Getting ClassCastException when accessing Blob object

Question

I am using weblogic 5.1 with service pack 10.
I need to query pdf data stored in a blob field in Oracle
8.1.6 server. The native code c:\weblogic\bin\oci816_8
is part of the path. When I query the database with
Oracle 8 client, I can get data.
driver: weblogic.jdbc20.oci.Driver
url: jdbc20:weblogic:oracle:mydb
What I have done is to get the blob object with:
Blob blob = rs.getBlob(5);
long len = blob.length();
But when I call the blob.length();
I got the a ClassCastException. I really appreicate
your comment.
The exception message is:
====================================================
java.lang.ClassCastException: java.lang.String
at weblogic.jdbc20.oci.Blob.length(Blob.java:75)
at com.agf.profile.ProfileServlet.doProcess(ProfileServlet.java:126)
at com.agf.profile.ProfileServlet.doGet(ProfileServlet.java:37)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:740)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:865)
at weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletSt
pl.java:120)
at weblogic.servlet.internal.ServletContextImpl.invokeServlet(Servle
textImpl.java:922)
at weblogic.servlet.internal.ServletContextImpl.invokeServlet(Servle
textImpl.java:886)
at weblogic.servlet.internal.ServletContextManager.invokeServlet(Ser
ContextManager.java:269)
at weblogic.socket.MuxableSocketHTTP.invokeServlet(MuxableSocketHTTP
a:380)
at weblogic.socket.MuxableSocketHTTP.execute(MuxableSocketHTTP.java:
at weblogic.kernel.ExecuteThread.run(ExecuteThread.java:129)
====================================================
Thanks,
Jian

Answer 1

hi jian,
it seems you are trying to access a column as a blob type when the data in
that column is not blob.
Make sure that your column number 5 is defined as Blob in the database.
I tried the following code and it worked fine for me.
Blob b=rs.getBlob("data");
long l=b.length();
byte bt[]=b.getBytes(1,(int)b.length());
File f=new
File("d:\\bea\\wlserver6.1\\config\\jdbcdomain\\applications\\defaultwebapp\
\blob_new.pdf");
FileOutputStream fos=new FileOutputStream(f);
fos.write(bt);
fos.close();
It was able to create the file blob_new.pdf
But when I tried the following code it gave me the same exception as you are
getting
Blob bb=rs.getBlob("id");
long ll=bb.length();
Where id is a column in the database of varchar type
I am using the following settings
driver: weblogic.jdbc.oci.Driver
url: jdbc:weblogic:oracle
i am using wl 6.1 and oracle 8
Hope this helps you.
johnny
"jian zhang" <[email protected]> wrote in message
news:[email protected]...
>
I am using weblogic 5.1 with service pack 10.
I need to query pdf data stored in a blob field in Oracle
8.1.6 server. The native code c:\weblogic\bin\oci816_8
is part of the path. When I query the database with
Oracle 8 client, I can get data.
driver: weblogic.jdbc20.oci.Driver
url: jdbc20:weblogic:oracle:mydb
What I have done is to get the blob object with:
Blob blob = rs.getBlob(5);
long len = blob.length();
But when I call the blob.length();
I got the a ClassCastException. I really appreicate
your comment.
The exception message is:
====================================================
java.lang.ClassCastException: java.lang.String
at weblogic.jdbc20.oci.Blob.length(Blob.java:75)
atcom.agf.profile.ProfileServlet.doProcess(ProfileServlet.java:126)
at com.agf.profile.ProfileServlet.doGet(ProfileServlet.java:37)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:740)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:865)
atweblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletSt
pl.java:120)
atweblogic.servlet.internal.ServletContextImpl.invokeServlet(Servle
textImpl.java:922)
atweblogic.servlet.internal.ServletContextImpl.invokeServlet(Servle
textImpl.java:886)
atweblogic.servlet.internal.ServletContextManager.invokeServlet(Ser
ContextManager.java:269)
atweblogic.socket.MuxableSocketHTTP.invokeServlet(MuxableSocketHTTP
a:380)
atweblogic.socket.MuxableSocketHTTP.execute(MuxableSocketHTTP.java:
>
at weblogic.kernel.ExecuteThread.run(ExecuteThread.java:129)
====================================================
Thanks,
Jian