Chapter 3 DynaScript Predefined Objects

java object

Object

Allows for manipulation of Java classes within PowerDynamo scripts.

The java object represents an object used for working with a Java class within your Web site.

Syntax

To use a java method:

java.MethodName( parameter ) 

Description

To use Java class objects within your Web site, your Web site must be configured to enable Java. Sybase Central allows for easy Java class setup for PowerDynamo Web sites. You should be aware of the following configuration options in the Configuration folder of Sybase Central if you want to create and use instances of Java class objects within your Dynamo scripts:

• Java VM PowerDynamo supports the Sun Java VM and the Microsoft VM. You must select one of these VMs for PowerDynamo to support Java.
• Java class cache size To improve performance, information about the methods and properties of Java classes is cached. This option enables you to set the cache size.
• Class path for the mapping You must specify a path for class files that are stored in a Dynamo Web site.

    

  Executing from within Sybase Central
  To execute scripts that use the java object from within Sybase Central, the mapping and Dynamo site name must be the same.

For more information on PowerDynamo configuration settings in Sybase Central, see "Changing Dynamo configuration settings" in the PowerDynamo User's Guide.

You must specify all parameters when you are working with the java object. Unlike other DynaScript objects, an error occurs if parameters are excluded when calling a Java class method or property.

Accessing Java methods and properties
You can access methods from any Java class. Properties, however, can be accessed only from JavaBeans.

Example

Let's assume we are working with this class:

class Fibonacchi
{
    public long prev1;
    public long prev;
    public long next;
    
    public long getPrev() { return prev; }
    public long getNext() { return next; }

    public Fibonacchi()
    {
        prev1 = 1;
        prev = 0;
        next = 0;
    }

    public void generateNext()
    {
        next = prev1 + prev;
        prev = prev1;
        prev1 = next;
    }
    
    static public double doubleme( double t ) 
    {
        return t*2;
    }
}

To call this class, your script might look something like this:

// call a static method on the class
result = java.CallStaticMethod( "Fibonacchi", "doubleme", 2.5 );
document.writeln( result );
// create a DynaScript object representing a Java class
fib = java.CreateObject( "Fibonacchi" );
// retrieve a property on the class
document.writeln( "The value of next is " + fib.next + " The value of prev is " + fib.prev );
for( i = 0; i < 20; i++ ) {
    // invoke a method on the class
    fib.generateNext();
    document.writeln( "The value of next is " + fib.next + " The value of prev is " + fib.prev );
}

For more information on using Java in your PowerDynamo scripts see "PowerDynamo and Java" in PowerDynamo User's Guide.

CreateComponent method

Syntax

java.CreateComponent( componentName [, managerUrl, id, password, narrowingComponent] )

Description

Creates an instance of an EAServer component, using CORBA naming services, through Java. The parameters are:

• componentName The name of the component.
• managerUrl An URL to Jaguar Manager. For example, "iiop://testMachine:9000". This parameter is required to call a component on another machine.
• id A Jaguar Manager user ID.
• password A Jaguar Manager password.
• narrowingComponent The name of the component you would like to narrow.
  
  The EAServer returns a component instance that must be narrowed (cast) to an instance of an interface that the component supports. The default interface is set to the name of the EAServer component that is being called. Use this only if you want to change the interface to something other than the default. For example, by default, the component SVU/SVUEnrollment is narrowed to the interface "SVU/SVUEnrollment". For more information on narrowing, see the EAServer Programmer's Guide.
  
  When you are generating stubs for your EAServer components, you can specify a Java package other than the default, in which to store the stubs. If this is the case, when the component is later being created by DynaScript, the location of the stubs must be specified. To specify a stub location that is something other than the default, the narrowing_component parameter of the CreateComponent method should be used. For example, if you have stored your Java stubs for the SVU Jaguar package in com/sybase/jaguar/sample/svu/SVUMetaData then you would use the following syntax to create an instance of a SVUMetaData component that resides in the SVU Jaguar package:
  
  

  java.CreateComponent( "SVU/SVUMetaData", "iiop://localhost:9000", "Jagadmin", "", " com/sybase/jaguar/sample/svu/SVUMetaData" );
  

If however, you used the default value when generating stubs for the SVU package, your syntax would look like this:

java.CreateComponent( "SVU/SVUMetaData" );

Setting the Java VM
The Java VM configuration option must be set to the Sun VM for scripts with this method to execute. Change the VM option using the Configuration\Default General Settings\Java VM folder in Sybase Central.

Return

A EAServer component object or null if the component cannot be created. This is a DynaScript Java object.

Example

This example creates an instance of a component called comp . Once the object is created, its method getMajors is called and the Record Set is displayed:

<HTML>
<H1>A CreateComponent example</H1>
<!--SCRIPT 
    document.writeln( "<H3>Testing SVUEnrollment getMajors</H3>" );
    comp = java.CreateComponent( "SVU/SVUEnrollment" ); 
    RecordSet = comp.getMajors();
    query = java.CallStaticMethod( "com.sybase.CORBA.jdbc11.SQL", "getResultSet", RecordSet);
    received = query.next();
        i = 0;
        while( received ) {
            metadata = query.getMetaData();
            document.writeln( "*****" );
            columns = metadata.getColumnCount();
            for( j = 1; j<= columns; j++ ) {
               value = query.getString( j );
               document.writeln( value );
            }
            received = query.next();
            i++;
        }
 -->
</HTML>

For information on result sets and the getResultSet method, see the EAServer Programmer's Guide.

site.GetErrorInfo( )
The site.GetErrorInfo( ) method may be used for retrieving error information.

See also

"Calling EAServer Component Methods from PowerDynamo" in the PowerDynamo User's Guide.

CreateObject method

Syntax

java.CreateObject( className [, list of constructor parameters ] )

Description

Instantiates a Java class object. The parameters are:

• className The name of the Java class.
• list of constructor parameters These parameters are passed to the Java class constructor.

Setting the Java VM
The Java VM configuration option must be set to the Sun VM for scripts with this method to execute. Change the VM option using the Configuration\Default General Settings\Java VM folder in Sybase Central.

Return

A DynaScript object representing the Java class. Returns null if the Java class cannot be created.

Example

This example creates an instance of Java class that performs the Fibonacchi mathematical procedure. It involves the GenerateNext method and returns results.

<!--SCRIPT
    fib = java.CreateObject( "Fibonacchi" );
    // retrieve a property on the class
    document.writeln( "The value of next is " + fib.next + " The value of prev is " + fib.prev );
    // set a property on the class
    fib.next = 5;
    for( i = 0; i < 20; i++ ) {
        // invoke a method on the class
        fib.generateNext();
        document.writeln( "The value of next is " + fib.next + " The value of prev is " + fib.prev );
}
--> 

See also

"PowerDynamo and Java" in the PowerDynamo User's Guide.

CallStaticMethod method

Syntax

java.CallStaticMethod( className, staticMethod [, list of method parameters] )

Description

Calls a static Java method. You need not create a Java object (java.CreateObject) to call static methods of that object. The parameters are:

• className The name of the Java class containing the static method.
• staticMethod The name of the static method to be called.
• list of method parameters Any parameters to be passed on to the static method.

Return

The return type is dependent on the type of return value of the static method.

Example

This example executes the static method doubleme of the class Fibonacchi . Calling a static method does not require that an object representing a Java class instance be created.

<!--SCRIPT
result = java.CallStaticMethod("Fibonacchi", "doubleme", 2.5);
document.writeln( result );

--> 

See also

"PowerDynamo and Java" in PowerDynamo User's Guide

GetHomeInterface method

Syntax

java.GetHomeInterface(component_name [, provider_url, user_id, password] )

Description

Allows access to the EJBHome interface for an EAServer component. The parameters are:

• component_name The name of the component to instantiate. Component names are composed as follows:
  [<server-context>]<package>/<comp>
  
  
  • server-context - the root naming context for the server where the component is installed. server-context is optional and necessary only if a root naming context has been set for the server. The root naming context can also be given as the initial context in the provider_url.
  • package - the EAServer package to which the component belongs, as displayed in Jaguar Manager.
  • component - the component name, as displayed in Jaguar Manager.
• You can view and edit this setting using the Naming Service tab of the Server Properties window from Jaguar Manager. The default for a new server is "/". If you specified an initial name context in GetHomeInterface()'s provider_url parameter, then the server context is assumed to be relative to this initial name context. For example, if the provider_url parameter is set to iiop://localhost:9000/USA/Sybase, and your server's root context is USA/Sybase/Engineering, then you can resolve component names as Engineering/package/component.
• provider_url The provider_url is optional and defaults to "iiop://localhost:9000". If used, it identifies the URL of the JNDI name server. This parameter should be of the form iiop://<hostname>[:<iiop-port>][/<initial-context>] where:
  
  
  • hostname Is the host machine name for the EAServer that serves as the name server for your application.
  • iiop-port Is the IIOP port number for the server.
  • initial-context Is the optional initial naming context, which can be used to set a default prefix for name resolution. For example, if you specify USA/Sybase/, then the component_name parameter is assumed to be relative to this location in the name hierarchy. When specifying the initial context, the trailing slash is optional; it is added automatically if you do not specify an initial context that ends with a slash.
• user_id The user name for the EAServer session. If authorization is enabled for your EAServer, this parameter is used to authorize access to EAServer components.
  
  The user_id parameter is optional and defaults to "guest."
• password The password for the EAServer session. If authorization is enabled for your EAServer, the password is used to authorize access to EAServer components.
  
  The password parameter is optional and the default is no password.

   The Dynamo methods GetHomeInterface and GetUserTransaction enable access to EJB interfaces of EAServer components. To access EJB interfaces of EAServer components, Dynamo requires an EAServer client jar file, easclient.jar, from your EAServer installation. Refer to PowerDynamo installation instructions for your platform and ensure that this file is included in your JAGUARCLASSES (Solaris) or CLASSPATH (NT) variable.

Example

Use java.GetHomeInterface to create an instance of the EJBHome interface for the component Test/Cart . Then use the Home interface to create an actual instance of Test/Cart . You need to use the JNDI name of the Object, for instance Cart, if the JNDI name of the component is Cart:

carthomeObj = java.GetHomeInterface("Cart")    cartObj = carthomeObj.create("John", "7506");    cartObj.addItem(66)    cartObj.addItem(22)    cartObj.purchase()    carthomeObj.remove(...)

   If you create a EJB from a tool like PowerJ, the wizard prompts you for a unique name ( this is the JNDI name used for the lookup ). Normally the name for the remote interface ( the code running on the client side to invoke the remote method ) and the JNDI name are the same.

See also

"PowerDynamo and Java" in the PowerDynamo User's Guide

GetUserTransaction method

Syntax

java.GetUserTransaction(  [ <provider_url>, <user_id>, <password>] )

Description

Allows access to the EJB UserTransaction object. The parameters are:

• provider_url The provider_url is optional and defaults to "iiop://localhost:9000". It identifies the URL of the JNDI name server. This parameter should be of the form iiop://<hostname>[:<iiop-port>][/<initial-context>] where:
  
  
  • hostname Is the host machine name for the EAServer that serves as the name server for your application.
  • iiop-port Is the IIOP port number for the server.
  • initial-context Is the optional initial naming context, which can be used to set a default prefix for name resolution. For example, if you specify USA/Sybase/, all names that you resolve with the context are assumed to be relative to this location in the name hierarchy. When specifying the initial context, the trailing slash is optional; it is added automatically if you do not specify an initial context that ends with a slash.
• user_id The user name for the EAServer session. If authorization is enabled for your EAServer this optional parameter, which defaults to "guest," is used to authorize access to EAServer components.
• password The password for the EAServer session. If authorization is enabled for your EAServer, this optional parameter, which defaults to no password, is used to authorize access to EAServer components.

   The Dynamo methods GetHomeInterface and GetUserTransaction enable access to EJB interfaces of EAServer components. To access EJB interfaces of EAServer components, Dynamo requires an EAServer client jar file, easclient.jar, from your EAServer installation. Refer to PowerDynamo installation instructions for your platform and ensure that this file is included in your JAGUARCLASSES (Solaris) or CLASSPATH (NT) variable.

Comments

The components that participate in the transaction managed with the UserTransaction object must be in the same server as the UserTransaction object, which cannot be assumed if an EAServer cluster is used to ensure that this requirement is met:

1. Use the same name server to create the UserTransaction object that was used when creating the component instances. That is, supply the same provider_url to GetUserTransaction() and GetHomeInterface() , CreateComponent() . The initial-context values of the URLs can differ.
2. Get the UserTransaction object and begin the transaction before creating any component instances.
3. In addition, follow the same restrictions as other Java clients when using the UserTransaction object. See to the EAServer Programmer's Guide and EAServer Reference Manual for details.

The UserTransaction interface defines exceptions that are thrown when errors occur. For example, TransactionRolledbackException is thrown when commit() is called after setRollbackOnly() has already been called for a transaction.

As many of the methods in the UserTransaction interface for example, return void, begin() , commit() , rollback() , these exceptions are the only way to detect errors.

In DynaScript, exceptions are passed to the user through the site.GetErrorInfo() method. That is, the exception is converted to an error string. For example:

    ut.begin()
    ...
    ut.commit()
    errMsg = site.GetErrorInfo();
    if ((errMsg != null) && (errMsg != ""))
    {
        /* the transaction was not committed */
    }

The UserTransaction.getStatus() method returns an integer value indicating the status of the current transaction. Dynamo users can include the script ~/system/utils/usertran.ssc to get the definitions of variables that map to the integer values returned by getStatus() .

    import "~/system/utils/usertran.ssc"

    ...

    ut = java.GetUserTransaction(...);
    ut.begin()
    status = ut.getStatus();
    if (status != UserTran.STATUS_ACTIVE)
    {        /* the transaction was not started */    }
    ...

Example

Use java.GetUserTransaction to get the UserTransaction object, instantiate the components that will participate in the transaction, begin the transaction, perform the operations required in the transaction, and commit the transaction.

    ut = java.GetUserTransaction("iiop://my-host:9000")
    acctHome = java.GetHomeInterface("Account", "iiop://my-host:9000")
    acct1 = acctHome.create("John", "Doe", "111-11-1111")
    acct2 = acctHome.create("Jane", "Doe", "222-22-2222")
    acct3 = = java.CreateComponent("Bank/Account", "iiop://my-host:9000")
    ut.begin();
    errMsg = site.GetErrorInfo();
    if ((errMsg != null) && (errMsg != ""))
    {
        /* handle error, the transaction did not begin return
    }
    acct1.withdraw(100);
    acct2.deposit(50);
    acct3.deposit(50);
    ut.commit();
    errMsg = site.GetErrorInfo();
    if ((errMsg != null) && (errMsg != ""))
    {
        /* handle error, the transaction did not commit return
    }

See also

"PowerDynamo and Java" in the PowerDynamo User's Guide.

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