Spring 实例化bean

Spring实例化bean一般有3种方式:通过bean的自身构造函数,通过工厂类和通过别的实体bean的方法.

通过bean的自身构造函数是最普通也是最常用的一种,在XML配置如下:

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

通过工厂类构造bean:

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

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

通过别的实体bean的方法:

<bean id="serviceLocator" class="examples.DefaultServiceLocator"/>

<bean id="clientService"
factory-bean="serviceLocator"
factory-method="createClientServiceInstance"/>

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