|
注解其實可以看成是一個特殊的 Class 。 只不過不用關(guān)鍵字 class 而已， 而是用 聲明 @Target 說明注解使用的地方(目的地) {類上，字段上，或是方法上？？ etc... }。 類上面：TYPE 字段上：FIELD 方法上：METHOD @Retention 注解的生存周期(能在什么時候有效) 可選值為：源代碼 ？ 一直到運行時都有效 ？etc... RUNTIME 一直到運行時都有效，說明程序運行時可以通過反射得到注解的信息。 @Target({TYPE, FIELD, METHOD}) @Retention(RUNTIME) public @interface Resource { /** * The JNDI name of the resource. For field annotations, * the default is the field name. For method annotations, * the default is the JavaBeans property name corresponding * to the method. For class annotations, there is no default * and this must be specified. */ String name() default ""; /** * The Java type of the resource. For field annotations, * the default is the type of the field. For method annotations, * the default is the type of the JavaBeans property. * For class annotations, there is no default and this must be * specified. */ Class type() default java.lang.Object.class; /** * The two possible authentication types for a resource. */ enum AuthenticationType { CONTAINER, APPLICATION } /** * The authentication type to use for this resource. * This may be specified for resources representing a * connection factory of any supported type, and must * not be specified for resources of other types. */ AuthenticationType authenticationType() default AuthenticationType.CONTAINER; /** * Indicates whether this resource can be shared between * this component and other components. * This may be specified for resources representing a * connection factory of any supported type, and must * not be specified for resources of other types. */ boolean shareable() default true; /** * A product specific name that this resource should be mapped to. * The name of this resource, as defined by the <code>name</code> * element or defaulted, is a name that is local to the application * component using the resource. (It's a name in the JNDI * <code>java:comp/env</code> namespace.) Many application servers * provide a way to map these local names to names of resources * known to the application server. This mapped name is often a * <i>global</i> JNDI name, but may be a name of any form. <p> * * Application servers are not required to support any particular * form or type of mapped name, nor the ability to use mapped names. * The mapped name is product-dependent and often installation-dependent. * No use of a mapped name is portable. */ String mappedName() default ""; /** * Description of this resource. The description is expected * to be in the default language of the system on which the * application is deployed. The description can be presented * to the Deployer to help in choosing the correct resource. */ String description() default ""; }
|
|
|
來自： CevenCheng > 《Java高級》
