Example Java iterator function

The UDREnv interface provides all necessary methods and constants. A Java™ UDR can return only one value; therefore, there can be only one column in the virtual column list in the FROM clause.

The following example demonstrates how to write a Java iterator function and use it in FROM clause; relevant DataBlade® API and iterator states are highlighted.

The iterator UDR jenv_iter() takes an integer parameter and returns a row of CHAR(40) columns. The parameter passed in determines the number of rows it returns.

public interface UDREnv
{
...
// for maintaining state across UDR invocations
void setUDRState(Object state);
Object getUDRState();
// for set/iterator processing
public static final int UDR_SET_INIT = 1;
public static final int UDR_SET_RETONE = 2;
public static final int UDR_SET_END = 3;
int getSetIterationState();
void setSetIterationIsDone(boolean value);

...
}
import java.lang.*;
import java.sql.*;
import com.informix.udr.*;
import informix.jvp.*;
public class Env
{
    public int count;
    //
    // test UDR meta
    //
    
    public static String envTest1(int i, String xchar, String
xvchar, String xlvarchar)
    throws SQLException
    {
UDREnv env = UDRManager.getUDREnv();
String res = env.getName() + "#" + 
env.getReturnTypeName() + "#";
String param[] = env.getParamTypeName();
for (int j = 0; j < param.length; ++ j)
    res += param[j] + "#";

res += i + xchar + xvchar + xlvarchar;
return res;
    }
    public static String envTest2(int i, String s[])
    throws SQLException
    {
UDREnv env = UDRManager.getUDREnv();
UDRLog log = env.getLog();
String res = env.getName() + "#" + 
env.getReturnTypeName() + "#";
String param[] = env.getParamTypeName();
for (int j = 0; j < param.length; ++ j)
    res += param[j] + "#";
res += i;
log.log(res);
s[0] = res;
return res;
    }
    //
    //test env state, iterator, log, traceable, and 
properties
    //
    public static String envIter(int num)
throws SQLException
    {
UDREnv env = UDRManager.getUDREnv();
UDRLog log = env.getLog();
UDRTraceable tr = env.getTraceable();
JVPProperties pr = env.getProperties();
int iter = env.getSetIterationState();
Env state = (Env)env.getUDRState();
        if (iter == UDREnv.UDR_SET_INIT)
    {
    state = new Env();
    state.count = num;
    env.setUDRState(state);
    log.log("SET INIT" + state.count + " " + 
state.toString());

    tr.tracePrint("UDR.ENVITER", 0, "SET INIT");
       env.setSetIterationIsDone(false);
    pr.setProperty("ENVITERPROP", "AFTER INIT");
    return "INIT";
    }
        else if (iter == UDREnv.UDR_SET_END)
    {
    log.log("SET DONE");
    tr.tracePrint("UDR.ENVITER", 0, "SET DONE");
       env.setSetIterationIsDone(true);
    return "DONE";
    }
        else if (iter == UDREnv.UDR_SET_RETONE)
    {
    log.log("SET RETONE" + state.count + " " + 
state.toString());
    tr.tracePrint("UDR.ENVITER", 0, "SET RETONE");
    String prv = pr.getProperty("ENVITERPROP");

    if (state.count <= 0)
env.setSetIterationIsDone(true);
    else
env.setSetIterationIsDone(false);
    -- state.count;
    pr.setProperty("ENVITERPROP", "AFTER RETONE" + 
(state.count + 1));
    return new String("ELEMENT " + (state.count + 1) ); 
//+ prv);
    }
        else
    throw new SQLException("Bad iter code");
    }
}

The following statement creates the Java iterator UDR, jenv_iter().

create function jenv_iter(int)
    returning char(40)
    with (class = "jvp", iterator)
    external name ˋEnv.envIter(int)'
    language java;