Retrieving binary content

[Ted Roeloffzen <te...@gmail.com>]

Hi all,

I have a question. In my application I have a node named Plugin with a
reference to a node named Image. The image node contains an image. Now in my
application i retrieve the Plugin node, but i can't figure out how to get
the node that it has a reference to and than how to retrieve the image it
contains. Can anybody help me with that?

Thanks,

Ted

Re: Retrieving binary content

[Ted Roeloffzen <te...@gmail.com>]

Thanks al lot.

Ted

Re: Retrieving binary content

[Jukka Zitting <ju...@gmail.com>]

Hi,

On 11/28/06, Ted Roeloffzen <te...@gmail.com> wrote:
> > A common pattern I use when processing stream data is:
> >
> >    InputStream data = ...;
> >    try {
> >        byte[] buffer = new byte[BUFFER_SIZE];
> >        for (int n = data.read(buffer); n != -1; n = data.read(buffer)) {
> >            // process n bytes of data in buffer
> >        }
> >    } finally {
> >        data.close();
> >    }
>
> When I do this, i need to know how large the buffer needs to be, but i don't
> know how big it is. Is there a way to go around that?

The for loop is designed to read the stream in blocks. For example, you can use:

    private static final int BUFFER_SIZE = 1000;

... in which case the stream is read in blocks of up to a thousand
bytes. Each iteration of the for loop body will process a block of n
bytes stored in the allocated buffer.

For example if you want to store the image in a file or send it over
the network, you can do that by by writing the byte blocks to a
respective OutputStream, like this:

    InputStream data = ...;
    try {
        OutputStream destination = ...;
        try {
            byte[] buffer = new byte[BUFFER_SIZE];
            for (int n = data.read(buffer); n != -1; n = data.read(buffer)) {
                destination.write(buffer, 0, n);
            }
        } finally {
            destination.close();
        }
    } finally {
        data.close();
    }

If you need the whole binary stream available in memory as a byte
array, then you can use a ByteArrayOutputStream to accumulate the
data:

    OutputStream destination = new ByteArrayOutputStream();
    InputStream data = ...;
    try {
        byte[] buffer = new byte[BUFFER_SIZE];
        for (int n = data.read(buffer); n != -1; n = data.read(buffer)) {
            destination.write(buffer, 0, n);
        }
    } finally {
        data.close();
    }
    byte[] bytes = destination.toByteArray();

I hope this helps! See
http://java.sun.com/docs/books/tutorial/essential/io/bytestreams.html
and the related documentation for more information.

BR,

Jukka Zitting

Re: Retrieving binary content

[Ted Roeloffzen <te...@gmail.com>]

>
>
>
> A common pattern I use when processing stream data is:
>
>    InputStream data = ...;
>    try {
>        byte[] buffer = new byte[BUFFER_SIZE];
>        for (int n = data.read(buffer); n != -1; n = data.read(buffer)) {
>            // process n bytes of data in buffer
>        }
>    } finally {
>        data.close();

 }



When I do this, i need to know how large the buffer needs to be, but i don't
know how big it is.
Is there a way to go around that?

Ted

Re: Retrieving binary content

[Jukka Zitting <ju...@gmail.com>]

Hi,

On 11/28/06, Ted Roeloffzen <te...@gmail.com> wrote:
> And how do I read the actual data with that inputstream?

It's a standard java.io.InputStream. See the javadocs for example at
http://java.sun.com/j2se/1.4.2/docs/api/java/io/InputStream.html.

A common pattern I use when processing stream data is:

    InputStream data = ...;
    try {
        byte[] buffer = new byte[BUFFER_SIZE];
        for (int n = data.read(buffer); n != -1; n = data.read(buffer)) {
            // process n bytes of data in buffer
        }
    } finally {
        data.close();
    }

Note especially the finally branch used to guarantee that the stream
gets closed even if an error occurs.

> Sorry if this is a stupid question, but i'm not that experienced.

No problem, stupid is the one who doesn't ask. :-)

BR,

Jukka Zitting

Re: Retrieving binary content

[Ted Roeloffzen <te...@gmail.com>]

And how do I read the actual data with that inputstream?
Sorry if this is a stupid question, but i'm not that experienced.

Ted


2006/11/28, Jukka Zitting <ju...@gmail.com>:
>
> Hi,
>
> On 11/28/06, Ted Roeloffzen <te...@gmail.com> wrote:
> > I have a question. In my application I have a node named Plugin with a
> > reference to a node named Image. The image node contains an image. Now
> in my
> > application i retrieve the Plugin node, but i can't figure out how to
> get
> > the node that it has a reference to and than how to retrieve the image
> it
> > contains. Can anybody help me with that?
>
> Something like this should work:
>
>    Node plugin = ...;
>    Node image = plugin.getProperty("...").getNode();
>    InputStream data = image.getProperty("...").getStream();
>
> BR,
>
> Jukka Zitting
>

Re: Retrieving binary content

[Jukka Zitting <ju...@gmail.com>]

Hi,

On 11/28/06, Ted Roeloffzen <te...@gmail.com> wrote:
> I have a question. In my application I have a node named Plugin with a
> reference to a node named Image. The image node contains an image. Now in my
> application i retrieve the Plugin node, but i can't figure out how to get
> the node that it has a reference to and than how to retrieve the image it
> contains. Can anybody help me with that?

Something like this should work:

    Node plugin = ...;
    Node image = plugin.getProperty("...").getNode();
    InputStream data = image.getProperty("...").getStream();

BR,

Jukka Zitting