Error using java.util.zip. * To unpack xlsx blob created using Apache POI

Question

The following code is a test program that creates an xlsx blob using the Apache POI and decompresses the blob (xlsx is in zip format) to check some values. The code is based on stack overflow questions, but I was not able to figure out how to work properly. The requirement for this is that the file system should not be affected, so we resort to threads.

The problem is that the line

int size = (int) entry.getSize(); 

always produces -1. However see comments before

 zipInput.closeEntry(); 

for an option that is included in the program, but it seems incorrect.

We do not want to use the POI to read the xlsx file because we are testing a problem where the POI does not seem to be working with Apache Struts, and we want to eliminate the case when we use the POI regardless of Struts is the culprit. Once this test passes, if the problem Struts reports remain, we know that we are looking at how we use the POI.

 /** * Short, Self Contained, Correct Example of * 1) creating an xlsx blob with test data; * 2) sending it to a stream; * 3) unzipping the xlsx; * 4) checking the worksheet xml file for * correct test values. * Heavily inlined from two other properly factored * files, one POI wrapper and one JUnit test case * (although the test is not a "unit test" since it * only tests third party library integration) * DEPENDENCIES * 1) poi-3.8.jar * 2) poi-ooxml-3.8.jar * 3) xmlbeans-2.6.0.jar * 4) dom4j-1.6.1.jar * 5) poi-ooxml-schemas-3.8.jar * Other solutions attempted: * 1) commons-compress: always returned byte array of proper size * but containing all zeros. * Note that we do NOT want to use the filesystem. This exercise's * purpose is to create dynamically generated xlsx files delivered * via HTTP. The filesystem is never involved. */ import java.io.ByteArrayInputStream; import java.io.ByteArrayOutputStream; import java.io.IOException; import java.util.ArrayList; import java.util.List; import java.util.zip.ZipEntry; import java.util.zip.ZipInputStream; import org.apache.poi.ss.usermodel.Row; import org.apache.poi.ss.usermodel.Sheet; import org.apache.poi.xssf.usermodel.XSSFWorkbook; public class CreateWorkbook { public static void main(String[] args) throws IOException { // create the data to place into workbook List<List<String>> resultset = new ArrayList<List<String>>(); List<String> row = new ArrayList<String>(); row.add("A1"); row.add("B1"); row.add("C1"); resultset.add(row); row = new ArrayList<String>(); row.add("A2"); row.add("B2"); row.add("C2"); resultset.add(row); row = new ArrayList<String>(); row.add("A3"); row.add("B3"); row.add("C3"); resultset.add(row); // create POI workbook and fill it with resultSet XSSFWorkbook workbook = new XSSFWorkbook(); Sheet s = workbook.createSheet(); for (int i = 0; i < resultset.size(); i++) { List<String> record = resultset.get(i); Row r = s.createRow(i); for (int j = 0; j < record.size(); j++) r.createCell(j).setCellValue(record.get(j)); } ByteArrayOutputStream out = new ByteArrayOutputStream(); workbook.write(out); out.flush(); // retrieve workbook data into a string and // test if the cell values (a1,b2,c3,etc) appear ByteArrayInputStream in = new ByteArrayInputStream(out.toByteArray()); // xlsx is a zipped archive so we need to unzip ZipInputStream zipInput = new ZipInputStream(in); assert zipInput.available() == 1; ZipEntry entry = zipInput.getNextEntry(); assert entry != null; while (entry != null) { // since this "if" condition passes during execution we // know that the stream contains a zip archive with // an entry called "xl/worksheets/sheet1.xml". Therefore, // ZipEntry retrieval appears to work correctly and the // archive has at least a partially correct zip format. if (entry.getName().equals("xl/worksheets/sheet1.xml")) { int size = (int) entry.getSize(); // ============================================== // always fails, reports -1 assert size > 0 : size; // ============================================== byte[] bytes = new byte[size]; int readbytes = zipInput.read(bytes, 0, size); assert readbytes > 0 : readbytes; // nothing after this line has been tested StringBuilder builder = new StringBuilder(); for (int i = 0; i < size; i++) builder.append(Character.toString((char) bytes[i])); String xml = builder.toString(); assert xml.contains("A1"); assert xml.contains("B2"); assert xml.contains("C3"); break; } // Swapping the order of these two lines actually // causes the program to go further, with size = 678 // and failing at the readbytes assertion rather than // the size assertion. // I thought swapping would mess everything up since // the entry would be closed immediately after obtaining // it. zipInput.closeEntry(); entry = zipInput.getNextEntry(); } zipInput.close(); in.close(); } } 

Answer 1

You definitely do not work with Zip.

Try this snippet:

  if (entry.getName().equals("xl/worksheets/sheet1.xml")) { ByteArrayOutputStream bos = new ByteArrayOutputStream(); IOUtils.copy(zipInput, bos); String xml = bos.toString(); assert xml.contains("A1"); assert xml.contains("B2"); assert xml.contains("C3"); break; }