JAVA自定义注解（2）

这个例子在实际应用中是比较有用的，用来将配置文件（*.properties)或者系统属性中的指定属性名称的值加载进来。此例是和Spring结合使用的，所以其他配置就略过了。

1、定义注解@Property

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1. packagecom.kute.test.selfannotation;
3. importjava.lang.annotation.ElementType;
4. importjava.lang.annotation.Retention;
5. importjava.lang.annotation.RetentionPolicy;
6. importjava.lang.annotation.Target;
8. /**
9. *自定义注解@Property
10. *加载配置文件和相应的属性
11. */
13. @Retention(RetentionPolicy.RUNTIME)
14. @Target({ElementType.TYPE,ElementType.METHOD})
15. public@interfaceProperty{
17. //属性名称
18. Stringname()default"";
19. }

2、解析注解

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1. packagecom.kute.test.selfannotation;
3. importjava.lang.reflect.Method;
4. importjava.util.Properties;
6. importorg.slf4j.Logger;
7. importorg.slf4j.LoggerFactory;
8. importorg.springframework.beans.BeansException;
9. importorg.springframework.beans.factory.InitializingBean;
10. importorg.springframework.beans.factory.config.BeanPostProcessor;
11. importorg.springframework.beans.factory.config.PropertyPlaceholderConfigurer;
12. importorg.springframework.util.ReflectionUtils;
14. publicclassPropertyParseextendsPropertyPlaceholderConfigurerimplements
15. BeanPostProcessor,InitializingBean{
17. privatestaticLoggerlogger=LoggerFactory.getLogger(PropertyParse.class);
18. privatePropertiespros=null;
20. //在spring容器实例化bean之后添加自己的逻辑
21. publicObjectpostProcessAfterInitialization(Objectbean,StringbeanName)
22. throwsBeansException{
23. returnbean;
24. }
26. //在spring容器实例化bean之前添加自己的逻辑
27. publicObjectpostProcessBeforeInitialization(Objectbean,StringbeanName)
28. throwsBeansException{
29. if(bean.getClass().getAnnotation(Property.class)!=null){
30. Method[]methods=bean.getClass().getDeclaredMethods();
31. for(Methodmethod:methods){
32. Propertyp=method.getAnnotation(Property.class);
33. if(p!=null){
34. //获得对应名称的属性的值
35. Objectpara=pros.getProperty(p.name());
36. //方法参数类型名称
37. StringparameterName=(method.getParameterTypes()[0]).getName();
39. if(parameterName.equals("java.lang.Integer")){
40. para=newInteger(para.toString());
41. }elseif(parameterName.equals(
42. "java.lang.Double")){
43. para=newLong(para.toString());
44. }elseif(parameterName.equals(
45. "java.lang.String")){
46. para=para.toString();
47. }
48. logger.info("获得了指定名称的属性的值："+para);
49. ReflectionUtils.invokeMethod(method,bean,
50. newObject[]{para});
51. }
52. }
53. }
54. returnbean;
55. }
57. //在初始化bean的时候执行该方法
58. publicvoidafterPropertiesSet()throwsException{
59. //此方法的作用是将配置的和系统属性加载进来
60. pros=mergeProperties();
61. }
63. }

3、应用注解

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1. packagecom.kute.test.selfannotation;
3. importjava.io.Serializable;
5. importorg.slf4j.Logger;
6. importorg.slf4j.LoggerFactory;
8. @Property
9. publicclassTeacherimplementsSerializable{
11. privatestaticfinallongserialVersionUID=7651360997972750779L;
12. privatestaticLoggerlogger=LoggerFactory.getLogger(Teacher.class);
14. @Property(name="third.kute.blog")
15. publicvoidsetValue(Stringvalue){
16. logger.info("成功设String值："+value);
17. }
19. @Property(name="second.kute.age")
20. publicvoidsetValue(Integervalue){
21. logger.info("成功设Integer值："+value);
22. }
24. @Property(name="first.kute.name")
25. publicvoidsetValue(Doublevalue){
26. logger.info("成功设Double值："+value);
27. }
28. }

4、配置文件（部分）（applicationContext.xml)

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1. <!--PropertyParse此bean是继承了PropertyPlaceholderConfigurer来加载配置文件-->
2. <beanclass="com.kute.test.selfannotation.PropertyParse">
3. <!--除了支持配置的*.properties外，还支持获取系统属性(System.getProperties()-->
4. <propertyname="systemPropertiesModeName"value="SYSTEM_PROPERTIES_MODE_OVERRIDE"/>
5. <!--资源找不到不抛出异常-->
6. <propertyname="ignoreResourceNotFound"value="true"/>
7. <propertyname="locations">
8. <list>
9. <value>classpath*:/first.properties</value>
10. <value>classpath*:/second.properties</value>
11. <value>classpath*:/third.properties</value>
12. </list>
13. </property>
14. </bean>

5、文件内容

first.properties

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1. first.kute.name=36.0
2. first.kute.age=111111
3. first.kute.blog=http://blog.youkuaiyun.com/kutekute

second.properties

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1. second.kute.name=37.0
2. second.kute.age=222222
3. second.kute.blog=http://blog.youkuaiyun.com/kutekute

third.properties

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1. third.kute.name=38.0
2. third.kute.age=333333
3. third.kute.blog=http://blog.youkuaiyun.com/kutekute