情况如下; 我有一个简单的程序，它使用Apache Poi库在现有的xlsx文件的末尾添加一行数据。见下文
File file = new File(input);
XSSFWorkbook workbook = new XSSFWorkbook(file);
XSSFSheet sheet = workbook.getSheetAt(0);
XSSFRow row = sheet.createRow(sheet.getLastRowNum() + 1);
在此之后，我将迭代该行并设置CellValues。但问题是在代码的第二行，如上所示，我得到一个内存不足错误。有没有办法将一行数据添加到现有的xlsx文件而不必完全读取文件？
答案 0 :(得分：1)
您可以尝试XSSF and SAX (Event API)。
答案 1 :(得分：1)
如果由于内存不足错误导致XSSFWorkbook失败，并且需要阅读和编写工作簿，那么SXSSF和{{1}都不会解析器会有所帮助。这只是为了写作。另一个只是为了阅读。
以下两种方法都需要有关SAX文件格式Office Open XML的知识。通常，*.xlsx文件是*.xlsx存档，其中包含ZIP个文件和特殊目录结构中的其他文件。因此，可以使用XML软件解压缩*.xlsx文件，以查看ZIP文件。文件格式首先由Ecma标准化。因此，对于进一步的回顾，我更喜欢Ecma Markup Language Reference。例如Row。
两个示例中使用的XML必须至少有一个工作表，第一个工作表必须至少有一行。
一种方法可能是使用XMLBeans的ReadAndWriteTest.xlsx方法。我最喜欢的参考是grepcode。
示例：
DOM此代码在import org.apache.poi.openxml4j.opc.OPCPackage;
import org.apache.poi.openxml4j.opc.PackagePart;
import org.apache.poi.xssf.model.SharedStringsTable;
import java.io.File;
import java.io.OutputStream;
import org.openxmlformats.schemas.spreadsheetml.x2006.main.WorksheetDocument;
import org.openxmlformats.schemas.spreadsheetml.x2006.main.CTWorksheet;
import org.openxmlformats.schemas.spreadsheetml.x2006.main.CTSheetData;
import org.openxmlformats.schemas.spreadsheetml.x2006.main.CTRst;
import org.openxmlformats.schemas.spreadsheetml.x2006.main.CTCell;
import org.openxmlformats.schemas.spreadsheetml.x2006.main.STCellType;
import org.openxmlformats.schemas.officeDocument.x2006.relationships.STRelationshipId;
import org.apache.xmlbeans.XmlOptions;
import javax.xml.namespace.QName;
import java.util.Map;
import java.util.HashMap;
import java.util.regex.Pattern;
class DOMReadAndWriteTest {
public static void main(String[] args) {
try {
File file = new File("ReadAndWriteTest.xlsx");
//we only open the OPCPackage, we don't create a Workbook
OPCPackage opcpackage = OPCPackage.open(file);
//if there are strings in the SheetData, we need the SharedStringsTable
PackagePart sharedstringstablepart = opcpackage.getPartsByName(Pattern.compile("/xl/sharedStrings.xml")).get(0);
SharedStringsTable sharedstringstable = new SharedStringsTable();
sharedstringstable.readFrom(sharedstringstablepart.getInputStream());
//get the PackagePart of the first sheet
PackagePart sheetpart = opcpackage.getPartsByName(Pattern.compile("/xl/worksheets/sheet1.xml")).get(0);
//get the worksheet from the first sheet's XML
//if it even fails while parsing this, then this approach is not usable
WorksheetDocument worksheetdocument = WorksheetDocument.Factory.parse(sheetpart.getInputStream());
CTWorksheet worksheet = worksheetdocument.getWorksheet();
CTSheetData sheetdata = worksheet.getSheetData();
//put some data in 10 new rows"
for (int i = 0; i < 10; i++) {
int rowsCount = sheetdata.sizeOfRowArray();
CTCell ctcell= sheetdata.addNewRow().addNewC();
CTRst ctstr = CTRst.Factory.newInstance();
ctstr.setT("new Row " + (rowsCount + 1));
int sRef = sharedstringstable.addEntry(ctstr);
ctcell.setT(STCellType.S);
ctcell.setV(Integer.toString(sRef));
ctcell=sheetdata.getRowArray(rowsCount).addNewC();
ctcell.setV(""+rowsCount+"."+(i+1)+""+((i+2>9)?0:i+2));
}
//write the SharedStringsTable
OutputStream out = sharedstringstablepart.getOutputStream();
sharedstringstable.writeTo(out);
out.close();
//create XmlOptions for saving the worksheet
XmlOptions xmlOptions = new XmlOptions();
xmlOptions.setSaveOuter();
xmlOptions.setUseDefaultNamespace();
xmlOptions.setSaveAggressiveNamespaces();
xmlOptions.setCharacterEncoding("UTF-8");
xmlOptions.setSaveSyntheticDocumentElement(new QName(CTWorksheet.type.getName().getNamespaceURI(), "worksheet"));
Map<String, String> map = new HashMap<String, String>();
map.put(STRelationshipId.type.getName().getNamespaceURI(), "r");
xmlOptions.setSaveSuggestedPrefixes(map);
//save the worksheet
out = sheetpart.getOutputStream();
worksheet.save(out, xmlOptions);
out.close();
opcpackage.close();
} catch (Exception ex) {
ex.printStackTrace();
}
}
}
的sheet1中写入10个新行，而不打开整个工作簿。但它必须至少打开并解析sheet1和ReadAndWriteTest.xlsx。如果即使失败了，那么这种方法也无法使用。
另一种方法可能是使用StAX。此API可以读取和写入XML事件驱动。它使用流媒体。
示例：
SharedStringsTable此代码还在import org.apache.poi.openxml4j.opc.OPCPackage;
import org.apache.poi.openxml4j.opc.PackagePart;
import org.apache.poi.xssf.model.SharedStringsTable;
import org.openxmlformats.schemas.spreadsheetml.x2006.main.CTRst;
import javax.xml.stream.XMLEventFactory;
import javax.xml.stream.XMLEventReader;
import javax.xml.stream.XMLEventWriter;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLOutputFactory;
import javax.xml.stream.events.Characters;
import javax.xml.stream.events.StartElement;
import javax.xml.stream.events.EndElement;
import javax.xml.stream.events.Attribute;
import javax.xml.stream.events.XMLEvent;
import javax.xml.namespace.QName;
import java.io.File;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Arrays;
import java.util.List;
import java.util.regex.Pattern;
class StaxReadAndWriteTest {
public static void main(String[] args) {
try {
File file = new File("ReadAndWriteTest.xlsx");
OPCPackage opcpackage = OPCPackage.open(file);
//if there are strings in the sheet data, we need the SharedStringsTable
//if it even fails while parsing this SharedStringsTable, then this approach is not usable
//then we must stream this XML event driven also.
PackagePart sharedstringstablepart = opcpackage.getPartsByName(Pattern.compile("/xl/sharedStrings.xml")).get(0);
SharedStringsTable sharedstringstable = new SharedStringsTable();
sharedstringstable.readFrom(sharedstringstablepart.getInputStream());
PackagePart sheetpart = opcpackage.getPartsByName(Pattern.compile("/xl/worksheets/sheet1.xml")).get(0);
XMLEventReader reader = XMLInputFactory.newInstance().createXMLEventReader(sheetpart.getInputStream());
XMLEventWriter writer = XMLOutputFactory.newInstance().createXMLEventWriter(sheetpart.getOutputStream());
XMLEventFactory eventFactory = XMLEventFactory.newInstance();
int rowsCount = 0;
while(reader.hasNext()){ //loop over all XML in sheet1.xml
XMLEvent event = (XMLEvent)reader.next();
writer.add(event); //by default write each readed event
if(event.isStartElement()){
StartElement startElement = (StartElement)event;
QName startElementName = startElement.getName();
if(startElementName.getLocalPart().equalsIgnoreCase("row")) { //start element of row
boolean rowStart = true;
rowsCount++;
do {
event = (XMLEvent)reader.next(); //find this row's end
writer.add(event); //by default write each readed event
if(event.isEndElement()){
EndElement endElement = (EndElement)event;
QName endElementName = endElement.getName();
if(endElementName.getLocalPart().equalsIgnoreCase("row")) { //end element of row
rowStart = false;
//we assume that there is nothing else (character data) between end element of row and next element
XMLEvent nextElement = (XMLEvent)reader.peek();
QName nextElementName = null;
if (nextElement.isStartElement()) nextElementName = ((StartElement)nextElement).getName();
else if (nextElement.isEndElement()) nextElementName = ((EndElement)nextElement).getName();
if(!nextElementName.getLocalPart().equalsIgnoreCase("row")) { //next is not start element of row
//we have the last row, so we write new rows now
for (int i = 0; i < 10; i++) {
StartElement newRowStart = eventFactory.createStartElement(new QName("row"), null, null);
writer.add(newRowStart);
//start cell A
Attribute attribute = eventFactory.createAttribute("t", "s");
List attributeList = Arrays.asList(attribute);
StartElement newCellStart = eventFactory.createStartElement(new QName("c"), attributeList.iterator(), null);
writer.add(newCellStart);
CTRst ctstr = CTRst.Factory.newInstance();
ctstr.setT("new Row " + (rowsCount +1));
int sRef = sharedstringstable.addEntry(ctstr);
StartElement newCellValue = eventFactory.createStartElement(new QName("v"), null, null);
writer.add(newCellValue);
Characters value = eventFactory.createCharacters(Integer.toString(sRef));
writer.add(value);
EndElement newCellValueEnd = eventFactory.createEndElement(new QName("v"), null);
writer.add(newCellValueEnd);
EndElement newCellEnd = eventFactory.createEndElement(new QName("c"), null);
writer.add(newCellEnd);
//end cell A
//start cell B
newCellStart = eventFactory.createStartElement(new QName("c"), null, null);
writer.add(newCellStart);
newCellValue = eventFactory.createStartElement(new QName("v"), null, null);
writer.add(newCellValue);
value = eventFactory.createCharacters(""+rowsCount+"."+(i+1)+""+((i+2>9)?0:i+2));
writer.add(value);
newCellValueEnd = eventFactory.createEndElement(new QName("v"), null);
writer.add(newCellValueEnd);
newCellEnd = eventFactory.createEndElement(new QName("c"), null);
writer.add(newCellEnd);
//end cell B
EndElement newRowEnd = eventFactory.createEndElement(new QName("row"), null);
writer.add(newRowEnd);
rowsCount++;
}
}
}
}
} while (rowStart);
}
}
}
writer.flush();
//write the SharedStringsTable
OutputStream out = sharedstringstablepart.getOutputStream();
sharedstringstable.writeTo(out);
out.close();
opcpackage.close();
} catch (Exception ex) {
ex.printStackTrace();
}
}
}
的sheet1中写入10个新行，而不打开整个工作簿。但它必须至少打开并解析ReadAndWriteTest.xlsx。如果即使这样失败，那么这种方法也是不可用的。但是当然即使SharedStringsTable也可以使用StAX进行流式传输。但正如您在示例中看到的那样生成行和单元格，这要复杂得多。因此，在此示例中，使用SharedStringsTable可以简化操作。
答案 2 :(得分：0)
（没有足够的声誉将此添加为评论） 您是否尝试过使用SXSSFWorkbook而不是XSSFWorkbook？