Android Open Source - DKO Query Snapshot

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License

The source code is released under:

GNU Lesser General Public License

Java Source Code

package org.kered.dko;
// ww w  . j a va 2 s. c o m
import java.io.File;
import java.io.IOException;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;

import javax.sql.DataSource;

import org.kered.dko.Constants.DB_TYPE;
import org.kered.dko.Constants.JOIN_TYPE;
import org.kered.dko.datasource.JDBCDriverDataSource;
import org.kered.dko.datasource.SingleThreadedDataSource;

class QuerySnapshot<T extends Table> implements Iterable<T> {

  private static final String PREFIX = "dko_snapshot_";
  private static final String EXT = ".sqlite.db";

  private final File f;
  private final boolean delete;
  private SingleThreadedDataSource ds;
  private final Query<T> q;
  private final String tmpTableName = genTmpTableName();
  private String sql;
  private List<Field<?>> fields;

  public QuerySnapshot(Query<T> q) {
    this.q = q;
    try {
      f = File.createTempFile(PREFIX, EXT);
      delete = true;
      f.deleteOnExit();
    } catch (IOException e) {
      throw new RuntimeException(e);
    }
    init();
  }

  private String genTmpTableName() {
    StringBuffer sb = new StringBuffer();
    sb.append(PREFIX);
    for (int i=0; i<8; ++i) {
      sb.append((char) ('A' + Math.random()*('Z'-'A')));
    }
    return sb.toString();
  }

  public QuerySnapshot(Query<T> q, File f) {
    this.q = q;
    if (f.isDirectory()) {
      try {
        this.f = File.createTempFile(PREFIX, EXT, f);
        delete = true;
        f.deleteOnExit();
      } catch (IOException e) {
        throw new RuntimeException(e);
      }
    } else {
      this.f = f;
      delete = false;
    }
    init();
  }

  private void init() {
    // make sure sqlite driver is loaded...
    org.kered.dko.persistence.Util.getDS();
    String url = "jdbc:sqlite:" + f.getPath();
    ds = new SingleThreadedDataSource(new JDBCDriverDataSource(Constants.DB_TYPE.SQLITE3, url), 10000, false);

    Map<Field, String> fieldNameOverrides = LocalJoin.load(q, tmpTableName, ds);
    
    StringBuffer sb = new StringBuffer();
    sb.append("select ");
    fields = q.getSelectFields();
    for (Field<?> field : fields) {
      String fieldName = fieldNameOverrides.get(field);
      if (fieldName==null) fieldName = field.NAME;
      sb.append(tmpTableName).append(".").append(fieldName).append(", ");
    }
    sb.delete(sb.length()-2, sb.length()).append(" "); // delete the last comma
    sb.append("from ").append(tmpTableName);
    sql = sb.toString();
  }

  @Override
  public Iterator<T> iterator() {
    if (q instanceof DBQuery) {
      return new SelectFromOAI<T>((DBQuery<T>) q, buildSrcIterator());
    } else {
      throw new RuntimeException("not implemented (yet) for this query implementation: "+ q.getClass().getName());
    }
  }

  private PeekableClosableIterator<Object[]> buildSrcIterator() {
    return new PeekableClosableIterator<Object[]>() {
      Connection conn = null;
      private ResultSet rs = null;
      private Statement stmt = null;
      {
        try {
          conn = ds.getConnection();
          stmt = conn.createStatement();
          Util.log(sql, null);
          rs = stmt.executeQuery(sql);
        } catch (SQLException e) {
          throw new RuntimeException(e);
        }
      }
      private Object[] next = null;
      @Override
      public Object[] peek() {
        if (next!=null) return next;
        try {
          if (!rs.next()) return null;
          int leftSize = fields.size();
          next = new Object[leftSize];
          for (int i=0; i<leftSize; ++i) {
            next[i] = Util.getTypedValueFromRS(rs, i+1, fields.get(i));
          }
          return next;
        } catch (SQLException e) {
          throw new RuntimeException(e);
        }
      }
      @Override
      public boolean hasNext() {
        if (next==null) peek();
        return next != null;
      }
      @Override
      public Object[] next() {
        Object[] ret = next;
        next = null;
        return ret;
      }
      @Override
      public void remove() {
        throw new UnsupportedOperationException();
      }
      @Override
      public void close() {
        try {
          if (rs!=null && !rs.isClosed()) {
            rs.close();
            rs = null;
          }
        } catch (SQLException e) {
          e.printStackTrace();
        }
        try {
          if (stmt!=null && !stmt.isClosed()) {
            stmt.close();
            stmt = null;
          }
        } catch (SQLException e) {
          e.printStackTrace();
        }
        try {
          if (conn!=null && !conn.isClosed()) {
            conn.close();
            conn = null;
          }
        } catch (SQLException e) {
          e.printStackTrace();
        }
      }
      @Override
      protected void finalize() throws Throwable {
        close();
        super.finalize();
      }
    };
  }

  @Override
  protected void finalize() throws Throwable {
    if (delete && f.exists()) f.delete();
    super.finalize();
  }

}

Java Source Code List

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