How to convert an InputStream to a DataHandler?

Question

I'm working on a java web application in which files will be stored in a database. Originally we retrieved files already in the DB by simply calling getBytes on our result set:

byte[] bytes = resultSet.getBytes(1); ... 

This byte array was then converted into a DataHandler using the obvious constructor:

dataHandler=new DataHandler(bytes,"application/octet-stream"); 

This worked great until we started trying to store and retrieve larger files. Dumping the entire file contents into a byte array and then building a DataHandler out of that simply requires too much memory.

My immediate idea is to retrieve a stream of the data in the database with getBinaryStream and somehow convert that InputStream into a DataHandler in a memory-efficient way. Unfortunately it doesn't seem like there's a direct way to convert an InputStream into a DataHandler. Another idea I've been playing with is reading chunks of data from the InputStream and writing them to the OutputStream of the DataHandler. But... I can't find a way to create an "empty" DataHandler that returns a non-null OutputStream when I call getOutputStream...

Has anyone done this? I'd appreciate any help you can give me or leads in the right direction.

Answer 1

An implementation of answer from "Kathy Van Stone":

At first create helper class, which create DataSource from InputStream:

public class InputStreamDataSource implements DataSource {     private InputStream inputStream;      public InputStreamDataSource(InputStream inputStream) {         this.inputStream = inputStream;     }      @Override     public InputStream getInputStream() throws IOException {         return inputStream;     }      @Override     public OutputStream getOutputStream() throws IOException {         throw new UnsupportedOperationException("Not implemented");     }      @Override     public String getContentType() {         return "*/*";     }      @Override     public String getName() {         return "InputStreamDataSource";     } } 

And then you can create DataHandler from InputStream:

DataHandler dataHandler = new DataHandler(new InputStreamDataSource(inputStream)) 

imports:

import javax.activation.DataSource; import java.io.OutputStream; import java.io.InputStream; 

Answer 2

I also ran into this issue. If your source data is a byte[] Axis already has a class that wraps the InputStream and creates a DataHandler object. Here is the code

//this constructor takes byte[] as input ByteArrayDataSource rawData= new ByteArrayDataSource(resultSet.getBytes(1)); DataHandler data= new DataHandler(rawData); yourObject.setData(data); 

Related imports

import javax.activation.DataHandler; import org.apache.axiom.attachments.ByteArrayDataSource; 

Hope it helps!