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
3ff7
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

转载于:https://www.cnblogs.com/shirui/p/9674428.html