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/**
* com.mckoi.database.Variable 11 Jul 2000
*
* Mckoi SQL Database ( http://www.mckoi.com/database )
* Copyright (C) 2000, 2001, 2002 Diehl and Associates, Inc.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* Version 2 as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License Version 2 for more details.
*
* You should have received a copy of the GNU General Public License
* Version 2 along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* Change Log:
*
*
*/
package com.mckoi.database;
/**
* This represents a column name that may be qualified. This object
* encapsulated a column name that can be fully qualified in the system. Such
* uses of this object would not typically be used against any context. For
* example, it would not be desirable to use ColumnName in DataTableDef
* because the column names contained in DataTableDef are within a known
* context. This object is intended for use within parser processes where
* free standing column names with potentially no context are required.
*
* NOTE: This object is NOT immutable.
*
* @author Tobias Downer
*/
public final class Variable implements java.io.Serializable, Cloneable {
static final long serialVersionUID = -8772800465139383297L;
/**
* Static that represents an unknown table name.
*/
private static final TableName UNKNOWN_TABLE_NAME =
new TableName("##UNKNOWN_TABLE_NAME##");
/**
* The TableName that is the context of this column. This may be
* UNKNOWN_TABLE_NAME if the table name is not known.
*/
private TableName table_name;
/**
* The column name itself.
*/
private String column_name;
/**
* Constructs the ColumnName.
*/
public Variable(TableName table_name, String column_name) {
if (table_name == null || column_name == null) {
throw new NullPointerException();
}
this.table_name = table_name;
this.column_name = column_name;
}
public Variable(String column_name) {
this(UNKNOWN_TABLE_NAME, column_name);
}
public Variable(Variable v) {
this.table_name = v.table_name;
this.column_name = v.column_name;
}
/**
* Returns the TableName context.
*/
public TableName getTableName() {
if (!(table_name.equals(UNKNOWN_TABLE_NAME))) {
return table_name;
}
return null;
}
/**
* Returns the column name context.
*/
public String getName() {
return column_name;
}
/**
* Attempts to resolve a string '[table_name].[column]' to a Variable
* instance.
*/
public static Variable resolve(String name) {
int div = name.lastIndexOf(".");
if (div != -1) {
// Column represents '[something].[name]'
String column_name = name.substring(div + 1);
// Make the '[something]' into a TableName
TableName table_name = TableName.resolve(name.substring(0, div));
// Set the variable name
return new Variable(table_name, column_name);
}
else {
// Column represents '[something]'
return new Variable(name);
}
}
/**
* Attempts to resolve a string '[table_name].[column]' to a Variable
* instance. If the table name does not exist, or the table name schema is
* not specified, then the schema/table name is copied from the given object.
*/
public static Variable resolve(TableName tname, String name) {
Variable v = resolve(name);
if (v.getTableName() == null) {
return new Variable(tname, v.getName());
}
else if (v.getTableName().getSchema() == null) {
return new Variable(
new TableName(tname.getSchema(), v.getTableName().getName()),
v.getName());
}
return v;
}
/**
* Returns a ColumnName that is resolved against a table name context only
* if the ColumnName is unknown in this object.
*/
public Variable resolveTableName(TableName tablen) {
if (table_name.equals(UNKNOWN_TABLE_NAME)) {
return new Variable(tablen, getName());
}
else {
return new Variable(table_name.resolveSchema(tablen.getSchema()),
getName());
}
}
/**
* Sets this Variable object with information from the given Variable.
*/
public Variable set(Variable from) {
this.table_name = from.table_name;
this.column_name = from.column_name;
return this;
}
/**
* Sets the column name of this variable. This should be used if the
* variable is resolved from one form to another.
*/
public void setColumnName(String column_name) {
if (column_name == null) {
throw new NullPointerException();
}
this.column_name = column_name;
}
/**
* Sets the TableName of this variable.
*/
public void setTableName(TableName tname) {
if (table_name == null) {
throw new NullPointerException();
}
this.table_name = tname;
}
// ----
/**
* Performs a deep clone of this object.
*/
public Object clone() throws CloneNotSupportedException {
return super.clone();
}
/**
* To string.
*/
public String toString() {
if (getTableName() != null) {
return getTableName() + "." + getName();
}
return getName();
}
/**
* To a differently formatted string.
*/
public String toTechString() {
TableName tn = getTableName();
if (tn != null) {
return tn.getSchema() + "^" + tn.getName() + "^" + getName();
}
return getName();
}
/**
* Equality.
*/
public boolean equals(Object ob) {
Variable cn = (Variable) ob;
return cn.table_name.equals(table_name) &&
cn.column_name.equals(column_name);
}
/**
* Comparable.
*/
public int compareTo(Object ob) {
Variable cn = (Variable) ob;
int v = table_name.compareTo(cn.table_name);
if (v == 0) {
return column_name.compareTo(cn.column_name);
}
return v;
}
/**
* Hash code.
*/
public int hashCode() {
return table_name.hashCode() + column_name.hashCode();
}
// /**
// * The name of the variable.
// */
// private String name;
//
// /**
// * Constructs the variable.
// */
// public Variable(String name) {
// this.name = name;
// }
//
// /**
// * Renames the variable to a new name. This should only be used as part
// * of resolving an variable alias or lookup.
// */
// public void rename(String name) {
// this.name = name;
// }
//
// /**
// * Returns the name of the variable.
// */
// public String getName() {
// return name;
// }
//
//
//
// public String toString() {
// return name;
// }
}