EM 431ASA and the new SQLJ standards

Shannon WhiteSoftware DeveloperiAnywhere Solutionsshannon.white@sybase.com

What is SQLJ?

• SQLJ1: ANSI NCITS 331.1-2000• Calling java methods from SQL

• SQLJ2: ANSI NCITS 331.2-2000• Mapping java types to SQL types

• To be merged in SQL/JRT for SQL/2000• Not covered here:

• SQLJ0: The Java language bindings

Why SQLJ?

• SQL PSM (Persistent Stored Modules)• Not object-oriented• Small standard library• Only usable within a database server• Small developer community• Vendor specific variations

• Java• Object-oriented• Large library of standard packages• Ubiquitous from client tier to server tier• Large developer community

SQLJ1 Overview

• Java classes in SQL• Installing/updating/removing classes• Name resolution path within java classes• Privileges for accessing java classes

• Calling java static methods from SQL• Returning out and inout parameters• Returning SQL result sets from java

SQLJ2 Overview

• Syntax for mapping SQL types to java classes:• Creating/dropping of mapping• Instantiation of java objects from SQL• Calling methods on java objects from SQL• Ordering of java objects referenced from SQL

• Persistence of java objects• Java class must implement Serializable or

SQLData

Support for Java in the ASA database server

• Java supported in the database server since ASA 6.0• Java VM runs in-process• Java support fully integrated throughout

• Access to java from SQL• Access to SQL through JDBC• Persistence of java object data in the database• Transfer of java objects between client and server• Support for JDK 1.3 in upcoming ASA 8.0 release

Mapping java classes to SQL types

• Install a java class using the install statement:

install java {new|update} [jar ‘jar-name’]from {file <file-name> | <expr>}

• Corresponding SQL type(s) automatically created• SQL type name is same as fully qualified java name• Ex.

• Java class BigDecimal in package java.math• Corresponding SQL type:

java.math.BigDecimal

Installing from a file

• Install a class from a file

install java newfrom file ‘d:\\java\\myClass.class’

• Creates the SQL type myClass

• Install a class from a jar file

install java new jar ‘testjar’from file ‘d:\\mytest.jar’

• Creates a SQL type for each class in mytest.jar

Installing from a variable

Example:

create variable @byte_code long binary;set @byte_code = 0xCAFEBABE…;install java update from @byte_code;

• Useful in several circumstances:• Class file not accessible from server• Class byte code not stored in file• Used in ASA unload/reload, dbtran and SQL Remote

Java methods and fields

• Java static and instance methods callable from SQL• Java static and instance fields SQL-accessible• Method and field names map to same name in SQL• Syntax for accessing static methods and fields:

• The java SQL type name prefixes the method or field• Accessing instance methods and fields:

• Java instance reference prefixes the method or field• Instance references include

• Java-typed column references• Java-typed SQL variables• Java-typed expressions

Calling a java method

• Examples:• Converting from decimal to hexadecimal

select java.lang.Integer.toString( 90, 16 )

produces row:5a

• Setting a standard scalecreate variable bd java.math.BigDecimal;set bd = new

java.math.BigDecimal( ‘123.456’ );select bd.setScale( 1, ROUND_UP );

produces row:123.5

Out and inout parameters

• Not naturally a part of java• Uses java arrays of unit lengthExample:

void myMethod( int[] myout ) { myout[0] = 123; }

Maps to:

create variable out_var int;call myInstance.myMethod( out_var );

Value of out_var is 123

Returning SQL result sets

• Not naturally a part of java• Uses arrays of java.sql.ResultSetExample:

void getRSet( ResultSet[] rset ) { rset[0] = …; }

Maps to:

select myInstance.getRSet();

Accessing SQL from java

• Server-side JDBC 2.0 driver• Full access to power of SQL

• Prepared statements• Batch statements• Result sets• Scrollable cursors• Updateable cursors• Database and result set meta data

Persistence of java objects

• Java objects stored in Java-typed table columns• Live across server shutdown and restart• Compact binary representation

create table ttt ( bd java.math.BigDecimal );insert into ttt values

(new java.math.BigDecimal(‘123.456’));select bd.negate() from ttt;

Produces row:

-123.456

Java objects between client and server

• JDBC• ASA JDBC driver JConnect• setObject() and getObject() methods

• ODBC/OLEDB, OpenClient, DBLIB• Objects sent as long binary SQL type• Object must be java.io.Serializable• Sun serialization

• SQLRemote• Objects sent as long binary• Serialization used is more compact

Is Java worth the trouble?

Is it worth switching development from SQL to java?• Java is the considered “better” language

• Object-oriented, standard• Exploding development community• Large pre-existing code base

Is that enough to justify a switch?• Switch costs

• Acquiring java programmer experience• Maintenance of legacy SQL procedures

Java cons

• Starting the java VM• Can take a couple seconds to create first VM

• Garbage collection• Can occur at inopportune times• Can make it difficult to predict execution time

• Java is all unicode• Unicode to/from native character set costs

• Sun serialization is slow and bulky• Persisting java object usually slower than storing

constituent data

More than just a better language

The ASA support provides dramatic new capabilities not required by SQLJ and not available in SQL

• ASA 7.0• Multi-threading within a connection• Access to the file system (java.io.*)• Access to the internet (java.net.*)

• ASA 8.0• Remote procedure calls (java.rmi.*)• Enhanced security features (ASA 8.0)• JDK 1.3 support

Multi-threading

• Use standard java.lang.Thread API• Java threads can be spawned, interrupted, and killed• Threads execute concurrently on the same connection• Only single-threaded access to JDBC• Child threads killed when parent thread exits VM• Daemon threads not allowed

File I/O

• Support for JDK’s java.io package• Access to file system from perspective of server• Features abstraction of file and pathnames• Access restricted by default• Access granted via database option and

SecurityManager

Socket support

• Support for JDK’s java.net package• Provides classes for implementing network apps• Access restricted by default• Access granted via database option and

SecurityManager

RPC

• Support for JDK’s java.rmi package• Provides classes for distributed programming• JDK 1.3 includes support for CORBA’s IIOP• Access restricted by default• Access granted via database option and

SecurityManager

Security

• SecurityManager• Java object that governs access to permission-

sensitive resources• Ex. file I/O, sockets• Extend to enterprise-specific resources

• DBA can associate user with a SecurityManager• Limits user’s access to resources accessible from java• Default restricts access to file I/O and sockets

JDK 1.3 support

• Previous support based on JDK 1.1.6• ASA 8.0 beta provides JDK1.3.0 support• ASA 8.0 release will likely provide JDK 1.3.1 support• New capabilities

• Collections framework• JDBC 2.0• Reference Objects• JNDI• RMI over IIOP• Reflection enhancements

Future development

• Just-in-time (JIT) compiler• Already in ASE 12.5

• Dynamic class loading• JDK 1.4• J2ME

Conclusion

• Java in the database server can be useful• Has to be more than a “better” language• Must provide capabilities not available in SQL

• ASA provides java in the database server• Multi-threading• I/O, sockets, RPC• JDK 1.3