1. Autowire可以让你隐式地注入依赖.(it internally uses setter or constructor injection)
2.优点:减少代码量.
3.缺点:无法被程序员控制. 不能用在基本数据类型和string值.
4. Autowiring Modes模式
| 1) | no | It is the default autowiring mode. It means no autowiring bydefault. |
| 2) | byName | The byName mode injects the object dependency according to name of the bean. In such case, property name and bean name must be same. It internally calls setter method. |
| 3) | byType | The byType mode injects the object dependency according to type. So property name and bean name can be different. It internally calls setter method. |
| 4) | constructor | The constructor mode injects the dependency by calling the constructor of the class. It calls the constructor having large number of parameters. |
| 5) | autodetect | It is deprecated since Spring 3. |
byName和byType在另一片随笔中..
constructor则是和构造函数中的形参有关.
根据构造函数中的形参,如果有bean和形参名相同,就会将该bean注入到 autowire类型是constructor的bean中(前提是参数类型相同).
constructor mode会按照最多参数的构造函数优先注入.
如果有一个无参,单参,双参构造函数,会先调用双参构造函数.
autowire="no" 是默认的,等价于autowire="default".
===========================Dependency Injection with Factory Method in Spring
Spring Framework provides facility to inject bean suing factory method. To do so, we can use two attributes of bean element.
1. factory-method: represents the factory method that will be invoked to inject the bean.
2.factory-bean: represents the reference of the bean by which factory method will be invoked.
only used when factory method is non-static.
一个返回类的实例的方法叫做工厂方法.
public class A[
public static A getA(){
return new A();
}
}
工厂方法有三种类型:
1.返回自身类的实例的static factory method ,使用单例模式(singleton design pattern)
<bean id="a" class="com.javatpoint.A" factory-method="getA"></bean>
2.返回其他类实例的static factory method , 运行时决定其实例化对象.
<bean id="b" class="com.javatpoint.A" factory-method="getB"></bean>
3.non-static factory方法:返回另一个类的实例.
<bean id="a" class="com.javatpoint.A"></bean>
<bean id="b" class="com.javatpoint.A" factory-method="getB" factory-bean="a"></bean>
=========
Attribute : factory-method
The name of a factory method to use to create this object. Use constructor-arg elements to specify arguments to
the factory method, if it takes arguments.Autowiring does not apply to factory methods.
使用constructor-arg元素来为工厂方法设置参数,如果它接收参数,autowiring就不会应用于工厂方法.
If the "class" attribute is present, the factory method will be a static method on the class specified by the "class" attribute on this bean
definition.
如果"class"属性存在,工厂方法就是class属性指定的类的一个静态方法.
Often this will be the same class as that of the constructed object - for example, when the factory
method is used as an alternative to a constructor.
通常,该类和构造的对象是同一类:比如当工厂方法被用作constructor的替代方法时.
However, it may be on a different class. In that case, the
created object will *not* be of the class specified in the "class" attribute.
然而,也可能是不同的类.
在这种情况下.被创建的对象不属于class属性中定义的类.
This is analogous to FactoryBean behavior.
这和FactoryBean的行为很相似.
If the "factory-bean" attribute is present, the "class" attribute is not used, and the factory method will
be an instance method on the object returned from a getBean call with the specified bean name.
如果factory-bean属性存在,而class属性不存在,工厂方法就会是getBean方法返回的对象对应的实例方法.
The factory
bean may be defined as a singleton or a prototype.
factory bean可以被定义成单例子或者多例模型.
The factory method can have any number of arguments.Autowiring is not supported.
工厂方法可以有任意数量的参数.但不支持autowiring.
Use indexed constructor-arg elements in conjunction with the factory-method
attribute.
使用constructor-arg来和工厂方法拼接.
Setter Injection can be used in conjunction with a factory method.
Setter Injection可以使用在工厂方法中.
Method Injection cannot, as the factory method returns an instance, which will be used when the container creates the bean.
Data Type : string