关于spring:Spring事务传播行为

本文出处Spring 事务流传行为
转载请阐明出处

在Spring @Transactional 申明式事务有一个项属性propagation事务流传行为，是一个Propagation 枚举类，有7种类型，对应不同应用场景。上面说下这些枚举代码含意，在联合代码加深了解，坚固学习。

事务流传级别生效

先做一个小试验，写一个长久化的save办法，设置成禁用事务，用事务办法去调用它，看会产生什么成果。

    @Transactional(propagation = Propagation.NEVER)    public void save(Users users){        usersRepository.save(users);    }    @Transactional    public void multSave(){        Users users = getUsers();        save(users);    }

依照下面字段含意解析，save办法不反对事务，在以后事务运行会抛出异样。可是执行后果不是意料那样，没有抛出异样，数据写入到数据库了。并且咱们能够在改一次save办法，间接抛出一个RuntimeTime异样，你会发现后果更加显著。

    @Transactional(propagation = Propagation.NEVER)    public void save(Users users){        usersRepository.save(users);        throw new RuntimeException("4322");    }    @Transactional    public void multSave(){        Users users = getUsers();        save(users);    }

你会发现save 办法 数据回滚了。

在做多几次这种试验你就会发现，在同一个类中，最外层事务注解属性会笼罩办法内所有事务注解，比方你的外层设置默认事务流传行为，无论调用那种行为都会依照默认属性，外层没有设置事务，调用办法有事务也不会失效的。这个不难理解，实现Spring 事务一个基于AOP的代理类，它依据指标办法注解来加强办法，这个是运行时动静执行的，办法内其余办法没有代理类的性能加强，就相当于一般办法成果了。千万不要在同一个类外面测试事务流传行为，否则你永远都都得不到论断的。

进入办法验证

默认事务

    @Transactional    public void save(){        Employee employee = new Employee();        employee.setDepartmentId(2);        employee.setName("Jorry");        employee.setSalary(60000);        repository.save(employee);        throw new RuntimeException("33333");    }    @Transactional    public void multSave(){        Users users = getUsers();        save(users);        employeeService.save();    }

执行后果： users、employee写入失败，employee的办法抛出异样触发回滚，也会导致外层办法回滚。在同一个事务中，只有触发回滚，事务内所有数据操作都会回滚的。

反对事务

    @Transactional(propagation = Propagation.SUPPORTS)    public void save(){        Elimployee employee = new Employee();        employee.setDepartmentId(2);        employee.setName("Jorry");        employee.setSalary(60000);        repository.save(employee);    }    @Transactional    public void multSave(){        Users users = getUsers();        save(users);        employeeService.save();        throw new RuntimeException("3333");    }

执行成果: Usres和Elimployee 都进行回滚了。SUPPORTS会退出调用者事务中，和调用者事务是同一个事务，如果在事务中出现异常全副回滚。即便在employeeService.save() 抛出异样,成果一样的。

开启新事务

    @Transactional(propagation = Propagation.REQUIRES_NEW)    public void save(){        Employee employee = new Employee();        employee.setDepartmentId(2);        employee.setName("Jorry");        employee.setSalary(60000);        repository.save(employee);        throw new RuntimeException("3333");    }    @Transactional    public void multSave(){        Users users = getUsers();        save(users);        try {            employeeService.save();        }catch (RuntimeException e){        }

执行后果： empoyee回滚，users写入数据库胜利。要解决employeeService.save()异样，不然异样会导致multSave出现异常事务回滚了。退出一个对照，在把employeeService.save()改成默认属性，发现users,employee 都会回滚了，还会抛出一个异样

org.springframework.transaction.UnexpectedRollbackException: Transaction silently rolled back because it has been marked as rollback-only

Spring官网文档说到如果内部事务（内部调用者不晓得）将事务无提醒地标记为仅回滚，则内部调用者仍会调用commit。内部调用者须要接管一个，UnexpectedRollbackException以分明地批示已执行回滚。

强制不应用事务

    @Transactional(propagation = Propagation.NEVER)    public void save(){        Employee employee = new Employee();        employee.setDepartmentId(2);        employee.setName("Jorry");        employee.setSalary(60000);        repository.save(employee);    }    @Transactional    public void multSave(){        Users users = getUsers();        save(users);        employeeService.save();    }

执行后果: 两个表都写入失败，employeeService.save() 抛出异样

org.springframework.transaction.IllegalTransactionStateException: Existing transaction found for transaction marked with propagation 'never'

不反对事务

    @Transactional(propagation = Propagation.NOT_SUPPORTED)    public void save(){        Employee employee = new Employee();        employee.setDepartmentId(2);        employee.setName("Jorry");        employee.setSalary(60000);        repository.save(employee);        throw new RuntimeException("33333");    }    @Transactional    public void multSave(){        Users users = getUsers();        save(users);        employeeService.save();    }

执行后果：employee胜利写入数据库，employee 将事务挂了，用无事务办法执行，users受到异样抛出，触发事务回滚。如果你把employeeService.save()解决一下，两种表操作都写入胜利了。

强制事务

    @Transactional(propagation = Propagation.MANDATORY)    public void save(){        Employee employee = new Employee();        employee.setDepartmentId(2);        employee.setName("Jorry");        employee.setSalary(60000);        repository.save(employee);    }    public void multSave(){        Users users = getUsers();        save(users);        employeeService.save();    }

执行后果: users 胜利写入数据库，employee写入失败并且抛出异样

org.springframework.transaction.IllegalTransactionStateException: No existing transaction found for transaction marked with propagation 'mandatory'

嵌套事务

    @Transactional    public void multSave(){        Users users = getUsers();        save(users);        employeeService.save();    }    @Transactional(propagation = Propagation.NESTED)    public void save(){        Employee employee = new Employee();        employee.setDepartmentId(2);        employee.setName("Jorry");        employee.setSalary(60000);        repository.save(employee);    }

执行后果： employeeService.save()抛出一个异样，如同JPA的实现不反对嵌套执行，这个看不到成果了。

org.springframework.transaction.NestedTransactionNotSupportedException: JpaDialect does not support savepoints - check your JPA provider's capabilities