Annotation中使用springEL表達式

模仿spring的CachePut等註解，因爲CachePut等註解的限制，沒法知足當前的需求，自定義了新註解並實現方式

• 編寫註解

package com.example.providerserver.el;


import org.springframework.core.annotation.AliasFor;

import java.lang.annotation.*;

@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Documented
public @interface CacheTest {

    @AliasFor("value")
    String key()  default "";

    @AliasFor("key")
    String value() default "";
}

• 編寫AOP切面

package com.example.providerserver.el;

import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Pointcut;
import org.springframework.core.LocalVariableTableParameterNameDiscoverer;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.Expression;
import org.springframework.expression.ExpressionParser;
import org.springframework.expression.spel.standard.SpelExpressionParser;
import org.springframework.expression.spel.support.StandardEvaluationContext;
import org.springframework.stereotype.Component;

import java.lang.reflect.Method;

@Component
@Aspect
public class CacheAOP {

    @Pointcut(value="@annotation(CacheTest)")
    private void getPointcut() {

    }

    @Around("getPointcut()")
    public Object preProcessQueryPattern(ProceedingJoinPoint point) throws Throwable {
        String targetName = point.getTarget().getClass().getName();
        String simpleName = point.getTarget().getClass().getSimpleName();
        String methodName = point.getSignature().getName();
        Object[] arguments = point.getArgs();
        Class targetClass = Class.forName(targetName);
        Method[] methods = targetClass.getMethods();
        String key = "";
        String[] paramNames = {};
        for(Method method:methods){
            if(method.getName().equals(methodName)){
                key = method.getAnnotation(CacheTest.class).key();
                System.out.println("key is "+key);
                paramNames = getParamterNames(method);
            }
        }

        ExpressionParser parser = new SpelExpressionParser();
        Expression expression = parser.parseExpression(key);
        EvaluationContext context = new StandardEvaluationContext();
        for(int i=0;i<arguments.length;i++){
            context.setVariable(paramNames[i],arguments[i]);
        }
        System.out.println(expression.getValue(context,String.class));
        return point.proceed();
    }

    public String[] getParamterNames(Method method){
        LocalVariableTableParameterNameDiscoverer u =
                new LocalVariableTableParameterNameDiscoverer();
        return  u.getParameterNames(method);
    }

//    public static void main(String[] args) {
//        LocalVariableTableParameterNameDiscoverer u =
//                new LocalVariableTableParameterNameDiscoverer();
//        Test test = new Test();
//        Method[] methods = test.getClass().getMethods();
//        for(Method method :methods){
//            if(method.getName().equals("test")){
//                System.out.println(u.getParameterNames(method).toString());
//            }
//        }
//    }

}

• 測試

@CacheTest(key = "#result.name+'.nbper'")
    public String hello(Result result){
        return  result.getName();
    }

在調用hello方式中傳入參數"hello"  最終將打印出 「hello.abc」

目前還不支持「#p0」的寫法，研究中