使用Apache POI編寫包含60多個列的大型Excel工作表

Question

我正在嘗試使用從數據庫中獲取的數據創建多個Excel工作表。 每個Excel工作表包含60多個列和大約5萬條記錄（可能有所不同）。 問題是系統花費大量時間（5分鍾以上），然后最終出現java.lang.OutOfMemoryError: GC overhead limit exceeded異常。

我嘗試將列數減少到僅6，這樣就大大縮短了周轉時間。

這是生成Excel工作表的字節數組的代碼：

int rowIndex = 0;
while (iterator.hasNext()) {
        List<CustomCellDataBean> cellData = iterator.next();

        // Insert generic data
        Row dataContentRow = sheet.createRow((short) rowIndex);

        for (int counter = 0; counter < cellData.size(); counter++) {
            CustomCellDataBean cd = cellData.get(counter);
            if (cd.getValue() != null) {
            // switch case based on the datatype of the cell
                switch (cd.getType()) {
                }
            }
        }
        rowIndex++;
}
// write to ByteArrayOutputStream and return the array of bytes

已經提到了幾個SO問題，但無法找出有用的東西。 想知道是否應該嘗試解決該問題。

Answer 1

沒有更多信息，我只能猜測您的真正問題是什么。 但是我可以告訴你，apache poi可以創建具有1000列以上和2萬行以上的顏色，樣式和內容的Excel工作表（已經完成）。

確保使用apache.poi API的流式API

org.apache.poi.xssf.streaming

這是Apache的演示

大網格演示

更新

正如它在演示中所指出的那樣，我鏈接到您的用戶可能應該使用新的SXSSF用戶模型（如果我記得正確的話，我會使用該模型），因為它可以為您處理所有流式傳輸內容；-)

SXSSF（流用戶模型API）

Answer 2

似乎有些倒退，但是當使用帶有POI的大型數據集時，我更喜歡手動構建工作表。 這是我使用的幫助程序類，可幫助您入門：

public class Worksheet {
private static Logger logger = Logger.getLogger(Worksheet.class);

/**
 * XML data for building the worksheet.
 */
public StringBuilder data = new StringBuilder();

/**
 * The name of this worksheet's entry in the XLSX file.
 */
public String zipEntryName;

/**
 * Tracks the last row written to the spreadsheet.
 */
// xslx rows start at 1
// Changed lastRow to init at 0 after using startRow() for headers.
public int lastRow = 0;

/**
 * Tracks the last cell written to the spreadsheet.
 */
public int lastCell = 0;

/**
 * Stores any styles that have been generated using XSSF.
 */
public HashMap<String, XSSFCellStyle> styles = new HashMap<String, XSSFCellStyle>();

/**
 * Tracks any merged cells so that they can be appended to the worksheet XML.
 */
public List<String> merged = new ArrayList<String>();

private boolean inRow = false;

private XSSFSheet myWorksheet = null;

public void setPOIWorksheet(XSSFSheet sheet){
    myWorksheet = sheet;
    this.zipEntryName = sheet.getPackagePart().getPartName().getName().substring(1);
}
public XSSFSheet getPOIWorksheet(){
    return this.myWorksheet;
}

/**
 * Write the raw XML data of newSheets to the existing XLSX file in workbook.
 * @param workbook The current XSLX file to overwrite data in.
 * @param newSheets A Collection of Worksheet objects containing the XML data to insert into workbook.
 * @param newFile The OutputStream to write the new XLSX file to.
 */
public static void writeWorksheetsToWorkbook(InputStream workbook, Collection<Worksheet> newSheets, OutputStream newFile)
{
    ZipOutputStream zipStream = null;
    try{
        zipStream = new ZipOutputStream(newFile);
        ZipInputStream zip = new ZipInputStream(workbook);
        ZipEntry entry;
        // Copy unaffected entries.
        while((entry = zip.getNextEntry()) != null){
            boolean found = false;
            for(Worksheet ws : newSheets){
                if(entry.getName().equals(ws.zipEntryName)){
                    found = true;
                    break;
                }
            }
            if(!found){
                zipStream.putNextEntry(new ZipEntry(entry.getName()));
                byte[] buffer = new byte[1];
                while((zip.read(buffer, 0, 1)) > -1)
                    zipStream.write(buffer);
            }
        }
        // Insert XML for entries being replaced.
        for(Worksheet ws : newSheets){
            zipStream.putNextEntry(new ZipEntry(ws.zipEntryName));
            byte[] data = ws.data.toString().getBytes();
            zipStream.write(data, 0, data.length);
        }
    }catch(Exception e){
        logger.error("Error creating xlsx", e);
    }finally{
        if(zipStream != null) try{ zipStream.close(); }catch(Exception e){}
        if(newFile != null) try{ newFile.close(); }catch(Exception e){}
    }
}

/**
 * Write the raw XML data of newSheets to the existing XLSX file in workbook.
 * @param workbook The current XSLX file to overwrite data in.
 * @param newSheets A Collection of Worksheet objects containing the XML data to insert into workbook.
 * @param return A byte[] containing the new workbook.
 */
public static byte[] writeWorksheetsToWorkbook(InputStream workbook, Collection<Worksheet> newSheets){
    ByteArrayOutputStream bout = new ByteArrayOutputStream();
    writeWorksheetsToWorkbook(workbook, newSheets, bout);
    return bout.toByteArray();
}

public Worksheet setWorksheetName(XSSFSheet xssfWS){
    zipEntryName = xssfWS.getPackagePart().getPartName().getName().substring(1);

    return this;
}

/**
 * Write all of the XML used for starting the worksheet.
 */
public Worksheet startWorksheet(){
    data.append("<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n");
    data.append("<worksheet xmlns=\"http://schemas.openxmlformats.org/spreadsheetml/2006/main\" ");
    data.append("xmlns:r=\"http://schemas.openxmlformats.org/officeDocument/2006/relationships\" ");
    data.append("xmlns:mc=\"http://schemas.openxmlformats.org/markup-compatibility/2006\" >\n");
    data.append("<sheetData>\n");

    return this;
}

/**
 * Write the XML for closing the worksheet, including merged cell data.
 */
public Worksheet closeWorksheet(){
    data.append("</sheetData>\n");

    if(merged.size() > 0){
        data.append("<mergeCells count=\"");
        data.append(merged.size());
        data.append("\">");
        for(String cells : merged){
            data.append("<mergeCell ref=\"");
            data.append(cells);
            data.append("\"/>");
        }
        data.append("</mergeCells>\n");
    }       
    data.append("</worksheet>\n");

    return this;
}

/**
 * Method for adding a new row to an Excel file.  This was added as part of Period Compliance Report because
 * we're not iterating over data like previous reports.
 * 
 * This will automatically close the previous row if left open.
 */
public Worksheet startRow(){
    lastCell = 0;
    if(inRow)
        endRow();

    lastRow++;
    data.append("<row r=\""+lastRow+"\">");
    inRow = true;

    return this;
}

/**
 * Method for closing a row in an Excel file.
 */
public Worksheet endRow(){
    data.append("</row>\n");
    inRow = false;

    return this;
}

/**
 * Method for adding Date data to an Excel file cell.
 * @param value The data to be added to the cell.
 */
public Worksheet addDateCell(String value){
    return addTextCell(value, null);
}
/**
 * Method for adding Date data to an Excel file cell.
 * @param value The data to be added to the cell.
 * @param formatting Any style formatting to be used.
 */
public Worksheet addDateCell(String value, String formatting){
    return addTextCell(value, formatting);
}

/**
 * Method for adding String data to an Excel file cell. This was added as part of Period Compliance Report because
 * we're not iterating over data like previous reports.
 * @param value The data to be added to the cell.
 */
public Worksheet addTextCell(String value){
    return addTextCell(value, null);
}
/**
 * Method for adding String data to an Excel file cell.
 * @param value The data to be added to the cell.
 * @param formatting Any style formatting used on the cell.
 */
public Worksheet addTextCell(String value, String formatting){
    return addCell(StringEscapeUtils.escapeXml(value), formatting, false, 0);
}
/**
 * Method for adding String data to an Excel file cell.
 * @param value The data to be added to the cell.
 * @param formatting Any style formatting used on the cell.
 * @param mergeRight The number of cells to the right of this one that should be merged.
 */
public Worksheet addMergedTextCell(String value, String formatting, int mergeRight){
    return addCell(StringEscapeUtils.escapeXml(value), formatting, false, mergeRight);
}


/**
 * Method for adding numerical data to an Excel file cell.
 * @param value The data to be added to the cell.
 */
public Worksheet addNumberCell(String value){
    return addNumberCell(value,  null);
}
/**
 * Method for adding numerical data to an Excel file cell.
 * @param value The data to be added to the cell.
 */
public Worksheet addNumberCell(Number value){
    return addNumberCell(value.toString(), null);
}
/**
 * Method for adding numerical data to an Excel file cell.
 * @param value The data to be added to the cell.
 * @param formatting Any style formatting used on the cell.
 */
public Worksheet addNumberCell(String value, String formatting){
    return addCell(value, formatting, true, 0);
}
/**
 * Method for adding numerical data to an Excel file cell.
 * @param value The data to be added to the cell.
 * @param formatting Any style formatting used on the cell.
 */
public Worksheet addNumberCell(Number value, String formatting){
    return addCell(value.toString(), formatting, true, 0);
}
/**
 * Method for adding numerical data to an Excel file cell.
 * @param value The data to be added to the cell.
 * @param formatting Any style formatting used on the cell.
 * @param mergeRight The number of cells to the right of this one that should be merged.
 */
public Worksheet addMergedNumberCell(String value, String formatting, int mergeRight){
    return addCell(value, formatting, true, mergeRight);
}
/**
 * Method for adding numerical data to an Excel file cell.
 * @param value The data to be added to the cell.
 * @param formatting Any style formatting used on the cell.
 * @param mergeRight The number of cells to the right of this one that should be merged.
 */
public Worksheet addMergedNumberCell(Number value, String formatting, int mergeRight){
    return addCell(value.toString(), formatting, true, mergeRight);
}

/**
 * Method for adding data to an Excel file cell.
 * @param value The data to be added to the cell.
 * @param element The cell location on the table row.
 * @param formatting The formatting style to use.
 * @param mergeRight The number of cells that should be merged to the right.
 * @return This Worksheet.
 */
private Worksheet addCell(String value, String formatting, boolean number, int mergeRight){
    String ref = addCell(value, formatting, number);

    if(mergeRight > 0){
        String right = null;
        for(int i = 1; i <= mergeRight; i++)
            right = addCell("", formatting, false);
        merged.add(ref+":"+right);
    }

    return this;
}
/**
 * Method for adding data to an Excel file cell.
 * @param value The data to be added to the cell.
 * @param element The cell location on the table row.
 * @param formatting The formatting style to use.
 * @return A String with the new cell's location.
 */
private String addCell(String value, String formatting, boolean number){
    String ref = new CellReference(lastRow-1,lastCell).formatAsString();
    data.append("<c ");
    if(formatting != null && styles.containsKey(formatting)){
        XSSFCellStyle style = styles.get(formatting);
        data.append("s=\"");
        data.append(style.getIndex());
        data.append("\" ");
    }else if(formatting != null)
        logger.debug("could not find style "+formatting);
    data.append("r=\"");
    data.append(ref);
    data.append((number) ? "\">" : "\" t=\"inlineStr\">");
    /*if(formatting == null) data.append((number) ? "\">" : "\" t=\"inlineStr\">");
    else{
        data.append("\" t=\"");
        data.append(formatting);
        data.append("\">");
    }*/
    data.append((number) ? "<v>" : "<is><t>");
    data.append(value);
    data.append((number) ? "</v>" : "</t></is>");
    data.append("</c>");
    lastCell++;

    return ref;
}

/**
 * Adds a bunch of cells to a row quickly.
 * @param fields The fields to be added.
 */
public Worksheet quickAdd(String... fields){
    if(!inRow)
        startRow();
    for(int i = 0; i < fields.length; i++)
        addTextCell(fields[i]);

    return this;
}
}