1、@Resource注解与@Autowired类似,也是用来提供依赖注入的,
@Resource注解是Java层面所提供的注解,@Autowired是Spring所提供的注解,
@Resource注解中有一个name属性,针对name属性是否有值,@Resource底层流程是不同的。
@Resource如果name属性有值,那么Spring容器将根据beanName去容器里面找到对应的bean,找不到会报错
如果没有值,则:
1、先判断该属性名字在Spring容器中是否存在Bean对象。
2、如果存在,则成功找到Bean对象进行注入。
3、如果不存在,则根据属性类型去Spring容器找bean对象,找到一个进行注入。
@Resource注解代码:是在rt.jar包下,就是Root包下面的
@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 name of the resource that the reference points to. It can
* link to any compatible resource using the global JNDI names.
*
* @since Common Annotations 1.1
*/
String lookup() 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 "";
}