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for the Java Programming Language - Classes

The CodeBase classes are extensive enough to provide a complete database solution and still small enough to enable fast downloading in the Client/Server version. They represent a balance between size, functionality and the ability to easily scale from standalone to client/server. Of course because we provide full client-side source code, you can always add to the Java classes any additional functionality you may require. The following table lists the Java classes provided with all versions of CodeBase for the Java Programming Language:

Code4 Class

CodeBase uses the Code4 class to specify initialize CodeBase, and to set various process-wide behaviors, such as locking and file access methods, and to perform actions such as connecting to the database server (C/S only). Generally, only one Code4 class object is used in any one application. Under client/server the Code4.connect() method must be executed successfully before a Data4 table object can be constructed and used to manipulate a data file.

Code4 ClassMethods
accessMode	lockClear	unlock
connect	readLock	unlockAuto
defaultUnique	readOnly
lock	safety

Example using Code4 class (client/server)

import codebase.*;

import java.applet.Applet;
import java.io.IOException;
import java.net.UnknownHostException;

class Example1
{
  public static void main(String args[])
 		  throws Error4,UnknownHostException,IOException
  {
     Code4cs client = new Code4cs();
     client.connect(null, 23165, "user1", "");
     client.safety(true);
     client.accessMode(Code4.DENY_WRITE);
     Data4cs dataFile = new Data4cs(client,"NAMES");
     dataFile.top();
     System.out.println("At the top of the data file");
     dataFile.close();
  }
}

Data4 Class

The Data4 class contains instance methods that are used to store and retrieve information from data files. Each data file has a current record and a selected index. The Data4 class also keeps track of the end of file (eof) and the beginning of file (bof). The Data4 constructor can not be executed successfully until a Code4 object is created and initialize.

A new data file may be created by calling Data4.create() after the Data4 constructor has been called. A particular data file may be opened more than once in an application and thus there may be multiple instances of a Data4 class for a particular data file. Any desired field objects may be created only after a data file has been opened or created.

Data4 Class Methods
Data4	createIndex	openIndex	reindex
append	go	pack	seek
blank	lockAdd	position	seekUnicode
bottom	lockAddAll	positionSet	select
close	lockAddFile	recCount	top
create	open	recNo	update

Example using Data4 class:

import codebase.*;

import java.io.IOException;
import java.net.UnknownHostException;

class Example
{
  public static void main(String args[])
     throws Error4,IOException,UnknownHostException
  {

     int recCount;

     Code4cs client = new Code4cs();
     client.connect(null, -1, "user1", "");
     Data4cs dataFile = new Data4cs(client,"Country" );
     Field4stringBuffer country = new Field4stringBuffer(dataFile,"Country");
     dataFile.bottom();
     //now change the last record
     country.set(StringBuffer("Italy"));
     dataFile.update();
     System.out.println(country.get());
     dataFile.close();
  }
}

Field Manipulation Classes

The various Field4... classes are used to access and store field values from the current record of the data file. Each of these classes can be mapped to several different field types, representing the various data types of the .DBF file format.

For every field in the data file that needs to be accessed, an appropriate object must be created and associated with a field. Each of these objects has an instance variable called contents that contains the value of that field from the current record. It is through the variable contents that the field can be retrieved and modified directly. When the data file is positioned to a new record, the field values of the new record are copied into the instance variables of the field objects associated with the data file.

CodeBase contains the following Field classes:

• Field4stringBuffer
• Field4stringBufferUnicode
• Field4double
• Field4date
• Field4boolean

Field4stringBufferUnicode class can be mapped to any field type, which includes Character, Date, Double, Logical, Numeric, Floating Point, Memo, General and Binary.

Field4double class can be mapped to Numeric, Floating Point and Character fields.

Field4date class can be mapped to a Date or Character field.

Field4boolean class can be mapped to Logical and Character fields.

Example using Field4 class:

import codebase.*;
import java.util.Date;
import java.io.IOException;
import java.net.UnknownHostException;

class Example
{
  public static void main(String args[])
     throws Error4,IOException,UnknownHostException
  {
     Code4cs client = new Code4cs();
     client.connect("", -1, "user1", "");
     Data4cs db=new Data4cs(client);
     db.open("INFO");
     Field4double age=new Field4double(db,"AGE");
     Field4date bdate=new Field4date(db,"BIRTH_DATE");
     db.top();
     Date now = new Date();
     long milliAge=now.getTime()-bdate.contents.getTime();
     int dayAge=(int)(((milliAge/1000)/3600)/24);
     System.out.println(bdate.get() + " "+now);
     System.out.println("Age in days based on birth date: " + dayAge);
     System.out.println("Age based on age field " + age.get());
     db.close();
  }
}