seata数据源代理

seata数据源代理流程

1-SeataDataSourceAutoConfiguration

创建SeataAutoDataSourceProxyCreator对象，默认seata模式为AT

2-SeataAutoDataSourceProxyCreator

• 设置advisor用于来接实现DataSource接口的实现类
  

  public SeataAutoDataSourceProxyCreator(boolean useJdkProxy, String[] excludes, String dataSourceProxyMode) {
        setProxyTargetClass(!useJdkProxy);
        this.excludes = new HashSet<>(Arrays.asList(excludes));
        // AT
        this.dataSourceProxyMode = dataSourceProxyMode;
        this.advisors = buildAdvisors(dataSourceProxyMode);
    }
  
    private Object[] buildAdvisors(String dataSourceProxyMode) {
        Advice advice = new SeataAutoDataSourceProxyAdvice(dataSourceProxyMode);
        return new Object[]{new DefaultIntroductionAdvisor(advice)};
    }
  

• 重写wrapIfNecessary，设置数据源代理
  

  @Override
    protected Object wrapIfNecessary(Object bean, String beanName, Object cacheKey) {
        // we only care DataSource bean
        if (!(bean instanceof DataSource)) {
            return bean;
        }
  
        // when this bean is just a simple DataSource, not SeataDataSourceProxy
        LOGGER.error("bean={}", bean.getClass().getSimpleName());
        if (!(bean instanceof SeataDataSourceProxy)) {
            Object enhancer = super.wrapIfNecessary(bean, beanName, cacheKey);
            // this mean this bean is either excluded by user or had been proxy before
            if (bean == enhancer) {
                return bean;
            }
            // else, build proxy,  put <origin, proxy> to holder and return enhancer
            DataSource origin = (DataSource) bean;
            SeataDataSourceProxy proxy = buildProxy(origin, dataSourceProxyMode);
            DataSourceProxyHolder.put(origin, proxy);
            LOGGER.error("bean2origin={}, proxy={}, proxy.targetDataSource={}", origin.getClass().getSimpleName(), proxy.getClass().getSimpleName(), proxy.getTargetDataSource());
            return enhancer;
        }
  
        /*
         * things get dangerous when you try to register SeataDataSourceProxy bean by yourself!
         * if you insist on doing so, you must make sure your method return type is DataSource,
         * because this processor will never return any subclass of SeataDataSourceProxy
         */
        LOGGER.warn("Manually register SeataDataSourceProxy(or its subclass) bean is discouraged! bean name: {}", beanName);
        SeataDataSourceProxy proxy = (SeataDataSourceProxy) bean;
        DataSource origin = proxy.getTargetDataSource();
        LOGGER.error("TargetDataSource={}", origin.getClass().getSimpleName());
        Object originEnhancer = super.wrapIfNecessary(origin, beanName, cacheKey);
        // this mean origin is either excluded by user or had been proxy before
        if (origin == originEnhancer) {
            return origin;
        }
        // else, put <origin, proxy> to holder and return originEnhancer
        DataSourceProxyHolder.put(origin, proxy);
        return originEnhancer;
    }
  

3-SeataAutoDataSourceProxyAdvice

所有实现DataSource接口的实现类都会再次被拦截，调用invoke方法

@Override
    public Object invoke(MethodInvocation invocation) throws Throwable {
        // check whether current context is expected
        if (!inExpectedContext()) {
            return invocation.proceed();
        }

        Method method = invocation.getMethod();
        String name = method.getName();
        Class<?>[] parameterTypes = method.getParameterTypes();

        Method declared;
        try {
            declared = DataSource.class.getDeclaredMethod(name, parameterTypes);
        } catch (NoSuchMethodException e) {
            // mean this method is not declared by DataSource
            return invocation.proceed();
        }

        // switch invoke instance to its proxy
        DataSource origin = (DataSource) invocation.getThis();
        SeataDataSourceProxy proxy = DataSourceProxyHolder.get(origin);
        Object[] args = invocation.getArguments();
        LOGGER.error("执行类={}，执行方法={},方法参数={}", proxy.getClass().getSimpleName(), declared.getName(), args);
        return declared.invoke(proxy, args);
    }