Spring Boot事务：理解事务的传播

╰半橙微兮° 2021-10-13 02:19 335阅读 0赞

在我之前的教程中，[Spring Boot事务管理例子][Spring Boot]中，我们了解了事务的声明式实现和管理。在这片文章中，我们会  
来看事务的传播性以及不同的传播类型。下一篇文章中，我们将会学习[Spring Boot 事务回滚][Spring Boot 1]和[Spring Boot事务隔离级别][Spring Boot 2]。

## 事务的传播性是什么？ ##

任何应用程序都涉及许多服务或组件，这些服务或组件需要调用其他服务或组件。事务传播指示任何组件或服务是否会参与或将参与事务，以及\_\_如果调用组件/服务已经创建或尚未创建事务，它将如何执行\_\_。

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTI5MzQzMjU_size_16_color_FFFFFF_t_70]

## 准备开始 ##

我们将利用上一章已经开发好的`Spring Boot`事务项目。它已经具有`Organization Service`,该服务调用了`Employee Service`和`Health Insurance Service`。

并且，在之前的例子中，[我们只是在`Organization Service`上添加了事务注解][Organization Service]。  
但是，假设用户希望同时调用`Employee Service`，即：

客户端通过`Organization Service`来调用`Employee Service`：

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTI5MzQzMjU_size_16_color_FFFFFF_t_70 1]  
客户端直接调用`Employee Service`

![在这里插入图片描述][20190820213248692.png]  
因为可以直接调用`Employee Service`，我们将对`Employee Service`使用事务注解。所以，`Employee Service`和`Organization Service`都将使用事务注解。

我们将通过观察`Employee Service`和`Organization Service`的行为来观察各种传播场景。有六种类型的事务传播：

*  REQUIRED
 *  SUPPORTS
 *  NOT\_SUPPORTED
 *  REQUIRES\_NEW
 *  NEVER
 *  MANDATORY

事务传播，**默认是`REQUIRED`**

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTI5MzQzMjU_size_16_color_FFFFFF_t_70 2]  
左侧：如果`insertEmployee()`方法被直接调用，它会自己创建一个自己的新的事务。

右侧：如果`insertEmployee()`方法是从另外一个服务中调用的;

*  如果调用的service已经有一个事务，那么该方法就会使用已经存在的事务
 *  如果调用的service中不存在事务，那么方法就会创建一个新的事务  
    所以如果存在事务，那么`insertEmployee()`方法就会继续使用原有的事务，否则就会利用`REQUIRED`来创建一个新的事务。

在这里，`Organization Service`和`Employee Service`都定义了事务的传播行为为`Required`这也是默认的事务传播行为，

**代码**：

下面是`Organization Service`的代码：

package com.javainuse.service.impl;
    
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Service;
    import org.springframework.transaction.annotation.Transactional;
    import com.javainuse.model.Employee;
    import com.javainuse.model.EmployeeHealthInsurance;
    import com.javainuse.service.EmployeeService;
    import com.javainuse.service.HealthInsuranceService;
    import com.javainuse.service.OrganizationService;
    
    @Service
    @Transactional
    public class OrganzationServiceImpl implements OrganizationService { 
    	
    	@Autowired
    	EmployeeService employeeService;
    	
    	@Autowired
    	HealthInsuranceService healthInsuranceService;
    	
    	@Override
    	public void joinOrganization(Employee employee, EmployeeHealthInsurance employeeHealthInsurance) { 
    		employeeService.insertEmployee(employee);
    		
    		if (employee.getEmpId().equals("emp1")) { 
    			throw new RuntimeException("thowing exception to test transaction rollback");
    		}
    		
    		healthInsuranceService.registerEmployeeHealthInsurance(employeeHealthInsurance);
    	}
    	
    	@Override
    	public void leaveOrganization(Employee employee, EmployeeHealthInsurance employeeHealthInsurance) { 
    		employeeService.deleteEmployeeById(employee.getEmpId());
    		healthInsuranceService.deleteEmployeeHealthInsuranceById(employeeHealthInsurance.getEmpId());
    	}
    }

`Employee Service`的代码如下所示：

**输出**

\_\_通过使用`OrganizationService`\_\_调用`EmployeeService`:

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTI5MzQzMjU_size_16_color_FFFFFF_t_70 3]

直接调用`employeeService`：

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTI5MzQzMjU_size_16_color_FFFFFF_t_70 4]

## 事务传播行为-SUPPORTS ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTI5MzQzMjU_size_16_color_FFFFFF_t_70 5]  
从上图可以看出来两点

*  当`EmployeeService`中方法`insertEmployee()`被直接调用的话，如果使用的事务传播行为为SUPPORTS，那么它不会自己创建自己新的事务
 *  当`EmployeeService`中`insertEmployee()`通过`OrganizationService`调用的时候，如果`OrganizationService`存在事务，那么`insertEmployee`就会沿用`OrganizationService`的事务传播行为，  
    否则如果`OrganizationService`不存在事务传播行为，那么`insertEmployee()`方法就会执行，但是不会开启任何事务。

在上面的示例中，`OrganizationService`的事务传播行为定义为`REQUIRED`,`EmployeeService`的事务定义为`SUPPORTS`

**代码**：

`OrganizationService`的实现如下：

package com.javainuse.service.impl;
    
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Service;
    import org.springframework.transaction.annotation.Transactional;
    import com.javainuse.model.Employee;
    import com.javainuse.model.EmployeeHealthInsurance;
    import com.javainuse.service.EmployeeService;
    import com.javainuse.service.HealthInsuranceService;
    import com.javainuse.service.OrganizationService;
    
    @Service
    @Transactional
    public class OrganzationServiceImpl implements OrganizationService { 
    
    	@Autowired
    	EmployeeService employeeService;
    
    	@Autowired
    	HealthInsuranceService healthInsuranceService;
    
    	@Override
    	public void joinOrganization(Employee employee, EmployeeHealthInsurance employeeHealthInsurance) { 
    		employeeService.insertEmployee(employee);
    		if (employee.getEmpId().equals("emp1")) { 
    		throw new RuntimeException("thowing exception to test transaction rollback");
    		}
    		healthInsuranceService.registerEmployeeHealthInsurance(employeeHealthInsurance);
    	}
    	
    	@Override
    	public void leaveOrganization(Employee employee, EmployeeHealthInsurance employeeHealthInsurance) { 
    		employeeService.deleteEmployeeById(employee.getEmpId());
    		healthInsuranceService.deleteEmployeeHealthInsuranceById(employeeHealthInsurance.getEmpId());
    	}
    }

`Employee Service`的代码如下所示：

**输出**：

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTI5MzQzMjU_size_16_color_FFFFFF_t_70 6]

## 事务传播行为:`NOT_SUPPORTED` ##

![\[外链图片转存失败(img-CpzTju2a-1566307900626)(C:\\Users\\liyongyong\\Desktop\\spring\_boot\_transaction\_propagation\_009.png)\]][img-CpzTju2a-1566307900626_C_Users_liyongyong_Desktop_spring_boot_transaction_propagation_009.png]

从上面的描述中可以知道，当`EmployeeService`中`insertEmployee被设定事务传播行为为`NOT\_SUPPORTED`的时候， 直接调用该方法或者通过`OrganizationService`调用，该方法都不会创建事务或者沿用`OrganizationService\`的事务。

**代码**：

`OrganizationService`的实现如下：\`

package com.javainuse.service.impl;
     
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Service;
    import org.springframework.transaction.annotation.Transactional;
    import com.javainuse.model.Employee;
    import com.javainuse.model.EmployeeHealthInsurance;
    import com.javainuse.service.EmployeeService;
    import com.javainuse.service.HealthInsuranceService;
    import com.javainuse.service.OrganizationService;
    
    @Service
    @Transactional
    public class OrganzationServiceImpl implements OrganizationService { 
    
    	@Autowired
    	EmployeeService employeeService;
    	
    	@Autowired
    	HealthInsuranceService healthInsuranceService;
    	
    	@Override
    	public void joinOrganization(Employee employee, EmployeeHealthInsurance employeeHealthInsurance) { 
    		employeeService.insertEmployee(employee);
    		if (employee.getEmpId().equals("emp1")) { 
    			throw new RuntimeException("thowing exception to test transaction rollback");
    		}
    		healthInsuranceService.registerEmployeeHealthInsurance(employeeHealthInsurance);
    	}
    	
    	@Override
    	public void leaveOrganization(Employee employee, EmployeeHealthInsurance employeeHealthInsurance) { 
    		employeeService.deleteEmployeeById(employee.getEmpId());
    		healthInsuranceService.deleteEmployeeHealthInsuranceById(employeeHealthInsurance.getEmpId());
    	}
    }

`EmployeeService`的实现：

**输出**：

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTI5MzQzMjU_size_16_color_FFFFFF_t_70 7]

## 事务的传播行为`REQUIRES_NEW` ##

![\[外链图片转存失败(img-scz5W9d9-1566307900629)(C:\\Users\\liyongyong\\Desktop\\spring\_boot\_transaction\_propagation\_011.png)\]][img-scz5W9d9-1566307900629_C_Users_liyongyong_Desktop_spring_boot_transaction_propagation_011.png]

从图中的描述中可以知道，无论是直接被调用还是通过其他的`Service`来调用，事务的传播行为`REQUIRES_NEW`总是会创建自己的事务。

**代码**：

`OrganizationService`的实现如下：\`

package com.javainuse.service.impl;
     
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Service;
    import org.springframework.transaction.annotation.Transactional;
    import com.javainuse.model.Employee;
    import com.javainuse.model.EmployeeHealthInsurance;
    import com.javainuse.service.EmployeeService;
    import com.javainuse.service.HealthInsuranceService;
    import com.javainuse.service.OrganizationService;
    
    @Service
    @Transactional
    public class OrganzationServiceImpl implements OrganizationService { 
    	
    	@Autowired
    	EmployeeService employeeService;
    	
    	@Autowired
    	HealthInsuranceService healthInsuranceService;
    	
    	@Override
    	public void joinOrganization(Employee employee, EmployeeHealthInsurance employeeHealthInsurance) { 
    		employeeService.insertEmployee(employee);
    		
    		if (employee.getEmpId().equals("emp1")) { 
    			throw new RuntimeException("thowing exception to test transaction rollback");
    		}
    		
    		healthInsuranceService.registerEmployeeHealthInsurance(employeeHealthInsurance);
    	}
    	
    	@Override
    	public void leaveOrganization(Employee employee, EmployeeHealthInsurance employeeHealthInsurance) { 
    		employeeService.deleteEmployeeById(employee.getEmpId());
    		healthInsuranceService.deleteEmployeeHealthInsuranceById(employeeHealthInsurance.getEmpId());
    	}
    }

`EmployeeService`的实现：

**输出**：

![\[外链图片转存失败(img-JY3oHdqE-1566307900630)(C:\\Users\\liyongyong\\Desktop\\spring\_boot\_transaction\_propagation\_012.png)\]][img-JY3oHdqE-1566307900630_C_Users_liyongyong_Desktop_spring_boot_transaction_propagation_012.png]

![\[外链图片转存失败(img-1slkp2R0-1566307900631)(C:\\Users\\liyongyong\\Desktop\\spring\_boot\_transaction\_propagation\_013.png)\]][img-1slkp2R0-1566307900631_C_Users_liyongyong_Desktop_spring_boot_transaction_propagation_013.png]

## 事务的传播行为:`NEVER` ##

![\[外链图片转存失败(img-RmJGIdHY-1566307900632)(C:\\Users\\liyongyong\\Desktop\\spring\_boot\_transaction\_propagation\_014.png)\]][img-RmJGIdHY-1566307900632_C_Users_liyongyong_Desktop_spring_boot_transaction_propagation_014.png]

从上图可以知道，如果该方法直接被调用，它不会自己创建一个事务；如果该方法被其它的进行调用，如果调用的`Service`方法存在事务，那么就会抛出一个异常。  
否则，它不会创建事务，然后自己运行。

**代码**：

`OrganizationService`的实现如下：\`

package com.javainuse.service.impl;
    
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Service;
    import org.springframework.transaction.annotation.Transactional;
    import com.javainuse.model.Employee;
    import com.javainuse.model.EmployeeHealthInsurance;
    import com.javainuse.service.EmployeeService;
    import com.javainuse.service.HealthInsuranceService;
    import com.javainuse.service.OrganizationService;
    
    @Service
    @Transactional
    public class OrganzationServiceImpl implements OrganizationService { 
    
    	@Autowired
    	EmployeeService employeeService;
    	
    	@Autowired
    	HealthInsuranceService healthInsuranceService;
    	
    	@Override
    	public void joinOrganization(Employee employee, EmployeeHealthInsurance employeeHealthInsurance) { 
    		employeeService.insertEmployee(employee);
    		
    		if (employee.getEmpId().equals("emp1")) { 
    			throw new RuntimeException("thowing exception to test transaction rollback");
    		}
    		
    		healthInsuranceService.registerEmployeeHealthInsurance(employeeHealthInsurance);
    	}
    	
    	@Override
    	public void leaveOrganization(Employee employee, EmployeeHealthInsurance employeeHealthInsurance) { 
    		employeeService.deleteEmployeeById(employee.getEmpId());
    		healthInsuranceService.deleteEmployeeHealthInsuranceById(employeeHealthInsurance.getEmpId());
    	}
    }

`EmployeeService`实现：

**输出**：

![\[外链图片转存失败(img-XwOPQdEb-1566307900633)(C:\\Users\\liyongyong\\Desktop\\spring\_boot\_transaction\_propagation\_015.png)\]][img-XwOPQdEb-1566307900633_C_Users_liyongyong_Desktop_spring_boot_transaction_propagation_015.png]

## 事务的传播行为：`MANDATORY` ##

![\[外链图片转存失败(img-SNTbbJul-1566307900634)(C:\\Users\\liyongyong\\Desktop\\spring\_boot\_transaction\_propagation\_016.png)\]][img-SNTbbJul-1566307900634_C_Users_liyongyong_Desktop_spring_boot_transaction_propagation_016.png]

如果方法上指定的事务传播行为为`MANDATORY`,直接被调用的时候会抛出异常；如果被其它服务调用，存在事务传播行为就会沿用，否则就会抛出异常。

**代码**：

`OrganizationService`的实现如下：\`

`EmployeeService`实现：

**输出**：

![\[外链图片转存失败(img-zfBk8eDD-1566307900635)(C:\\Users\\liyongyong\\Desktop\\spring\_boot\_transaction\_propagation\_017.png)\]][img-zfBk8eDD-1566307900635_C_Users_liyongyong_Desktop_spring_boot_transaction_propagation_017.png]

## 事务传播行为总结 ##

*  **REQUIRED** ：一直在事务中执行，如果这里存在事务，它会使用已经存在的事务；如果不存在事务，它会新建一个事务。
 *  **SUPPORTS**： 它可能在事务中运行，也可能不在事务中运行。如果当前事务存在，则支持它。如果不存在，则在没有事务的情况下执行。
 *  **NOT\_SUPPORTED** ： 始终在没有事务的情况下执行。如果存在现有事务，则挂起该事务。
 *  **REQUIRES\_NEW** ： 始终在新事务中执行。如果存在现有事务，则挂起该事务。
 *  **NEVER** ： 在没有任何事务的情况下执行。如果存在现有事务，则引发异常
 *  **MANDATORY** ：始终在事务中执行。如果存在现有事务，则使用该事务。如果没有现有事务，它将引发异常。

> 原文链接：https://dzone.com/articles/spring-boot-transactions-tutorial-understanding-tr  
> 作者：Rida Shaikh  
> 译者：lee  
> ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTI5MzQzMjU_size_16_color_FFFFFF_t_70 8]

[Spring Boot]: https://dzone.com/articles/spring-boot-transaction-management-hello-world-exa
[Spring Boot 1]: https://www.javainuse.com/spring/boot-rollback
[Spring Boot 2]: https://www.javainuse.com/spring/boot-transaction-isolation
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTI5MzQzMjU_size_16_color_FFFFFF_t_70]: /images/20211013/1fdd50c31e2c4ff58f70c2ced509279a.png
[Organization Service]: https://www.javainuse.com/spring/boot-transaction
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTI5MzQzMjU_size_16_color_FFFFFF_t_70 1]: /images/20211013/b7febeaff8414498a630e77fb46ad33f.png
[20190820213248692.png]: /images/20211013/1547fd3bb8cc4ada9003691e1f592bfe.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTI5MzQzMjU_size_16_color_FFFFFF_t_70 2]: /images/20211013/fee5c1347d4a419ebf243fa23fd781e1.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTI5MzQzMjU_size_16_color_FFFFFF_t_70 3]: /images/20211013/68d6175c950947da812fcc00e874a881.png
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[img-CpzTju2a-1566307900626_C_Users_liyongyong_Desktop_spring_boot_transaction_propagation_009.png]: /images/20211013/96eec4811f5540199d671b870eed1f83.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTI5MzQzMjU_size_16_color_FFFFFF_t_70 7]: /images/20211013/9b8ed5ccf98a47fdb9d2376d9ea4366c.png
[img-scz5W9d9-1566307900629_C_Users_liyongyong_Desktop_spring_boot_transaction_propagation_011.png]: /images/20211013/e41efd8fa2334c23be9e92fd567e16ac.png
[img-JY3oHdqE-1566307900630_C_Users_liyongyong_Desktop_spring_boot_transaction_propagation_012.png]: /images/20211013/8a4147ea2abc468e8302f8f5e542558a.png
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[img-XwOPQdEb-1566307900633_C_Users_liyongyong_Desktop_spring_boot_transaction_propagation_015.png]: /images/20211013/2ec885bd87614b339d8d8464410798d4.png
[img-SNTbbJul-1566307900634_C_Users_liyongyong_Desktop_spring_boot_transaction_propagation_016.png]: /images/20211013/1729066360ae48f6b6c1d422c2c9f21a.png
[img-zfBk8eDD-1566307900635_C_Users_liyongyong_Desktop_spring_boot_transaction_propagation_017.png]: /images/20211013/d137166b9c9d44f7b0aacf4893e8487b.png
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