Spring: FactoryBean的用法

1.定义实体类：

package cn.edu.tju;


import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;

public class Person implements ApplicationContextAware {
	private String username;
	private String password;
	private ApplicationContext applicationContext;

	public String getUsername() {
		return username;
	}

	public void setUsername(String username) {
		this.username = username;
	}

	public String getPassword() {
		return password;
	}

	public void setPassword(String password) {
		this.password = password;
	}

	public void init(){
		this.username="new"+username;
	}

	@Override
	public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
		this.applicationContext=applicationContext;
	}
}

2.定义类，实现FactoryBean接口，其中泛型为上述实体类

package cn.edu.tju;

import org.springframework.beans.factory.FactoryBean;

public class MyFactoryBean implements FactoryBean<Person> {
	@Override
	public Person getObject() throws Exception {
		Person p=new Person();
		p.setUsername("Newton");
		p.setPassword("newton");
		return p;
	}

	@Override
	public Class<?> getObjectType() {
		return Person.class;
	}

	@Override
	public boolean isSingleton() {
		return true;
	}
}

3.配置上述FactoryBean的实现类MyFactoryBean到spring 容器：

	<bean id="myFactoryBean" class="cn.edu.tju.MyFactoryBean"/>

4.在程序中通过getBean获取，并强转成实体类

		Person p=(Person)applicationContext.getBean("myFactoryBean");
		System.out.println(p.getUsername()+","+p.getPassword());

5.通过“&myFactoryBean"可以获取到MyFactoryBean 本身，而不是其所生产的对象：

		MyFactoryBean myFactoryBean=(MyFactoryBean) applicationContext.getBean("&myFactoryBean");

容器创建完成后，实体类的对象并不存在，只有调用getBean(“myFactoryBean”)进行获取时才创建实体类对象。
通过getBean多次获取时，得到的是同一个实体类对象