spring的事务传播机制

嫌弃内容代码复杂的可直接看思维导图大纲即可

基本概念

指的就是当一个事务方法被另一个事务方法调用时，这个事务方法应该如何进行

七种行为和测试

PROPAGATION_REQUIRED

默认，当前存在事务，则加入该事务；不存在事务，创建新事务。

public class PropagationService {

    @Autowired
    private
    PropagationMapper propagationMapper;

    @Autowired
    @Lazy
    PropagationService propagationService;

    @Transactional(rollbackFor = Exception.class)
    public void insertPropagationA() throws Exception {
        Propagation propagationA = Propagation.builder()
                .type("Propagation.REQUIRED")
                .comment("propagationA").build();
        propagationMapper.insert(propagationA);
        propagationServiceSelf.insertPropagationB();
        throw new Exception();
    }

    @Transactional(rollbackFor = Exception.class,propagation = org.springframework.transaction.annotation.Propagation.REQUIRED)
    public void insertPropagationB() throws Exception {
        Propagation propagationB = Propagation.builder()
                .type("Propagation.REQUIRED")
                .comment("propagationB").build();
        Propagation propagationBB = Propagation.builder()
                .type("Propagation.REQUIRED")
                .comment("propagationBB").build();
        propagationMapper.insert(propagationB);
        propagationMapper.insert(prop

@Test
    //Given A传播行为required 和B为required,WHE A发生异常,THEN A插入失败，B插入失败
    public void testRequired() throws Exception {
        propagationService.insertPropagationA();
    }

PROPAGATION_REQUIRED_NEW

始终以新的事务运行，当前存在事务，则挂起原事务；不存在事务，创建新事务

@Test
    //Given 同样代码更改B为required_new, WHE A发生异常, THEN B插入成功，A插入失败
    public void testRequiredNew() throws Exception {
        propagationService.insertPropagationA();
    }

PROPAGATION_SUPPORTS

支持当前事务。当前存在事务，则支持该事务；不存在事务，以非事务方式执行

    @Test
    //Given 更改B为required_supports, A不开启事物， WHE B发生异常, THEN A、B插入成功BB失败;A开启事物因为有异常发生全失败
    public void testRequiredSupports() throws Exception {
        propagationService.insertPropagationA();
    }

//@Transactional(rollbackFor = Exception.class)
    public void insertPropagationA() throws Exception {
        Propagation propagationA = Propagation.builder()
                .type("Propagation.REQUIRED")
                .comment("propagationA").build();
        propagationMapper.insert(propagationA);
        propagationServiceSelf.insertPropagationB();
        throw new Exception();
    }

    @Transactional(rollbackFor = Exception.class,propagation = org.springframework.transaction.annotation.Propagation.SUPPORTS)
    public void insertPropagationB() throws Exception {
        Propagation propagationB = Propagation.builder()
                .type("Propagation.REQUIRED")
                .comment("propagationB").build();
        Propagation propagationBB = Propagation.builder()
                .type("Propagation.REQUIRED")
                .comment("propagationBB").build();
        propagationMapper.insert(propagationB);
        int a =  1/0;
        propagationMapper.insert(propagationBB);
    }

PROPAGATION_NO_SUPPORTED

非事务方式执行，当前存在事务，则挂起该事务

    @Test
    //Given 更改B为required_not_supports, A开启事物， WHEN A发生异常, THEN A插入失败、B插入成功
    public void testRequiredNotSupports() throws Exception {
        propagationService.insertPropagationA();
    }

    @Transactional(rollbackFor = Exception.class)
    public void insertPropagationA() throws Exception {
        Propagation propagationA = Propagation.builder()
                .type("Propagation.REQUIRED")
                .comment("propagationA").build();
        propagationMapper.insert(propagationA);
        propagationServiceSelf.insertPropagationB();
        throw new Exception();
    }

    @Transactional(rollbackFor = Exception.class,propagation = org.springframework.transaction.annotation.Propagation.NOT_SUPPORTED)
    public void insertPropagationB() throws Exception {
        Propagation propagationB = Propagation.builder()
                .type("Propagation.REQUIRED")
                .comment("propagationB").build();
        Propagation propagationBB = Propagation.builder()
                .type("Propagation.REQUIRED")
                .comment("propagationBB").build();
        propagationMapper.insert(propagationB);
        propagationMapper.insert(propagationBB);
    }

PROPAGATION_NEVER

非事务方式执行，当前存在事务，则抛出异常();

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

at org.springframework.transaction.support.AbstractPlatformTransactionManager.handleExistingTransaction(AbstractPlatformTransactionManager.java:413)

    @Transactional(rollbackFor = Exception.class)
    public void insertPropagationA() throws Exception {
        Propagation propagationA = Propagation.builder()
                .type("Propagation.REQUIRED")
                .comment("propagationA").build();
        propagationMapper.insert(propagationA);
        propagationServiceSelf.insertPropagationB();
        //throw new Exception();
    }

    @Transactional(rollbackFor = Exception.class,propagation = org.springframework.transaction.annotation.Propagation.NEVER)
    public void insertPropagationB() throws Exception {
        Propagation propagationB = Propagation.builder()
                .type("Propagation.REQUIRED")
                .comment("propagationB").build();
        Propagation propagationBB = Propagation.builder()
                .type("Propagation.REQUIRED")
                .comment("propagationBB").build();
        propagationMapper.insert(propagationB);
        propagationMapper.insert(propagationBB);
    }

    @Test
    //Given 更改B为required_never, A开启事物， 调用方法B时报错
    public void testRequiredNever() throws Exception {
        propagationService.insertPropagationA();
    }

PROPAGATION_NESTED

当前存在事务，则嵌套在该事务下起新事务执行；不存在事务，创建新事务。

    @Test
    //Given 更改B为required_nested, A开启事物， 调用方法B,后抛出异常,都失败;A开启事物，调用方法B，B抛出异常，A catch，A成功，B失败
    public void testRequiredNested() throws Exception {
        propagationService.insertPropagationA();
    }

    @Transactional(rollbackFor = Exception.class)
    public void insertPropagationA() throws Exception {
        Propagation propagationA = Propagation.builder()
                .type("Propagation.REQUIRED")
                .comment("propagationA").build();
        propagationMapper.insert(propagationA);
        try{
            propagationServiceSelf.insertPropagationB();
        }catch(Exception e){

        }
    }

    @Transactional(rollbackFor = Exception.class,propagation = org.springframework.transaction.annotation.Propagation.NESTED)
    public void insertPropagationB() throws Exception {
        Propagation propagationB = Propagation.builder()
                .type("Propagation.REQUIRED")
                .comment("propagationB").build();
        Propagation propagationBB = Propagation.builder()
                .type("Propagation.REQUIRED")
                .comment("propagationBB").build();
        propagationMapper.insert(propagationB);
        int a = 1/0;
        propagationMapper.insert(propagationBB);
    }

PROPAGATION_MANDATORY

事务方式运行，当前不存在事务，则抛出异常

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

at org.springframework.transaction.support.AbstractPlatformTransactionManager.getTransaction(AbstractPlatformTransactionManager.java:362)

//@Transactional(rollbackFor = Exception.class)
    public void insertPropagationA() throws Exception {
        Propagation propagationA = Propagation.builder()
                .type("Propagation.REQUIRED")
                .comment("propagationA").build();
        propagationMapper.insert(propagationA);
        propagationServiceSelf.insertPropagationB();

    }

    @Transactional(rollbackFor = Exception.class,propagation = org.springframework.transaction.annotation.Propagation.MANDATORY)
    public void insertPropagationB() throws Exception {
        Propagation propagationB = Propagation.builder()
                .type("Propagation.REQUIRED")
                .comment("propagationB").build();
        Propagation propagationBB = Propagation.builder()
                .type("Propagation.REQUIRED")
                .comment("propagationBB").build();
        propagationMapper.insert(propagationB);
        propagationMapper.insert(propagationBB);
    }

    @Test
    //Given 更改B为required_mandatory, WHEN A不开启事物，调用方法B, THEN调用B抛出异常;
    public void testRequiredMandatory() throws Exception {
        propagationService.insertPropagationA();
    }

Transactional失效

spring的事物是基于AOP代理实现的，也就是说背@Transactional修饰的方法所在类会有一个代理类，通过这个代理类实现的。并且也需要底层数据库支持事物，还需要在同一个库中，多个方法运行调用需要在同一个线程中。基于这情况大概失效场景分为两部分

非代理类方向

• 数据库引擎不支持索引如MyISAm

• 数据源未配置事物管理器

• 数据库分布式部署，需要Seata技术解决

• 多线程，两个事务方法不在同一个线程

代理类方向

• 类未交给spring，代理自然无法生成

• 自身调用，相当于this，代理类未生效

• 事务方法修饰如非public、final、static修饰导致不能被代理

• 异常类型错误，声明式事务默认对runtimeException、Error才可以触发回滚

• 对抛出的异常，catch后处理不当。如吞了异常。

• 设置了错误的传播行为

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