public class MemoryBlob extends Object implements WritableBlob
Constructor and Description |
---|
MemoryBlob() |
Modifier and Type | Method and Description |
---|---|
InputStream |
getInputStream()
Get an input stream to read the data in the blob.
|
long |
getLength()
Get the length of the data in the blob, i.e. the number of bytes.
|
BlobOutputStream |
getOutputStream()
Create an output stream to write data to the blob.
|
boolean |
isSupportingReadUncommitted()
Determine whether the blob supports reading in state NEW or UNCOMMITTED.
|
long |
readFrom(InputStream in,
long length)
Read data from the given input stream and write it to the blob.
|
long |
readFrom(InputStream in,
long length,
boolean commit)
Read data from the given input stream and write it to the blob.
|
void |
release()
Release all resources held by this blob.
|
void |
writeTo(OutputStream os)
Write the data to a given output stream.
|
public boolean isSupportingReadUncommitted()
WritableBlob
false
and the blob is in state NEW or UNCOMMITTED, any call to a method
defined by the Blob
superinterface will result in an IllegalStateException
.
If this method returns true
, then any data written to the blob will be
immediately available for reading. This is also true for an input stream obtained from
Blob.getInputStream()
before the data is written. This implies that it is possible
for the input stream to first report the end of the stream and later allow reading additional
data. Therefore, a pair of streams obtained from WritableBlob.getOutputStream()
and
Blob.getInputStream()
behaves differently than a PipedOutputStream
and PipedInputStream
pair, because in this situation
PipedInputStream
would block.isSupportingReadUncommitted
in interface WritableBlob
true
if the blob allows reading the data in state NEW or UNCOMMITTED;
false
if the blob allows read operations only in state COMMITTEDpublic long getLength()
Blob
public BlobOutputStream getOutputStream()
WritableBlob
Precondition: The blob is in state NEW.
Postcondition: The blob is in state UNCOMMITTED.
Note that the pre- and postconditions imply that this method may be called at most once for a given blob instance.
Calls to methods of the returned output stream will modify the state of the blob according to the following rules:
OutputStream.close()
will change the state to COMMITTED.
IOException
if the state is COMMITTED, i.e. if the stream has already been
closed.
getOutputStream
in interface WritableBlob
public long readFrom(InputStream in, long length, boolean commit) throws StreamCopyException
WritableBlob
A call to this method has the same effect as requesting an output stream using
WritableBlob.getOutputStream()
and copying the data from the input stream to that
output stream, but the implementation will achieve this result in a more efficient way.
Precondition: The blob is in state NEW or UNCOMMITTED.
Postcondition: The blob is in state UNCOMMITTED if commit
is
false
. It is in state COMMITTED if commit
is true
.
The precondition implies that this method may be used after a call to
WritableBlob.getOutputStream()
. In that case it is illegal to set commit
to
true
(because this would invalidate the state of the output stream).
The method transfers data from the input stream to the blob until one of the following conditions is met:
length
argument is different from -1
and the number of bytes transferred is equal to length
.
readFrom
in interface WritableBlob
in
- An input stream to read data from. This method will not
close the stream.length
- the number of bytes to transfer, or -1
if the method should
transfer data until the end of the input stream is reachedcommit
- indicates whether the blob should be in state COMMITTED after the operationStreamCopyException
public long readFrom(InputStream in, long length) throws StreamCopyException
WritableBlob
This method is similar to WritableBlob.readFrom(InputStream, long, boolean)
, except that the state
of the blob after the invocation (i.e. the commit
argument) is determined
automatically:
Precondition (state) | Postcondition (state) |
---|---|
NEW | COMMITTED |
UNCOMMITTED | UNCOMMITTED |
COMMITTED | illegal |
There are thus two usage patterns for this method:
WritableBlob.getOutputStream()
: some data is written using the output stream and some
data is written using this method (for efficiency reasons).
readFrom
in interface WritableBlob
in
- An input stream to read data from. This method will not
close the stream.length
- the number of bytes to transfer, or -1
if the method should
transfer data until the end of the input stream is reachedStreamCopyException
public InputStream getInputStream() throws IOException
Blob
getInputStream
in interface Blob
IOException
public void writeTo(OutputStream os) throws StreamCopyException
Blob
writeTo
in interface Blob
os
- The output stream to write the data to. This method will not close the stream.StreamCopyException
- Thrown if there is an I/O when reading the data from the blob or when writing it
to the stream. StreamCopyException.getOperation()
can be used to
determine whether the failed operation was a read or a write.public void release()
WritableBlob
release
in interface WritableBlob
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