分布式_事务_02_2PC框架raincat源码解析

一、前言

上一节已经将raincat demo工程运行起来了，这一节来分析下raincat的源码

二、协调者启动过程

主要就是在启动类中通过如下代码来启动 netty

nettyService.start()

三、参与者启动过程

1.参与者启动时序图

参与者在启动过程中，主要做了如下4件事：

（1）保存SpringContext上下文

（2）通过加载spi，来使用用户自定义配置

（3）启动Netty客户端，与txManager进行连接，并且维持心跳。

（4）启动事务补偿任务，建表，定时补偿。

（5）启动事务事件发布器。

如下图：

2.保存Spring上下文

源码见  SpringBeanUtils 类，设置Spring 上下文，并提供spring  bean 的注册与获取方法。

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.raincat.core.helper;

import org.springframework.context.ConfigurableApplicationContext;

/**
 * SpringBeanUtils.
 * @author xiaoyu
 */
public final class SpringBeanUtils {

    private static final SpringBeanUtils INSTANCE = new SpringBeanUtils();

    private ConfigurableApplicationContext cfgContext;

    private SpringBeanUtils() {
        if (INSTANCE != null) {
            throw new Error("error");
        }
    }

    /**
     * get SpringBeanUtils.
     * @return SpringBeanUtils
     */
    public static SpringBeanUtils getInstance() {
        return INSTANCE;
    }

    /**
     * acquire spring bean.
     *
     * @param type type
     * @param <T>  class
     * @return bean
     */
    public <T> T getBean(final Class<T> type) {
        return cfgContext.getBean(type);
    }

    /**
     * register bean in spring ioc.
     * @param beanName bean name
     * @param obj bean
     */
    public void registerBean(final String beanName, final Object obj) {
        cfgContext.getBeanFactory().registerSingleton(beanName, obj);
    }

    /**
     * set application context.
     * @param cfgContext application context
     */
    public void setCfgContext(final ConfigurableApplicationContext cfgContext) {
        this.cfgContext = cfgContext;
    }
}

3.加载spi

    /**
     * load spi.
     *
     * @param txConfig {@linkplain TxConfig}
     */
    private void loadSpi(final TxConfig txConfig) {
        //spi  serialize
        final SerializeProtocolEnum serializeProtocolEnum
                = SerializeProtocolEnum.acquireSerializeProtocol(txConfig.getSerializer());
        final ServiceLoader<ObjectSerializer> objectSerializers
                = ServiceBootstrap.loadAll(ObjectSerializer.class);
        final ObjectSerializer serializer =
                StreamSupport.stream(objectSerializers.spliterator(), false)
                        .filter(s -> Objects.equals(s.getScheme(), serializeProtocolEnum.getSerializeProtocol()))
                        .findFirst().orElse(new KryoSerializer());

        //spi  RecoverRepository support
        final CompensationCacheTypeEnum compensationCacheTypeEnum
                = CompensationCacheTypeEnum.acquireCompensationCacheType(txConfig.getCompensationCacheType());

        final ServiceLoader<TransactionRecoverRepository> recoverRepositories
                = ServiceBootstrap.loadAll(TransactionRecoverRepository.class);
        final TransactionRecoverRepository repository =
                StreamSupport.stream(recoverRepositories.spliterator(), false)
                        .filter(r -> Objects.equals(r.getScheme(), compensationCacheTypeEnum.getCompensationCacheType()))
                        .findFirst().orElse(new JdbcTransactionRecoverRepository());
        //将compensationCache实现注入到spring容器
        repository.setSerializer(serializer);
        SpringBeanUtils.getInstance().registerBean(TransactionRecoverRepository.class.getName(), repository);
    }

（1）作用

SPI的全名为Service Provider Interface，该机制其实就是为接口寻找服务实现类

（2）如何使用

当服务的提供者，提供了服务接口的一种实现之后，在jar包的META-INF/services/目录里同时创建一个以服务接口命名的文件。
该文件里就是实现该服务接口的具体实现类。
而当外部程序装配这个模块的时候，就能通过该jar包META-INF/services/里的配置文件找到具体的实现类名，并装载实例化，完成模块的注入。

八、参考资料

1.Java之SPI机制