从 JDK8 升级到 JDK11 后出现奇怪的 java.lang.InstantiationException 和 java.lang.NoSuchMethodException

Question

我有以下代码可以在 JDK8 下构建并正常工作：

@FunctionalInterface
public interface ThrowingFunction<T, R, E extends Throwable> {
    R apply(T t) throws E;

    static <T, R, E extends Throwable> Function<T, R> unchecked (ThrowingFunction<T, R, E> function) {
        return t -> {
            try {
                return function.apply(t);
            }
            catch (Throwable e) {
                throw new RuntimeException(e);
            }
        };
    }
}

并且：

@Component
public class CronJobDuplicationCheckStrategiesRegistry {

    private final Map<String, Set<CronJobDuplicationCheckStrategy>> duplicationStrategies;

    CronJobDuplicationCheckStrategiesRegistry(final CronJobsRegistry cronJobsRegistry) {
        duplicationStrategies = cronJobsRegistry.get()
            .stream()
            .collect(Collectors.toMap(
                clazz -> clazz.getName(),
                ThrowingFunction.unchecked(
                    clazz -> clazz.getDeclaredConstructor()
                                  .newInstance()
                                  .getDuplicationStrategies())));
    }

    public Set<CronJobDuplicationCheckStrategy> get(String jobClass) {
        return duplicationStrategies.get(jobClass);
    }
}

此代码无法在 JDK11 下编译并出现以下错误：

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.3:compile (default-compile) on project cron-api: Compilation failure: Compilation failure: 
[ERROR] /java/org/foo/src/main/java/org/foo/jobs/CronJobDuplicationCheckStrategiesRegistry.java:[26,120] unreported exception java.lang.NoSuchMethodException; must be caught or declared to be thrown
[ERROR] /java/org/foo/src/main/java/org/foo/src/main/java/org/foo/cron/jobs/CronJobDuplicationCheckStrategiesRegistry.java:[27,109] unreported exception java.lang.InstantiationException; must be caught or declared to be thrown

有人可以解释一下不满意的地方以及如何解决吗？

Answer 1

Could somebody please explain what it's unhappy about and how to fix it?

将 E 通用类型替换为实际 Throwable:

@FunctionalInterface
public interface ThrowingFunction<T, R> {
    R apply(T t) throws Throwable;

    static <T, R> Function<T, R> unchecked(ThrowingFunction<T, R> function) {
        return t -> {
            try {
                return function.apply(t);
            } catch (Throwable e) {
                throw new RuntimeException(e);
            }
        };
    }
}

... the following code which builds and works fine under JDK8

我认为问题出在捕获机制上，该机制与 E 泛型类型不兼容，并且与 JLS 8.1.2. Generic Classes and Type Parameters:

处的语句有关

It is a compile-time error if a generic class is a direct or indirect subclass of Throwable (§11.1.1).

This restriction is needed since the catch mechanism of the Java Virtual Machine works only with non-generic classes.

坦率地说，这是一个猜测，我不知道为什么这可以用 JDK 11 重现而不是 JDK 8 - 这很奇怪。

我希望我至少帮助你解决了这个问题。

从 JDK8 升级到 JDK11 后出现奇怪的 java.lang.InstantiationException 和 java.lang.NoSuchMethodException

Weird java.lang.InstantiationException and java.lang.NoSuchMethodException after upgrading from JDK8 to JDK11

java

generics

lambda

exception

java-11