وكلاء المعاملة ودلالة الأخطاء

package training.catalog;

import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

@Service
class TransferService {
    private final AccountRepository accounts;
    TransferService(AccountRepository accounts) { this.accounts = accounts; }

    @Transactional
    public void transfer(long from, long to, long cents) {
        if (cents <= 0) throw new IllegalArgumentException("amount");
        Account source = accounts.findById(from).orElseThrow();
        Account target = accounts.findById(to).orElseThrow();
        source.debit(cents);
        target.credit(cents);
    }
}

تحتاج العقود السياقية حفظ الثوابت؛ ولم تُرصد معاملة أوعزل أوتثبيت فعلي.

package training.catalog;

import java.util.List;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;

@Service
class ChunkWriter {
    private final ImportRepository rows;
    ChunkWriter(ImportRepository rows) { this.rows = rows; }
    @Transactional(propagation = Propagation.REQUIRES_NEW)
    public void write(List<ImportRow> chunk) { rows.saveAll(chunk); }
}

@Service
class ImportCoordinator {
    private final ChunkWriter writer;
    ImportCoordinator(ChunkWriter writer) { this.writer = writer; }
    public void run(List<List<ImportRow>> chunks) {
        for (var chunk : chunks) writer.write(chunk);
    }
}

تعبر النداءات حدود كائنات مُدارة، ويحتاج أثرها تكاملاً وتخزيناً؛ ولم تُنفذ.