环境:SpringBoot2.3.8.RELEASE + JDK1.8
本文教你如何在SpringBoot环境下使得自定义的注解能够使用${xxx}表达式。
相关依赖
-
org.aspectj -
aspectjrt -
-
org.aspectj -
aspectjweaver -
runtime -
自定义注解
- @Retention(RetentionPolicy.RUNTIME)
- @Target(ElementType.METHOD)
- @Documented
- public @interface Manufactur {
- String value() default "" ; // 厂商编号
- }
AOP
需要AOP在方法执行器对方法上的注解进行解析处理,获取占位符对应的值
- @Component
- @Aspect
- public class ManufacturAspect implements EnvironmentAware {
-
- private static final Logger logger = LoggerFactory.getLogger(ManufacturAspect.class) ;
-
- private Environment environment;
-
- @Pointcut("@annotation(com.pack.annotation.Manufactur)")
- private void info() {}
-
- @Before("info()")
- public void execBefore(JoinPoint jp) {
- MethodSignature sign = (MethodSignature) jp.getSignature() ;
- Method method = sign.getMethod() ;
- Manufactur manu = method.getAnnotation(Manufactur.class) ;
- String value = manu.value() ;
- logger.info("获取到注解值:{}", value) ;
- BusinessService.code.set(this.environment.resolvePlaceholders(value)) ;
- }
-
- @Override
- public void setEnvironment(Environment environment) {
- this.environment = environment ;
- }
-
- }
该类实现了EnvironmentAware 用于获取Environment对象,该对象能够获取当前环境下的所有相关配置信息。同时通过该类的resolvePlaceholders方法能够解析占位符对应的内容值。
Service中使用
- @Service
- public class BusinessService {
-
- public static ThreadLocal
code = new ThreadLocal() ; -
- private static Logger logger = LoggerFactory.getLogger(BusinessService.class) ;
-
- @Manufactur("${manufactur.code}-#{1 + 3}")
- public String invoke(String id) {
- String sno = code.get() ;
- logger.info("自定义注解动态获取属性值:{}", sno) ;
- // todo
- return sno ;
- }
-
- }
在AOP中将解析后的值已经存入到了ThreadLocal中。
测试
- @RestController
- @RequestMapping("/business")
- public class BusinessController {
-
- @Resource
- private BusinessService bs ;
-
- @GetMapping("/{id}")
- public Object home(@PathVariable String id) {
- return bs.invoke(id) ;
- }
-
- }
到此一个自定义注解中支持占位符就完成了,还是非常简单的。