Re: [appengine-java] bulkloader dump and restore

[Ikai L (Google)]

Len,

I assume you are doing this by having different application versions for a
Python application and Java application as documented here:

http://googleappengine.blogspot.com/2009/06/10-things-you-probably-didnt-know-about.html

Then redefining your Java data class in Python in your Exporter class and
passing a string similar to this to appcfg.py:

appcfg.py --server=python.latest.YOURAPPID.appspot.com download_data APPDIR
 --filename=output.csv --kind=Thing --config_file=APPDIR/thing_exporter.py

There's a trick you'll need to export the key. Here's my Thing.java (
http://pastie.org/706983):

import com.google.appengine.api.datastore.Key;
import javax.jdo.annotations.*;

@PersistenceCapable(identityType = IdentityType.APPLICATION)
public class Thing {

    @PrimaryKey
    @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
    private Key key;

    @Persistent
    private String name;

    @Persistent
    private int number;

    public Thing(String name, int number) {
        this.name = name;
        this.number = number;
    }

    public Key getKey() {
        return key;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getNumber() {
        return number;
    }

    public void setNumber(int number) {
        this.number = number;
    }

}

Here's the corresponding Python exporter code (http://pastie.org/706981):

from google.appengine.ext import db
from google.appengine.tools import bulkloader

class Thing(db.Model):
  name = db.StringProperty()
  number = db.IntegerProperty()

def AddKeys(entity_generator):
    for entity in entity_generator:
        entity['key'] = entity.key()
        yield entity

class ThingExporter(bulkloader.Exporter):
    def __init__(self):
        bulkloader.Exporter.__init__(self, 'Thing',
                                     [('key', str, None),
                   ('name', str, None),
                                      ('number', str, None)
                                     ])


    def output_entities(self, entity_generator):
        bulkloader.Exporter.output_entities(self, AddKeys(entity_generator))

exporters = [ThingExporter]

The magic here is in the AddKey that you define. You add the "key" field to
the objects in each iteration of your loop exporting an entity.

On Fri, Nov 13, 2009 at 4:15 PM, lent <lentakeu...@gmail.com> wrote:

> Hello,
>
> I got python bulkloader upload data and download data working with
> loader and exporter for my java app.  Do the bulkloader dump and
> restore options work when used with java app?  They don't seem to work
> for me.  I get an error like:
> BadRequestError: app xxx cannot access app bulkload.latest.xxx's data
>
> When doing download data, how can I get the id field exported, i.e.
> what do you need to specify in the exporter to export the id field?  I
> tried field names such as key and id (of type db.Key) but they didn't
> work.
>
> Regards,
> Len
>
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-- 
Ikai Lan
Developer Programs Engineer, Google App Engine

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