前言
在最近的工作中,公司要把以前php寫的代碼先一部分轉爲java,裏面在一個方法裏面需要對多個數據源進行事務的管理。在這篇文章裏面我會介紹一些自己在解決這個問題時的一些思路和我的解決辦法。
問題引入:
由於是定時任務,需要在同一個方法裏面對多個數據源進行操作,但是因爲是不同數據源因此使用事務的會發現會報錯。
public int addWithTransation() {
int currentTimeMills = (int) Instant.now().getEpochSecond();
CreditRecord creditRecordA = new CreditRecord();
creditRecordA.setId(3L);
creditRecordA.setBeforeAmount(100);
creditRecordA.setChangeAmount(50);
creditRecordA.setAfterAmount(150);
creditRecordA.setCreateTime(currentTimeMills);
creditRecordA.setUpdateTime(currentTimeMills);
CreditRecord creditRecordB = new CreditRecord();
creditRecordB.setId(3L);
creditRecordB.setBeforeAmount(0);
creditRecordB.setChangeAmount(-50);
creditRecordB.setAfterAmount(-50);
creditRecordB.setCreateTime(currentTimeMills);
creditRecordB.setUpdateTime(currentTimeMills);
this.baseMapper.insert(creditRecordA);
creditRecordDB2Service.add(creditRecordB);
if(true){
throw new RuntimeException("拋出異常");
}
return 1;
}
這是個簡單的例子,在creditRecordDB1Service裏面使用另一個數據源的creditRecordDB2Service去add的時候,一旦添加了事務之後,發現只有creditRecordDB1Service的能夠回滾,creditRecordDB2Service的add方法是不能回滾的,且creditRecordDB2Service連接的是creditRecordDB1Service的數據源。
爲了弄清原理,我後面看了一下源碼。爲什麼加了事務之後,DataSource仍然是第一個Datasource.
從@Transation的註解裏面並沒有介紹從哪被攔截,但其實這與spring的aop有關。想要知道具體內容可參考這位大佬的文章,過程鏈條比較長,我仍在理清當中。
通過aop的註冊,找到TransactionAttributeSourcePointcut的代理類的matcher方法。
去找到方法是否有@Transation的註解。
獲取到目標bean匹配的增強器之後,會爲bean創建代理,在執行代理類的目標方法時,會調用Advisor的getAdvice獲取MethodInterceptor並執行其invoke方法,而BeanFactoryTransactionAttributeSourceAdvisor的getAdvice方法會返回我們在文章開始看到的爲其織入的另外一個bean,也就是TransactionInterceptor,它實現了MethodInterceptor。
在經過TransactionInterceptor後,經由AbstractPlatformTransactionManager來操作dataSource.在其繼承類DataSourceTransactionManager中的doBegin方法裏面,我們可以看到:
在與數據庫獲取連接的時候通過obtainDataSource().getConnection()拿到了DataSource來創建數據庫連接。
而DataSource在代理的時候被初始化,設置了DataSource.
從獲取數據庫的連接起,在這事務中只用一個數據源。
好,爲了解決使用事務的時候,在與數據庫連接時就定好了datasource不能改變的問題。我們通過配置指定datasource給指定的mapper就能解決這個問題了。
@Configuration
@MapperScan(basePackages = "com.example.multisource.dao.db1", sqlSessionFactoryRef = "db1SqlSessionFactory")
//通過將指定的mapper指定給特定sqlsessionFactory,解決事務下datasource不能變更問題
public class Db1Config {
@Bean(name = "db1")
@ConfigurationProperties(prefix = "spring.datasource.druid.db1" )
public DataSource db1() {
return DruidDataSourceBuilder.create().build();
}
// 事務控制器
@Bean(name = "db1TransactionManager")
@Primary
public DataSourceTransactionManager dp1TransactionManager() {
return new DataSourceTransactionManager(db1());
}
@Bean(name = "db1SqlSessionFactory")
@Primary
public SqlSessionFactory db1SqlSessionFactory(@Qualifier("db1") DataSource db1)
throws Exception {
final MybatisSqlSessionFactoryBean sessionFactory = new MybatisSqlSessionFactoryBean();
sessionFactory.setDataSource(db1);
sessionFactory.setMapperLocations(new PathMatchingResourcePatternResolver()
.getResources("classpath:/mapper/db1/*.xml"));
/*設置sql控制檯打印*/
com.baomidou.mybatisplus.core.MybatisConfiguration configuration = new com.baomidou.mybatisplus.core.MybatisConfiguration();
configuration.setLogImpl(StdOutImpl.class);
sessionFactory.setConfiguration(configuration);
return sessionFactory.getObject();
}
}
@Configuration
@MapperScan(basePackages = "com.example.multisource.dao.db2", sqlSessionFactoryRef = "db2SqlSessionFactory")
public class Db2Config {
@Bean(name = "db2")
@ConfigurationProperties(prefix = "spring.datasource.druid.db2" )
public DataSource db2() {
return DruidDataSourceBuilder.create().build();
}
@Bean(name = "db2TransactionManager")
@Primary
public DataSourceTransactionManager db2TransactionManager() {
return new DataSourceTransactionManager(db2());
}
@Bean(name = "db2SqlSessionFactory")
@Primary
public SqlSessionFactory db2SqlSessionFactory(@Qualifier("db2") DataSource db2)
throws Exception {
final MybatisSqlSessionFactoryBean sessionFactory = new MybatisSqlSessionFactoryBean();
sessionFactory.setDataSource(db2);
sessionFactory.setMapperLocations(new PathMatchingResourcePatternResolver()
.getResources("classpath:/mapper/db2/*.xml"));
/*設置sql控制檯打印*/
com.baomidou.mybatisplus.core.MybatisConfiguration configuration = new com.baomidou.mybatisplus.core.MybatisConfiguration();
configuration.setLogImpl(StdOutImpl.class);
sessionFactory.setConfiguration(configuration);
return sessionFactory.getObject();
}
}
解決報錯時回滾
網上看到了許多demo,但是大多有缺失或者說話只說一半。
我大體的思路就是@Transation這個註解不能duplicate,那我就自己寫一個自定義註解,來啓動兩個transationmanager來啓動兩個事務。
自定義註解(比較粗糙,如果有人想用的話得需要自己改一下,可以傳入數組來for循環啓動事務)
/**
* @ClassName DataSource
* @Author kris
* @Date 2020/5/29
**/
@Target({ElementType.METHOD,ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface MultiTm {
}
AOP
@Component
@Slf4j
@Aspect
@Order(-1)
public class TsetAspect {
@Pointcut("@within(com.example.multisource.annonation.MultiTm) || @annotation(com.example.multisource.annonation.MultiTm)")
public void TsetAspect(){
}
@Around(value = "TsetAspect()")
public Object transactionalGroupAspectArround(ProceedingJoinPoint pjp) throws Throwable{
// db1Manager.setDataSource((DataSource) SpringContextUtil.getBean("db1"));
// db2Manager.setDataSource((DataSource) SpringContextUtil.getBean("db2"));
DataSourceTransactionManager db1Manager = (DataSourceTransactionManager) SpringContextUtil
.getBean("db1TransactionManager");
TransactionStatus transactionDB1Status = db1Manager
.getTransaction(new DefaultTransactionDefinition());
DataSourceTransactionManager db2Manager = (DataSourceTransactionManager) SpringContextUtil
.getBean("db2TransactionManager");
TransactionStatus transactionDB2Status = db2Manager
.getTransaction(new DefaultTransactionDefinition());
try{
Object obj = pjp.proceed();
db2Manager.commit(transactionDB2Status);
//這點很重要,不這樣寫會transation is not active。因爲是db1Manager先啓動,db2Manager再啓動,因此db2Manager其實在包在了db1Manager裏面的,所以commit或者rollback的時候要先commit或rollback db2Manager。符合後進先出原則,可以Stack來優化。
db1Manager.commit(transactionDB1Status);
return obj;
}catch(Exception e){
log.info(e.getMessage());
db2Manager.rollback(transactionDB2Status);
db1Manager.rollback(transactionDB1Status);
return null;
}
}
}
這點很重要,不這樣寫會transation is not active。因爲是db1Manager先啓動,db2Manager再啓動,因此db2Manager其實在包在了db1Manager裏面的,所以commit或者rollback的時候要先commit或rollback db2Manager。符合後進先出原則,可以Stack來優化。
根據上面做點優化:
@Component
@Slf4j
@Aspect
@Order(-1)
public class TsetAspect {
@Pointcut("@within(com.example.multisource.annonation.MultiTm) || @annotation(com.example.multisource.annonation.MultiTm)")
public void TsetAspect(){
}
@Around(value = "TsetAspect() && @annotation(multiTm)")
public Object transactionalGroupAspectArround(ProceedingJoinPoint pjp, MultiTm multiTm) throws Throwable{
Stack<DataSourceTransactionManager> dataSourceTransactionManagerStack = new Stack<>();
Stack<TransactionStatus> transactionStatusStack = new Stack<>();
if (multiTm.transactionManagers().length<1){
log.info("[開啓事務失敗]:無指定多數據源管理器");
return null;
}
for(String transationMangaeName: multiTm.transactionManagers()){
DataSourceTransactionManager dbManager = (DataSourceTransactionManager) SpringContextUtil.getBean(transationMangaeName);
TransactionStatus transactionDBStatus = dbManager.getTransaction(new DefaultTransactionDefinition());
dataSourceTransactionManagerStack.push(dbManager);
transactionStatusStack.push(transactionDBStatus);
}
try{
Object obj = pjp.proceed();
while(!dataSourceTransactionManagerStack.isEmpty()){
dataSourceTransactionManagerStack.pop().commit(transactionStatusStack.pop());
}
return obj;
}catch(Exception e){
log.info(e.getMessage());
while(!dataSourceTransactionManagerStack.isEmpty()){
dataSourceTransactionManagerStack.pop().rollback(transactionStatusStack.pop());
}
return null;
}
}
}
@Target({ElementType.METHOD,ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface MultiTm {
String[] transactionManagers() default {};
}
@Override
@MultiTm(transactionManagers={"db1TransactionManager","db2TransactionManager"})
public int addWithTransation() {
int currentTimeMills = (int) Instant.now().getEpochSecond();
CreditRecord creditRecordA = new CreditRecord();
creditRecordA.setId(3L);
creditRecordA.setBeforeAmount(100);
creditRecordA.setChangeAmount(50);
creditRecordA.setAfterAmount(150);
creditRecordA.setCreateTime(currentTimeMills);
creditRecordA.setUpdateTime(currentTimeMills);
CreditRecord creditRecordB = new CreditRecord();
creditRecordB.setId(3L);
creditRecordB.setBeforeAmount(0);
creditRecordB.setChangeAmount(-50);
creditRecordB.setAfterAmount(-50);
creditRecordB.setCreateTime(currentTimeMills);
creditRecordB.setUpdateTime(currentTimeMills);
this.baseMapper.insert(creditRecordA);
creditRecordDB2Service.add(creditRecordB);
if(true){
throw new RuntimeException("拋出異常");
}
return 1;
}
實際運行方法
@MultiTm
// @Transactional("db1TransactionManager")
// @Transactional("db2TransactionManager")
public int addWithTransation() {
int currentTimeMills = (int) Instant.now().getEpochSecond();
CreditRecord creditRecordA = new CreditRecord();
creditRecordA.setId(3L);
creditRecordA.setBeforeAmount(100);
creditRecordA.setChangeAmount(50);
creditRecordA.setAfterAmount(150);
creditRecordA.setCreateTime(currentTimeMills);
creditRecordA.setUpdateTime(currentTimeMills);
CreditRecord creditRecordB = new CreditRecord();
creditRecordB.setId(3L);
creditRecordB.setBeforeAmount(0);
creditRecordB.setChangeAmount(-50);
creditRecordB.setAfterAmount(-50);
creditRecordB.setCreateTime(currentTimeMills);
creditRecordB.setUpdateTime(currentTimeMills);
this.baseMapper.insert(creditRecordA);
creditRecordDB2Service.add(creditRecordB);
if(true){
throw new RuntimeException("拋出異常");
}
return 1;
}
Github demo連接-各位同學也可以已此做個參考,有問題也可以和我聯繫,歡迎大家指導一下。看demo裏面的controller下的mixAddWithTransation方法即可
參考鏈接