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VISUAL J++

Colorado Technical University

IT420

Tim Peterson

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J++ Advantages

• There are many Rapid Application Development (RAD) environments for JAVA.

• Many work on only pure Java.

• J++ provides many features that can be utilized by Windows systems.

• J++ is an excellent tool for accessing databases.

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J++ Overview

• J++ is compatible with SUN’s Java Development Kit (JDK).

• J++ includes Windows Foundation Classes (WFC).

• J++ does not support Java Foundation Classes, Java Beans, or Enterprise Java Beans.

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J++ Overview - Cont’d

• Visual J++ allows users to use DHTML.

• Visual J++ includes many wizards to help you with development efforts.

• J++ is targeted towards people building Windows based corporate intranets.

• J++ is OOP which makes it better than languages such as Vbasic.

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Windows Foundation Classes

• WFC is used integrate the Windows platform with the Java language.

• Reasons to use WFC:– Performance is greatly increased.– WFC has a data binding model.– WFC also supports ADO and binds them.

• If we were to implement our Java code on other platforms, we would not use WFC.

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WFC Implementation

• WFC is implemented as a Java class layer.

• WFC provides an object oriented set of classes.

• WFC allows for URL requests that in turn contain database connectivity.

• With WFC, you can return HTML to a range of platforms including Windows CE devices, Web TV, and Macintosh.

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WFC Implementation - Cont’d

• WFC allows a developer to use any method (member function) contained within a DLL.

• WFC applications will not run on non-windows platforms.’

• J++ provides an alternative to using Visual Basic and C++.

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Component Object Model (COM)

• COM is an integral part of developing Windows-specific intranet applications.

• In J++, all Java objects become COM objects.• Key elements of the WFC API include:

– UI based on either Win32 or DHTML

– Data binding to a database.

– Operations can be performed when connected to the Internet or in an off-line mode.

– DOS command line operation.

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WFC Packages

• The main packages provided in WFC are as follows:

• com.ms.wfc.app com.ms.wfc.io

• com.ms.wfc.ax com.ms.wfc.ole32

• com.ms.wfc.core com.ms.wfc.ui

• com.ms.wfc.data com.ms.wfc.util

• com.ms.wfc. html com.ms.wfc.win32

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GUI Classes

• GUI classes from package wfc.ui provide:– Provides for control of GUI objects. Examples:

• Setting and retrieving control properties.

• Event management of controls.

• Methods dealing with parent/child relationships of controls.

• Methods affecting control layouts.

• Low level control processing.

• Windows handles, messages, and thread invocation.

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System Classes

• Part of wfc.app.

• With WFC, one can manipulate the OS.

• The developer can encapsulate memory and file objects.

• Underlying OS platform can be accessed using J/Direct.

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UI/DHTML Code Example

Import wfc.ui.*

{

Form queryForm = new Form();

Button submit = new Button();

submit.setText (“Submit”)

submit.setPosition(20,50);

queryForm.add(submit);

}

Import wfc.html.*{

DhPanel queryForm = new DhPanel();DhButton submit = new DhButton();submit.setText (“Submit”)submit.setPosition(20,50);queryForm.add(submit);

}

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DHTML Advantages

• Allows you to create cross-platform code.

• It provides for user interaction and data presentation using the following combinations:– HTML– Scripts– Document Object Model

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DHTML Advantages - Cont’d

• Allows the developer to control the Web Page.

• DHTML pages can be authored using J++.

• J++ then generates DHTML code on the fly.

• To use DHTML in J++, you must extend the DhModule class.

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Example J++ Extending DHTM

Public class NewDHTMLClass extends DhModule

{

public void documentLoad(Object sender, DHEvent e)

{

DhDocument Dhdoc = getDocument();

Dhdoc.add(new

DhText(“Text to see in Web page”));

}

}

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DHTML Event Handling

• You work with events using delegates.

• A delegate declaration extends .com.ms.lang.Delegate.

• A delegate instance can call a method on an object and pass data to that method.

• Mainly used to bind events to handler methods.

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WFC Designer

• WFC Designer tool is best way to build Windows GUIs using J++.

• With this tool, you can bind data sources to any visual control using drag and drop.

• Applications built using WFC designer are true Windows applications.

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WFC Designer - Cont’d

• In general, when using the WFC designer, the following should be accomplished:– Ensure that data controls are added to the toolbox.

– Retrieve a set of records

– Display the data on the form

– Navigate the records.

• If the above can be done, the integrity of the WFC is most likely sound.

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DataSource Control

• In the WFC designer, the DataSource control provides for data access for J++.

• DataSource combines the functionality of Connection, Command, and Recordset objects.

• DataSource only retrieves data and does not display it.

• To being using DataSource, it must be added to a form.

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DataSource Control - Cont’d

• To connect to a database, you must set the connectionString property. To access an ODBC data source, the string is as follows:

DSN=Nwind; UID=peterson; PWD=password

• To access an Access database, the string is as follows:

Provider=Microsoft.Jet.OLEDB.3.51;

Data Source=filename;

User ID=UserID; Password=password;

• After this, then the SQL command is entered.

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DataBinder Control

• Now that the records have been retrieved, the data must be bound to a display.

• If an attempt is made to updated a read-only recordset, and ADO exception is generated.

• The DataBinder can only bind components that exist on the same WFC design surface.

• DataBinder does not provide any means to validate changes made to a property’s value.

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DataBinder Control - Cont’d

• Components of bound properties can provide events.

• To support a property change request, a <PropertyName>Changing event exists.

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Universal Data Access

• UDA is Microsoft’s solution to providing high-performance access to data.

• UDA enables access to any data source on any platform.

• An API is included for this.

• Components that make this possible are ADO, Remote Data Services, OLE DB, and ODBC.

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Java ActiveX Data Objects

• JADO builds on ADO to present a simplified API.

• JADO components include:– Connection objects– Command objects– Recordset objects

• Purpose of JADO is to provide access to, to edit, and to update data sources.

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JADO Abilities

• Establish a connection to a data source.

• Create an object.

• Parameterize SQL statements with variable parameters using the Parameter object.

• Execute the commands using the Connection, Command, or Recordset object.

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JADO Abilities - Cont’d

• Edit Recordsets.

• Cache returned rows using a Recordset object.

• Update data source with cached data.

• Sort, filter, and navigate data in cache.

• Commit and rollback changes and then end the connection using the Connection object.

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Connection Object

• Connection object is an open connection to a data source.

• JADO accesses data and services from an OLE DB provider.

• The connection object specifies:– the particular provider– associated parameters

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Connection Object Open and Close Methods

• The Open method establishes a physical connection to the data source.– Once live, you can issue commands against it.

• The Close method is used to close a connection or free associated system resources.

• Closing an object does not remove it from memory.

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Connection Object Transactions

• Transactions delimit the beginning and end of data access operations across a connection.

• JADO ensures that transaction is totally complete prior to issuing a Commit.

• If transaction is not completed, JADO issues a rollback.

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Command Object

• Command object is the definition of the command to run against a data source.

• Commands normally add, delete, update, or retrieve data in a data source.

• JADO optimizes the execution of the command.• With the Command object, multiple commands

can be associated with a single object.

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Parameter Object

• This object allows you to treat parameters like functions.

• All you need to know is this interface and how to pass to it.

• This is used with the command object.

• Use the CreateParameter method to create objects and use Append to add them to the Parameters collection.

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Recordset Object

• A recordset object reflects data from a row-returning query.

• This object represents the set of records from a table or results from an executed command.

• Recordset is used to examine and update data.

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Recordset Object Capabilities

• Recordset Objects perform the following:– Manage state of the Recordset.– Add, update, and delete rows– Traverse rows– Specify available rows– Specify order of rows– Update the data source with changes to rows.

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Recordset Object Cursors

• Recordsets are created using rows and columns.• JADO provides for four cursor types:

– Dynamic

– Keyset

– Static

– Forward-only

• CursorType property must be set prior to opening the Recordset.

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Field Object

• To modify data in a data source, the Field objects are first modified.

• Field objects can perform:– Get or set data in Field with Value Property.– Get the name of the field (Name Property).– Get attributes (Type, Precision, and Numeric

scale).

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Field Object - Cont’d

– Obtain size of a field with DefinedSize and ActualSize properties.

– Manipulate binary and char files with AppendChunk and GetChunk.

– Determine functionality of a field by using the attributes property.

• The value property of a field is handled as a variant.

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Error Object

• Errors with JADO usually are:– Failure to establish a connection.– Failure to execute a command.– Failure to perform an operation on an object in

a suitable state.

• Errors are placed in the Errors collection of the Connection object.

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Error Object Properties

• The Error object allows you to use the following properties:– Description– Number– Source– HelpFile and HelpContext – SQL State and NativeError

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Collections

• Under JADO, Collections exist for:– Parameter Objects– Field Objects– Error Objects

• Data is retrieved using the collection method by name, text string, or integer number referencing it’s position in the collection.

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Using Recordsets Remotely

• JADO also provides the ability to develop off-network.

• Users can download Remoteable Recordsets (a subset of the source data).

• Developers can then create code to modify this Recordset off-line.

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Visual Database Tools

• Data View - used to connect to any ODBC or OLE DB database.

• Database Designer - used to create and modify SQL server databases.

• Query Designer - used to design, execute, and save SQL queries.

• Stored Procedure Editor - Used to create STPs.• Stored Procedure Debugger - Used to debug STPs.