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• ResultSetIterator.java

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com.rapiddweller.jdbacl.ResultSetIterator Maven / Gradle / Ivy

/*
 * (c) Copyright 2007-2014 by Volker Bergmann. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, is permitted under the terms of the
 * GNU General Public License.
 *
 * For redistributing this software or a derivative work under a license other
 * than the GPL-compatible Free Software License as defined by the Free
 * Software Foundation or approved by OSI, you must first obtain a commercial
 * license to this software product from Volker Bergmann.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * WITHOUT A WARRANTY OF ANY KIND. ALL EXPRESS OR IMPLIED CONDITIONS,
 * REPRESENTATIONS AND WARRANTIES, INCLUDING ANY IMPLIED WARRANTY OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE
 * HEREBY EXCLUDED. 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 com.rapiddweller.jdbacl;

import com.rapiddweller.common.HeavyweightIterator;
import org.slf4j.LoggerFactory;
import org.slf4j.Logger;

import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;

/**
 * Wraps a ResultSet into the semantic of a {@link HeavyweightIterator}.
 * 

 * Created: 15.08.2007 18:19:25
 *
 * @author Volker Bergmann
 * @see HeavyweightIterator
 */
public class ResultSetIterator implements HeavyweightIterator {

  private static final Logger LOGGER = LoggerFactory.getLogger(ResultSetIterator.class);

  private final ResultSet resultSet;
  private Boolean hasNext;
  private String[] columnLabels;
  private boolean closed;
  private final String query;

  // constructors ----------------------------------------------------------------------------------------------------

  /**
   * Instantiates a new Result set iterator.
   *
   * @param resultSet the result set
   */
  public ResultSetIterator(ResultSet resultSet) {
    this(resultSet, "");
  }

  /**
   * Instantiates a new Result set iterator.
   *
   * @param resultSet the result set
   * @param query     the query
   */
  public ResultSetIterator(ResultSet resultSet, String query) {
    if (resultSet == null) {
      throw new IllegalArgumentException("resultSet is null");
    }
    this.resultSet = resultSet;
    this.hasNext = null;
    this.closed = false;
    this.query = query;
  }

  // interface -------------------------------------------------------------------------------------------------------

  /**
   * Get column labels string [ ].
   *
   * @return the string [ ]
   */
  public String[] getColumnLabels() {
    if (columnLabels == null) {
      try {
        ResultSetMetaData metaData = resultSet.getMetaData();
        int n = metaData.getColumnCount();
        columnLabels = new String[n];
        for (int i = 0; i < n; i++) {
          columnLabels[i] = metaData.getColumnLabel(i + 1);
        }
      } catch (SQLException e) {
        throw new RuntimeException("Error querying column meta data", e);
      }
    }
    return columnLabels;
  }

  @Override
  public boolean hasNext() {
    if (LOGGER.isDebugEnabled()) {
      LOGGER.debug("hasNext() called on: " + this);
    }
    if (hasNext != null) {
      return hasNext;
    }
    if (closed) {
      return false;
    }
    try {
      if (LOGGER.isDebugEnabled()) {
        LOGGER.debug("hasNext() checks resultSet availability of: " + this);
      }
      hasNext = resultSet.next();
      if (!hasNext) {
        close();
      }
      return hasNext;
    } catch (SQLException e) {
      throw new RuntimeException("Error in query: " + query, e);
    }
  }

  @Override
  public ResultSet next() {
    if (LOGGER.isDebugEnabled()) {
      LOGGER.debug("next() called on: " + this);
    }
    if (!hasNext()) {
      throw new IllegalStateException("No more row available. Use hasNext() for checking availability.");
    }
    hasNext = null;
    return resultSet;
  }

  @Override
  public void remove() {
    throw new UnsupportedOperationException("Not supported");
  }

  @Override
  public synchronized void close() {
    if (closed) {
      return;
    }
    LOGGER.debug("closing {}", this);
    hasNext = false;
    DBUtil.closeResultSetAndStatement(resultSet);
    closed = true;
  }

  // java.lang.Object overrides --------------------------------------------------------------------------------------

  @Override
  public String toString() {
    return getClass().getSimpleName() + '[' + query + ']';
  }

}