Greetings from the Edge: Using javaobj in DATA Step

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Greetings from the EdgeUsing javaobj in DATA
Step
Richard A. DeVenezia
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Java is ...

• java.sun.comThe 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

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javaobj is ...

• DATA Step
• Experimental
• Part of broader initiative
• Component Interface
• Object Dot Syntax

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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()

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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

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SAS session

• CLASSPATH
• Location of Java classes
• Configuration options
• Host preset environment variable
• Command line-set CLASSPATH myPathCLASSPATH
• configuration file (sasv9.cfg)-set CLASSPATH
  myPathCLASSPATH

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Java coding pattern

• public class Class
• private double variable
• public double getVariable()
• return this.variable
• public void setVariable(double variable)
• this.variable variable

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Declare statement

• declare javaobj var
• var _NEW_ javaobj
• ('Class' ,arg-1,,arg-N)
• - or -
• declare javaobj
• var ('Class' ,arg-1,,arg-N)

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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 ?

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Accessing methods and fields

• public Type Method (args)
• obj.callTypeMethod ( Method, args, return )
• fields
• obj.getsetTypeField ( field, value )

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HelloSAS.java

• public class HelloSAS
• public HelloSAS ()
• public String getMessage ()
• return "Hello SAS"

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HelloSAS.sas

• data _null_
• declare javaobj j (HelloSAS')
• length message 200
• j.callStringMethod ('getMessage', message)
• put message
• run
• --- log --
• messageHello SAS

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Gotchas

• Classes are cached per SAS session
• Java class recompiled ?
• Restart SAS
• Signature Types
• pass double, String, Object (new)
• return double, String

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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

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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.version1.4.1_01-b01
• java.vm.vendorSun Microsystems Inc.

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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.

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A Case for Persistence

• Creating SAS Table from Query
• Query -gt ResultSet
• Requires Two SAS Passes
• ResultSetMetaData
• Read ResultsSet into Data Set
• Same Query for each pass
• not wanted

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Databases

• Commercial
• Open source
• Postgresql, mySQL
• communities of devoted developers and users
• JDBC
• 109 drivers
• trademark
• not an acronym (just like ess-a-ess)

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Persistence RMI

• Objects can persist outside SAS
• in RMI server process
• Obtaining reference and access
• requires Java wrapper class

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Gateway - an RMI Scheme

• Server
• DATA Step is client of server
• via a wrapper
• Server allocates resources
• Returns handles
• Methods

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Gateway Implementation

• Three Classes
• An Interface
• GatewayInterface
• An Implementation
• GatewayManager
• A Server
• GatewayServer

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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

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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(driverCl
  ass) System.out.println ("connecting to
  "databaseURL) con DriverManager.getConnectio
  n (databaseURL, username,
  password) System.out.println
  ("connected")

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GatewayServer

• Hosts a GatewayManager
• protected static final String RMI_NAME
  "JDBC-GATEWAY-MANAGER" public static void
  main(String args)try LocateRegistry.crea
  teRegistry(1099) GatewayManager manager new
  GatewayManager (5) Naming.rebind (RMI_NAME,
  manager) System.out.println (
  manager.getClass().getName() " ready to
  manage " 5 " connections.")

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GatewayServer

• getReferenceToPersistentManager()
• Convience method
• Client starts immediately after server
• for (i0ilt4i) try remote
  Naming.lookup(RMI_NAME) catch
  (java.rmi.NotBoundException e)
  Thread.currentThread().sleep(250/ms/)

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DataStepGatewayAdapter

• Reimplements GatewayInterface
• delegates everything to
• performs typecasting where needed
• public class DataStepGatewayAdapter private
  GatewayInterface dbi public DataStepGatewayAdap
  ter() throws Exception dbi
  GatewayServer.getReferenceToPersistentManager
  () public int getStatementHandle (double
  cHandle) throws Exception return
  dbi.getStatementHandle ( (int) cHandle)

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SAS Macros

• Facilitate use of Gateway
• startServer
• getConnectionHandle
• getStatementHandle
• jdbcLoadTable
• jdbcQuery

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Using the macros

• let jdbc_server_policy gateway.policy
• let jdbc_driver org.postgresql.Driver
• let db_url jdbcpostgresql//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 )

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Using the macros

• jdbcLoadTable (
• cHandlecHandle,
• datasashelp.zipcode,
• obs20)
• jdbcQuery (
• cHandlecHandle,
• sqlSELECT FROM ZIPCODE, outWORK.ZIPCODE)

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JDBC connection pattern

• Class.forName(jdbcDriver)
• Connection con DriverManager.getConnection
• ( URL, username, password )
• jdbcDriver org.postgresql.Driver
• URL jdbcpostgresql//www.devenezia.com5434/se
  sug03demo
• username sesug03demo
• password D3m0oeoe

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Conclusion

• Javaobj opens new horizons
• Hybrid solutions
• Combine best features of different technologies
• Web
• www.devenezia.com/papers/sesug-2003