TransactionTemplate继承于TransactionOperations和InitializingBean这两个接口。其中InitializingBean接口中的afterPropertiesSet方法，Spring Bean初始化完成后执行，TransactionTemplate用来检查事务管理器是否已经初始化完毕，如下所示。

  1.     @Override
  2.     public void afterPropertiesSet() {
  3.         if (this.transactionManager == null) {
  4.             throw new IllegalArgumentException("Property 'transactionManager' is required");
  5.         }
  6.     }

继承于TransactionOperations的execute方法是事务执行的核心方法，事务执行分成三个步骤：

  • 获取事务连接；
  • 执行目标方法；
  • 提交或者回滚事务； ```java public T execute(TransactionCallback action) throws TransactionException {
    1.   if (this.transactionManager instanceof CallbackPreferringPlatformTransactionManager) {
    2.       return ((CallbackPreferringPlatformTransactionManager) this.transactionManager).execute(this, action);
    3.   }
    4.   else {
    5.       //1.获取事务连接
    6.       TransactionStatus status = this.transactionManager.getTransaction(this);
    7.       T result;
    8.       try {
    9.           //2.执行业务方法
    10.           result = action.doInTransaction(status);
    11.       }
    12.       catch (RuntimeException ex) {
    13.           // Transactional code threw application exception -> rollback
    14.           rollbackOnException(status, ex);
    15.           throw ex;
    16.       }
    17.       catch (Error err) {
    18.           // Transactional code threw error -> rollback
    19.           rollbackOnException(status, err);
    20.           throw err;
    21.       }
    22.       catch (Throwable ex) {
    23.           // Transactional code threw unexpected exception -> rollback
    24.           rollbackOnException(status, ex);
    25.           throw new UndeclaredThrowableException(ex, "TransactionCallback threw undeclared checked exception");
    26.       }
    27.       //3.提交事务
    28.       this.transactionManager.commit(status);
    29.       return result;
    30.   }
    }

```

参考

https://www.cnblogs.com/dennyzhangdd/p/9602673.html