Spring中 FactoryBean和bean

1.整合spring+hibernate中，讓spring接管hibernate的session工廠有一段代碼

1. <bean id="sFactory" class="org.springframework.orm.hibernate3.LocalSessionFactoryBean">

1. public class LocalSessionFactoryBean extends AbstractSessionFactoryBean implements BeanClassLoaderAware

1. public abstract class AbstractSessionFactoryBean
2. implements FactoryBean<SessionFactory>, InitializingBean, DisposableBean, PersistenceExceptionTranslator

發現了實現了一個factoryBean<T>,裡面給了個泛型(SeesionFactory).

注：這個bean和其他的bean不一樣,spring中有兩種bean.
普通bean和bean工廠,即FactoryBean. FactoryBean 返回的不是這個類的實例，其返回的是該工廠Bean的getObject()方法所返回的對象
普通的Bean直接返回指定類(配置中的class屬性的值)的一個實例.

一個小例子：

1. package org.ymm.entity;
3. import org.springframework.beans.factory.FactoryBean;
5. /**
6. * TestBean 類實現了FactoryBean<T>
7. * @author witho_000
8. *
9. */
11. public class TestBean implements FactoryBean<Object>{
13. public Object getObject() throws Exception {
14. // TODO Auto-generated method stub
15. return "string類型";
16. }
18. @Override
19. public Class<?> getObjectType() {
20. // TODO Auto-generated method stub
21. return null;
22. }
24. @Override
25. public boolean isSingleton() {
26. // TODO Auto-generated method stub
27. return false;
28. }
30. }

1. <?xml version="1.0" encoding="UTF-8"?>
2. <beans xmlns="http://www.springframework.org/schema/beans"
3. xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
4. xmlns:context="http://www.springframework.org/schema/context"
5. xsi:schemaLocation="http://www.springframework.org/schema/beans
6. http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
7. http://www.springframework.org/schema/context
8. http://www.sprinsgframework.org/schema/context/spring-context-3.0.xsd">
10. <!-- 測試factorybean -->
12. <bean id="factorybean1" class="org.ymm.entity.TestBean" />
14. </beans>

1. package org.ym.test;
3. import org.springframework.context.ApplicationContext;
4. import org.springframework.context.support.ClassPathXmlApplicationContext;
5. import org.ymm.entity.TestBean;
7. /**
8. * Tester測試類
9. * @author witho_000
10. *
11. */
13. public class Tester {
15. public static void main(String[] args) {
17. ApplicationContext cont=new ClassPathXmlApplicationContext("beans.xml");
18. String s= cont.getBean("&factorybean1",String.class);
19. System.out.println(s.getClass());
20. }
21. }

網上找到的小技巧：
String s= cont.getBean("&factorybean1",String.class);
bean的id前加個&得到的就是TestBean