charger.db

Class TextDatabase

Object

charger.db.TextDatabase

All Implemented Interfaces:

CGDatabase

public class TextDatabase
extends Object
implements CGDatabase

Embodies accessibility to a tab-delimited text database. The database is first "activated" -- i.e., the file is located and verified, its name stored in the ActiveDatabases table in the Hub. There is a separate TextDatabase instance associated with each real database. Once "activated" a database file is associated with the same TextDatabase instance for the duration of the session, no matter how many graphs refer to it, or how many concepts in a single graph refer to it.

Author:

Harry S. Delugach ( delugach@uah.edu ) Copyright 1998-2020 by Harry S. Delugach

Field Summary

Fields

Modifier and Type	Field and Description
(package private) boolean	Attached
(package private) String	currentfilename Once the database file is opened, this class leaves the file open; it's up to its user to close it with closeDB().
(package private) String[]	DBValidNames
(package private) FileInputStream	fis
(package private) BufferedReader	in
(package private) boolean	openAndReady
(package private) int	primaryKey

Constructor Summary

Constructors

Constructor and Description
TextDatabase(String fname)

Method Summary

Modifier and Type	Method and Description
void	closeDB() Close the database file.
String	doLookup(String keytype, String keyvalue, String targettype) Searches the database file for the appropriate value; the "guts" of a database lookup.
int	getFieldPosition(String Field)
String[]	getFields()
String	getName() Accesses the name by which the database will be known to graphs.
int	getPrimaryKey()
String	getPrimaryKeyString()
String[]	getValidNames()
boolean	isOpened()
boolean	isReady()
void	makeReady() set up the database file for reading data
boolean	open(String fname) Initializes the file "in" for reading.
void	resetDB() Rewinds the database file so that the first line of read data can be read.
void	setPrimaryKey(int keyIndex)
void	setPrimaryKey(String keyType)
EditFrame	setupGraph(int key) Creates a new editing window with a graph already created for accessing this database.
private void	showRecordLine(String[] holder, String s)

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

currentfilename

String currentfilename

Once the database file is opened, this class leaves the file open; it's up to its user to close it with closeDB().

DBValidNames

String[] DBValidNames

primaryKey

int primaryKey

fis

FileInputStream fis

in

BufferedReader in

openAndReady

boolean openAndReady

Attached

boolean Attached

Constructor Detail

TextDatabase

public TextDatabase(String fname)
             throws CGFileException

Throws:

CGFileException

Method Detail

getName

public String getName()

Description copied from interface: CGDatabase

Accesses the name by which the database will be known to graphs. This means a valid referent for a "Database" concept in an editor frame.

Specified by:

getName in interface CGDatabase

Returns:

current file name of the database that's attached to me.

See Also:

GraphUpdater

open

public boolean open(String fname)
             throws CGFileException

Initializes the file "in" for reading. Only called once per file per session. Sets up access to the database file, loads up the valid names from 1st line of file.

Parameters:

fname - path-qualified name of file to be opened.

Throws:

CGFileException

resetDB

public void resetDB()

Rewinds the database file so that the first line of read data can be read. Closes the actual file and re-opens it (since we can't be certain the file supports a reset). Checks for any errors in case the file has been modified or moved since it was last opened.

Specified by:

resetDB in interface CGDatabase

closeDB

public void closeDB()

Close the database file.

Specified by:

closeDB in interface CGDatabase

isOpened

public boolean isOpened()

Returns:

true if the database file is currently open; false otherwise.

isReady

public boolean isReady()

Returns:

true if the database file is open and ready to read data.

getValidNames

public String[] getValidNames()

Returns:

list of strings in this file which are valid field or column names

setPrimaryKey

public void setPrimaryKey(int keyIndex)

setPrimaryKey

public void setPrimaryKey(String keyType)

getPrimaryKey

public int getPrimaryKey()

getPrimaryKeyString

public String getPrimaryKeyString()

makeReady

public void makeReady()

set up the database file for reading data

getFields

public String[] getFields()
                   throws CGFileException

Returns:

returns the next line of the database, from wherever we last read a line. null if at the end of the file Check end of file here; it doesn't work!!!

Throws:

CGFileException

getFieldPosition

public int getFieldPosition(String Field)

Parameters:

Field - the text representation of a database field name

Returns:

array index of which column the field refers to; -1 if not found

doLookup

public String doLookup(String keytype,
                       String keyvalue,
                       String targettype)

Searches the database file for the appropriate value; the "guts" of a database lookup.

Specified by:

doLookup in interface CGDatabase

Parameters:

keytype - The field name used as a key; e.g., "Employee"

keyvalue - The key's value; e.g., "John Smith"

targettype - The field name (column) whose value is being sought; e.g., "Phone Number"

Returns:

targetvalue column's value that matches the keytype's keyvalue; e.g., "(804) 555-1212"

showRecordLine

private void showRecordLine(String[] holder,
                            String s)

setupGraph

public EditFrame setupGraph(int key)
                     throws CGException

Creates a new editing window with a graph already created for accessing this database.

Parameters:

key - index into the DBValidNames array; -1 if there is no key.

Returns:

reference to the new window

Throws:

CGException