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Greetings from the Edge:
Using javaobj in DATA Step
Richard A. DeVenezia
Java is ...
• java.sun.com
“The Java 2 Platform provides robust end-to-end solutions
for networked applications as well as a trusted standard
for embedded applications”
• Widespread
• Networked
• Applications
– Analysis and management
javaobj is ...
• DATA Step
• Experimental
• Part of broader initiative
– Component Interface
– Object Dot Syntax
Component Interface is ...
• support.sas.com/rnd/...
“DATA Step Component Interface provides a mechanism
for accessing predefined component objects from within a
DATA Step program.”
• Instantiate
– Create an object
– declare Type var, var = _new_
• Access
– var.method()
Java development
• Free kit
– java.sun.com/j2se
– compiler, packager and loader
javac, jar, java
– Runtime Environment
– Online training
• Tutorials
– numerous web sites and publications
SAS session
• CLASSPATH
– Location of Java classes
• Configuration options
– Host preset environment variable
– Command line
-set CLASSPATH myPath;%CLASSPATH%
– configuration file (sasv9.cfg)
-set CLASSPATH “myPath;%CLASSPATH%”
Java coding pattern
public class Class
{
private double variable;
public double getVariable()
{
return this.variable;
}
public void setVariable(double variable)
{
this.variable = variable;
}
}
Declare statement
declare javaobj var;
var = _NEW_ javaobj
('Class' [,arg-1[,…[,arg-N]]) ;
- or declare javaobj
var ('Class' [,arg-1[,…[,arg-N]]) ;
Signature
public void setX (double X) { this.X = X }
public void setX (String X) {
try {
this.X = Double.parseDouble(X);
} catch (Exception e) {
this.X = Double.Nan;
}
}
• Pattern of argument types
• Correspondence
• DATA Step ERROR: ?
Accessing methods and fields
• public Type Method (args…) {…}
• obj.callTypeMethod ( ‘Method’, args…, return );
• fields:
obj.[get|set]TypeField ( ‘field’, value );
HelloSAS.java
public class HelloSAS
{
public HelloSAS () {}
public String getMessage ()
{
return "Hello SAS";
}
}
HelloSAS.sas
data _null_;
declare javaobj j (’HelloSAS');
length message $200;
j.callStringMethod ('getMessage', message);
put message=;
run;
--- log -message=Hello SAS
Gotchas
• Classes are cached per SAS session
• Java class recompiled ?
– Restart SAS
• Signature Types
– pass double, String, Object (new)
– return double, String
Example 8 - Enumeration
import java.util.Enumeration;
public class Example8 {
private Enumeration e;
public Example8 () {
e = System.getProperties().propertyNames();
}
public String getProperty () {
if (e.hasMoreElements()) {
String p = (String) e.nextElement();
return p + "=" + System.getProperty(p);
}
else {
return null;
}
}
}
Example 8 - DATA Step
data _null_;
dcl javaobj j ('Example8');
length s $200;
j.callStringMethod ('getProperty', s);
do while (s ne '');
put s;
j.callStringMethod ('getProperty', s);
end;
run;
--- log --…
java.vm.version=1.4.1_01-b01
java.vm.vendor=Sun Microsystems Inc.
Object Persistence
• No
– javaobj gone when DATA Step ends
– obj.delete() recommended
• Birdie:
“An instantiated javaobj creates a JNI reference
which will not be garbage collected. The
reference needs to be explicitly deleted.”
A Case for Persistence
• Creating SAS Table from Query
• Query -> ResultSet
• Requires Two SAS Passes
– ResultSetMetaData
– Read ResultsSet into Data Set
• Same Query for each pass
– not wanted
Databases
• Commercial
• Open source
– Postgresql, mySQL
– communities of devoted developers and users
• JDBC
– 109 drivers
– trademark
– not an acronym (just like ess-a-ess)
Persistence == RMI
• Objects can persist outside SAS
– in RMI server process
• Obtaining reference and access
– requires Java wrapper class
Gateway - an RMI Scheme
• Server
• DATA Step is client of server
– via a wrapper
• Server allocates resources
– Returns handles
– Methods
Gateway Implementation
• Three Classes
• An Interface
– GatewayInterface
• An Implementation
– GatewayManager
• A Server
– GatewayServer
GatewayInterface
• Declares methods
public int getConnectionHandle (
String driverClass, String databaseURL,
String username, String password )
throws RemoteException;
public int getStatementHandle (int cHandle)
throws RemoteException;
public int executeQuery (int handle, String
sql) throws RemoteException;
GatewayManager
• Implements the Interface
public int getConnectionHandle (
String driverClass, String databaseURL,
String username, String password)
throws RemoteException
{
…
try {
System.out.println ("loading "+driverClass);
Class.forName(driverClass);
System.out.println ("connecting to "+databaseURL);
con = DriverManager.getConnection
(databaseURL, username, password);
System.out.println ("connected");
}
…
GatewayServer
• Hosts a GatewayManager
protected static final String
RMI_NAME = "JDBC-GATEWAY-MANAGER";
public static void main(String args[]){
…
try {
LocateRegistry.createRegistry(1099);
GatewayManager manager = new GatewayManager (5);
Naming.rebind (RMI_NAME, manager);
}
…
System.out.println ( manager.getClass().getName()
+ " ready to manage " + 5 + " connections.");
GatewayServer
• getReferenceToPersistentManager()
– Convience method
– Client starts immediately after server
for (i=0;i<4;i++) {
try {
remote = Naming.lookup(RMI_NAME);
}
catch (java.rmi.NotBoundException e)
{ Thread.currentThread().sleep(250/*ms*/); }
}
DataStepGatewayAdapter
• Reimplements GatewayInterface
– delegates everything to
– performs typecasting where needed
public class DataStepGatewayAdapter
{ private GatewayInterface dbi;
public DataStepGatewayAdapter() throws Exception {
dbi = GatewayServer.getReferenceToPersistentManager ();}
public int getStatementHandle (double cHandle) throws Exception
{ return dbi.getStatementHandle ( (int) cHandle); }
SAS Macros
• Facilitate use of Gateway
• startServer
• getConnectionHandle
• getStatementHandle
• jdbcLoadTable
• jdbcQuery
Using the macros
%let jdbc_server_policy = gateway.policy;
%let jdbc_driver = org.postgresql.Driver;
%let db_url =
jdbc:postgresql://www.devenezia.com:5434/sesug03demo;
%let username = sesug03demo ;
%let password = D3m0oeoe;
%let cHandle =;
%getConnectionHandle ( driver = &jdbc_driver ,
url = &db_url , user = &username , pass =
&password , cHandle_mv = cHandle );
Using the macros
%jdbcLoadTable (
cHandle=&cHandle,
data=sashelp.zipcode,
obs=20);
%jdbcQuery (
cHandle=&cHandle,
sql=SELECT * FROM ZIPCODE,
out=WORK.ZIPCODE);
JDBC connection pattern
Class.forName(jdbcDriver);
Connection con =
DriverManager.getConnection
( URL, username, password );
• jdbcDriver = “org.postgresql.Driver”
•
URL =
“jdbc:postgresql://www.devenezia.com:5434/sesug03demo”;
• username = “sesug03demo” ;
• password = “D3m0oeoe”;
Conclusion
• Javaobj opens new horizons
• Hybrid solutions
– Combine best features of different technologies
• Web
www.devenezia.com/papers/sesug-2003