Java——反射三種方式的效率對比

轉載自：https://blog.csdn.net/aitcax/article/details/52694423

1 使用field(效率最高)

            long start = System.nanoTime();
            Field[] fields = CallCount.class.getDeclaredFields();
            for (String str : dateList) {
                boolean exist = false;
                for (Field field : fields){
                    field.setAccessible(true);
                    if (field.getName().endsWith(str)) {
                        int value = 0;
                        for (CallCount callCount : callCountList) {
                            value += (Integer)field.get(callCount);
                        }
                        resultList.add(value);
                        exist = true;
                        break;
                    }
                }
                if (!exist) {
                    resultList.add(0);
                }
            }
            long end = System.nanoTime();
            log.info("old call cost :" + (end-start));

2 使用 org.apache.commons.beanutils.BeanUtils來獲取屬性

            long start = System.nanoTime();
            for (String str : dateList) {
                Integer value = getMinuteAccessCount(str, callCountList);
                resultList.add(value);
            }
            long end = System.nanoTime();
            log.info("new call cost :" + (end-start));

        private Integer getMinuteAccessCount(String minute, List<CallCount> callCountList) {
        Integer result = 0;
        String propertyName = "logMinute" + minute;
        for (CallCount callCount : callCountList) {
            int value = 0;
            try {
                value = Integer.valueOf(BeanUtils.getProperty(callCount, propertyName));
            } catch (NumberFormatException | IllegalAccessException | InvocationTargetException | NoSuchMethodException e) {
                e.printStackTrace();
            }
            result += value;
        }
        return result;
    }

3  使用java.lang.reflect.Method獲取值

 

 

            long start = System.nanoTime();
            for (String str : dateList) {
                Integer value = getMinuteAccessCount(str, callCountList);
                resultList.add(value);
            }
            long end = System.nanoTime();
            log.info("new call cost :" + (end-start));

        private Integer getMinuteAccessCount(String minute, List<CallCount> callCountList) {
        Integer result = 0;
        for (CallCount callCount : callCountList) {
            int value = 0;
            try {
                Method method = callCount.getClass().getDeclaredMethod("getLogMinute"+minute);
                Object obj = method.invoke(callCount);
                value = (Integer)obj;
            } catch (NumberFormatException | IllegalAccessException | InvocationTargetException | NoSuchMethodException e) {
                e.printStackTrace();
            }
            result += value;
        }
        return result;
    }

4 耗時對比，在使用相同的查詢條件，相同的數據的情況下。通過實驗得到以下兩組數據（耗時/納秒）

1 old call cost :517599
1 old call cost :347916
1 old call cost :337312
1 old call cost :177893
1 old call cost :131709
1 old call cost :82789
1 old call cost :63973

3 new call cost :925383
3 new call cost :794016
3 new call cost :912382

 

1 old call cost :755016
1 old call cost :365364
1 old call cost :231944
1 old call cost :123498
1 old call cost :103315
1 old call cost :92025
1 old call cost :81762

2 new call cost :139741338
2 new call cost :3387140
2 new call cost :2230497
2 new call cost :9215854
2 new call cost :2313970
2 new call cost :1549374
2 new call cost :1884291
2 new call cost :1100880
2 new call cost :1488138

每組數據前的數字代表之前取值的方式。
由數據對比可以看出，耗時最小的，始終是方式1，並且方式1在多次調用時，耗時是逐步減少的，可能是有緩存機制。
耗時第二少的是方式3，耗時最多的是方式2.

5 解析

方式1，采用了最基本的java反射方式，使用Filed，循環bean的Field，得到Object，再轉換為Integer類型。
方式2，采用了看似最簡潔的BeanUitls，根據屬性名，獲取屬性值。這樣最耗時。
方式3，采用了獲取bean的Method，然后invoke的方式來獲取值。
---------------------
作者：aitcax
來源：CSDN
原文：https://blog.csdn.net/aitcax/article/details/52694423