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Cannot Reference “XxxClass.xxxmember” Before Supertype Constructor Has Been Called

2023-06-15 12:35 由 buguge 发表于 #后端开发

百度翻译：在调用超类型构造函数之前无法引用“XxxClass.xxx” ----- 我的理解：在一个类的构造器方法还未执行的时候，我们无法使用这个类的成员属性或成员方法。

 

下面是会出现此错误的示例代码

public class MyException extends RuntimeException {
    private int errorCode = 0;
    
    public MyException(String message) {
        super(message + getErrorCode()); // compilation error
    }

    public int getErrorCode() {
        return errorCode;
    }
}

IDE提示错误：Cannot reference 'MyException.getErrorCode' before supertype constructor has been called.

 

 


说说我怎么遇到这个问题的？

我有一个组件工具类。

 1 @Slf4j
 2 public class Many2OneProcessor<T> {
 3 
 4     private static ScheduledExecutorService scheduledThreadPool = Executors.newScheduledThreadPool(15);
 5 
 6     /**
 7      * 将多长时间的多次操作合并成1次，单位：秒
 8      */
 9     private final long intervalSecond;
10     /**
11      * 每次处理多少条数据
12      */
13     private final int perBatchCount;
14     /**
15      * 批次处理逻辑代码
16      */
17     private final Consumer<List<T>> yourBusinessCode;
18     private final ...
19 
20     public Many2OneProcessor(long intervalSecond, Class<T> tClass, Consumer<List<T>> yourBusinessCode) {
21         this(intervalSecond, Integer.MAX_VALUE, tClass, yourBusinessCode);
22     }
23 
24     public Many2OneProcessor(long intervalSecond, int perBatchCount, Class<T> tClass, Consumer<List<T>> yourBusinessCode) {
25         
26         ...此处省略若干行
27         
28     }    
29     
30     public void produce(T t) {
31         redisUtil.lSet(LIST_KEY, t, HOURS.toMillis(1));
32         scheduledThreadPool.schedule(this::consumeMsg, intervalSecond, TimeUnit.SECONDS);
33     }
34 
35     public void consumeMsg() {
36         redisLockTemplate.execute(LOCK_KEY, TimeUnit.SECONDS.toMillis(intervalSecond - 1), false, () -> {
37             
38             ...
39             
40             List<T> tList = new ArrayList<>(perBatchCount + 1);
41             for (int j = 0; j < perBatchCount; j++) {
42                 Object o = redisUtil.lPop(LIST_KEY);
43                 if (o == null) break;
44                 tList.add((T) o);
45             }
46             if (perBatchCount != Integer.MAX_VALUE && redisUtil.lGetListSize(LIST_KEY) > 0) {
47                 scheduledThreadPool.schedule(this::consumeMsg, intervalSecond, TimeUnit.SECONDS);
48             }
49             
50             ...
51             yourBusinessCode.accept(tList);
52             
53         });
54     }
55 }

 

注意到其中的两处 Integer.MAX_VALUE，这无形中提高了代码理解和维护（重点是前者）的成本。

于是，做个小小的重构。改为下面这样，代码的可理解方面，更上一层楼。

public class Many2OneProcessor<T> {
    /**
     * 每次处理多少条数据
     */
    private final int perBatchCount;
    private static final int PER_BATCH_COUNT_DEFAULT = Integer.MAX_VALUE;
    
    public Many2OneProcessor(long intervalSecond, Class<T> tClass, Consumer<List<T>> yourBusinessCode) {
        this(intervalSecond, PER_BATCH_COUNT_DEFAULT, tClass, yourBusinessCode);
    }
    
    public void consumeMsg() {
        ...
        
            if (perBatchCount != PER_BATCH_COUNT_DEFAULT && redisUtil.lGetListSize(LIST_KEY) > 0) {
        ...
    }
}

 

注意，常量 PER_BATCH_COUNT_DEFAULT 定义为static，否则会出现上面的预编译错误：Cannot reference 'Many2OneProcessor.PER_BATCH_COUNT_DEFAULT' before supertype constructor has been called。另外，在重构过程中，我使用了一种方案，见下图，也出现了这个错误：Cannot reference 'Many2OneProcessor.perBatchCount' before supertype constructor has been called

 

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