Koherent App Engine Library is a library for Google App Engine for Java.

It includes "DatastoreMap" which enable to operate Datastores like java.util.HashMap, "DatastoreOutputStream" which enable to write data to Datastores like java.util.FileOutputStream and so on.

"CachedDatastoreMap" is also available which is DatastoreMap transparently cache data using Memcache. "FastDatastoreMap" and "FastCachedDatastoreMap" provides faster way to operate Datastores whose put or remove methods always return null.

License

This library is distributed under Apache 2.0 License. See LICENSE, which is a file included in the same directory as this file, for more information.

Sample Codes

DatastoreMap

// operates Datastores like java.util.HashMap

Map<String, Integer> map = new DatastoreMap<String, Integer>("people");

map.put("Tom", 27); map.put("Mary", 21); map.put("John", 23);

int ageOfMary = map.get("Mary");

map.remove("Tom");

DatastoreInputStream

// operates Datastores like java.io.FileInputStream

BufferedWriter writer = null; try { writer = new BufferedWriter(new OutputStreamWriter( new DatastoreOutputStream("sample")));

writer.write("Hello");
writer.newLine();
writer.write("World");
writer.newLine();

writer.flush();

} catch (IOException e) { e.printStackTrace(); } finally { if (writer != null) { writer.close(); } }

DatastoreOutputStream

// operates Datastores like java.io.FileOutputStream

BufferedReader reader = null; try { reader = new BufferedReader(new InputStreamReader( new DatastoreInputStream("sample")));

String line;
while ((line = reader.readLine()) != null) {
    System.out.println(line);
}

} catch (IOException e) { e.printStackTrace(); } finally { if (reader != null) { reader.close(); } }

How to Use

Download koherent-appengine-lib.jar and copy it into /WEB-INF/lib of a Web Application Project of Google App Engine. If you use Eclipse, you also set Build Path (Right Click on the project -> Properties -> Java Build Path -> Libraries -> Add JARs).

Classes

org.koherent.collection.appengine

DatastoreMap : operates Datastores in the same way as java.util.Map MemcacheMap : operates Memcache in the same way as java.util.Map CachedDatastoreMap : DatastoreMap which transparently cache data to Memcache FastDatastoreMap : fast DatastoreMap whose put and remove methods always return null FastMemcacheMap : fast MemcacheMap whose put and remove methods always return null FastCachedDatastoreMap : fast CachedDatastoreMap whose put and remove methods always return null

org.koherent.io.appengine

DatastoreInputStream : operates Datastores in the same way as java.io.InputStream DatastoreOutputStrem : operates Datastores in the same way as java.io.OutputStream DatastoreReader : operates Datastores in the same way as java.io.Reader DatastoreWriter : operates Datastores in the same way as java.io.Writer

7th Mar 2010