Setter-Based DI in Spring

Setter-Based DI

For setter-based DI, the container will call setter methods of our class after invoking a no-argument constructor or no-argument static factory method to instantiate the bean.

# Setter-Based DI
@Bean
public Store store() {
    
    
    Store store = new Store();
    store.setItem(new item1());
    return store;
}

# use XML
<bean id="store" class="org.baeldung.store.Store">
    <property name="item" ref="item1" />
</bean>

Constructor-Based DI 和 Setter-Based DI 可以组合使用
Constructor-Based DI ：强制性的依赖，即刚需（ mandatory dependencies）
Setter-Based DI ：可有可无，即可选（ optional dependencies）

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参考：
Intro to Inversion of Control and Dependency Injection with Spring