How to convert oracle BLOB to String

Question

Hi,
I am working on an GIS project using Oracle database which stores the spatial data. When I read the polygon points data which is saved as BLOB type in database table and convert the BLOB to byte[], there is no problem. However when the data is converted to Character, those characters are not recognized something like this:
�����������?�����?���w�����������������!����?o����s��8��n�����H��?
������������������ �?&�?�����|��?��������?���������������L�?
This is the method I used to convert BLOB to String below:
-----mapb is the BLOB instance.
byte[] images = mapb.getBytes(1,(int)mapb.length());
String newstring = new String(images);
Is that decoding problem?
Can somebody help me for this problem?
Thanks in advance!
XR

Answer 1

Hi,
Thanks for reply,
Actually the data is ESRI spatial data saved in ORACLE database.
the BLOB is not a column, it is part of column of st_geometry.
I looked at some docs in ESRI, they save points which is the last part of st_geometry field with BLOB type. I use the jdbc to get the geometry data and use STRUCT and Datum class to get all members of the st_geometry data. There are 14 members in the field, I can cast most of them into String through Datum instance, but the object #14 is BLOB, will not allow me cast it to String directly, so I use byte[] and cast it though new String().
some of the lines here:
STRUCT st = (oracle.sql.STRUCT) rs.getObject("shape");
Datum[] dtms = st.getOracleAttributes();
BLOB mapb = null;
for (int i=0;i<dtms.length;i++){
if (!(dtms[i] == null)){
if (i==13){
mapb = (BLOB)dtms;
} else {
log.info("data" + i + "=" + dtms[i].stringValue());
byte[] images = mapb.getBytes(1,(int)mapb.length());
String newstring = new String(images);
Thanks again for your reply.
XR