Spring多数据源事务

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：

github.com/xbmchina/mu…

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>
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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。

public class DataSourceKey {
    /** 数据库源one*/
    public static final String ONE= "one";

    /** 数据库源two*/
    public static final String TWO= "two";
}
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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。

public class DynamicDataSourceContextHolder {
	
	private static ThreadLocal<Object> CONTEXT_HOLDER = ThreadLocal.withInitial(() -> DataSourceKey.MASTER.getName());
	
	public static List<Object> dataSourceKeys = new ArrayList<Object>();
	
	public static void setDataSourceKey(String key){
		CONTEXT_HOLDER.set(key);
	}
	
	public static Object getDataSourceKey(){
		return CONTEXT_HOLDER.get();
	}
	
	public static void clearDataSourceKey(){
		CONTEXT_HOLDER.remove();
	}
	
	public static Boolean containDataSourceKey(String key){
		return dataSourceKeys.contains(key);
	}
		
}
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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。

public class DynamicDataSource extends AbstractRoutingDataSource {

    /**
     * 取得当前使用那个数据源。
     */
    @Override
    protected Object determineCurrentLookupKey() {
        return DataSourceContextHolder.getDatasourceType();
    }

}
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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")
public class MyBatisConfig extends AbstractDataSourceConfig {

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

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

    static final String MAPPER_LOCATION = "classpath:mapper/*.xml";


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

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



    @Bean("dynamicDataSource")
    public DynamicDataSource dynamicDataSource(@Qualifier("dataSourceOne")DataSource dataSourceOne, @Qualifier("dataSourceTwo")DataSource dataSourceTwo) {
        Map<Object, Object> targetDataSources = new HashMap<>();
        targetDataSources.put("one",dataSourceOne);
        targetDataSources.put("two",dataSourceTwo);

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

    @Bean(name = "sqlSessionFactoryOne")
    public SqlSessionFactory sqlSessionFactoryOne(@Qualifier("dataSourceOne") DataSource dataSource)
            throws Exception {
        return createSqlSessionFactory(dataSource);
    }

    @Bean(name = "sqlSessionFactoryTwo")
    public SqlSessionFactory sqlSessionFactoryTwo(@Qualifier("dataSourceTwo") DataSource dataSource)
            throws Exception {
        return createSqlSessionFactory(dataSource);
    }




    @Bean(name = "sqlSessionTemplate")
    public CustomSqlSessionTemplate sqlSessionTemplate(@Qualifier("sqlSessionFactoryOne")SqlSessionFactory factoryOne, @Qualifier("sqlSessionFactoryTwo")SqlSessionFactory factoryTwo) throws Exception {
        Map<Object,SqlSessionFactory> sqlSessionFactoryMap = new HashMap<>();
        sqlSessionFactoryMap.put("one",factoryOne);
        sqlSessionFactoryMap.put("two",factoryTwo);

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

    /**
     * 创建数据源
     * @param dataSource
     * @return
     */
    private SqlSessionFactory createSqlSessionFactory(DataSource dataSource) throws Exception{
        SqlSessionFactoryBean bean = new SqlSessionFactoryBean();
        bean.setDataSource(dataSource);
        bean.setVfs(SpringBootVFS.class);
        bean.setTypeAliasesPackage(ALIASES_PACKAGE);
        bean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources(MAPPER_LOCATION));
        return bean.getObject();
    }
}

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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;

public class DataSourceAspect {
    protected static final ThreadLocal<String> preDatasourceHolder = new ThreadLocal<>();

    /**
     * @param clazz
     * @param name
     * @return
     */
    private static Method 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();
        }
        return null;
    }

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

    }

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

    }

    /**
     * @param jp
     * @return
     */
    public String 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()")
    public void restoreDataSourceAfterMethodExecution() {
        DataSourceContextHolder.setDatasourceType(preDatasourceHolder.get());
        preDatasourceHolder.remove();
    }

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

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

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

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