Spring

创建一个 Bean 实例对象的方法通常有如下方式：

• 调用构造器创建 Bean 实例
• 调用静态工厂方法创建 Bean 实例
• 调用实例工厂方法创建 Bean 实例

使用构造器创建 Bean 实例

XML 配置：

<bean id="exampleBean" class="examples.ExampleBean"/>
<bean name="anotherExample" class="examples.ExampleBeanTwo"/>

使用静态工厂方法创建 Bean 实例

XML 配置：

<bean id="clientService" class="examples.ClientService" factory-method="createInstance"/>

静态工厂类：

public class ClientService {
    private static ClientService clientService = new ClientService();
    private ClientService() {}
    public static ClientService createInstance() {
        return clientService;
    }
}

使用实例工厂方法创建 Bean 实例

XML 配置：

<!-- the factory bean, which contains a method called createInstance() -->
<bean id="serviceLocator" class="examples.DefaultServiceLocator">
    <!-- inject any dependencies required by this locator bean -->
</bean>

<!-- the bean to be created via the factory bean -->
<bean id="clientService" factory-bean="serviceLocator" factory-method="createClientServiceInstance"/>

实例工厂类：

public class DefaultServiceLocator {
    private static ClientService clientService = new ClientServiceImpl();
    private DefaultServiceLocator() {}
    public ClientService createClientServiceInstance() {
        return clientService;
    }
}