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Java Forum / JavaBeans / May 2005EJB / CMP: storing large files in DB
Hi I'm working on a ejb application which has a database table to store files as 'bytea' datatype in a postgres database. My first try was to read the files into a byte[] on the client and call the setData(byte[] b) method on the written entity bean. This works great for small files, but if the files get bigger ( some mb ) this results in an out of memory error in JBoss. The better way would be to use Streams to read and write the data to the database, but i don't know how to access the streams in the entity-bean from the client, as rmi can only transfer serializable objects, but not streams. Has anybody done this before or has a simple answer how to handle this? Thanks in advance Johannes Hermen Luxembourg > Hi I'm working on a ejb application which has a database table to store > files as 'bytea' datatype in a postgres database. [quoted text clipped - 6 lines] > serializable objects, but not streams. > Has anybody done this before or has a simple answer how to handle this? Have you looked at ResultSet.getBinaryStream()? Joost > Have you looked at ResultSet.getBinaryStream()? Yes, sure, thats not the problem. the thing is how to access the stream from outside the entity bean on the client site. Greets Johannes Hermen >>Have you looked at ResultSet.getBinaryStream()? > > Yes, sure, thats not the problem. the thing is how to access the stream from > outside the entity bean on the client site. Ah, than why don't you implement the needed part of an InputStream's interface in your bean as a wrapper around the BinaryStream? >>> Have you looked at ResultSet.getBinaryStream()? >> [quoted text clipped - 4 lines] > Ah, than why don't you implement the needed part of an InputStream's > interface in your bean as a wrapper around the BinaryStream? In response to my own remark: because transient fields do not survive a passivation/activation process as one might expect as they are serialized in the process. Mmm. Store it in an MBean? Wait. If you want the client to access the data as a stream and work with it as such, why are you using EJB?! The point of EJB is to hide the internal format of the data, and allow you to work with the data as objects. That's not what you want, so I'd reccomend dumping the EJB and going with simple DAO/JavaBeans. > Wait. If you want the client to access the data as a stream and work > with it as such, why are you using EJB?! The point of EJB is to hide > the internal format of the data, and allow you to work with the data as > objects. That's not what you want, so I'd reccomend dumping the EJB and > going with simple DAO/JavaBeans. We also have int, string, floats etc. An OutputAtream in itself is just a datatype. Probably for a large Word file, bitmap or JPEG file as an attribute of an object (or the main part of the object itself) which is implented as a blob in a database. Are you sure that EJB CMP is the best strategy? While using DAOs is without doubt the best architecture, you may like to look at POJOs - maybe JDBC DAOs? You can read some more about the technology choices here: http://www.codefutures.com/weblog/corporate/archives/2005/02/data_persistenc.html I've seen similar projects with a very simple JDBC DAOs - with lots of blobs. Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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