Re: Calling Java from RPG

Hi Nick,

/QIBM/UserData/Java400/ext is the Java "extensions" directory. It's supposed to be used for extensions to the Java language, not for your own code.

It's not the "default directory of your CLASSPATH" because it's not part of your CLASSPATH. Indeed, the files in that directory are loaded before the CLASSPATH is even considered.

One of the biggest problems with using the extensions directory is that any code in that directory is loaded automatically for every Java program. That means you can never have two versions (such as test & production versions) running on the same system, because the stuff in the ext directory is *always* loaded first.

My recommendation is that you remove it from the ext directory. Instead, create your own directory. Maybe with something like this:

CRTDIR ('/java')
CRTDIR ('/java/publicclasses')

Put all of your classes you want to be available to everyone into that directory, and then set the CLASSPATH envvar to point to that directory.

ADDENVVAR ENVVAR(CLASSPATH) VALUE('/java/publicclasses')

That's just a suggestion though. The reason your example doesn't work is that it's expecting the Difference class to be in a subdirectory named "levenshtein". So for every directory in yoru CLASSPATH, it's looking for a subdirectory named levenshtein that contains a Difference class.

In the above example, if the CLASSPATH is /java/publicclasses then your code is looking for a file in the IFS named /java/publicclasses/levenshtein/Difference.class -- because of the way you coded it, it's looking for a levenshtein/Difference.class in all of your CLASSPATH directories.


Nick Arndt wrote:

Hi all I have a need to call a java program from RPG. Here is my
prototypes:

d Levenshtein pr o extproc(*java:
d 'levenshtein.Difference':
d *constructor)

d LD pr 10i 0 extproc(*java:
d
'levenshtein.Difference':
d 'LD')
d iString1 like(String1)
d iString2 like(String1)
d Class s o class(*java:
d 'levenshtein.Difference')
d String1 s o CLASS(*JAVA:'java.lang.String')

/free

// constructor for java class
Class = Levenshtein();

When I try to call the above constructor I get an RNX0301 NoClassDefFound

Here is my java program:
The Program is in a Jar file located in QIBM\UserData\Java400\ext
Is this the default directory for the classpath var or do i have to change
it to look here?

package levenshtein;


public class Difference {
//*****************************
// Compute Levenshtein distance
//*****************************

public int LD (String s, String t) {
int d[][]; // matrix
int n; // length of s
int m; // length of t
int i; // iterates through s
int j; // iterates through t
char s_i; // ith character of s
char t_j; // jth character of t
int cost; // cost

// Step 1

n = s.length ();
m = t.length ();
if (n == 0) {
return m;
}
if (m == 0) {
return n;
}
d = new int[n+1][m+1];

// Step 2

for (i = 0; i <= n; i++) {
d[i][0] = i;
}
for (j = 0; j <= m; j++) {
d[0][j] = j;
}
// Step 3
for (i = 1; i <= n; i++) {
s_i = s.charAt (i - 1);
// Step 4
for (j = 1; j <= m; j++) {
t_j = t.charAt (j - 1);

// Step 5

if (s_i == t_j) {
cost = 0;
}
else {
cost = 1;
}
// Step 6

d[i][j] = Minimum (d[i-1][j]+1, d[i][j-1]+1, d[i-1][j-1] +
cost);

}

}

// Step 7

return d[n][m];

}


// get minimum of three values
private int Minimum (int a, int b, int c) {
int mi;

mi = a;
if (b < mi) {
mi = b;
}
if (c < mi) {
mi = c;
}
return mi;
}
}