SqlSentencesParser.java

/* vim: set ts=2 et sw=2 cindent fo=qroca: */

package com.globant.katari.tools;

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

import org.apache.commons.lang.Validate;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/** Parses a text files consisting of sql sentences separated by ';'.
 *
 * This parses is very naive, it considers a line ending in ; as a sentence
 * separator. If the ; is followed by white space, it is not considered the end
 * of the line.
 */
public class SqlSentencesParser {

  /** The class logger.
   */
  private static Logger log =
    LoggerFactory.getLogger(SqlSentencesParser.class);

  /** The reader with the sentences to parse.
   *
   * This is never null.
   */
  private BufferedReader sentences;

  /** The file name to read the sentences from.
   *
   * This is only used for error messages. It is never null.
   */
  private String fileName;

  /** Construct a SqlSentencesParser.
   *
   * @param theFileName The name of the file to parse, it cannot be null.
   */
  public SqlSentencesParser(final String theFileName) {
    Validate.notNull(theFileName, "The sql file name to parse cannot be null.");
    log.trace("Entering SqlSentencesParser('" + theFileName + "')");
    fileName = theFileName;
    try {
      sentences = new BufferedReader(new FileReader(theFileName));
    } catch (final IOException e) {
      throw new RuntimeException("Error opening " + theFileName, e);
    }
    log.trace("Leaving SqlSentencesParser");
  }

  /** Obtains the next sentence in the file.
   *
   * @return the next sentence in the file, or null if it reached the end.
   */
  public String readSentence() {
    log.trace("Entering readSentence");

    StringBuffer sentence = null;
    try {
      String line = null;
      while (null != (line = sentences.readLine())) {
        // I read a line, initialize the StringBuffer.
        if (sentence == null) {
          // Skip empty lines between sentences.
          if (line.length() == 0) {
            continue;
          }
          sentence = new StringBuffer();
        }
        if (line.endsWith(";")) {
          sentence.append(line.substring(0, line.length() - 1));
          return sentence.toString();
        } else {
          sentence.append(line);
          sentence.append("\n");
        }
      }
    } catch (IOException e) {
      throw new RuntimeException("Error reading from " + fileName, e);
    }
    if (sentence == null) {
      log.trace("Leaving runSqlSentences with null");
      return null;
    } else {
      log.trace("Leaving runSqlSentences");
      return sentence.toString();
    }
  }
}