spring的事務傳播機制

嫌棄內容程式碼複雜的可直接看思維導圖大綱即可

基本概念

指的就是當一個事務方法被另一個事務方法呼叫時，這個事務方法應該如何進行

七種行為和測試

PROPAGATION_REQUIRED

預設，當前存在事務，則加入該事務；不存在事務，建立新事務。

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傳播行為required 和B為required,WHE A發生異常,THEN A插入失敗，B插入失敗
    public void testRequired() throws Exception {
        propagationService.insertPropagationA();
    }

PROPAGATION_REQUIRED_NEW

始終以新的事務執行，當前存在事務，則掛起原事務；不存在事務，建立新事務

@Test
    //Given 同樣程式碼更改B為required_new, WHE A發生異常, THEN B插入成功，A插入失敗
    public void testRequiredNew() throws Exception {
        propagationService.insertPropagationA();
    }

PROPAGATION_SUPPORTS

支援當前事務。當前存在事務，則支援該事務；不存在事務，以非事務方式執行

    @Test
    //Given 更改B為required_supports, A不開啟事物， WHE B發生異常, THEN A、B插入成功BB失敗;A開啟事物因為有異常發生全失敗
    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

非事務方式執行，當前存在事務，則掛起該事務

    @Test
    //Given 更改B為required_not_supports, A開啟事物， WHEN A發生異常, THEN A插入失敗、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

非事務方式執行，當前存在事務，則丟擲異常();

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為required_never, A開啟事物， 呼叫方法B時報錯
    public void testRequiredNever() throws Exception {
        propagationService.insertPropagationA();
    }

PROPAGATION_NESTED

當前存在事務，則巢狀在該事務下起新事務執行；不存在事務，建立新事務。

    @Test
    //Given 更改B為required_nested, A開啟事物， 呼叫方法B,後丟擲異常,都失敗;A開啟事物，呼叫方法B，B丟擲異常，A catch，A成功，B失敗
    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

事務方式執行，當前不存在事務，則丟擲異常

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為required_mandatory, WHEN A不開啟事物，呼叫方法B, THEN呼叫B丟擲異常;
    public void testRequiredMandatory() throws Exception {
        propagationService.insertPropagationA();
    }

Transactional失效

spring的事物是基於AOP代理實現的，也就是說背@Transactional修飾的方法所在類會有一個代理類，通過這個代理類實現的。並且也需要底層資料庫支援事物，還需要在同一個庫中，多個方法執行呼叫需要在同一個執行緒中。基於這情況大概失效場景分為兩部分

非代理類方向

• 資料庫引擎不支援索引如MyISAm

• 資料來源未設定事物管理器

• 資料庫分散式部署，需要Seata技術解決

• 多執行緒，兩個事務方法不在同一個執行緒

代理類方向

• 類未交給spring，代理自然無法生成

• 自身呼叫，相當於this，代理類未生效

• 事務方法修飾如非public、final、static修飾導致不能被代理

• 異常型別錯誤，宣告式事務預設對runtimeException、Error才可以觸發回滾

• 對丟擲的異常，catch後處理不當。如吞了異常。

• 設定了錯誤的傳播行為