spring註解切面封裝並解析spring的EL表達式自定義緩存註解

學習了自定義緩存註解，在這裏做下記錄
以下代碼簡單的實現了一個緩存的流程：查詢數據時先查詢redis緩存，緩存中沒有就去Mysql中取出並緩存到redis中。
這次要替代一個以前從來沒遇到過的點，就是spring的EL表達式的解析

/**
     * 使用SPEL進行key的解析
     *
     * @param expressionString 表達式字符串
     * @param method           方法對象，用於獲取參數名
     * @param args             方法的參數值
     * @return
     */
    private String parseExpression(String expressionString, Method method, Object[] args) {
        //獲取被攔截方法參數名列表
        LocalVariableTableParameterNameDiscoverer discoverer = new LocalVariableTableParameterNameDiscoverer();
        String[] paramNameArr = discoverer.getParameterNames(method);
        //SPEL解析
        ExpressionParser parser = new SpelExpressionParser();
        StandardEvaluationContext context = new StandardEvaluationContext();
        for (int i = 0; i < paramNameArr.length; i++) {
            context.setVariable(paramNameArr[i], args[i]);
        }
        String result = parser.parseExpression(expressionString).getValue(context, String.class);
        return result;
    }

基於spring註解切面實現的redis切面緩存

import com.annotation.MyAnnotation;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.reflect.MethodSignature;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.core.DefaultParameterNameDiscoverer;
import org.springframework.data.redis.core.RedisTemplate;
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;

@Aspect
@Component
public class MyAnnotationAspect {

    @Autowired
    private RedisTemplate<Object, Object> redisTemplate;

    @Around("@annotation(com.annotation.MyAnnotation)")
    public Object MyAnnotation(ProceedingJoinPoint proceedingJoinPoint) throws Throwable {
        System.out.println("進入註解片面~~~~~~~~");

        //疑問key的內容-根據方法參數1,獲取到方法註解裏面的key內容-反射知識
        MethodSignature signature = (MethodSignature) proceedingJoinPoint. getSignature();
        Method method = proceedingJoinPoint.getTarget().getClass().getMethod(signature.getName(),signature.getMethod().getParameterTypes());
        MyAnnotation myAnnotation = method.getAnnotation(MyAnnotation.class);
        //反射技術-JDK最底層的API
        String keyEL = myAnnotation.key();
        System.out.println("註解中key的值keyEL："+keyEL);
        // 2.拿到方法的參數名和參數值, 方便解析key表達式
        // 創建解析器
        ExpressionParser parser = new SpelExpressionParser();
        Expression expression = parser. parseExpression (keyEL);
        //設置解析上下文(有哪些佔位荷,以及每種佔位符的值-根據方法的參數名和參數值
        EvaluationContext context = new StandardEvaluationContext();
        //參歌
        Object [] args = proceedingJoinPoint. getArgs();
        String [] parameterNames=new DefaultParameterNameDiscoverer().getParameterNames(method);
        for (int i =0; i < parameterNames.length; i++){
            System.out.println("參數名:"+ parameterNames[i]+"; 參數值:"+args[i]);
            context.setVariable(parameterNames[i],args[i]);
        }
        // T0D0 3,解析表達式,生成最終的key
        String key = expression.getValue(context).toString();
        //1 redis緩存一性能需求-查詢併發量
        System.out.println("緩存中有數據: "+key);
        Object o = redisTemplate.opsForValue().get(key);
        if (o != null){
            //緩存中有數據直接返回數據
            return o;
        }

        Object proceed = proceedingJoinPoint.proceed();

        if (proceed != null){
            //緩存數據
            redisTemplate.opsForValue().set(key,proceed);
        }

        System.out.println("結束註解片面~~~~~~~~");

        return proceed;
    }


}

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target(value = ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface MyAnnotation {

    String key();

}

@MyAnnotationAspect(key = "#argid") 
@Override
    public Object testAnnotation(String argid,String arg01){

        System.out.println("testAnnotation: argid="+argid+"; arg01="+arg01);
        AdminUser byname = null;
        AdminUser byname = adminUserMapper.findByname(argid);

        return byname;
    }