Spring在web使用中获得Bean的方法

Spring在web应用中获得Bean的方法

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Spring在web应用中获得Bean的方法博客分类：?

SpringBeanWebSpringServletprototype

一：使用ApplicationContext获得Bean

首先新建一个类，该类必须实现ApplicationContextAware接口，改接口有一个方法，public void setApplicationContext(ApplicationContext applicationContext)throws BeansException ，

也就是说框架会自动调用这个方法返回一个ApplicationContext对象。具体类如下：

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Java代码??

1. public?class?SpringContextUtils?implements?ApplicationContextAware{//Spring的工具类，用来获得配置文件中的bean??
2. ??????
3. ????private?static?ApplicationContext?applicationContext?=?null;??
4. ??
5. ????/***?
6. ?????*?当继承了ApplicationContextAware类之后，那么程序在调用?
7. ?????*?getBean(String)的时候会自动调用该方法，不用自己操作?
8. ?????*/??
9. ????public?void?setApplicationContext(ApplicationContext?applicationContext)throws?BeansException?{??
10. ????????SpringContextUtils.applicationContext?=?applicationContext;??
11. ????}??
12. ????public?static?ApplicationContext?getApplicationContext()?{??
13. ????????return?applicationContext;??
14. ????}??
15. ????/***?
16. ?????*?根据一个bean的id获取配置文件中相应的bean?
17. ?????*?@param?name?
18. ?????*?@return?
19. ?????*?@throws?BeansException?
20. ?????*/??
21. ????public?static?Object?getBean(String?name)?throws?BeansException?{??
22. ????????return?applicationContext.getBean(name);??
23. ????}??
24. ????/***?
25. ?????*?类似于getBean(String?name)只是在参数中提供了需要返回到的类型。?
26. ?????*?@param?name?
27. ?????*?@param?requiredType?
28. ?????*?@return?
29. ?????*?@throws?BeansException?
30. ?????*/??
31. ????public?static?Object?getBean(String?name,?Class?requiredType)?throws?BeansException?{??
32. ????????return?applicationContext.getBean(name,?requiredType);??
33. ????}??
34. ???????????
35. ??????????/**?
36. ??????????*?如果BeanFactory包含一个与所给名称匹配的bean定义，则返回true??
37. ??????????*?@param?name?
38. ??????????*?@return?boolean?
39. ??????????*/??
40. ????public?static?boolean?containsBean(String?name)?{??
41. ?????????return?applicationContext.containsBean(name);??
42. ????}??
43. ???????????
44. ??????????/**?
45. ??????????*?判断以给定名字注册的bean定义是一个singleton还是一个prototype。?
46. ??????????*?如果与给定名字相应的bean定义没有被找到，将会抛出一个异常（NoSuchBeanDefinitionException）????
47. ??????????*?@param?name?
48. ??????????*?@return?boolean?
49. ??????????*?@throws?NoSuchBeanDefinitionException?
50. ??????????*/??
51. ????public?static?boolean?isSingleton(String?name)?throws?NoSuchBeanDefinitionException?{??
52. ??????????return?applicationContext.isSingleton(name);??
53. ????}??
54. ???????????
55. ??????????/**?
56. ??????????*?@param?name?
57. ??????????*?@return?Class?注册对象的类型?
58. ??????????*?@throws?NoSuchBeanDefinitionException?
59. ??????????*/??
60. ????public?static?Class?getType(String?name)?throws?NoSuchBeanDefinitionException?{??
61. ?????????return?applicationContext.getType(name);??
62. ????}??
63. ???????????
64. ??????????/**?
65. ??????????*?如果给定的bean名字在bean定义中有别名，则返回这些别名????
66. ??????????*?@param?name?
67. ??????????*?@return?
68. ??????????*?@throws?NoSuchBeanDefinitionException?
69. ??????????*/??
70. ????public?static?String[]?getAliases(String?name)?throws?NoSuchBeanDefinitionException?{??
71. ?????????return?applicationContext.getAliases(name);??
72. ????}??
73. }??

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该类中有一个getBean(String name)方法，该方法用applicationContext去获得Bean实例，而applicationContext

是由系统启动时自动设置的。注意，在applicationContext.xml配置文件中需要把该类加上。<bean id="springUtils" style="font-size: 12px; background-color: transparent; width: 679px; margin-left: 9px; padding: 1px;">Java代码??

1. public?class?SpringBeanFactoryUtils?implements?BeanFactoryAware?{??
2. ??
3. ????private?static?BeanFactory?beanFactory?=?null;??
4. ????private?static?SpringBeanFactoryUtils?factoryUtils?=?null;??
5. ??????
6. ????public?void?setBeanFactory(BeanFactory?beanFactory)?throws?BeansException?{??
7. ????????SpringBeanFactoryUtils.beanFactory?=?beanFactory;??
8. ????}??
9. ????public?static?BeanFactory?getBeanFactory()?{??
10. ????????return?beanFactory;??
11. ????}??
12. ????public?static?SpringBeanFactoryUtils?getInstance(){??
13. ????????if(factoryUtils==null){??
14. ????????????//factoryUtils?=?(SpringBeanFactoryUtils)beanFactory.getBean("springBeanFactoryUtils");??
15. ????????????factoryUtils?=?new?SpringBeanFactoryUtils();??
16. ????????}??
17. ????????return?factoryUtils;??
18. ????}??
19. ????public?static?Object?getBean(String?name){??
20. ????????return?beanFactory.getBean(name);??
21. ????}??
22. }??

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不过应该注意的是，改类中有一个getInstance方法，由于该代码是网上摘抄的，他提供了这么一个方法，目的是利用单例模式获得该类的一个实例，但由于getBean(String name)方法是静态的，所以用不用单例都无关紧要，经过测试，两种方法都行的通。另外一点就是必须把该类添加到applicationContext.xml的配置文件中<bean id="springBeanFactoryUtils" style="font-size: 12px; background-color: transparent; width: 679px; margin-left: 9px; padding: 1px;">Java代码??

1. WebApplicationContext?webcontext?=?(WebApplicationContext)context.getAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE);??

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?其中context是servlet的上下文，在servlet中可以通过this.getServletContext()或者request.getSession().getServletContext();获得servletContext。但是一点，spring的配置文件必须在WEB-INF下。WebApplicationContext 有一个方法getBean（String name）;其实WebApplicationContext 就是ApplicationContext的另一种形式而已。

?????? 另外，在普通的java类中，即不是在servlet中可以用ContextLoader获得。ContextLoader是org.springframework.web.context包当中的一个类。

Java代码??

1. private?static?WebApplicationContext?webApplication?=?ContextLoader.getCurrentWebApplicationContext();??

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?用这种方法就能获取一个WebApplicationContext 的对象。

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最后经过测试，在重复100000次的基础上，第一二中方法只用了16毫秒，而第三种方法消耗了62毫秒，所以推荐使用第一二种方法。