Annotation详细介绍
转自:http://snkcxy.iteye.com/blog/1821512如约所致~ Annotation详细介绍博客分类：

?javaJava代码??
1. package?com.cxy.annotation;??
2. ??
3. import?java.lang.annotation.ElementType;??
4. import?java.lang.annotation.Retention;??
5. import?java.lang.annotation.RetentionPolicy;??
6. import?java.lang.annotation.Target;??
7. import?java.lang.reflect.Method;??
8. ??
9. /**?
10. ?*?@author?cxy?
11. ?*/??
12. public?class?AnnotationDetailTest??
13. {??
14. ????public?static?void?main(String[]?args)?throws?Exception??
15. ????{??
16. ????????CxyLogAp.Processor(Aclass.class);??
17. ????}??
18. }??
19. ??
20. /**?
21. ?*?一个测试用的类，这个类的method1和method3被@CxyLog标记?
22. ?*/??
23. class?Aclass??
24. {??
25. ????@CxyLog??
26. ????public?static?void?method1(){System.out.println("method1执行");}??
27. ????public?static?void?method2(){System.out.println("method2执行");}??
28. ????@CxyLog??
29. ????public?static?void?method3(){System.out.println("method3执行");}??
30. ????public?static?void?method4(){System.out.println("method4执行");}??
31. }??
32. ??
33. /**?
34. ?*?一个简单的annotation，打上这个标记的我们就给这个方法加入日志打印功能?
35. ?*?1.@Retention(RetentionPolicy.RUNTIME)?解释：保留注释到程序运行?
36. ?*?2.@Target(ElementType.METHOD)?解释：这个annotation是标记在方法上的?
37. ?*/??
38. @Retention(RetentionPolicy.RUNTIME)???
39. @Target(ElementType.METHOD)???
40. @interface?CxyLog{}???
41. ??
42. ??
43. /**这个类是@CxyLog的annotation处理器?
44. ?*/??
45. class?CxyLogAp??
46. {??
47. ????//处理器?处理@CxyLog标记??
48. ????public?static?void?Processor(Class?clz)?throws?Exception??
49. ????{??
50. ????????for(Method?m:clz.getMethods())??
51. ????????{??
52. ????????????//如果当前访问的方法打上了@CxyLog标识，那么就加入打印语句??
53. ????????????if(m.isAnnotationPresent(CxyLog.class))??
54. ????????????{??
55. ????????????????m.invoke(null);??
56. ????????????????System.out.println("日志："+clz+"."+m.getName()+"执行！");??
57. ????????????}else??
58. ????????????{??
59. ????????????????//因为他会执行所有的方法，包括父类的很多方法，所以这里我们限定一下只做我们定义的method开头的方法??
60. ????????????????if(m.getName().contains("method"))??
61. ????????????????{??
62. ????????????????????m.invoke(null);??
63. ????????????????}??
64. ????????????}??
65. ????????}??
66. ????}??
67. }??

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结果图：


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例二：

Java代码??
1. package?com.cxy.annotation;??
2. ??
3. import?java.lang.annotation.Annotation;??
4. import?java.lang.annotation.ElementType;??
5. import?java.lang.annotation.Retention;??
6. import?java.lang.annotation.RetentionPolicy;??
7. import?java.lang.annotation.Target;??
8. import?java.lang.reflect.Method;??
9. ??
10. /**?
11. ?*?@author?cxy?
12. ?*/??
13. public?class?AnnotationDetailTest1??
14. {??
15. ????public?static?void?main(String[]?args)?throws?Exception??
16. ????{??
17. ????????CxyAction.commonAuthoritymethod();??
18. ????????CxyAction.advanceAuthoritymethod();??
19. ????????System.out.println("=============================");??
20. ????????//以下面的两种方式执行这两个方法??
21. ????????CxyAuthorityAp.Processor(CxyAction.class,?"commonAuthoritymethod");??
22. ????????System.out.println("------------------------------");??
23. ????????CxyAuthorityAp.Processor(CxyAction.class,?"advanceAuthoritymethod");??
24. ????}??
25. }??
26. ??
27. /**?测试目标类，提供了两个不同权限的方法?
28. ?*/??
29. class?CxyAction??
30. {??
31. ????public?static?CxyBo?bo=new?CxyCommonBo();?//初始时候装配的是普通权限的bo??
32. ??????
33. ????//普通权限就能访问的方法??
34. ????@CxyAuthority(authority="c",boName=CxyCommonBo.class)??
35. ????public?static?void?commonAuthoritymethod()??
36. ????{??
37. ????????bo.doSomething();??
38. ????}???
39. ??????
40. ????//高级权限能访问的方法???
41. ????@CxyAuthority(authority="a",boName=CxyAdvancedBo.class)??
42. ????public?static?void?advanceAuthoritymethod()??
43. ????{??
44. ????????bo.doSomething();??
45. ????}???
46. }??
47. ??
48. /**?一个接口为了演示动态装配而生?
49. ?*/??
50. interface?CxyBo??
51. {??
52. ????public?void?doSomething();??
53. }??
54. ??
55. /**?普通权限的bo?
56. ?*/??
57. class?CxyCommonBo?implements?CxyBo??
58. {??
59. ????//普通业务逻辑??
60. ????@Override??
61. ????public?void?doSomething()??
62. ????{??
63. ????????System.out.println("执行：普通权限处理方法");??
64. ????}??
65. }??
66. ??
67. /**?高级权限的bo?
68. ?*/??
69. class?CxyAdvancedBo?implements?CxyBo??
70. {??
71. ????//高级业务逻辑??
72. ????@Override??
73. ????public?void?doSomething()??
74. ????{??
75. ????????System.out.println("执行：高级权限处理方法");??
76. ????}??
77. }??
78. ??
79. //权限annotation，根据这个标记的authority值来判断装配哪个业务逻辑类??
80. @Retention(RetentionPolicy.RUNTIME)???
81. @Target(ElementType.METHOD)???
82. @interface?CxyAuthority??
83. {??
84. ????String?authority();?//代表权限??
85. ????Class?boName();?//代表这个权限用什么bo去处理??
86. }??
87. ??
88. /**这个类是@CxyAuthority的annotation处理器?
89. ?*/??
90. class?CxyAuthorityAp??
91. {??
92. ????//处理器?处理@CxyAuthority标记??
93. ????public?static?void?Processor(Class?clz,String?methodName)?throws?Exception??
94. ????{??
95. ????????Method?m=clz.getMethod(methodName,?null);?//获得指定类的指定方法??
96. ????????Annotation[]?aArray=m.getAnnotations();?//获得方法所有的annotation??
97. ????????for(Annotation?one:aArray)??
98. ????????{??
99. ????????????if(one?instanceof?CxyAuthority)??
100. ????????????{??
101. ????????????????CxyBo?tempBo=(CxyBo)?((CxyAuthority)one).boName().newInstance();??
102. ????????????????if("c".equals(((CxyAuthority)one).authority()))??
103. ????????????????{??
104. ????????????????????System.out.println("装配信息：普通权限bo装配成功");??
105. ????????????????????//这里还可以做一些权限控制的操作??
106. ????????????????}else?if("a".equals(((CxyAuthority)one).authority()))??
107. ????????????????{??
108. ????????????????????System.out.println("装配信息：高级权限bo装配成功");??
109. ????????????????????//这里还可以做一些权限控制的操作??
110. ????????????????}??
111. ????????????????tempBo.doSomething();??
112. ????????????}??
113. ????????}??
114. ????}??
115. }??

?结果图：


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