背景

出于某些性能上的要求我们基于当前代码做了读写分离读写分离规划

方案

我们使用Spring的AbstractRoutingDataSource来做读写分离

该类提供了determineCurrentLookupKey进行db的获取

可以粗略的认为AbstractRoutingDataSource为一个组合的dataSource

而我们可以根据业务来进行dataSource的选择

那么很简单我们可以考虑在特殊的业务下面进行切换随后db在getConnection时将会使用到真实的dataSource

/**
 * Retrieve the current target DataSource. Determines the
 * {@link #determineCurrentLookupKey() current lookup key}, performs
 * a lookup in the {@link #setTargetDataSources targetDataSources} map,
 * falls back to the specified
 * {@link #setDefaultTargetDataSource default target DataSource} if necessary.
 * @see #determineCurrentLookupKey()
 */
protected DataSource determineTargetDataSource() {
   Assert.notNull(this.resolvedDataSources, "DataSource router not initialized");
   Object lookupKey = determineCurrentLookupKey();
   DataSource dataSource = this.resolvedDataSources.get(lookupKey);
   if (dataSource == null && (this.lenientFallback || lookupKey == null)) {
      dataSource = this.resolvedDefaultDataSource;
   }
   if (dataSource == null) {
      throw new IllegalStateException("Cannot determine target DataSource for lookup key [" + lookupKey + "]");
   }
   return dataSource;
}
 
/**
 * Determine the current lookup key. This will typically be
 * implemented to check a thread-bound transaction context.
 * <p>Allows for arbitrary keys. The returned key needs
 * to match the stored lookup key type, as resolved by the
 * {@link #resolveSpecifiedLookupKey} method.
 */
protected abstract Object determineCurrentLookupKey();

很明显当lookupKey为空可以fallback到默认dataSource

<bean id="dataSource-normal" class="org.springframework.jndi.JndiObjectFactoryBean">
    <property name="jndiName" value="java:comp/env/jdbc/erp"/>
</bean>
 
 
<bean id="dataSource-slow" class="org.springframework.jndi.JndiObjectFactoryBean">
    <property name="jndiName" value="java:comp/env/jdbc/erp-slow"/>
</bean>
 
<bean id="dataSource-report" class="org.springframework.jndi.JndiObjectFactoryBean">
    <property name="jndiName" value="java:comp/env/jdbc/erp-saiku"/>
</bean>
<bean id="dataSource-readOnly" class="org.springframework.jndi.JndiObjectFactoryBean">
    <property name="jndiName" value="java:comp/env/jdbc/erp-readOnly"/>
</bean>
 
<bean id="dataSource" class="com.air.tqb.aop.DataSourceRouter">
    <property name="defaultTargetDataSource" ref="dataSource-normal"/>
    <property name="targetDataSources">
        <map>
            <entry key="normal" value-ref="dataSource-normal"/>
            <entry key="slow" value-ref="dataSource-slow"/>
            <entry key="report" value-ref="dataSource-report"/>
            <entry key="readOnly" value-ref="dataSource-readOnly"/>
        </map>
    </property>
</bean>

因此我们可以定义多个数据源这样可以根据对应的key来设置到不同的数据源当然当没有key返回时将返回normal数据源

可是由于变量共享【DataSourceRouter需要从某个方法获取当前的dataSource类型】那么普通变量必将导致dataSource会被其他线程操作

因此此处考虑threadLocal 源码分析之ThreadLocal

因此很明显方案比较明确

定义本地线程变量存储当前db路由key
根据某些方法名称或者注解等设置特定的db 路由key
根据当前线程变量路由key返回特定的dataSource

这样一个简单的方案就出现了根据不同的routingkey返回不同的connection

实现

定义db类型枚举

public enum DataSourceType {
 
    NORMAL("normal"), SLOW("slow"), REPORT("report"),READONLY("readOnly");
 
    DataSourceType(String value) {
        this.value = value;
    }
 
    private String value;
 
    public String getValue() {
        return value;
    }
}

新建本地线程变量

public static String getDataSourceRouting() {
    return DATASOURCE_ROUTING_TL.get();
}
 
public static void setDataSourceRouting(String routingKey) {
    DATASOURCE_ROUTING_TL.set(routingKey);
}

根据方法注解或者名称等设置对应routing key

@Aspect
@Component
@Order(Ordered.HIGHEST_PRECEDENCE + 2)
public class DataSourceRoutingAspect {
 
    private static final Log logger = LogFactory.getLog(DataSourceRoutingAspect.class);
 
 
    @Around("execution(public * com.air.tqb.service..*.*(..)) && @annotation(com.air.tqb.annoate.DataSource) && @annotation(dataSource)")
    public Object setDataSource(ProceedingJoinPoint joinPoint, DataSource dataSource) throws Throwable {
        DataSourceType dataSourceType = dataSource.value();
        try {
            WxbStatic.setDataSourceRouting(dataSourceType.getValue());
            if (logger.isDebugEnabled()) {
                logger.debug("DataSourceType[" + dataSourceType.getValue() + "] set.");
            }
            return joinPoint.proceed();
        } finally {
            WxbStatic.clearDataSourceRouting();
            if (logger.isDebugEnabled()) {
                logger.debug("DataSourceType[" + dataSourceType.getValue() + "] remove.");
            }
        }
 
    }
 
 
    @Around("execution(public * com.air.tqb.service.report..*.*(..))")
    public Object setDataSource(ProceedingJoinPoint joinPoint) throws Throwable {
        DataSourceType dataSourceType = DataSourceType.READONLY;
        try {
            WxbStatic.setDataSourceRouting(dataSourceType.getValue());
            if (logger.isDebugEnabled()) {
                logger.debug("report DataSourceType[" + dataSourceType.getValue() + "] set.");
            }
            return joinPoint.proceed();
        } finally {
            WxbStatic.clearDataSourceRouting();
            if (logger.isDebugEnabled()) {
                logger.debug("report DataSourceType[" + dataSourceType.getValue() + "] remove.");
            }
        }
 
    }
}

根据本地线程变量返回特定的routingKey

public class DataSourceRouter extends AbstractRoutingDataSource {
    @Override
    protected Object determineCurrentLookupKey() {
        return WxbStatic.getDataSourceRouting();
    }
}

实战

根据某些注解设置不同的数据源比如

@Override
@DataSource(DataSourceType.READONLY)
public PageResult<CustomerCarVO> getPageCustomerCarList(CustomerCarVO customerCarVO, int curPage) throws Exception {
    return super.getPageList("getPageCustomerCarList", "getCountBy", customerCarVO, curPage, AppConstant.MIDPAGESIZE);
}

读写分离实现

背景

方案

实现

实战

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