Migration from DSAPI v. 1 to DSAPI v. 2
Creating a Stream Writer and Writing a Blob to a Stream
Blobs are written to a stream as they are written anywhere else in Tupelo. Instead of creating a StreamWriter, you need to obtain a StreamingContext, create a time-annotated resource to associate the blob with a URI and a timestamp, and then write it to Tupelo using a regular BlobWriter operator and the streaming context. E.g.
| Code Block |
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Contex context = ...// a regular tupelo context
//Create a context with time-annotating capabilities
DataSource dataSource =
DataSourceFactory.getDataSource(DBType.MYSQL,"jdbc:mysql://host/db","user","password");
Context timeAnnotatingContext = new CompositeContext(context,dataSource,DBType.MYSQL);
//Create a time-annotated resource
Resource streamResource = Resource.uriRef("urn:stream");
Resource dataPointResource = TimeAnnotatedResource.create(streamResource,
TemporalAnnotation.getInstant(System.currentTimeMillis()));
//Write the blob to Tupelo
BlobWriter bw = new BlobWriter(dataPoint);
bw.setInputStream(new FileInputStream("data000.jpg"));
context.perform(bw); |
Creating a Stream Reader and Reading a Blob from a Stream
In a similar way, blobs are read from a StreamingContext using regular Tupelo operators such as BlobFetcher. E.g.
| Code Block |
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Contex context = ...// a regular tupelo context
//Create a context with time-annotating capabilities
DataSource dataSource =
DataSourceFactory.getDataSource(DBType.MYSQL,"jdbc:mysql://host/db","user","password");
Context timeAnnotatingContext = new CompositeContext(context,dataSource,DBType.MYSQL);
//Create a time-annotated resource
Resource streamResource = Resource.uriRef("urn:stream");
Resource dataPointResource = TimeAnnotatedResource.create(streamResource,
TemporalAnnotation.getLast()));
//fetch the data using a BlobFetcher
BlobFetcher bf = new BlobFetcher();
bf.setSubject(dataPointResource);
context.perform(bf);
//read the data and do something with it
processBlob(bf.getInputStream()); |