Spring多数据源事务

用户3467126

发布于 2020-01-13 09:31:24

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前言

接着上一篇文章Spring事务基础，本文主要是关于Spring多数据源的情况下如何保证事务正常回滚。这里也是使用大家广泛使用的jta-atomikos进行，我只是做一些总结方便以后自己直接拿来用。

如果你非常着急，那么可以直接下载这个项目看看即可：

https://github.com/xbmchina/multidatatsource-druid/tree/master/multidatasource-atomikos

总体思路

网上已经有很多关于jta-atomikos的相关文章，本文可能有点绕，不容易看得懂，所以在此描述一下思路：

1、配置mybatis以及druid使得其能够实现连接多个数据源。 2、通过自定义数据源，将多个数据源的事务整合成一个SqlSession，进而实现统一管理事务。 3、利用AOP以及自定义注解实现动态的切换数据源（即是A的dao应该连接A的数据源。）。

更多详细了解可以查看源码，或者下面的简单介绍。

添加依赖

主要依赖就是jta-atomikos，其余的mybatis与druid的相关依赖就不粘贴了。

<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-aop</artifactId>
</dependency>
<!--atomikos transaction management-->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-jta-atomikos</artifactId>
</dependency>

配置多个数据源

1、首先，定义一个枚举来说明一下当前数据源实例key有哪些。

publicclassDataSourceKey{
/** 数据库源one*/
publicstaticfinalString ONE= "one";

/** 数据库源two*/
publicstaticfinalString TWO= "two";
}

2、其次，使用ThreadLocal存储当前使用数据源实例的key。ThreadLocal实例化的时候给一个master的默认值，也就是默认数据源是master数据源。

publicclassDynamicDataSourceContextHolder{

privatestaticThreadLocal<Object> CONTEXT_HOLDER = ThreadLocal.withInitial(() -> DataSourceKey.MASTER.getName());

publicstaticList<Object> dataSourceKeys = newArrayList<Object>();

publicstaticvoid setDataSourceKey(String key){
        CONTEXT_HOLDER.set(key);
}

publicstaticObject getDataSourceKey(){
return CONTEXT_HOLDER.get();
}

publicstaticvoid clearDataSourceKey(){
        CONTEXT_HOLDER.remove();
}

publicstaticBoolean containDataSourceKey(String key){
return dataSourceKeys.contains(key);
}

}

3、重写AbstractRoutingDataSource的determineCurrentLookupKey方法，在访问数据库时会调用该类的 determineCurrentLookupKey() 方法获取数据库实例的 key。

publicclassDynamicDataSourceextendsAbstractRoutingDataSource{

/**
     * 取得当前使用那个数据源。
     */
@Override
protectedObject determineCurrentLookupKey() {
returnDataSourceContextHolder.getDatasourceType();
}

}

4、通过SqlSessionFactory 重新组装整合多个数据源，最终返回sqlSessionTemplate给到dao层。

@Configuration
@MapperScan(basePackages = MyBatisConfig.BASE_PACKAGE, sqlSessionTemplateRef = "sqlSessionTemplate")
publicclassMyBatisConfigextendsAbstractDataSourceConfig{

//mapper模式下的接口层
staticfinalString BASE_PACKAGE = "cn.xbmchina.multidatasourceatomikos.mapper";

//对接数据库的实体层
staticfinalString ALIASES_PACKAGE = "ccn.xbmchina.multidatasourceatomikos.domain";

staticfinalString MAPPER_LOCATION = "classpath:mapper/*.xml";


@Primary
@Bean(name = "dataSourceOne")
publicDataSource dataSourceOne(Environment env) {
String prefix = "spring.datasource.druid.one.";
return getDataSource(env,prefix,"one");
}

@Bean(name = "dataSourceTwo")
publicDataSource dataSourceTwo(Environment env) {
String prefix = "spring.datasource.druid.two.";
return getDataSource(env,prefix,"two");
}



@Bean("dynamicDataSource")
publicDynamicDataSource dynamicDataSource(@Qualifier("dataSourceOne")DataSource dataSourceOne, @Qualifier("dataSourceTwo")DataSource dataSourceTwo) {
Map<Object, Object> targetDataSources = newHashMap<>();
        targetDataSources.put("one",dataSourceOne);
        targetDataSources.put("two",dataSourceTwo);

DynamicDataSource dataSource = newDynamicDataSource();
        dataSource.setTargetDataSources(targetDataSources);
        dataSource.setDefaultTargetDataSource(dataSourceOne);
return dataSource;
}

@Bean(name = "sqlSessionFactoryOne")
publicSqlSessionFactory sqlSessionFactoryOne(@Qualifier("dataSourceOne") DataSource dataSource)
throwsException{
return createSqlSessionFactory(dataSource);
}

@Bean(name = "sqlSessionFactoryTwo")
publicSqlSessionFactory sqlSessionFactoryTwo(@Qualifier("dataSourceTwo") DataSource dataSource)
throwsException{
return createSqlSessionFactory(dataSource);
}




@Bean(name = "sqlSessionTemplate")
publicCustomSqlSessionTemplate sqlSessionTemplate(@Qualifier("sqlSessionFactoryOne")SqlSessionFactory factoryOne, @Qualifier("sqlSessionFactoryTwo")SqlSessionFactory factoryTwo) throwsException{
Map<Object,SqlSessionFactory> sqlSessionFactoryMap = newHashMap<>();
        sqlSessionFactoryMap.put("one",factoryOne);
        sqlSessionFactoryMap.put("two",factoryTwo);

CustomSqlSessionTemplate customSqlSessionTemplate = newCustomSqlSessionTemplate(factoryOne);
        customSqlSessionTemplate.setTargetSqlSessionFactorys(sqlSessionFactoryMap);
return customSqlSessionTemplate;
}

/**
     * 创建数据源
     * @param dataSource
     * @return
     */
privateSqlSessionFactory createSqlSessionFactory(DataSource dataSource) throwsException{
SqlSessionFactoryBean bean = newSqlSessionFactoryBean();
        bean.setDataSource(dataSource);
        bean.setVfs(SpringBootVFS.class);
        bean.setTypeAliasesPackage(ALIASES_PACKAGE);
        bean.setMapperLocations(newPathMatchingResourcePatternResolver().getResources(MAPPER_LOCATION));
return bean.getObject();
}
}

5、使用AOP，以自定义注解注解在的方法为切点，动态切换数据源

import cn.xbmchina.multidatasourceatomikos.annotations.TargetDataSource;
import cn.xbmchina.multidatasourceatomikos.db.DataSourceContextHolder;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.After;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.annotation.Pointcut;

import java.lang.reflect.Method;

publicclassDataSourceAspect{
protectedstaticfinalThreadLocal<String> preDatasourceHolder = newThreadLocal<>();

/**
     * @param clazz
     * @param name
     * @return
     */
privatestaticMethod findUniqueMethod(Class<?> clazz, String name) {
Class<?> searchType = clazz;
while(searchType != null) {
Method[] methods = (searchType.isInterface() ? searchType.getMethods() : searchType.getDeclaredMethods());
for(Method method : methods) {
if(name.equals(method.getName())) {
return method;
}
}
            searchType = searchType.getSuperclass();
}
returnnull;
}

@Pointcut("@annotation(cn.xbmchina.multidatasourceatomikos.annotations.TargetDataSource)")
protectedvoid datasourceAspect() {

}

/**
     * 根据@TargetDataSource的属性值设置不同的dataSourceKey,以供DynamicDataSource
     */
@Before("datasourceAspect()")
publicvoid changeDataSourceBeforeMethodExecution(JoinPoint jp) {
String key = determineDatasource(jp);
if(key == null) {
DataSourceContextHolder.setDatasourceType(null);
return;
}
        preDatasourceHolder.set(DataSourceContextHolder.getDatasourceType());
DataSourceContextHolder.setDatasourceType(key);

}

/**
     * @param jp
     * @return
     */
publicString determineDatasource(JoinPoint jp) {
String methodName = jp.getSignature().getName();
Class targetClass = jp.getSignature().getDeclaringType();
String dataSourceForTargetClass = resolveDataSourceFromClass(targetClass);
String dataSourceForTargetMethod = resolveDataSourceFromMethod(targetClass, methodName);
String resultDS = determinateDataSource(dataSourceForTargetClass, dataSourceForTargetMethod);
return resultDS;
}

/**
     *
     */
@After("datasourceAspect()")
publicvoid restoreDataSourceAfterMethodExecution() {
DataSourceContextHolder.setDatasourceType(preDatasourceHolder.get());
        preDatasourceHolder.remove();
}

/**
     * @param targetClass
     * @param methodName
     * @return
     */
privateString resolveDataSourceFromMethod(Class targetClass, String methodName) {
Method m = findUniqueMethod(targetClass, methodName);
if(m != null) {
TargetDataSource choDs = m.getAnnotation(TargetDataSource.class);
return resolveDataSourceName(choDs);
}
returnnull;
}

/**
     * @param classDS
     * @param methodDS
     * @return
     */
privateString determinateDataSource(String classDS, String methodDS) {
return methodDS == null? classDS : methodDS;
}

/**
     * @param targetClass
     * @return
     */
privateString resolveDataSourceFromClass(Class targetClass) {
TargetDataSource classAnnotation = (TargetDataSource) targetClass.getAnnotation(TargetDataSource.class);
returnnull!= classAnnotation ? resolveDataSourceName(classAnnotation) : null;
}

/**
     * @param ds
     * @return
     */
privateString resolveDataSourceName(TargetDataSource ds) {
return ds == null? null: ds.value();
}
}