Since this question seems to be rather: "What is the most lightweight way creating Office Open XML files for Excel (*.xlsx)?", I will providing an example which does not need any libraries except the default java.lang, java.io and java.util.zip.
A *.xlsx file is nothing else than a ZIP archive containing XML files and other files in a directory structure. So all we need is a possibility for creating, reading and writing ZIP archives and creating, reading and writing XML files. For the ZIP part I am using java.util.zip and for the XML part I am using string manipulation. This, creating and manipulating XML via string manipulation, is not the most recommended way for manipulating XML but it is the most lightweight way since it does not needs any additional XML libraries.
Complete example:
import java.io.OutputStream;
import java.io.ByteArrayOutputStream;
import java.util.zip.*;
public class CreateXLSXFromScratch {
//some static parts of the XLSX file:
static String content_types_xml = "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"no\"?><Types xmlns=\"http://schemas.openxmlformats.org/package/2006/content-types\"><Default ContentType=\"application/vnd.openxmlformats-package.relationships+xml\" Extension=\"rels\"/><Default ContentType=\"application/xml\" Extension=\"xml\"/><Override ContentType=\"application/vnd.openxmlformats-officedocument.extended-properties+xml\" PartName=\"/docProps/app.xml\"/><Override ContentType=\"application/vnd.openxmlformats-package.core-properties+xml\" PartName=\"/docProps/core.xml\"/><Override ContentType=\"application/vnd.openxmlformats-officedocument.spreadsheetml.sharedStrings+xml\" PartName=\"/xl/sharedStrings.xml\"/><Override ContentType=\"application/vnd.openxmlformats-officedocument.spreadsheetml.styles+xml\" PartName=\"/xl/styles.xml\"/><Override ContentType=\"application/vnd.openxmlformats-officedocument.spreadsheetml.sheet.main+xml\" PartName=\"/xl/workbook.xml\"/><Override ContentType=\"application/vnd.openxmlformats-officedocument.spreadsheetml.worksheet+xml\" PartName=\"/xl/worksheets/sheet1.xml\"/></Types>";
static String docProps_app_xml = "<?xml version=\"1.0\" encoding=\"UTF-8\"?><Properties xmlns=\"http://schemas.openxmlformats.org/officeDocument/2006/extended-properties\"><Application>" + "Created Low level From Scratch" + "</Application></Properties>";
static String docProps_core_xml = "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"no\"?><cp:coreProperties xmlns:cp=\"http://schemas.openxmlformats.org/package/2006/metadata/core-properties\" xmlns:dc=\"http://purl.org/dc/elements/1.1/\" xmlns:dcterms=\"http://purl.org/dc/terms/\" xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\"><dcterms:created xsi:type=\"dcterms:W3CDTF\">" + java.time.Instant.now().truncatedTo(java.time.temporal.ChronoUnit.SECONDS).toString() + "</dcterms:created><dc:creator>" + "Axel Richter from scratch" + "</dc:creator></cp:coreProperties>";
static String _rels_rels_xml = "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"no\"?><Relationships xmlns=\"http://schemas.openxmlformats.org/package/2006/relationships\"><Relationship Id=\"rId1\" Target=\"xl/workbook.xml\" Type=\"http://schemas.openxmlformats.org/officeDocument/2006/relationships/officeDocument\"/><Relationship Id=\"rId2\" Target=\"docProps/app.xml\" Type=\"http://schemas.openxmlformats.org/officeDocument/2006/relationships/extended-properties\"/><Relationship Id=\"rId3\" Target=\"docProps/core.xml\" Type=\"http://schemas.openxmlformats.org/package/2006/relationships/metadata/core-properties\"/></Relationships>";
static String xl_rels_workbook_xml_rels_xml = "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"no\"?><Relationships xmlns=\"http://schemas.openxmlformats.org/package/2006/relationships\"><Relationship Id=\"rId1\" Target=\"sharedStrings.xml\" Type=\"http://schemas.openxmlformats.org/officeDocument/2006/relationships/sharedStrings\"/><Relationship Id=\"rId2\" Target=\"styles.xml\" Type=\"http://schemas.openxmlformats.org/officeDocument/2006/relationships/styles\"/><Relationship Id=\"rId3\" Target=\"worksheets/sheet1.xml\" Type=\"http://schemas.openxmlformats.org/officeDocument/2006/relationships/worksheet\"/></Relationships>";
static String xl_sharedstrings_xml = "<?xml version=\"1.0\" encoding=\"UTF-8\"?><sst count=\"0\" uniqueCount=\"0\" xmlns=\"http://schemas.openxmlformats.org/spreadsheetml/2006/main\"/>";
static String xl_styles_xml = "<?xml version=\"1.0\" encoding=\"UTF-8\"?><styleSheet xmlns=\"http://schemas.openxmlformats.org/spreadsheetml/2006/main\"><numFmts count=\"0\"/><fonts count=\"1\"><font><sz val=\"11.0\"/><color indexed=\"8\"/><name val=\"Calibri\"/><family val=\"2\"/><scheme val=\"minor\"/></font></fonts><fills count=\"2\"><fill><patternFill patternType=\"none\"/></fill><fill><patternFill patternType=\"darkGray\"/></fill></fills><borders count=\"1\"><border><left/><right/><top/><bottom/><diagonal/></border></borders><cellStyleXfs count=\"1\"><xf numFmtId=\"0\" fontId=\"0\" fillId=\"0\" borderId=\"0\"/></cellStyleXfs><cellXfs count=\"1\"><xf numFmtId=\"0\" fontId=\"0\" fillId=\"0\" borderId=\"0\" xfId=\"0\"/></cellXfs></styleSheet>";
static String xl_workbook_xml = "<?xml version=\"1.0\" encoding=\"UTF-8\"?><workbook xmlns=\"http://schemas.openxmlformats.org/spreadsheetml/2006/main\" xmlns:r=\"http://schemas.openxmlformats.org/officeDocument/2006/relationships\"><workbookPr date1904=\"false\"/><bookViews><workbookView activeTab=\"0\"/></bookViews><sheets><sheet name=\"" + "Sheet1" + "\" r:id=\"rId3\" sheetId=\"1\"/></sheets></workbook>";
static String xl_worksheets_sheet1_xml = "<?xml version=\"1.0\" encoding=\"UTF-8\"?><worksheet xmlns=\"http://schemas.openxmlformats.org/spreadsheetml/2006/main\"><dimension ref=\"A1\"/><sheetViews><sheetView workbookViewId=\"0\" tabSelected=\"true\"/></sheetViews><sheetFormatPr defaultRowHeight=\"15.0\"/><sheetData/><pageMargins bottom=\"0.75\" footer=\"0.3\" header=\"0.3\" left=\"0.7\" right=\"0.7\" top=\"0.75\"/></worksheet>";
public static void main(String[] args) throws Exception {
// result goes into a ByteArrayOutputStream
ByteArrayOutputStream resultout = new ByteArrayOutputStream();
// needed objects
ZipEntry zipentry = null;
byte[] data = null;
// create ZipOutputStream
ZipOutputStream zipout = new ZipOutputStream(resultout);
// create the static parts of the XLSX ZIP file:
zipentry = new ZipEntry("[Content_Types].xml");
zipout.putNextEntry(zipentry);
data = content_types_xml.getBytes();
zipout.write(data, 0, data.length);
zipout.closeEntry();
zipentry = new ZipEntry("docProps/app.xml");
zipout.putNextEntry(zipentry);
data = docProps_app_xml.getBytes();
zipout.write(data, 0, data.length);
zipout.closeEntry();
zipentry = new ZipEntry("docProps/core.xml");
zipout.putNextEntry(zipentry);
data = docProps_core_xml.getBytes();
zipout.write(data, 0, data.length);
zipout.closeEntry();
zipentry = new ZipEntry("_rels/.rels");
zipout.putNextEntry(zipentry);
data = _rels_rels_xml.getBytes();
zipout.write(data, 0, data.length);
zipout.closeEntry();
zipentry = new ZipEntry("xl/_rels/workbook.xml.rels");
zipout.putNextEntry(zipentry);
data = xl_rels_workbook_xml_rels_xml.getBytes();
zipout.write(data, 0, data.length);
zipout.closeEntry();
zipentry = new ZipEntry("xl/sharedStrings.xml");
zipout.putNextEntry(zipentry);
data = xl_sharedstrings_xml.getBytes();
zipout.write(data, 0, data.length);
zipout.closeEntry();
zipentry = new ZipEntry("xl/styles.xml");
zipout.putNextEntry(zipentry);
data = xl_styles_xml.getBytes();
zipout.write(data, 0, data.length);
zipout.closeEntry();
zipentry = new ZipEntry("xl/workbook.xml");
zipout.putNextEntry(zipentry);
data = xl_workbook_xml.getBytes();
zipout.write(data, 0, data.length);
zipout.closeEntry();
// preparing the sheet data:
Object[][] sheetData = new Object[][] {
{"Text", "Value", "Formula"},
{"Text1", 1.23456, "=SIN(B2)"},
{"Text2", 2.34567, "=SQRT(B3)"},
{"Text3", 123.456, "=B4/10"}
};
String sheetdata = "<sheetData>";
int r = 0;
char c = 'A'; --c;
for (Object[] rowData : sheetData) {
sheetdata += "<row r=\"" + ++r + "\">";
c = 'A'; --c;
for (Object cellData : rowData) {
sheetdata += "<c r=\"" + Character.toString(++c) + r + "\"";
if (cellData instanceof String && ((String)cellData).startsWith("=")) {
sheetdata += "><f>" + ((String)cellData).replace("=", "") + "</f></c>";
} else if (cellData instanceof String) {
sheetdata += " t=\"inlineStr\"><is><t>" + ((String)cellData) + "</t></is></c>";
} else if (cellData instanceof Double) {
sheetdata += "><v>" + ((Double)cellData) + "</v></c>";
}
}
sheetdata += "</row>";
}
sheetdata += "</sheetData>";
// get the static sheet xml into a buffer for further processing
StringBuffer xl_worksheets_sheet1_xml_buffer = new StringBuffer(xl_worksheets_sheet1_xml);
// get position of the <dimension ref=\"A1\"/> in the static xl_worksheets_sheet1_xml
int dimensionstart = xl_worksheets_sheet1_xml_buffer.indexOf("<dimension ref=\"A1\"/>");
// replace the <dimension ref=\"A1\"/> with the new dimension
xl_worksheets_sheet1_xml_buffer = xl_worksheets_sheet1_xml_buffer.replace(
dimensionstart,
dimensionstart + "<dimension ref=\"A1\"/>".length(),
"<dimension ref=\"A1:" + Character.toString(c) + r + "\"/>");
// get position of the <sheetData/> in the static xl_worksheets_sheet1_xml
int sheetdatastart = xl_worksheets_sheet1_xml_buffer.indexOf("<sheetData/>");
// replace the <sheetData/> with the prepared sheet date string
xl_worksheets_sheet1_xml_buffer = xl_worksheets_sheet1_xml_buffer.replace(
sheetdatastart,
sheetdatastart + "<sheetData/>".length(),
sheetdata);
// create the xl/worksheets/sheet1.xml
zipentry = new ZipEntry("xl/worksheets/sheet1.xml");
zipout.putNextEntry(zipentry);
data = xl_worksheets_sheet1_xml_buffer.toString().getBytes();
zipout.write(data, 0, data.length);
zipout.closeEntry();
zipout.finish();
// now ByteArrayOutputStream resultout contains the XLSX file data
// writing this data into a file
try (java.io.FileOutputStream fileout = new java.io.FileOutputStream("test.xlsx")) {
resultout.writeTo(fileout);
resultout.close();
}
}
}
*.xlsxfile is nothing else than aZIParchive containingXMLfiles and other files in a directory structure. So all you need is a possibility for reading and rewritingZIParchives and reading and rewritingXMLfiles using yourandroidpseudoJavalanguage. So if all existent libraries do not fit your requirements, then do it using your own low level code. No? – Axel Richter