自定义注释中的Spring表达式语言

我想在自定义注释中使用Spring Expression Language。 此注释将由自定义Aspect使用。

看一下这个：

@StatisticEventTrigger(value = TestStatisticEvent.class, expression = "#p1") public void someOtherMethod(String arg1, Long arg2) { 

如您所见，我想使用表达式（在本例中）来检索一些特定的参数。

当我有我的Aspect，触发带注释的方法时，我想评估spring表达式（以编程方式）来检索用于进一步业务的值;）

有任何想法吗？ 到目前为止谷歌不是我的朋友！

Answer 1

我想通过SpEL如何做到这一点。 我使用了以下表达式：

 @EventTrigger(value = EventTestModel.class, expression = "new Object[]{arguments[1], arguments[2]}") 

并遵循Java代码：

 ExpressionParser parser = new SpelExpressionParser(); StandardEvaluationContext context = new StandardEvaluationContext(expressionEvaluationTarget); Object[] eventPayloadModels = parser.parseExpression(expression).getValue(context); 

工作良好 ;）

UPDATE

这是一个完整的代码示例：

 import com.example.AbstractEvent; import org.aopalliance.intercept.MethodInterceptor; import org.aopalliance.intercept.MethodInvocation; import org.apache.log4j.Logger; import org.springframework.expression.ExpressionParser; import org.springframework.expression.spel.standard.SpelExpressionParser; import org.springframework.expression.spel.support.StandardEvaluationContext; import org.springframework.util.StringUtils; public class AnnotationEventTriggerAspect implements MethodInterceptor { private static final Logger LOG = Logger.getLogger(AnnotationEventTriggerAspect.class); private IEventHandler eventHandler; @Override public Object invoke(MethodInvocation invocation) throws Throwable { if (LOG.isDebugEnabled()) { LOG.debug("Invoking event event trigger for method: " + invocation.getMethod().getDeclaringClass() + "." + invocation.getMethod().getName()); } EventTrigger annotation = invocation.getMethod().getAnnotation(EventTrigger.class); Class eventClass = annotation.value(); if (eventClass == null) { throw new IllegalArgumentException("No event class provided for event event trigger annotation at method " + invocation.getMethod().getDeclaringClass() + "." + invocation.getMethod()); } AbstractEvent event = eventClass.newInstance(); String expression = annotation.expression(); Object result = invocation.proceed(); Object expressionEvaluationTarget = invocation; Object eventPayloadModels = invocation.getArguments(); if (annotation.useResult()) { expressionEvaluationTarget = result; eventPayloadModels = new Object[]{result}; } if (StringUtils.hasText(expression)) { ExpressionParser parser = new SpelExpressionParser(); StandardEvaluationContext context = new StandardEvaluationContext(expressionEvaluationTarget); eventPayloadModels = parser.parseExpression(expression).getValue(context); } if (eventPayloadModels != null) { if (eventPayloadModels.getClass().isArray()) { for (Object arg : (Object[]) eventPayloadModels) { event.addPayloadModel(arg); } } else { event.addPayloadModel(eventPayloadModels); } } eventHandler.post(event); return result; } public IEventHandler getEventHandler() { return eventHandler; } public void setEventHandler(IEventHandler eventHandler) { this.eventHandler = eventHandler; } 

}