www.pudn.com > town-1[1].0.4.rar > KeyDef.java

package com.workingdogs.town; 
 
import java.util.Vector; 
 
/* 
Town, a Java JDBC abstraction layer 
Copyright (C) 1999  Serge Knystautas, Jon S. Stevens 
 
This library is free software; you can redistribute it and/or 
modify it under the terms of the GNU Library General Public 
License as published by the Free Software Foundation; either 
version 2 of the License, or (at your option) any later version. 
 
This library 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 
Library General Public License for more details. 
 
You should have received a copy of the GNU Library General Public 
License along with this library; if not, write to the 
Free Software Foundation, Inc., 59 Temple Place - Suite 330, 
Boston, MA  02111-1307, USA. 
*/ 
/** 
A KeyDef is a way to define the key columns in a table. The KeyDef is 
generally used in conjunction with a TableDataSet. 
Essentially a KeyDef is what forms the WHERE clause for an UPDATE or DELETE. 
 
In order to use the KeyDef, you simply use it like this: 
 
KeyDef kd = new KeyDef().addAttrib("key_column_a"); 
TableDataSet tds = new TableDataSet ( connection, "table", kd ); 
Record rec = tds.getRecord(0); 
rec.setValue("column_name", "new value" ); 
rec.save(); 
tds.close(); 
 
In the above example, Record 0 is retrieved from the database table 
and the following update statement is generated: 
 
UPDATE table SET column_name=? WHERE key_column_a=? 
 
 
@author Jon S. Stevens jon@working-dogs.com 
@author Serge Knystautas sergek@lokitech.com 
@version 1.0 
*/ 
public class KeyDef 
{ 
    Vector data = new Vector (); 
    public KeyDef() 
    { 
        super(); 
        // KeyDef is 1 based. 
        data.addElement (""); 
    } 
    /** 
        Adds the named attribute to the KeyDef. 
 
        @returns a copy of itself 
      */ 
    public KeyDef addAttrib(String name) 
    { 
        data.addElement (name); 
        return this; 
    } 
    /** 
        Determines if the KeyDef contains the requested Attribute. 
 
        @returns true if the attribute has been defined. false otherwise. 
      */ 
    public boolean containsAttrib (String name) 
    { 
        return !(data.indexOf ((Object) name) == -1); 
    } 
    /** 
        getAttrib is 1 based. Setting pos to 0 will attempt to return pos 1. 
 
        @returns value of Attribute at pos as String. null if value is not found. 
      */ 
    public String getAttrib (int pos) 
    { 
        if (pos == 0) 
            pos = 1; 
 
        try 
        { 
            return (String) data.elementAt (pos); 
        } 
        catch (ArrayIndexOutOfBoundsException e) 
        { 
            return null; 
        } 
    } 
    /** 
        KeyDef's are 1 based, so this overrides the Vector.size() method and 
        returns size - 1; 
 
        @returns the number of elements in the KeyDef that were set by addAttrib() 
        @see #addAttrib(java.lang.String) 
      */ 
    public int size() 
    { 
        return data.size() - 1; 
    } 
}