Would you provide a code sample of it? I don't know how to do serializer in
hadoop.
I am using the following class as type of my "value" object:
private static class StringArrayWritable extends ArrayWritable {
private StringArrayWritable (String [] aSString) {
super (aSString);
}
}
Thanks.
Aaron Kimball-3 wrote:
>
> The text serializer will pull out an entire string by using a null
> terminator at the end.
>
> If you need to know the number of string objects, though, you'll have to
> serialize that before the strings, then use a for loop to decode the rest
> of
> them.
> - Aaron
>
> On Tue, Jun 2, 2009 at 6:01 PM, dealmaker <vin...@gmail.com> wrote:
>
>>
>> Thanks. The number of elements in this array of String is unknown until
>> run
>> time. If datainput treats it as a byte array, I still have to know the
>> size
>> of each String. How do I do that? Would you suggest some code samples
>> or
>> links that deal with similar situation like this? The only examples I
>> got
>> are the ones about counting number of words which deal with integers.
>> Thanks.
>>
>>
>> Aaron Kimball-3 wrote:
>> >
>> > Hi,
>> >
>> > You can't just turn either of these two types into arrays of strings
>> > automatically, because they are interfaces to underlying streams of
>> data.
>> > You are required to know what protocol you are implementing -- i.e.,
>> how
>> > many fields you are transmitting -- and manually read through that many
>> > fields yourself. For example, a DataInput object is effectively a
>> pointer
>> > into a byte array. There may be many records in that byte array, but
>> you
>> > only want to read the fields of the first record out.
>> >
>> > For DataInput / DataOutput, you can UTF8-decode the next field by
>> calling
>> > Text.readString(dataInput) and Text.writeString(dataOutput).
>> > For ResultSet, you want resultSet.getString(fieldNum)
>> >
>> > As (yet another) shameless plug ( :smile: ), check out the tool we just
>> > released, which automates database import tasks. It auto-generates the
>> > classes necessary for your tables, too.
>> > http://www.cloudera.com/blog/2009/06/01/introducing-sqoop/
>> >
>> > At the very least, you might want to play with it a bit and read its
>> > source
>> > code so you have a better idea of how to implement your own class
>> (since
>> > you're doing some more creative stuff like building up associative
>> arrays
>> > for each field).
>> >
>> > Cheers,
>> > - Aaron
>> >
>> > On Mon, Jun 1, 2009 at 9:53 PM, dealmaker <vin...@gmail.com> wrote:
>> >
>> >>
>> >> bump. Does anyone know?
>> >>
>> >> I am using the following class of arraywritable:
>> >>
>> >> private static class StringArrayWritable extends ArrayWritable {
>> >> private StringArrayWritable (String [] aSString) {
>> >> super (aSString);
>> >> }
>> >> }
>> >>
>> >>
>> >> dealmaker wrote:
>> >> >
>> >> > Hi,
>> >> > How do I convert DataInput to array of String?
>> >> > How do I convert ResultSet to array of String?
>> >> > Thanks. Following is the code:
>> >> >
>> >> > static class Record implements Writable, DBWritable {
>> >> > String [] aSAssoc;
>> >> >
>> >> > public void write(DataOutput arg0) throws IOException {
>> >> > throw new UnsupportedOperationException("Not supported yet.");
>> >> > }
>> >> >
>> >> > public void readFields(DataInput in) throws IOException {
>> >> > this.aSAssoc = // How to convert DataInput to String Array?
>> >> > }
>> >> >
>> >> > public void write(PreparedStatement arg0) throws SQLException {
>> >> > throw new UnsupportedOperationException("Not supported yet.");
>> >> > }
>> >> >
>> >> > public void readFields(ResultSet rs) throws SQLException {
>> >> > this.aSAssoc = // How to convert ResultSet to String Array?
>> >> > }
>> >> > }
>> >> >
>> >> >
>> >>
>> >> --
>> >> View this message in context:
>> >>
>> http://www.nabble.com/How-do-I-convert-DataInput-and-ResultSet-to-array-of-String--tp23770747p23826464.html
>> >> Sent from the Hadoop core-user mailing list archive at Nabble.com.
>> >>
>> >>
>> >
>> >
>>
>> --
>> View this message in context:
>> http://www.nabble.com/How-do-I-convert-DataInput-and-ResultSet-to-array-of-String--tp23770747p23843679.html
>> Sent from the Hadoop core-user mailing list archive at Nabble.com.
>>
>>
>
>
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