Re: Front-ending Java for RPG -- Anybody here familiar with it besides Scott?

On 2/11/2013 5:39 PM, James H. H. Lampert wrote:

Dear Buck (et al):

Excuse my top-posting, but I noticed that a number of JDBC objects need
to be explicitly disposed of. Does anything here have that requirement?

JDBCR4 has an interesting way to handle that. It isn't often that we
need to individually free memory; more typically we free up a group of
objects when we're done with a series of functions. Check out
jdbc_begin_object_group and jdbc_end_object_group in JDBCR4.

At any rate, thanks, Buck; I think you almost certainly managed to save
my butt here.

I found Scott's coding / thinking quite clear despite my utter amateur
status as an OO programmer. What I personally found helpful was to look
at the Javadoc and the RPG code at the same time. Then, writing new
wrappers was not so hard. I tend to work in short bursts: first, an
object declaration and a compile. Then a PR declaration and a compile.
Baby steps.

One other thing, though: how do you pass a java "null" from RPG?

Not sure I've actually done that, but I'd go with myJavaObject = *null;

On 2/11/13 12:24 PM, Buck Calabro wrote:

#b D DatabaseMetaData...
#b D s O CLASS(*JAVA:
#b D 'java.sql.DatabaseMetaData')

. . .

#b D DB_GetMetaData...
#b D PR like(DatabaseMetaData)
#b D conn like(Connection) const

. . .

#b d getDatabaseMetaData...
#b d pr extproc(*JAVA:
#b d 'java.sql.Connection':
#b d 'getMetaData')
#b d like(DatabaseMetaData)

. . .

#b P DB_GetMetaData B export
#b D DB_GetMetaData PI like(DatabaseMetaData)
#b D conn like(Connection) const
#b D temp s like(DatabaseMetaData)
#b D dbmd s like(DatabaseMetaData)
#b /free
#b jdbc_begin_object_group(50);
#b
#b monitor;
#b temp = getDatabaseMetaData( conn );
#b jdbc_end_object_group(temp: dbmd);
#b on-error;
#b jdbc_end_object_group();
#b return *NULL;
#b endmon;
#b
#b return dbmd;
#b /end-free
#b P E

More fragmentary code to read the keys. I thought it was an interesting
problem and had some time while I was crunching a 15M row database.

d catalog s like(jString)
d schema s like(jString)
d table s like(jString)
d keysRS s like(ResultSet)
d keysRSMeta s like(ResultSetMetaData)
d keysColCount s 10i 0
d c s 10i 0
d column s 100a varying
d success s 1n

// getPrimaryKeys
// returns a result set of keys
// or SQLException if error
#b d getDatabaseMetaData_getPrimaryKeys...
#b d pr ExtProc(*JAVA:
#b d 'java.sql.DatabaseMetaData':
#b d 'getPrimaryKeys')
#b d like(ResultSet)
#b D catalog like(jString)
#b D schema like(jString)
#b D table like(jString)

#b d char2str pr like(jString)
#b d EXTPROC(*JAVA
#b d :'java.lang.String'
#b d :*CONSTRUCTOR)
#b d inp_char 32767A VARYING const


// after getting database metadata, get primary key info
catalog = char2str('cccccc');
schema = char2str('ssssss');
table = char2str('tttttt');
keysRS = getDatabaseMetaData_getPrimaryKeys(dbmd:
catalog:
schema:
table);

keysRSMeta = JDBC_GetMetaData(keysRS);
keysColCount = JDBC_GetColCount(keysRSMeta);

// print the column names of the metadata result set
for c = 1 to keysColCount;
column = JDBC_GetColName(keysRSMeta:
c);
except prtCol;
endfor;

// print the actual keys
success = *on;

dow success;
success = JDBC_nextRow(keysRS);

if success;
for c = 1 to keysColCount;
column = JDBC_GetCol(keysRS:
c:
nullInd);
if nullInd;
column = 'null';
endif;
except prtCol;

endfor;
else;
except noNextRow;
endif;
enddo;

--buck