Manipulating Zip Files with PeopleCode

I've seen a few forum posts that show how to zip files using both Exec and the XML Publisher PSXP_RPTDEFNMANAGER:Utility app package. Those are great options, but might not fit every scenario. Since the Java API includes support for zip files, let's investigate how we can use it to create or extract zip files.

Java allows developers to create zip files by writing data to a ZipOutputStream. We've used OutputStreams a few times on this blog to write data to files. A ZipOutputStream is just a wrapper around an OutputStream that writes contents in the zip file format. Here is an example of reading a text file and writing it out to a ZipOutputStream

REM ** The file I want to compress;
Local string &fileNameToZip = "c:\temp\blah.txt";

REM ** The internal zip file's structure -- internal location of blah.txt;
Local string &zipInternalPath = "my/internal/zip/folder/structure";

Local JavaObject &zip = CreateJavaObject("java.util.zip.ZipOutputStream", CreateJavaObject("java.io.FileOutputStream", "c:\temp\compressed.zip", True));

Local JavaObject &file = CreateJavaObject("java.io.File", &fileNameToZip);
REM ** We will read &fileNameToZip into a buffer and write it out to &zip;
Local JavaObject &buf = CreateJavaArray("byte[]", 1024);

Local number &byteCount;
Local JavaObject &in = CreateJavaObject("java.io.FileInputStream", &fileNameToZip);

Local JavaObject &zipEntry = CreateJavaObject("java.util.zip.ZipEntry", &zipInternalPath | "/" | &file.getName());

REM ** Make sure zip entry retains original modified date;
&zipEntry.setTime(&file.lastModified());

&zip.putNextEntry(&zipEntry);

&byteCount = &in.read(&buf);

While &byteCount > 0
   &zip.write(&buf, 0, &byteCount);
   &byteCount = &in.read(&buf);
End-While;

&in.close();
&zip.flush();
&zip.close();

To add multiple files to a single zip file, we can convert the above code into a function (preferably a FUNCLIB function) and then call it multiple times, once for each file:

Function AddFileToZip(&zipInternalPath, &fileNameToZip, &zip)
   Local JavaObject &file = CreateJavaObject("java.io.File", &fileNameToZip);
   REM ** We will read &fileNameToZip into a buffer and write it out to &zip;
   Local JavaObject &buf = CreateJavaArray("byte[]", 1024);
   
   Local number &byteCount;
   Local JavaObject &in = CreateJavaObject("java.io.FileInputStream", &fileNameToZip);
   
   Local JavaObject &zipEntry = CreateJavaObject("java.util.zip.ZipEntry", &zipInternalPath | "/" | &file.getName());
   
   REM ** Make sure zip entry retains original modified date;
   &zipEntry.setTime(&file.lastModified());
   
   &zip.putNextEntry(&zipEntry);
   
   &byteCount = &in.read(&buf);
   
   While &byteCount > 0
      &zip.write(&buf, 0, &byteCount);
      &byteCount = &in.read(&buf);
   End-While;
   
   &in.close();
End-Function;


Local JavaObject &zip = CreateJavaObject("java.util.zip.ZipOutputStream", CreateJavaObject("java.io.FileOutputStream", "c:\temp\compressed.zip", True));

AddFileToZip("folder1", "c:\temp\file1.txt", &zip);
AddFileToZip("folder1", "c:\temp\file2.txt", &zip);
AddFileToZip("folder2", "c:\temp\file1.txt", &zip);
AddFileToZip("folder2", "c:\temp\file2.txt", &zip);

&zip.flush();
&zip.close();

The contents to zip doesn't have to come from a static file in your file system. It could come from the database or... well, anywhere. Here is an example of zipping static text. In this example I intentionally left the internal zip file path (folder) blank to show how to create a zip file with no structure.

Local JavaObject &textToCompress = CreateJavaObject("java.lang.String", "This is some text to compress... probably a bloated XML document or something ;)");
Local string &zipInternalFileName = "contents.txt";

Local JavaObject &zip = CreateJavaObject("java.util.zip.ZipOutputStream", CreateJavaObject("java.io.FileOutputStream", "c:\temp\compressed.zip", True));
Local JavaObject &zipEntry = CreateJavaObject("java.util.zip.ZipEntry", &zipInternalFileName);
Local JavaObject &buf = &textToCompress.getBytes();
Local number &byteCount = &buf.length;

&zip.putNextEntry(&zipEntry);

&zip.write(&buf, 0, &byteCount);

&zip.flush();
&zip.close();

And, finally, unzipping files. The following example prints the text inside each file from a zip file named "compressed.zip" that contains four fictitious text files named file1.txt, file2.txt, file3.txt, and file4.txt.

Local JavaObject &zipFileInputStream = CreateJavaObject("java.io.FileInputStream", "c:\temp\compressed.zip");
Local JavaObject &zipInputStream = CreateJavaObject("java.util.zip.ZipInputStream", &zipFileInputStream);
Local JavaObject &zipEntry = &zipInputStream.getNextEntry();
Local JavaObject &buf = CreateJavaArray("byte[]", 1024);
Local number &byteCount;

While &zipEntry <> Null
   
   If (&zipEntry.isDirectory()) Then
      REM ** do nothing;
   Else
      Local JavaObject &out = CreateJavaObject("java.io.ByteArrayOutputStream");
      &byteCount = &zipInputStream.read(&buf);
      
      While &byteCount > 0
         &out.write(&buf, 0, &byteCount);
         &byteCount = &zipInputStream.read(&buf);
      End-While;
      
      &zipInputStream.closeEntry();
      MessageBox(0, "", 0, 0, &out.toString());
      /*Else
         &log.writeline("&zipEntry is a directory named " | &zipEntry.getName);*/
   End-If;
   
   &zipEntry = &zipInputStream.getNextEntry();
End-While;

&zipInputStream.close();
&zipFileInputStream.close();

What about unzipping binary files into the file system? I'll let you write that one.

Password protected zip files? Java doesn't make this easy. There are a few Java libraries, but as Chris Rigsby points out here, using non-standard Java classes (including your own) can be hazardous. At this time, it seems the best way to password protect a zip file is to use Exec to call a command line zip program. On Linux with the zip utility, use the -P parameter to encrypt with a password.