databaseinfofactory.java

OA典型例子

package com.sure.dataabstraction;

import java.util.Properties;

/**
 *  this is DatabaseInfoFactory which create DatabaseInfo from your property or
 *  create a defatul DatabaseInfo (DatabaseInfoDefatul) if you setup your
 *  DatabaseInfo implemention class name, it will create your DatabaseInfo you
 *  want.
 *
 *@author     Mengzy
 *@date       2002-8-16
 */
public class DatabaseInfoFactory {

    //get default DatabaseInfo , this return DatabaseInfoDefault instance
    /**
     *  Gets the defaultDatabaseInfo attribute of the DatabaseInfoFactory class
     *
     *@return    The defaultDatabaseInfo value
     */
    public static DatabaseInfo getDefaultDatabaseInfo() {
	String className = null;
	className = System.getProperty(CLASS_NAME);
	if (className == null) {
	    DatabaseInfo info = null;
	    try {
		info = new DatabaseInfoDefault();
	    } catch (Exception ex) {
		System.err.println(ex);
		throw new RuntimeException(ex.getMessage());
	    }
	    return info;
	} else {
	    Properties pro = new Properties();
	    pro.setProperty(CLASS_NAME, className);
	    DatabaseInfo instance = null;
	    try {
		instance = getDatabaseInfo(pro);
	    } catch (DBException e) {
		instance = new DatabaseInfoDefault();
	    }
	    return instance;
	}
    }


    /**
     *  Gets the databaseInfo attribute of the DatabaseInfoFactory class
     *
     *@param  pro              Description of the Parameter
     *@return                  The databaseInfo value
     *@exception  DBException  Description of the Exception
     */
    public static DatabaseInfo getDatabaseInfo(Properties pro) throws DBException {
	DatabaseInfo instance = null;

	//get class name and this class must implements DatabaseInfo interface
	String className = pro.getProperty(CLASS_NAME);
	if (className == null) {
	    throw new DBException("Can not find " + CLASS_NAME + " property, set it first");
	}
	try {
	    //get it by class name , you must import this class in your project otherwise it
	    //throw a DBException class not found;
	    Class cl = Class.forName(className);
	    instance = (DatabaseInfo) cl.newInstance();
	    return instance;
	} catch (Exception ce) {
	    throw new DBException(ce.getMessage());
	}
    }


    //defatul property name , you can set System property by this name
    private final static String CLASS_NAME = "com.sure.databaseInfo.class";
}