SQL stored procedure to convert a blob field to XML - sql

Question

I have an xml file stored in the DB. this xml file is converted to a zipped byte[] and then stored in the db as shown below:
ByteArrayOutputStream byteOut = null;
ZipOutputStream out = null;
try {
byteOut = new ByteArrayOutputStream();
out = new ZipOutputStream(byteOut);
out.setLevel(level);
ZipInput entry = new ZipStringInput("string", xmlString));
out.putNextEntry(getZipEntry(encrypt, entry.getEntryName()));
InputStream in = entry.getInputStream();
byte[] buffer = new byte[BUFFER];
for (int length; (length = in.read(buffer)) != -1; ) {
out.write(buffer, 0, length);
}
out.finish();
saveToDB(byteOut.toByteArray()
In java I can easily fetch it like shown below (simplified wihtout catch, close etc.,):
byte[] xmlBytes = (byte[])blob;
ByteArrayOutputStream out = new ByteArrayOutputStream();
try (ByteArrayInputStream byteIn = new ByteArrayInputStream(xmlBytes );) {
try (ZipInputStream zipIn = new ZipInputStream(byteIn);) {
for (ZipEntry entry; (entry = zipIn.getNextEntry()) != null;) {
byte[] buffer = new byte[32768];
for (int length; (length = zipIn.read(buffer, 0, buffer.length)) != -1;) {
out.write(buffer, 0, length);
}
}
return out.toString("UTF-8"));
}
Oracle DB: Now I have to task to do the same in a SQL stored procedure. how do I do it. I have tried combinations of lz_uncompress, lob.substr etc., I can see the bytes, but not sure how to convert it to the XML file.
CREATE OR REPLACE PROCEDURE print_clob AS
v_clob CLOB;
v_varchar VARCHAR2(32767);
v_start PLS_INTEGER := 1;
v_buffer PLS_INTEGER := 32767;
blob_in BLOB;
x XMLTYPE;
BEGIN
dbms_lob.createtemporary(v_clob, true);
FOR i IN (
SELECT
blobdata AS blob_in
FROM
myTable
WHERE
id = 123
) LOOP
FOR j IN 1..ceil(dbms_lob.getlength(i.blob_in) / v_buffer) LOOP
v_varchar := dbms_lob.substr(i.blob_in, v_buffer, v_start);
dbms_lob.writeappend(v_clob, length(v_varchar), v_varchar);
v_start := v_start + v_buffer;
END LOOP;
dbms_output.put_line(v_clob ); prints some binary stirng looking like '504B0304140008000800E0843E4200000000000000000.....'
-- dbms_output.put_line(UTL_RAW.CAST_TO_NVARCHAR2(v_clob )); -> throws error
-- dbms_output.put_line(utl_compress.lz_uncompress(v_clob )); -> throws error
--x := xmltype.createxml(v_clob); -> Throws error that the input it not an XML <, but some randoms tring
-- dbms_output.put_line(x.getclobval());
END LOOP;
END;

Answer 1

You are trying to substring a BLOB and stick it into a CLOB without any conversion. If the BLOB is compressed, you'll need to uncompress it first with utl_compress.lz_uncompress. Then once uncompressed, you need to convert it to a CLOB using dbms_lob.converttoclob.