I believe in this case you'll want to make Sample and Address writable as well.
On 10/10/07, Steve Schlosser <[EMAIL PROTECTED]> wrote:
> Hello all
>
> Is there a best practice for using my own classes as keys and values?
>
> My first attempt at doing this was successful - I built a
> BigIntegerWritable class using IntWritable as a template. It was easy
> because BigInteger has methods converting to and from byte arrays,
> which I could then write into the DataOutput or read from the
> DataInput.
>
> It seems like I should be able to use object serialization to write
> to/read from the DataOutput/Input objects and make my own classes
> implement the Writable interface. It seems like I should be able to
> do something like this:
>
> import java.io.*;
>
> import org.apache.hadoop.io.*;
>
> public class Sample implements Writable {
>
> Address address;
> SampleValue value; // sampled value at this point
>
> public Sample(Address a, SampleValue v) {
> address = a;
> value = v;
> }
>
> public SampleValue getValue() { return value;}
> public Address getAddress() { return address; }
>
> public String toString () {
> return (address.toString() + " " + value.toString());
> }
>
> [...]
>
> public void readFields(DataInput in) throws IOException {
> ObjectInputStream oin = new ObjectInputStream((DataInputBuffer)in);
>
> try {
> address = (Address)oin.readObject();
> value = (SampleValue)oin.readObject();
> } catch (ClassNotFoundException e) {
> throw new IOException(e.toString());
> }
>
> }
>
> public void write(DataOutput out) throws IOException {
> ObjectOutputStream oout = new
> ObjectOutputStream((DataOutputBuffer)out);
>
> oout.writeObject(address);
> oout.writeObject(value);
> }
> }
>
> This code compiles, but throws exceptions at runtime, complaining that
> WritableComparator can not access a member of class Sample with
> modifiers "". Can someone tell me what this exception is talking
> about?
>
> Do I need to implement a WritableComparator for each class that I want
> to implement Writable?
>
> Thanks again for the help.
>
> -steve
>
