@Transactional self-invocation problem là gì?

Self-invocation: method trong cùng class gọi method khác cũng trong class đó → @Transactional bị bỏ qua.

Spring transaction hoạt động qua AOP proxy — proxy bọc bean, chặn call từ ngoài để bắt đầu/kết thúc transaction. Khi method A gọi method B trong cùng class, gọi là this.B() — đi thẳng vào object, không qua proxy → transaction annotation trên B không có hiệu lực.

@Service
class OrderService {

  public void processOrders(List<Long> ids) {
    ids.forEach(id -> processOne(id));   // ❌ self-invocation!
  }

  @Transactional
  public void processOne(Long id) {
    // Transaction KHÔNG bắt đầu vì gọi qua this
  }
}

Cách fix:

1. Tách ra service khác:

@Service class OrderProcessor {
  @Transactional
  public void processOne(Long id) { ... }
}
// OrderService inject OrderProcessor

2. Self-inject (hack, không khuyến nghị):

@Service
class OrderService {
  @Lazy @Autowired
  private OrderService self;   // inject proxy của chính mình

  public void processOrders(List<Long> ids) {
    ids.forEach(id -> self.processOne(id));   // qua proxy ✅
  }
}

Nguyên tắc: @Transactional chỉ hoạt động với public method và call từ bên ngoài bean.

Đây cũng là lý do tương tự @Async, @Cacheable bị bỏ qua khi self-invoke.

Self-invocation: a method calling another method in the same class → @Transactional is ignored.

Spring transactions work via an AOP proxy — the proxy wraps the bean, intercepting calls from outside to start/end a transaction. When method A calls method B in the same class, it calls this.B() — directly on the object, bypassing the proxy → the transaction annotation on B has no effect.

@Service
class OrderService {

  public void processOrders(List<Long> ids) {
    ids.forEach(id -> processOne(id));   // ❌ self-invocation!
  }

  @Transactional
  public void processOne(Long id) {
    // Transaction DOES NOT start — called via this
  }
}

Fixes:

1. Extract to another service:

@Service class OrderProcessor {
  @Transactional
  public void processOne(Long id) { ... }
}
// OrderService injects OrderProcessor

2. Self-inject (hack, not recommended):

@Service
class OrderService {
  @Lazy @Autowired
  private OrderService self;   // injects own proxy

  public void processOrders(List<Long> ids) {
    ids.forEach(id -> self.processOne(id));   // goes through proxy ✅
  }
}

Rule: @Transactional only works on public methods called from outside the bean.

The same self-invocation issue applies to @Async, @Cacheable, and other AOP-based annotations.