Android Open Source - interdroid-vdb Avro Schema Registration Handler

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Copyright (c) 2008-2012 Vrije Universiteit, The Netherlands All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the follo...
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Java Source Code

/*
 * Copyright (c) 2008-2012 Vrije Universiteit, The Netherlands All rights
 * reserved.//from  w w  w.j  a  va 2s.  c o m
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 *
 * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * Neither the name of the Vrije Universiteit nor the names of its contributors
 * may be used to endorse or promote products derived from this software without
 * specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS IS''
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */
package interdroid.vdb.content.avro;

import interdroid.util.DbUtil;
import interdroid.vdb.Authority;
import interdroid.vdb.content.EntityUriBuilder;

import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.avro.Schema;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.net.Uri;

/**
 * This handler manages registration of a schema with the AvroProviderRegistry.
 *
 * @author nick &lt;palmer@cs.vu.nl&gt;
 *
 */
public final class AvroSchemaRegistrationHandler {
  /**
   * Access to LOG.
   */
  private static final Logger LOG =
      LoggerFactory.getLogger(AvroSchemaRegistrationHandler.class);

  /**
   * No construction.
   */
  private AvroSchemaRegistrationHandler() {

  }

  /*
   * Note, these live in this class instead of the AvroProviderRegistry
   * because we don't want to have to include that class in the client
   * library.
   */

  /**
   * The name for our schema table.
   */
  public static final String NAME = "schema_registry";
  /**
   * The namespace for the schema table.
   */
  public static final String NAMESPACE = "interdroid.vdb.content.avro";
  /**
   * The name and namespace make up the full name.
   */
  public static final String FULL_NAME = NAMESPACE + "." + NAME;

  /**
   * The key for the schema field.
   */
  public static final String KEY_SCHEMA = "schema";
  /**
   * The key for the name of the schema.
   */
  public static final String KEY_NAME = "name";
  /**
   * The key for the namespace of the field.
   */
  public static final String KEY_NAMESPACE = "namespace";

  /**
   * The URI for the provider registry.
   */
  public static final Uri URI = Uri.withAppendedPath(
      EntityUriBuilder.branchUri(Authority.VDB,
          NAMESPACE, "master"), NAME);

  /**
   * This returns a list of maps with data about the various providers
   * perfect for use in an android ListView.
   *
   * @param context the context to query in
   * @return a list of maps with data from the registration table
   */
  public static List<Map<String, Object>> getAllRepositories(
      final Context context) {
    Cursor c = null;
    List<Map<String, Object>> result = new ArrayList<Map<String, Object>>();
    try {
      c = context.getContentResolver().query(URI, null,
          null, null, KEY_NAMESPACE + " ASC, " + KEY_NAME + " ASC");
      if (c != null) {
        LOG.debug("Cursor has: {}", c.getCount());
        c.moveToFirst();
        int name = DbUtil.getFieldIndex(c, KEY_NAME);
        int namespace =  DbUtil.getFieldIndex(c, KEY_NAMESPACE);
        int schema =  DbUtil.getFieldIndex(c, KEY_SCHEMA);

        do {
          Map<String, Object> map = new HashMap<String, Object>();
          map.put(KEY_NAME, c.getString(name));
          map.put(KEY_NAMESPACE, c.getString(namespace));
          map.put(KEY_SCHEMA, c.getString(schema));
          result.add(map);
          c.moveToNext();
        } while (!c.isAfterLast());
      }
    } finally {
      if (c != null) {
        c.close();
      }
    }
    LOG.debug("Returning {} repository", result.size());
    return result;
  }

  /**
   * Delete a schema and the data on disk.
   *
   * @param context the context to work in
   * @param name the repository to delete
   */
  public static void delete(final Context context, final String name) {
    context.getContentResolver().delete(URI, KEY_NAMESPACE + " = ?",
        new String[] {name});
  }

  /**
   * Register a schema with the provider registry.
   *
   * @param context the context to work in
   * @param schema the schema to register
   * @throws IOException if something goes wrong writing the database
   */
  public static void registerSchema(final Context context,
      final Schema schema) throws IOException {
    // Have we already registered?
    Cursor c = null;
    try {
      LOG.debug("Checking for registration of {} {}", schema.getName(),
          schema.getNamespace());
      LOG.debug("Querying against URI: {}", URI);
      c = context.getContentResolver().query(URI,
          new String[] {KEY_SCHEMA},
          KEY_NAME + " = ? AND " + KEY_NAMESPACE + " = ?",
          new String[] {schema.getName(), schema.getNamespace()},
          null);
      LOG.debug("Got cursor: {}", c);
      if (c != null) {
        if (c.getCount() == 0) {
          LOG.debug("Not already registered.");
          ContentValues values = new ContentValues();
          values.put(KEY_SCHEMA, schema.toString());
          values.put(KEY_NAME, schema.getName());
          values.put(KEY_NAMESPACE, schema.getNamespace());
          context.getContentResolver().insert(URI, values);
        } else {
          // Do we need to update the schema then?
          LOG.debug("Checking if we need to update: {}", c.getCount());
          c.moveToFirst();
          String curString = c.getString(0);
          LOG.debug("Checking: {} against {}",
              curString, schema.toString());

          if (!curString.equals(schema.toString())) {
            LOG.debug("Update required.");

            ContentValues values = new ContentValues();
            values.put(KEY_SCHEMA, schema.toString());
            context.getContentResolver().update(URI,
                values, KEY_NAME + " = ?",
                new String[]{
                AvroSchemaRegistrationHandler.KEY_NAME});
          }
        }
      } else {
        LOG.error("Unexpected error registering schema");
        throw new RuntimeException("Unable to query Schema Registry!");
      }
    } finally {
      if (c != null) {
        c.close();
      }
    }
    LOG.debug("Schema registration complete.");
  }
}
Java Source Code List
