Java MDC 记录器 - MDC.put() 过多的方法

Question

请问有关使用 Java 的 MDC 的小问题。

起初，我有非常简单的方法，一些方法有很多参数(为了这个问题我缩短了参数列表以保持简短，但请想象很多参数)

 public String invokeMethodForPerson(int age, String name, boolean isCool, long distanceRun, double weight) {
        LOGGER.info("begin to invoke method invokeMethodForPerson");
        return methodForPerson(age, name, isCool, distanceRun, weight);
    }

    public String invokeMethodForCar(String model, boolean isElectric, long price, int numberOfDoors) {
        LOGGER.info("begin to invoke method invokeMethodForCar");
        return methodForCar(model, isElectric, price, numberOfDoors);
    }

    public String invokeMethodForFlower(String name, String color) {
        LOGGER.info("begin to invoke method invokeMethodForFlower");
        return methodForFlower(name, color);
    }

(本题不是关于如何重构一长串参数)

然后，我想利用 MDC。 MDC 非常有用，它允许在日志聚合器工具等中进行更好的搜索。将它们作为第一级而不是在记录器本身内部非常有帮助。

因此，为了利用 MDC，代码从简单的变成了现在类似的东西，这是我尝试过的。

public String invokeMethodForPerson(int age, String name, boolean isCool, long distanceRun, double weight) {
        MDC.put("age", age);
        MDC.put("name", name);
        MDC.put("isCool", isCool);
        MDC.put("distanceRun", distanceRun);
        MDC.put("weight", weight);
        LOGGER.info("begin to invoke method invokeMethodForPerson");
        return methodForPerson(age, name, isCool, distanceRun, weight);
    }

    public String invokeMethodForCar(String model, boolean isElectric, long price, int numberOfDoors) {
        MDC.put("model", model);
        MDC.put("isElectric", isElectric);
        MDC.put("price", price);
        MDC.put("numberOfDoors", numberOfDoors);
        LOGGER.info("begin to invoke method invokeMethodForCar");
        return methodForCar(model, isElectric, price, numberOfDoors);
    }

    public String invokeMethodForFlower(String name, String color) {
        MDC.put("name", name);
        MDC.put("color", color);
        LOGGER.info("begin to invoke method invokeMethodForFlower");
        return methodForFlower(name, color);
    }

问题:现在看代码，实际上 MDC.put() 的行数比实际的业务逻辑代码多

问题:对于许多参数，除了添加大量的 MDC.put() 行之外，是否有更简洁的方法来利用 MDC，如果可能的话，使用 AOP/aspects/advice/pointcut好吗？

谢谢

Answer 1

您可以创建自己的实用程序来使用 MDC。

public class MDCUtils {
    private MDCUtils() {

    }

    public static void putAll(Object... params) {
        if ((params.length & 1) != 0) {
            throw new IllegalArgumentException("Length is odd");
        }

        for (int i = 0; i < params.length; i += 2) {
            String key = Objects.requireNonNull((String) params[i]); //The key parameter cannot be null
            Object value = params[i + 1]; //The val parameter can be null only if the underlying implementation supports it.
            MDC.put(key, value);
        }
    }

    public static void putAll(Map<String, Object> map) {
        map.forEach(MDC::put);
    }

    public static <K extends String, V> void put(K k1, V v1, K k2, V v2) {
        putAll(k1, v1, k2, v2);
    }

    public static <K extends String, V> void put(K k1, V v1, K k2, V v2, K k3, V v3) {
        putAll(k1, v1, k2, v2, k3, v3);
    }
}

使用示例:

    public String invokeMethodForPerson(int age, String name, boolean isCool, long distanceRun, double weight) {
        MDCUtils.putAll("age",age, "name", name,"isCool", isCool,"distanceRun", distanceRun,"weight", weight);

        LOGGER.info("begin to invoke method invokeMethodForPerson");
        return methodForPerson(age, name, isCool, distanceRun, weight);
    }

更严格的例子:

    public String invokeMethodForFlower(String name, String color) {
        MDCUtils.put("name", name, "color", color);
        
        LOGGER.info("begin to invoke method invokeMethodForFlower");
        return methodForFlower(name, color);
    }

使用 Map.of 的示例，但它不支持可为 null 的值。

    public String invokeMethodForPerson(int age, String name, boolean isCool, long distanceRun, double weight) {
        MDCUtils.putAll(Map.of( "age",age,"name", name,"isCool", isCool,"distanceRun", distanceRun,"weight", weight));

        LOGGER.info("begin to invoke method invokeMethodForPerson");
        return methodForPerson(age, name, isCool, distanceRun, weight);
    }

更新:
AOP解决方案来自AspectJ
为方法和参数目标添加注解@LogMDC。这个想法是添加将所有方法参数或特定参数放入 MDC

的能力

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

@Target({ElementType.METHOD, ElementType.PARAMETER})
@Retention(RetentionPolicy.RUNTIME)
public @interface LogMDC {
}

添加方面，该方面将捕获用 @LogMDC 注释标记的方法并将参数存储到 MDC。

import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.reflect.MethodSignature;

import java.lang.annotation.Annotation;
import java.lang.reflect.Method;

@Aspect
public class MDCAspect {
    
    //match the method marked @LogMDC annotation
    @Before("@annotation(LogMDC) && execution(* *(..))")
    public void beforeMethodAnnotation(JoinPoint joinPoint) {
        String[] argNames = ((MethodSignature) joinPoint.getSignature()).getParameterNames();
        Object[] values = joinPoint.getArgs();
        if (argNames.length != 0) {
            for (int i = 0; i < argNames.length; i++) {
                MDC.put(argNames[i], values[i]);
            }
        }
    }

    //match the method which has any parameter with @LogMDC annotation
    @Before("execution(* *(.., @LogMDC (*), ..))")
    public void beforeParamsAnnotation(JoinPoint joinPoint) {
        MethodSignature methodSignature = (MethodSignature) joinPoint.getSignature();
        String[] argNames = methodSignature.getParameterNames();
        Object[] values = joinPoint.getArgs();
        Method method = methodSignature.getMethod();
        Annotation[][] parameterAnnotations = method.getParameterAnnotations();

        for (int i = 0; i < parameterAnnotations.length; i++) {
            Annotation[] annotations = parameterAnnotations[i];
            for (Annotation annotation : annotations) {
                if (annotation.annotationType() == LogMDC.class) {
                    MDC.put(argNames[i], values[i]);
                }
            }
        }
    }
}

使用示例。将方法的所有参数放入MDC

    @LogMDC
    public String invokeMethodForPerson(int age, String name, boolean isCool, long distanceRun, double weight) {
        LOGGER.info("begin to invoke method invokeMethodForPerson");
        return methodForPerson(age, name, isCool, distanceRun, weight);
    }

使用示例。仅将方法的特定参数放入MDC，用注解标记。

    public String invokeMethodForPerson(@LogMDC int age, @LogMDC String name, boolean isCool, long distanceRun, @LogMDC double weight) {
        LOGGER.info("begin to invoke method invokeMethodForPerson");
        return methodForPerson(age, name, isCool, distanceRun, weight);
    }

请注意，AspecJ 对性能有一点影响
Performance penalty for using AspectJ
Performance impact of using aop
Performance: using AspectJ to log run time of all methods

根据您的用例，您应该决定使用简单的 util 方法调用还是 aop 解决方案。