medic/src/main/java/cn/iocoder/dashboard/util/sping/SpringExpressionUtils.java

package cn.iocoder.dashboard.util.sping;

import cn.hutool.core.collection.CollUtil;
import cn.hutool.core.map.MapUtil;
import cn.hutool.core.util.ArrayUtil;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.reflect.MethodSignature;
import org.springframework.core.DefaultParameterNameDiscoverer;
import org.springframework.core.ParameterNameDiscoverer;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.ExpressionParser;
import org.springframework.expression.spel.standard.SpelExpressionParser;
import org.springframework.expression.spel.support.StandardEvaluationContext;

import java.lang.reflect.Method;
import java.util.Collections;
import java.util.List;
import java.util.Map;

/**
 * Spring EL 表达式的工具类
 *
 * @author mashu
 */
public class SpringExpressionUtils {

    private static final ExpressionParser EXPRESSION_PARSER = new SpelExpressionParser();
    private static final ParameterNameDiscoverer PARAMETER_NAME_DISCOVERER = new DefaultParameterNameDiscoverer();

    private SpringExpressionUtils() {
    }

    /**
     * 从切面中，单个解析 EL 表达式的结果
     *
     * @param joinPoint  切面点
     * @param expressionString EL 表达式数组
     * @return 执行界面
     */
    public static Object parseExpression(ProceedingJoinPoint joinPoint, String expressionString) {
        Map<String, Object> result = parseExpressions(joinPoint, Collections.singletonList(expressionString));
        return result.get(expressionString);
    }

    /**
     * 从切面中，批量解析 EL 表达式的结果
     *
     * @param joinPoint   切面点
     * @param expressionStrings EL 表达式数组
     * @return 结果，key 为表达式，value 为对应值
     */
    public static Map<String, Object> parseExpressions(ProceedingJoinPoint joinPoint, List<String> expressionStrings) {
        // 如果为空，则不进行解析
        if (CollUtil.isEmpty(expressionStrings)) {
            return MapUtil.newHashMap();
        }

        // 第一步，构建解析的上下文 EvaluationContext
        // 通过 joinPoint 获取被注解方法
        MethodSignature methodSignature = (MethodSignature) joinPoint.getSignature();
        Method method = methodSignature.getMethod();
        // 使用 spring 的 ParameterNameDiscoverer 获取方法形参名数组
        String[] paramNames = PARAMETER_NAME_DISCOVERER.getParameterNames(method);
        // Spring 的表达式上下文对象
        EvaluationContext context = new StandardEvaluationContext();
        // 给上下文赋值
        if (ArrayUtil.isNotEmpty(paramNames)) {
            Object[] args = joinPoint.getArgs();
            for (int i = 0; i < paramNames.length; i++) {
                context.setVariable(paramNames[i], args[i]);
            }
        }

        // 第二步，逐个参数解析
        Map<String, Object> result = MapUtil.newHashMap(expressionStrings.size(), true);
        expressionStrings.forEach(key -> {
            Object value = EXPRESSION_PARSER.parseExpression(key).getValue(context);
            result.put(key, value);
        });
        return result;
    }
}