Spring 事务：注解之外，更要看调用边界

import java.util.*;
public class Main {
  enum Propagation { REQUIRED,REQUIRES_NEW }
  static class UnexpectedRollback extends RuntimeException {}
  static class Physical { boolean rollbackOnly; final List<String> writes=new ArrayList<>(); }
  record Scope(Physical tx,boolean owner) {}
  static class Model {
    final Deque<Scope> scopes=new ArrayDeque<>(); final List<String> committed=new ArrayList<>();
    void begin(Propagation p) {
      Objects.requireNonNull(p);
      if(p==Propagation.REQUIRED && !scopes.isEmpty()) scopes.push(new Scope(scopes.peek().tx(),false));
      else scopes.push(new Scope(new Physical(),true)); // 新物理事务有独立待提交内容
    }
    void write(String value) {
      if(scopes.isEmpty()) throw new IllegalStateException("没有事务");
      scopes.peek().tx().writes.add(Objects.requireNonNull(value));
    }
    void finish(boolean success) {
      if(scopes.isEmpty()) throw new IllegalStateException("没有作用域");
      Scope scope=scopes.pop(); Physical tx=scope.tx();
      if(!success) tx.rollbackOnly=true; // 共享事务上的标记不可被外层 catch 清除
      if(!scope.owner()) return; // 参与者无权提前提交共享事务
      if(tx.rollbackOnly) {
        if(success) throw new UnexpectedRollback();
        return;
      }
      committed.addAll(tx.writes); // 只有物理事务所有者完成时发布写入
    }
  }
  static void eq(List<String> wanted,List<String> actual) { if(!wanted.equals(actual)) throw new AssertionError(actual); }
  public static void main(String[] args) {
    Model joined=new Model(); joined.begin(Propagation.REQUIRED); joined.write("A");
    joined.begin(Propagation.REQUIRED); joined.write("B"); joined.finish(true); joined.finish(true); eq(List.of("A","B"),joined.committed);
    Model marked=new Model(); marked.begin(Propagation.REQUIRED); marked.write("A");
    marked.begin(Propagation.REQUIRED); marked.write("B"); marked.finish(false);
    try { marked.finish(true); throw new AssertionError("应报告意外回滚"); }
    catch(UnexpectedRollback expected) { /* 外层正常返回不能覆盖回滚标记 */ }
    eq(List.of(),marked.committed);
    Model independent=new Model(); independent.begin(Propagation.REQUIRED); independent.write("A");
    independent.begin(Propagation.REQUIRES_NEW); independent.write("B"); independent.finish(true); independent.finish(false); eq(List.of("B"),independent.committed);
    Model innerFailed=new Model(); innerFailed.begin(Propagation.REQUIRED); innerFailed.write("A");
    innerFailed.begin(Propagation.REQUIRES_NEW); innerFailed.write("B"); innerFailed.finish(false); innerFailed.finish(true); eq(List.of("A"),innerFailed.committed);
    Model outerFailed=new Model(); outerFailed.begin(Propagation.REQUIRED); outerFailed.write("A");
    outerFailed.begin(Propagation.REQUIRED); outerFailed.write("B"); outerFailed.finish(true); outerFailed.finish(false); eq(List.of(),outerFailed.committed);
    try { new Model().write("x"); throw new AssertionError("应拒绝无事务写入"); }
    catch(IllegalStateException expected) { /* 错误输入 */ }
    System.out.println("PASS 7 propagation assertions");
  }
}