factorybean用法

待我称王封你为后i 2022-07-26 05:23 118阅读 0赞

***纸上得来终觉浅***

**1.什么是factorybean？**

factorybean是一个工厂类接口，用户可以通过实现该接口来定制实例化bean的逻辑

getObject():返回factorybean创建的bean实例

isSingleton():指定factorybean创建的bean实例的作用域

getObjectType():指所创建的bean实例的类型

**2.factorybean的作用？**

由上面可以发现，factorybean实际上把应该在bean配置文件中配置的信息，放在它的实现类中实现了，它起到了创建bean的作用。这样一来当有复杂的bean之间的关系的时候，就不用再在bean配置文件中配置了，可以在factorybean实现类中显式的写出。

**3.下面一个例子：**

public class phone {
    	private String size;
    	private String name;
    	private String logo;
    	public String getSize() {
    		return size;
    	}
    	public void setSize(String size) {
    		this.size = size;
    	}
    	public String getName() {
    		return name;
    	}
    	public void setName(String name) {
    		this.name = name;
    	}
    	public String getLogo() {
    		return logo;
    	}
    	public void setLogo(String logo) {
    		this.logo = logo;
    	}
    	@Override
    	public String toString() {
    		return "phone [size=" + size + ", name=" + name + ", logo=" + logo + "]";
    	}
    	
    }

public class people {
    private String name;
    private phone phone;
    public String getName() {
    	return name;
    }
    public void setName(String name) {
    	this.name = name;
    }
    public phone getPhone() {
    	return phone;
    }
    public void setPhone(phone phone) {
    	this.phone = phone;
    }
    @Override
    public String toString() {
    	return "people [name=" + name + ", phone=" + phone + "]";
    }
    }

public class peopleFactoryBean implements FactoryBean<people>{
    
    	private String phoneInfo;
    	public String getPhoneInfo() {
    		return phoneInfo;
    	}
    	public void setPhoneInfo(String phoneInfo) {
    		this.phoneInfo = phoneInfo;
    	}
    
    	@Override
    	public people getObject() throws Exception {
    		people people = new people();
    		phone phone = new phone();
    		String info[] = phoneInfo.split(",");
    		phone.setSize(info[0]);
    		phone.setName(info[1]);
    		phone.setLogo(info[2]);
    		people.setPhone(phone);
    		people.setName(info[3]);
    		return people;
    	}
    
    	@Override
    	public Class<?> getObjectType() {
    		return phone.class;
    	}
    
    	@Override
    	public boolean isSingleton() {
    		return false;
    	}
    	
    }

ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
    		people people = (people)ctx.getBean("people");
    		System.out.println("AnimalMain.main():"+people.toString());

**输出结果：**

AnimalMain.main():people \[name=majintao, phone=phone \[size=5.2, name=P7, logo=huawei\]\]

由上段代码可以看到，一些配置信息和bean之间的关系在peopleFactoryBean中已经实现了，这样省略了很多bean配置文件的配置，people这个bean和它所持有的phone都是在getobject中创建的。

注: 但是会有这样一个问题，如果有一天phone的属性增加一个字段，如果是一般的bean配置，只需要改phone类和配置文件即可，但在这里，就需要更改peopleFactoryBean的代码，这在我看来是丧失了部分的灵活性，不过在确定类及其属性不会更改的情况下，factorybean确实是省略配置的好办法.