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https://issues.apache.org/jira/browse/HADOOP-9240?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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David Parks updated HADOOP-9240:
--------------------------------
Affects Version/s: 1.0.3
> Making ArrayWritable typed
> --------------------------
>
> Key: HADOOP-9240
> URL: https://issues.apache.org/jira/browse/HADOOP-9240
> Project: Hadoop Common
> Issue Type: Improvement
> Components: io
> Affects Versions: 1.0.3
> Reporter: David Parks
> Priority: Minor
>
> ArrayWritable is just painful to use in practice, it would be nice if we had
> a typed version of ArrayWritable that had all the features of an ArrayList.
> It wasn't hard to write, and it doesn't cost more in terms of storage or CPU
> than an ArrayWritable.
> So I wonder why not include a more usable ArrayListWritable class with
> Hadoop? Code pasted below, unless there's a reason that this is a bad idea
> I'm happy to provide the unit test for it as well.
> @SuppressWarnings("serial")
> public class ArrayListWritable<E extends Writable> extends ArrayList<E>
> implements Writable {
> Class<E> type = null;
>
> public ArrayListWritable(Class<E> type){
> super();
> this.type = type;
> }
>
> public ArrayListWritable(){
> super();
> }
>
> public void setArrayClassType(Class<E> clazz){
> this.type = clazz;
> }
>
> @Override
> public void write(DataOutput out) throws IOException {
> if(type==null){ throw new IOException("Cannot write an " +
> getClass().getName() + " without the class type being set in the constructor
> or with setArrayClassType(...)"); };
> out.writeUTF(type.getCanonicalName());
> out.writeInt(size());
> for(E writable : this) writable.write(out);
> }
>
> @SuppressWarnings("unchecked")
> @Override
> public void readFields(DataInput in) throws IOException {
> clear();
>
> //Read the class name
> try {
> type = (Class<E>)Class.forName(in.readUTF());
> } catch (ClassNotFoundException e) {
> throw new IOException("Invalid connonical name read
> from input bytes", e);
> }
> //Read the size & set capacity of the arraylist
> int size = in.readInt();
> ensureCapacity(size);
>
> //Read in individual writables
> for (int i = 0; i < size; i++) {
> Writable value = WritableFactories.newInstance(type);
> value.readFields(in); // read a
> value
> add((E)value);
> // add it to the ArrayList
> }
> }
> }
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