Spring IoC Bean Configuration, Naming, and Instantiation Guide

2.3.1 XML configuration structure – A typical Spring beans file contains <beans>, optional <import> elements, multiple <bean> definitions, and <alias> entries, as illustrated by the sample XML block.

2.3.2 Bean configuration – Each <bean> defines a BeanDefinition that may include the fully‑qualified class name, scope, lazy‑init flag, lifecycle callbacks, constructor‑vs‑factory‑method creation mode, and references to other beans for dependency injection.

2.3.3 Bean naming – Beans can be identified by an id or a name; the first identifier is the primary name, subsequent names are aliases. Using id enables XML‑level validation of references, while name follows normal XML naming rules. Examples show four naming strategies: no id, explicit id, explicit name, and both id and name with aliases.

2.3.4 Bean instantiation – Spring can create beans in three ways:

Constructor instantiation (default or with arguments). Example class HelloImpl2 and XML:

<bean name="bean1" class="cn.javass.spring.chapter2.HelloImpl2"/>
<bean name="bean2" class="cn.javass.spring.chapter2.HelloImpl2">
    <constructor-arg index="0" value="Hello Spring!"/>
</bean>

Static factory method. Example factory class HelloApiStaticFactory and XML:

<bean id="bean3" class="cn.javass.spring.chapter2.HelloApiStaticFactory" factory-method="newInstance">
    <constructor-arg index="0" value="Hello Spring!"/>
</bean>

Instance factory method. Example factory bean HelloApiInstanceFactory and XML:

<bean id="beanInstanceFactory" class="cn.javass.spring.chapter2.HelloApiInstanceFactory"/>
<bean id="bean4" factory-bean="beanInstanceFactory" factory-method="newInstance">
    <constructor-arg index="0" value="Hello Spring!"/>
</bean>

JUnit test snippets demonstrate retrieving each bean by name or id and invoking sayHello() to verify successful instantiation.

2.3.5 Summary – The article covers the fundamentals of Spring IoC: container concepts, XML configuration, bean naming rules, and three bean creation strategies, preparing readers for the next topic of dependency injection.