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如何在可选类中自定义NoSuchelementException的错误消息

optional java

1

Georgi Michev · 技术社区 · 7 年前

我有个方法 NotFoundException 如果我的对象ID是 null .

public void removeStatementBundleService(String bundleId) throws NotFoundException {
    Optional<StatementBundle> bundleOpt = statementBundleRepository.findById(bundleId);

    if(bundleOpt.isPresent()) {
        StatementBundle bundle = bundleOpt.get();

        if(bundle.getStatements() != null && !bundle.getStatements().isEmpty()) {               
            for(Statement statement: bundle.getStatements()) {
                statementRepository.delete(statement);
            }
        }

        if(bundle.getFileId() != null) {
            try {
                fileService.delete(bundle.getFileId());
            } catch (IOException e) {
                e.printStackTrace();
            }   
        }

        statementBundleRepository.delete(bundle);

    } else {
        throw new NotFoundException("Statement bundle with id: " + bundleId + " is not found.");
    }
}

我发现这是不需要的,因为 java.util.Optional 使用类。在Oracle文档中,我发现 get() 被使用,然后就没有价值了 NoSuchElementException 被抛出。将错误消息添加到异常中的最佳方法是什么?我正试图打开 Optional Eclipse中的类尝试在其内部进行更改(不确定这是否是好的实践),但Eclipse不允许我访问这个类,另一方面,我读到这个类也是最终的。

3 回复 | 直到 7 年前

1

3

Peter Walser 7 年前

当解决 Optional value ,您可以直接

Optional<StatementBundle> bundleOpt = statementBundleRepository.findById(bundleId);
StatementBundle bundle = bundleOpt.orElseThrow(() 
    -> new NotFoundException("Statement bundle with id: " + bundleId + " is not found.");

StatementBundle bundle = statementBundleRepository.findById(bundleId)
    .orElseThrow(()
     -> new NotFoundException("Statement bundle with id: " + bundleId + " is not found.");

2

1

L.Spillner 7 年前

Optional orElseThrow(...) Supplier

StatementBundle bundle = bundleOpt.orElseThrow( ()->new NotFoundException("Statement bundle with id: " + bundleId + " is not found.") );

3

0

user9455968 7 年前

NoSuchElementException

try {
    try {
        // We simulate a failing .get() on an Optional.
        throw new NoSuchElementException("message from Optional.get()");
    } catch (NoSuchElementException ex) {
        // We wrap the exception into a custom exception and throw this.
        throw new MyException("my message", ex);
    }
} catch (MyException ex) {
    // Now we catch the custom exception and can inspect it and the
    // exception that caused it.
    System.err.println(ex.getClass().getCanonicalName()
            + ": " + ex.getMessage()
            + ": " + ex.getCause().getMessage());
}

MyException: my message: message from Optional.get()