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File Transformers
To transform data read from the file system to objects and the other way around, you need to do some work.
Unlike FileReadingMessageSource
and to a lesser extent FileWritingMessageHandler
, you probably need your own mechanism to get the job done.
For this, you can implement the Transformer
interface.
Alternatively, you can extend the AbstractFilePayloadTransformer
for inbound messages.
Spring Integration provides some obvious implementations.
See the Javadoc for the Transformer
interface to see which Spring Integration classes implement it.
Similarly, you can check the Javadoc for the AbstractFilePayloadTransformer
class to see which Spring Integration classes extend it.
FileToByteArrayTransformer
extends AbstractFilePayloadTransformer
and transforms a File
object into a byte[]
by using Spring’s FileCopyUtils
.
It is often better to use a sequence of transformers than to put all transformations in a single class.
In that case the File
to byte[]
conversion might be a logical first step.
FileToStringTransformer
extends AbstractFilePayloadTransformer
convert a File
object to a String
.
If nothing else, this can be useful for debugging (consider using it with a wire tap).
To configure file-specific transformers, you can use the appropriate elements from the file namespace, as the following example shows:
<int-file:file-to-bytes-transformer input-channel="input" output-channel="output"
delete-files="true"/>
<int-file:file-to-string-transformer input-channel="input" output-channel="output"
delete-files="true" charset="UTF-8"/>
The delete-files
option signals to the transformer that it should delete the inbound file after the transformation is complete.
This is in no way a replacement for using an AcceptOnceFileListFilter
when the FileReadingMessageSource
is being used in a multi-threaded environment (such as when you use Spring Integration in general).