Efren
A. Serra (Contractor)
DeVine Consulting, Inc.
Naval Research Laboratory
Marine Meteorology Division
7 Grace Hopper Ave.,
STOP 2
Monterey, CA 93943
Code 7542
Office: 831-656-4650
Efren,
Maybe somebody else on the list is an expert on using mySQL blobs in
Java and
can figure out how to make it work in Java, but I probably wont' be
able to
help in that regard. One way to get this to work it to implement your
own
database backend in Python. Others have created LAS backends using
Python. In this case it would receive a SOAP message containing the
XML
that specifies the query that needs to be made. Your code would be
responsible for interpreting the XML, making the query and creating the
netCDF
file that LAS needs to make the plots.
It's a shame to have to reinvent the wheel, but it's an approach that
would
certainly work.
Roland
Serra, Mr. Efren, Contractor, Code 7542
wrote:
Roland,
This one is
as bad as it gets, eh?
The data is being written using Python’s struct.pack. I’m able to read
using it Python’s MySQLdb and struct modules; however, Java’s
DataInputStream
returns garbage. Included are the two test scripts/Java code.
Python
code:
import
MySQLdb
import struct
conn =
MySQLdb.connect("localhost", "user", "passwd",
"argo2")
cursor
=
conn.cursor(MySQLdb.cursors.DictCursor)
sql =
"SELECT
profile_id,t,x,y,pres,pres_qc,psal,psal_qc,temp,temp_qc FROM profiles
WHERE
(temp<99999.0 OR temp>99999.0) AND ((x>=-180.0) AND (x
<=179.0))
AND ((y>=-90) AND (y<=89)) AND ((pres>=0) AND (pres<=5000))
AND
((t>=349069.0) AND (t<=349069.0));"
cursor.execute(sql)
result_set =
cursor.fetchall()
for row in
result_set:
col =
row["pres"]
print col
i=0
j=4
length =
col.buffer_info()[1] *
col.itemsize
while
(length):
print
struct.unpack('=f',
col[i:j].tostring())
i +=4
j +=4
length
-=4
print
"Number of rows returned:
%d" % cursor.rowcount
cursor.close()
conn.close()
Java
code:
import
java.io.*;
public class
argo2_test {
public
static void main (String
args[]) throws Exception
{
java.sql.Connection
conn;
java.sql.ResultSetMetaData meta;
java.sql.Statement stmt;
java.sql.ResultSet
result;
int i;
System.out.println("JDBC sample application starts...");
System.out.println("Application tries to register the driver.");
// this
is the
recommended way for registering Drivers
java.sql.Driver d =
(java.sql.Driver)Class.forName("com.mysql.jdbc.Driver").newInstance();
System.out.println("Driver
succesfully registered.");
// the
user is asked
for a connect string
System.out.println(
"Now sample application needs a connectstring in format:\n"
);
System.out.println(
"jdbc:mysql://<host>:<port>/<database>?<user
name>=value&<password>=value\n"
);
System.out.print("\nPlease enter the connect string >");
//BufferedReader reader
=
//
new BufferedReader(new InputStreamReader(System.in));
//String
sCon =
reader.readLine();
String
sCon =
"jdbc:mysql://localhost:3306/argo2?user=user&password=passwd";
// next,
the connection
is attempted
System.out.println("Attempting to connect :" + sCon);
conn =
java.sql.DriverManager.getConnection(sCon);
System.out.println("Driver
succesfully connected.");
String
sQuery =
"SELECT profile_id,t,x,y,pres,pres_qc,psal,psal_qc,temp,temp_qc FROM
profiles WHERE (temp<99999.0 OR temp>99999.0) AND ((x>=-180.0)
AND (x
<=179.0)) AND ((y>=-90) AND (y<=89)) AND ((pres>=0) AND
(pres<=5000)) AND ((t>=349069.0) AND (t<=349069.0));";
stmt=
conn.createStatement();
result =
stmt.executeQuery(sQuery);
System.out.println("Query executed and result set obtained.");
// we
get a
metadataobject containing information about the
//
obtained result set
System.out.println("Obtaining metadata information.");
meta =
result.getMetaData();
int cols
=
meta.getColumnCount();
System.out.println("Metadata information for columns is as follows:");
// we
dump the column
information about the result set
for
(i=1; i <= cols;
i++)
{
System.out.println("Column i:"+i+"
"+meta.getColumnName(i)+ "," +
meta.getColumnType(i) + "," + meta.getColumnTypeName(i) +
"," +
meta.getColumnDisplaySize(i));
}
// and
finally, we dump
the result set
System.out.println("Starting to dump result set.");
int cnt
= 1;
while(result.next())
{
System.out.print("\nRow "+cnt+" : ");
for (i=1; i <= cols; i++) {
switch (i) {
case 5:
try
{
java.sql.Blob blob = result.getBlob(i);
long blen = blob.length();
DataInputStream distream = new
DataInputStream(result.getBinaryStream(i));
System.out.println("Blob length: "+blen);
while (blen>0) {
float presVal = distream.readFloat();
System.out.println("pres value: "+presVal);
blen -= 4;
}
} catch (Exception ex) { ex.printStackTrace();}
break;
}
System.out.print(result.getString(i)+"\t");
}
cnt++;
}
stmt.close();
conn.close();
// and
not it is all
over
System.out.println("\nResult set dumped. Sample application
finishes.");
}
}
Efren
A. Serra (Contractor)
DeVine Consulting, Inc.
Naval Research Laboratory
Marine Meteorology Division
7 Grace Hopper Ave.,
STOP 2
Monterey, CA 93943
Code 7542
Office: 831-656-4650