factorybean用法

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;
}

}

<bean id="people" class="com.roadArchitectWeb.dao.peopleFactoryBean">
<property name="phoneInfo" value="5.2,P7,huawei,majintao"></property>
</bean>

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.