Java 数据对象(JDO)介绍(三)

王朝java/jsp·作者佚名  2008-05-31
窄屏简体版  字體: |||超大  

简介

下面的例子示范了JDO的基础应用。代码示范了如何向数据库添加数据和取回数据。所有的代码使用的都是SolarMetric's Kodo JDO实现。包括创建数据库的机制,使域对象类扩展PersistenceCapable接口的增强和厂商特定的PersistenceManagerFactory实现使用的都是Kodo JDO实现。其他的部分使用的是标准的JDO实现。

域对象

The samples will work with a small set of classes, which represent a Fleet of Vehicle objects. The two specific types of Vehicles defined are Bicycle and MotorVehicle. MotorVehicle objects have an Engine attribute.

例子是用了一个很小的类,这个类描述了一个Vehicle(交通工具) 对象的Fleet(车队)。Vehicle 定义了两个特定的对象Bicycle 和MotorVehicle 。MotorVehicle对象有一个Engine 属性。

域对象源代码

/**

* Fleet.Java

*/

package com.ociweb.jdodemo;

import java.util.Iterator;

import java.util.List;

import java.util.Vector;

public class Fleet {

private List vehicles = new Vector();

public void addVehicle(Vehicle vehicle) {

vehicles.add(vehicle);

}

public Iterator getVehicles() {

return vehicles.iterator();

}

public String toString() {

StringBuffer buffer = new StringBuffer("Fleet:\n");

Iterator iter = getVehicles();

while (iter.hasNext()) {

buffer.append("\t" + iter.next() + "\n");

}

return buffer.toString();

}

}

/**

* Vehicle.java

*/

package com.ociweb.jdodemo;

public class Vehicle {

private int numberOfWheels;

public Vehicle(int numberOfWheels) {

this.numberOfWheels = numberOfWheels;

}

public int getNumberOfWheels() {

return numberOfWheels;

}

}

/**

* Bicycle.java

*/

package com.ociweb.jdodemo;

public class Bicycle extends Vehicle {

private String model;

public Bicycle(String model) {

super(2);

this.model = model;

}

public String toString() {

return "Bike: Model " + model;

}

}

/**

* MotorVehicle.java

*/

package com.ociweb.jdodemo;

public class MotorVehicle extends Vehicle {

private Engine engine;

public MotorVehicle(int numberOfWheels, Engine engine) {

super(numberOfWheels);

this.engine = engine;

}

public String toString() {

return "MotorVehicle With " + getNumberOfWheels()

+ " Wheels. " + engine;

}

}

/**

* Engine.java

*/

package com.ociweb.jdodemo;

public class Engine {

private int numberOfCylinders;

public Engine(int numberOfCylinders) {

this.numberOfCylinders = numberOfCylinders;

}

public int getNumberOfCylinders() {

return numberOfCylinders;

 
 
 
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