ExportAsStream.java

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/*
 * Turró i Cutiller Foundation. License notice.
 * Copyright (C) 2021 Lluis Turró Cutiller <http://www.turro.org/>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
package org.turro.jpa.export;
 
import java.io.File;
import java.io.IOException;
import java.util.Collection;
import java.util.Date;
import java.util.function.BiFunction;
import java.util.stream.Stream;
import jxl.Workbook;
import jxl.write.DateTime;
import jxl.write.Label;
import jxl.write.WritableSheet;
import jxl.write.WritableWorkbook;
import jxl.write.WriteException;
import org.turro.elephant.db.WhereClause;
import org.turro.jpa.Dao;
import org.turro.log.WebLoggers;
import org.turro.sql.SqlClause;
import org.turro.time.Dates;
 
public class ExportAsStream {
 
  private static final int MAX_ROWS = 60000;
  
  private final Dao dao;
  private final SqlClause sc;
  private final WhereClause wc;
  private final Collection<String> columns;
  
  private int countCols = 0, countRows = 0;
  private BiFunction<Integer, Object, Object> replace = null;
  private WritableWorkbook ww;
  private WritableSheet ws;
 
  public ExportAsStream(Dao dao, Collection<String> columns, SqlClause sc) {
    this.dao = dao;
    this.columns = columns;
    this.sc = sc;
    this.wc = null;
  }
  
  public ExportAsStream(Dao dao, Collection<String> columns, WhereClause wc) {
    this.dao = dao;
    this.columns = columns;
    this.sc = null;
    this.wc = wc;
  }
  
  public void fieldReplacement(BiFunction<Integer, Object, Object> replace) {
    this.replace = replace;
  }
  
  public void generateExcel(File file) {
    try {
      ww = Workbook.createWorkbook(file);
      writeSheet();
      ww.write();
      ww.close();
    } catch (WriteException | IOException ex) {
      WebLoggers.severe(this).exception(ex).log();
    }
  }
 
  private void writeSheet() throws WriteException {
    checkSheet();
    for(String s : columns) {
      ws.addCell(new Label(countCols++, countRows, s));
    }
    if(sc != null) {
      try(Stream stream = dao.stream(Object[].class, sc)) {
        writeRows(stream);
      }
    } else if(wc != null) {
      try(Stream stream = dao.stream(Object[].class, wc)) {
        writeRows(stream);
      }
    }
  }
 
  private void writeRows(final Stream stream) {
    stream.forEach(objs -> {
      countCols = 0;
      countRows++;
      checkSheet();
      for(Object obj : (Object[]) objs) {
        try {
          if(replace != null) {
            obj = replace.apply(countCols, obj);
          }
          if(obj instanceof Number) {
            ws.addCell(new jxl.write.Number(countCols++, actualRow(),
                    ((Number)obj).doubleValue()));
          } else if(obj instanceof Date) {
            ws.addCell(new DateTime(countCols++, actualRow(), Dates.fromGTM((Date) obj).get()));
          } else if(obj instanceof Boolean) {
            ws.addCell(new Label(countCols++, actualRow(), ((Boolean) obj).toString()));
          } else {
            ws.addCell(new Label(countCols++, actualRow(), (String) obj));
          }
        } catch (WriteException ex) {
          WebLoggers.severe(this).exception(ex).log();
        }
      }
    });
  }
 
  private void checkSheet() {
    if(actualRow() == 0) {
      int sheetIndex = Math.abs(countRows / MAX_ROWS);
      ws = ww.createSheet("Sheet %d".formatted(sheetIndex), sheetIndex);
    }
  }
  
  private int actualRow() {
    return countRows % MAX_ROWS;
  }
  
}