreateFlag valueOf(String name)

指定した名前を持つこの型の列挙型定数を返します。 文字列は、この型の列挙型定数を宣言するのに使用した識別子と正確に 一致している必要があります。 (余分な空白文字を含めることはできません。)

パラメータ:

name - 返される列挙型定数の名前。

戻り値:

指定した名前の列挙型定数

例外:

IllegalArgumentException - この列挙型に、指定した名前の定数がない場合

NullPointerException - 引数がnullの場合

validate

public static void validate(EnumSet<CreateFlag> flag)

Validate the CreateFlag and throw exception if it is invalid

パラメータ:

flag - set of CreateFlag

例外:

HadoopIllegalArgumentException - if the CreateFlag is invalid

validate

public static void validate(Object path,
                            boolean pathExists,
                            EnumSet<CreateFlag> flag)
                     throws IOException

Validate the CreateFlag for create operation

パラメータ:

path - Object representing the path; usually String or Path

pathExists - pass true if the path exists in the file system

flag - set of CreateFlag

例外:

IOException - on error

HadoopIllegalArgumentException - if the CreateFlag is invalid

validateForAppend

public static void validateForAppend(EnumSet<CreateFlag> flag)

Validate the CreateFlag for the append operation. The flag must contain APPEND, and cannot contain OVERWRITE.