Transactional#Propagation事务传播行为

事务传播行为用来描述由某一个事务传播行为修饰的方法被嵌套进另一个方法时事务如何传播

一直对这7种传播行为记得不是特别清楚，也容易混淆，本文通过具体的例子来验证一下，每一种事务传播行为的实际效果。

tip: 参数String method是为了一次运行多个单元测试方法，可以直接从数据库知道哪个方法成功了

REQUIRED

@Transactional默认行为

在外围方法未开启事务的情况下Propagation.REQUIRED注解的内部方法会新开启自己的事务，且开启的事务相互独立，互不干扰。

外围方法开启事务的情况下Propagation.REQUIRED注解的内部方法会加入到外围方法的事务中，所有Propagation.REQUIRED修饰的内部方法和外围方法均属于同一事务，只要一个方法回滚，整个事务均回滚。

/**
 * @createDate:2019/6/14$14:02$
 * @author: Heyfan Xie
 */
@Service
public class RequiredService {

    private static final String TYPE = "required";

    @Autowired
    private RequiredUser1Service user1Service;

    @Autowired
    private RequiredUser2Service user2Service;


    /**
     * 外围方法没有事务
     *      调用有事务的方法1
     *      调用有事务的方法2
     * 外围方法抛出异常
     * ------------------
     * 结果:
     * 方法1执行成功
     * 方法2执行成功
     */
    public void notransactionExceptionRequiredRequried() {
        user1Service.addRequried(TYPE + 1);
        user2Service.addRequried(TYPE + 1);
        throw new RuntimeException();
    }


    /**
     * 外围方法没有事务
     *      调用有事务的方法1
     *      调用有事务的方法2
     *          方法2抛出异常
     * ------------------
     * 方法1执行成功
     * 方法2执行回滚
     */
    public void notransactionequiredRequriedException() {
        user1Service.addRequried(TYPE + 2);
        user2Service.addRequriedException(TYPE + 2);
    }

    /**
     * 外围方法有事务
     *      调用有事务的方法1
     *      调用有事务的方法2
     * 外围方法抛出异常
     * ------------------
     * 方法1执行回滚
     * 方法2执行回滚
     */
    @Transactional(propagation = Propagation.REQUIRED)
    public void transactionExceptionRequiredRequired(){
        user1Service.addRequried(TYPE + 3);
        user2Service.addRequried(TYPE + 3);
        throw new RuntimeException();
    }

    /**
     * 外围方法有事务
     *      调用有事务的方法1
     *      调用有事务的方法2
     *          方法2抛出异常
     * ------------------
     * 方法1执行回滚
     * 方法2执行回滚
     */
    @Transactional(propagation = Propagation.REQUIRED)
    public void transactionRequiredRequiredException(){
        user1Service.addRequried(TYPE + 4);
        user2Service.addRequriedException(TYPE + 4);
    }


    /**
     * 外围方法有事务
     *      调用有事务的方法1
     * try
     *      调用有事务的方法2
     *          方法2抛出异常
     * catch
     * ------------------
     * 方法1执行回滚
     * 方法2执行回滚
     */
    @Transactional(propagation = Propagation.REQUIRED)
    public void transactionRequiredRequiredExceptionTry(){
        user1Service.addRequried(TYPE + 5);
        try {
            user2Service.addRequriedException(TYPE + 5);
        } catch (Exception e) {
            System.out.println("方法回滚");
        }
    }
}

@Service
public class RequiredUser1Service {

    @Autowired
    private User1Repository user1Repository;

    @Transactional(propagation = Propagation.REQUIRED)
    public void addRequried(String method) {
        User1 user = new User1();
        user.setName(method + "张三");
        user1Repository.save(user);
    }
}

@Service
public class RequiredUser2Service {

    @Autowired
    private User2Repository user2Repository;

    @Transactional(propagation = Propagation.REQUIRED)
    public void addRequried(String method) {
        User2 user = new User2();
        user.setName(method + "李四");
        user2Repository.save(user);
    }


    @Transactional(propagation = Propagation.REQUIRED)
    public void addRequriedException(String method) {
        User2 user = new User2();
        user.setName(method + "王五");
        user2Repository.save(user);
        throw new RuntimeException();
    }
}

SUPPORTS

存在事务，就加入到事务中；不存在事务，就不创建自己的事务。

在外围方法未开启事务的情况下，Propagation.SUPPORTS注解的的方法会以无事务的方式运行。

在外围方法开启事务的情况下，Propagation.SUPPORTS注解的方法会加入当前事务。

@Service
public class SupportUser1Service {

    @Autowired
    private User1Repository user1Repository;

    @Transactional(propagation = Propagation.SUPPORTS)
    public void addSupport(String method) {
        User1 user = new User1();
        user.setName(method + "张三");
        user1Repository.save(user);
    }
}

@Service
public class SupportUser2Service {

    @Autowired
    private User2Repository user2Repository;

    @Transactional(propagation = Propagation.SUPPORTS)
    public void addSupport(String method) {
        User2 user = new User2();
        user.setName(method + "李四");
        user2Repository.save(user);
    }


    @Transactional(propagation = Propagation.SUPPORTS)
    public void addSupportException(String method) {
        User2 user = new User2();
        user.setName(method + "王五");
        user2Repository.save(user);
        throw new RuntimeException();
    }
}

MANDATORY

只能运行在一个已经存在的事务中，不能自己创建事务

在外围方法未开启事务的情况下，Propagation.MANDATORY注解的方法运行时会抛出错误:No existing transaction found for transaction marked with propagation 'mandatory'

在外围方法开启事务的情况下，Propagation.MANDATORY注解的方法会加入当前事务。

@Service
public class MandatoryUser1Service {

    @Autowired
    private User1Repository user1Repository;

    @Transactional(propagation = Propagation.MANDATORY)
    public void addMandatory(String method) {
        User1 user = new User1();
        user.setName(method + "张三");
        user1Repository.save(user);
    }
}

@Service
public class MandatoryUser2Service {

    @Autowired
    private User2Repository user2Repository;

    @Transactional(propagation = Propagation.MANDATORY)
    public void addMandatory(String method) {
        User2 user = new User2();
        user.setName(method + "李四");
        user2Repository.save(user);
    }


    @Transactional(propagation = Propagation.MANDATORY)
    public void addMandatoryException(String method) {
        User2 user = new User2();
        user.setName(method + "王五");
        user2Repository.save(user);
        throw new RuntimeException();
    }
}

REQUIRES_NEW

不管当前是否已经存在事务，都会新建一个事务

在外围方法未开启事务的情况下，Propagation.REQUIRES_NEW注解的内部方法会新开启自己的事务，且开启的事务相互独立，互不干扰。

在外围方法开启事务的情况下，Propagation.REQUIRES_NEW注解的内部方法依然会单独开启独立事务，且与外部方法事务也独立，内部方法之间、内部方法和外部方法事务均相互独立，互不干扰。

外围方法调用方式与REQUIRED一致，只是内部方法的注解改为了REQUIRES_NEW

@Service
public class RequiredNewUser1Service {

    @Autowired
    private User1Repository user1Repository;

    @Transactional(propagation = Propagation.REQUIRES_NEW)
    public void addRequriedNew(String method) {
        User1 user = new User1();
        user.setName(method + "张三");
        user1Repository.save(user);
    }
}

@Service
public class RequiredNewUser2Service {

    @Autowired
    private User2Repository user2Repository;

    @Transactional(propagation = Propagation.REQUIRES_NEW)
    public void addRequriedNew(String method) {
        User2 user = new User2();
        user.setName(method + "李四");
        user2Repository.save(user);
    }


    @Transactional(propagation = Propagation.REQUIRES_NEW)
    public void addRequriedNewException(String method) {
        User2 user = new User2();
        user.setName(method + "王五");
        user2Repository.save(user);
        throw new RuntimeException();
    }
}

NOT_SUPPORTED

当前方法不应该有事务，如果有事务存在，将它挂起，以无事务状态运行

不管外围方法是否有事务，NOT_SUPPORT都会以无事务的方式运行

外围方法调用方式与REQUIRED一致，只是内部方法的注解改为了NOT_SUPPORTED

@Service
public class NotSupportUser1Service {

    @Autowired
    private User1Repository user1Repository;

    @Transactional(propagation = Propagation.NOT_SUPPORTED)
    public void addNotSupport(String method) {
        User1 user = new User1();
        user.setName(method + "张三");
        user1Repository.save(user);
    }
}

@Service
public class NotSupportUser2Service {

    @Autowired
    private User2Repository user2Repository;

    @Transactional(propagation = Propagation.NOT_SUPPORTED)
    public void addNotSupport(String method) {
        User2 user = new User2();
        user.setName(method + "李四");
        user2Repository.save(user);
    }


    @Transactional(propagation = Propagation.NOT_SUPPORTED)
    public void addNotSupportException(String method) {
        User2 user = new User2();
        user.setName(method + "王五");
        user2Repository.save(user);
        throw new RuntimeException();
    }
}

NEVER

注释的业务方法绝对不能在事务中运行，否则抛出异常

在外围方法未开启事务的情况下，Propagation.NEVER注解的内部方法会以无事务的方式运行。

在外围方法开启事务的情况下，Propagation.NEVER注解的内部方法会因为不能加入到事务中，抛出异常Existing transaction found for transaction marked with propagation 'never'

@Service
public class NeverUser1Service {

    @Autowired
    private User1Repository user1Repository;

    @Transactional(propagation = Propagation.NEVER)
    public void addNever(String method) {
        User1 user = new User1();
        user.setName(method + "张三");
        user1Repository.save(user);
    }
}

@Service
public class NeverUser2Service {

    @Autowired
    private User2Repository user2Repository;

    @Transactional(propagation = Propagation.NEVER)
    public void addNever(String method) {
        User2 user = new User2();
        user.setName(method + "李四");
        user2Repository.save(user);
    }


    @Transactional(propagation = Propagation.NEVER)
    public void addNeverException(String method) {
        User2 user = new User2();
        user.setName(method + "王五");
        user2Repository.save(user);
        throw new RuntimeException();
    }
}

NESTED

在当前事务上开启一个子事务（Savepoint），如果提交主事务。那么连同子事务一同递交。如果提交子事务则保存点之前的所有事务都会被递交；如果当前不存在事务，就按REQUIRED方式

外围方法没有开启事务，Propagation.NESTED注解的内部方法会新开启自己的事务，且开启的事务相互独立，互不干扰。

外围方法开启事务，Propagation.NESTED注解的内部方法会在已存在的事务中开启一个子事务，抛出子事务的方法抛出异常可以被外围方法捕获，不会影响主事务；而外围方法的主事务回滚却会导致子事务也会回滚(与requried不同的是:nested的异常被捕获了不会影响外层方法的事务。)。

@Service
public class NestedUser1Service {

    @Autowired
    private User1Repository user1Repository;

    @Transactional(propagation = Propagation.NESTED)
    public void addNested(String method) {
        User1 user = new User1();
        user.setName(method + "张三");
        user1Repository.save(user);
    }
}

@Service
public class NestedUser2Service {

    @Autowired
    private User2Repository user2Repository;

    @Transactional(propagation = Propagation.NESTED)
    public void addNested(String method) {
        User2 user = new User2();
        user.setName(method + "李四");
        user2Repository.save(user);
    }


    @Transactional(propagation = Propagation.NESTED)
    public void addNestedException(String method) {
        User2 user = new User2();
        user.setName(method + "王五");
        user2Repository.save(user);
        throw new RuntimeException();
    }
}

如果按照上面的那种通过jpa的方式，当外围方法有事务的时候，运行会报错：JpaDialect does not support savepoints - check your JPA provider's capabilities
意思是通过jpa的方式不支持savepoints，
所以需要通过JdbcTemplte的方式运行,
这里另起了一个项目，spring boot 集成jdbc来测试:

@Service
public class NestedUser1Service {

    @Autowired
    private JdbcTemplate jdbcTemplate;

    @Transactional(propagation = Propagation.NESTED)
    public void addNested(String method) {
        String name = method + "张三";
        jdbcTemplate.execute("insert into user1(name) values('" + name + "')");
    }
}

@Service
public class NestedUser2Service {

    @Autowired
    private JdbcTemplate jdbcTemplate;

    @Transactional(propagation = Propagation.NESTED)
    public void addNested(String method) {
        String name = method + "李四";
        jdbcTemplate.execute("insert into user2(name) values('" + name + "')");
    }


    @Transactional(propagation = Propagation.NESTED)
    public void addNestedException(String method) {
        String name = method + "李四";
        jdbcTemplate.execute("insert into user2(name) values('" + name + "')");
        throw new RuntimeException();
    }
}

增加一个插入USER3在外层方法上，来验证回滚的范围，同时在所有的sql运行之后加入一行日志打印，指示插入操作是否执行了。

第一种方式：插入USER3在方法1方法2之后 （在最开头REQUIRED中的5种调用方式都按这种方式加入USER3的保存方法）

   @Autowired
    private JdbcTemplate jdbcTemplate;

    public void notransactionExceptionNotSupportNotSupport() {
        user1Service.addNested(TYPE + 1);
        user2Service.addNested(TYPE + 1);

        String name = TYPE + "1王五";
        jdbcTemplate.execute("insert into user3(name) values('" + name + "')");
        System.out.println("USER3 插入执行成功");
        throw new RuntimeException();
    }

第二种方式：插入USER3在方法1方法2 之前 （在最开头REQUIRED中的5种调用方式都按这种方式加入USER3的保存方法）

   @Autowired
    private JdbcTemplate jdbcTemplate;

    public void notransactionExceptionNotSupportNotSupport() {
        String name = TYPE + "1王五";
        jdbcTemplate.execute("insert into user3(name) values('" + name + "')");
        System.out.println("USER3 插入执行成功");

        user1Service.addNested(TYPE + 1);
        user2Service.addNested(TYPE + 1);

        throw new RuntimeException();
    }