设计模式

工厂模式生成bean

工厂模式分为静态工厂和实例工厂

静态工厂：

#静态工厂通过静态方法获取实例，实例为静态方法和类初始化一起

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

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

    // 静态方法
    public static ClientService createInstance() {
        return clientService;
    }
}

实例工厂

# 实例工厂有专门的工厂类，根据不同工厂方法获取不同的实例类型
# DefaultServiceLocator 为实例工厂类
<bean id="serviceLocator" class="examples.DefaultServiceLocator">
    <!-- inject any dependencies required by this locator bean -->
</bean>

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

<bean id="accountService"
    factory-bean="serviceLocator"
    factory-method="createAccountServiceInstance"/>

public class DefaultServiceLocator {

    private static ClientService clientService = new ClientServiceImpl();

    private static AccountService accountService = new AccountServiceImpl();

    public ClientService createClientServiceInstance() {
        return clientService;
    }

    public AccountService createAccountServiceInstance() {
        return accountService;
    }
}