Spring 下默认事务机制中@Transactional 无效的原因

Spring中 @Transactional 注解的限制
1. 同一个类中, 一个nan-transactional的方法去调用transactional的方法, 事务会失效

If you use (default) Spring Proxy AOP, then all AOP functionality provided by Spring (like @Transational) will only be taken into account if the call goes through the proxy. -- This is normally the case if the annotated method is invoked from another bean.

2. 在private方法上标注transactional, 事务无效

When using proxies, you should apply the @Transactional annotation only to methods with public visibility. If you do annotate protected, private or package-visible methods with the @Transactional annotation, no error is raised, but the annotated method does not exhibit the configured transactional settings. Consider the use of AspectJ (see below) if you need to annotate non-public methods.

这里有一个详细的说明 http://stackoverflow.com/questions/4396284/does-spring-transactional-attribute-work-on-a-private-method

测试代码

TestCase01.java

package com.rockbb.test.api.service;


public interface TestCase01 {
    void init();
    void clean();
    void txnInLocalPrivate();
    void txnInLocalPublic();
    void txnInOpenPublic();
    void txnInOpenPublicByInvokePrivate();
    void txnInOpenPublicByInvokePublic();
}

TestCase01Impl.java

package com.rockbb.test.impl.service.impl;

import com.rockbb.test.api.dto.AccountDTO;
import com.rockbb.test.api.dto.AccountDetailDTO;
import com.rockbb.test.api.service.TestCase01;
import com.rockbb.test.impl.mapper.AccountDetailMapper;
import com.rockbb.test.impl.mapper.AccountMapper;
import org.springframework.stereotype.Repository;
import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;

import javax.annotation.Resource;
import java.math.BigDecimal;

@Repository("testCase01")
public class TestCase01Impl implements TestCase01 {
    @Resource(name="accountMapper")
    private AccountMapper accountMapper;
    @Resource(name="accountDetailMapper")
    private AccountDetailMapper accountDetailMapper;

    @Resource(name="testCase01")
    private TestCase01 testCase01;

    /**
     * 无效, 未回退
     *
     * 结论: 在私有方法上加事务注解无效
     */
    @Override
    public void txnInLocalPrivate() {
        localPrivate();
    }

    /**
     * 无效, 未回退
     *
     * 结论: 在公有方法上事务注解, 再通过接口方法调用, 无效
     */
    @Override
    public void txnInLocalPublic() {
        localPublic();
    }

    /**
     * 有效, 无论下面调用的是否是私有方法
     *
     * 结论: 在接口方法上加事务, 无论下面调用的是否是私有方法, 都有效
     */
    @Override
    @Transactional(propagation = Propagation.REQUIRED, readOnly = false)
    public void txnInOpenPublic() {
        localPrivate();
    }

    @Override
    public void txnInOpenPublicByInvokePrivate() {

    }

    /**
     *
     * 结论: 普通接口方法直接调用同类带事务的方法, 无效. 通过接口调用则有效
     */
    @Override
    public void txnInOpenPublicByInvokePublic() {
        //txnInOpenPublic(); // 无效
        testCase01.txnInOpenPublic(); // 有效
    }

    @Override
    public void init() {
        accountMapper.truncate();
        for (int i = 0; i < 10; i++) {
            BigDecimal amount = BigDecimal.valueOf(i * 10);
            add(String.valueOf(i), BigDecimal.ZERO);
            increase(String.valueOf(i), BigDecimal.valueOf(100 + i));
        }
    }

    @Override
    public void clean() {
        accountMapper.truncate();
    }

    @Transactional(propagation = Propagation.REQUIRED, readOnly = false)
    private void localPrivate() {
        AccountDTO dto = new AccountDTO().initialize();
        dto.setId("test");
        dto.setAmount(BigDecimal.ZERO);
        accountMapper.insert(dto);
        throw new RuntimeException("localPrivate");
    }

    @Transactional(propagation = Propagation.REQUIRED, readOnly = false)
    public void localPublic() {
        AccountDTO dto = new AccountDTO().initialize();
        dto.setId("test");
        dto.setAmount(BigDecimal.ZERO);
        accountMapper.insert(dto);
        throw new RuntimeException("localPublic");
    }

    public void openPublic() {
        AccountDTO dto = new AccountDTO().initialize();
        dto.setId("test");
        dto.setAmount(BigDecimal.ZERO);
        accountMapper.insert(dto);
        throw new RuntimeException("openPublic");
    }

    private int add(String id, BigDecimal amount) {
        AccountDTO dto = new AccountDTO().initialize();
        dto.setId(id);
        dto.setAmount(amount);
        return accountMapper.insert(dto);
    }

    private int increase(String id, BigDecimal amount) {
        AccountDTO dto = accountMapper.select(id);
        AccountDetailDTO detail = new AccountDetailDTO().initialize();
        detail.setAmount(amount);
        detail.setPreAmount(dto.getAmount());
        dto.setAmount(dto.getAmount().add(amount));
        detail.setPostAmount(dto.getAmount());
        if (accountMapper.update(dto) != 1) {
            throw new RuntimeException();
        }
        return accountDetailMapper.insert(detail);
    }
}

TestCase02.java

package com.rockbb.test.api.service;

public interface TestCase02 {
    void txnInOpenPublicByPublic();
    void txnInOpenPublicByPrivate();
}

TestCase02Impl.java

package com.rockbb.test.impl.service.impl;

import com.rockbb.test.api.service.TestCase01;
import com.rockbb.test.api.service.TestCase02;
import org.springframework.stereotype.Repository;

import javax.annotation.Resource;

@Repository("testCase02")
public class TestCase02Impl implements TestCase02 {
    @Resource(name="testCase01")
    private TestCase01 testCase01;

    /**
     * 有效
     *
     * 结论: 在接口方法上加事务, 再被他类的接口方法调用, 无论此接口方法是否加事务, 都有效
     */
    @Override
    public void txnInOpenPublicByPublic() {
        testCase01.txnInOpenPublic();
    }

    /**
     * 有效
     *
     * 结论: 在接口方法上加事务, 再被他类的私有方法调用后, 依然有效
     */
    @Override
    public void txnInOpenPublicByPrivate() {
        localPrivate();
    }

    private void localPrivate() {
        testCase01.txnInOpenPublic();
    }
}

测试样例 AccountCheckTest.java

package com.rockbb.test.test;

import com.rockbb.test.api.service.TestCase01;
import com.rockbb.test.api.service.TestCase02;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

import javax.annotation.Resource;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = {"/spring/spring-commons.xml"})
public class AccountCheckTest {
    private static final Logger logger = LoggerFactory.getLogger(AccountCheckTest.class);
    @Resource(name="testCase01")
    private TestCase01 testCase01;
    @Resource(name="testCase02")
    private TestCase02 testCase02;

    @Test
    public void test01() {
        testCase01.init();
        try {
            testCase01.txnInLocalPrivate();
        } catch (Exception e) {
            logger.error(e.getMessage(), e);
        }
    }

    @Test
    public void test02() {
        testCase01.init();
        try {
            testCase01.txnInLocalPublic();
        } catch (Exception e) {
            logger.error(e.getMessage(), e);
        }
    }

    @Test
    public void test03() {
        testCase01.init();
        try {
            testCase01.txnInOpenPublic();
        } catch (Exception e) {
            logger.error(e.getMessage(), e);
        }
    }

    @Test
    public void test04() {
        testCase01.init();
        try {
            testCase02.txnInOpenPublicByPublic();
        } catch (Exception e) {
            logger.error(e.getMessage(), e);
        }
    }

    @Test
    public void test05() {
        testCase01.init();
        try {
            testCase02.txnInOpenPublicByPrivate();
        } catch (Exception e) {
            logger.error(e.getMessage(), e);
        }
    }

    @Test
    public void test06() {
        testCase01.init();
        try {
            testCase01.txnInOpenPublicByInvokePublic();
        } catch (Exception e) {
            logger.error(e.getMessage(), e);
        }
    }
}

结论

1. @Transactional 加于private方法, 无效
2. @Transactional 加于未加入接口的public方法, 再通过普通接口方法调用, 无效
3. @Transactional 加于接口方法, 无论下面调用的是private或public方法, 都有效
4. @Transactional 加于接口方法后, 被本类普通接口方法直接调用, 无效
5. @Transactional 加于接口方法后, 被本类普通接口方法通过接口调用, 有效
6. @Transactional 加于接口方法后, 被它类的接口方法调用, 有效
7. @Transactional 加于接口方法后, 被它类的私有方法调用后, 有效
8. 总结: Transactional是否生效, 仅取决于是否加载于接口方法, 并且是否通过接口方法调用(而不是本类调用)

@Transactional(readOnly = true) 的含义

执行单条查询语句时, 数据库默认支持SQL执行期间的读一致性. 而执行多条查询语句(例如统计查询, 报表查询)时, 多条查询SQL必须保证整体的读一致性, 否则在每条查询之间数据可能发生变动, 导致最终的查询结果出现数据不一致的错误，此时应该启用事务支持.

read-only="true"表示该事务为只读事务, 上面的多条查询可以使用只读事务. 由于只读事务不存在对数据的修改, 因此数据库将会为只读事务提供一些优化手段, 例如Oracle对于只读事务不启动回滚段, 不记录回滚log.

在JDBC中指定只读事务的办法为 connection.setReadOnly(true), Hibernate中指定只读事务的办法为 session.setFlushMode(FlushMode.NEVER). 在Spring的Hibernate封装中，指定只读事务的办法为bean配置文件中 prop属性增加“read-Only”.  或者用注解方式@Transactional(readOnly=true)

在将事务设置成只读后, 相当于将数据库设置成只读数据库, 此时若要进行写的操作会报错.