Why compress ? 

Often we need to transfer heavy files between Java and ABAP applications. This is a very common case when we have Frontend WebDynPro Java application and backend is ABAP (RFCs). Most types of computer files are fairly redundant — they have the same information listed over and over again.

For example in the following XML:

How to do this in Java and ABAP?

I faced a similar issue in my application where there was a need to pass a heavy XML Strings as import parameter of an RFC function module. Another RFC FM returned a heavy XML String as an export parameter. Various compression APIs are available for Java and ABAP language. I worked with the classes in “java.util.zip” (Java side) and cl_abap_gzip (ABAP side). The zipped string from java side was passed and accepted as byte[] and at ABAP side it is of XSTRING data type.

Lets say we wish to transfer heavy XML String ABC from Java to ABAP, we can use the following methods:

Zip method for Java:

public static byte[] zipString(String abc) {  byte[] abcZipped = null;ByteArrayInputStream bas =   new ByteArrayInputStream(abc.getBytes());  ByteArrayOutputStream out = new ByteArrayOutputStream();ZipOutputStream zos =   new ZipOutputStream(out);  String entryName = “UniqueEntryName”;ZipEntry ze =   new ZipEntry(entryName);try {  zos.putNextEntry(ze);  byte[] buf = new byte[1024];  int len;while ((len = bas.read(buf)) > 0) {  zos.write(buf, 0, len);  }  zos.flush();  zos.closeEntry();  zos.close();  bas.close();  abcZipped = out.toByteArray();  } catch (IOException e) {System.out.println(“Unable to zip :” + e.getMessage());  }  return abcZipped;   }

Unzip method in ABAP:

> method ZIPTOSTRING.CALL METHOD CL_ABAP_GZIP=>DECOMPRESS_TEXT  EXPORTING    GZIP_IN      = ZIPSTRING  IMPORTING    TEXT_OUT     = VALUESTRING.endmethod.

Zip method in ABAP:

method STRINGTOZIP.CALL METHOD cl_abap_gzip=>compress_text            EXPORTING              text_in  = VALUESTRING            IMPORTING              gzip_out = ZIPSTRING.endmethod.

Unzip method in Java:

public static String unzipByteArray(byte[] xyzZipped) {  String xyz = null;  byte[] zippedBytes = xyzZipped;ZipInputStream in = new ZipInputStream(new ByteArrayInputStream(  zippedBytes));  try {  ZipEntry entry = in.getNextEntry();  ByteArrayOutputStream out = new ByteArrayOutputStream();BufferedOutputStream bout =   new BufferedOutputStream(out);  byte[] buf = new byte[1024];  int len;while ((len = in.read(buf)) > 0) {  bout.write(buf, 0, len);  }  bout.flush();  xyz = out.toString(“UTF-8”);  out.close();  in.close();  } catch (IOException e) {System.out.println(“Unable to Unzip :” + e.getMessage());  }  return xyz;   }