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Cloud Native Java-OReilly 2017-ReadingNotes.md

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Cloud Native Java-OReilly 2017-ReadingNotes.md

Basics

  • SaaS的12 Factor：

Bootcamp: Introducing Spring Boot and Cloud Foundry

  • Spring Initializr：http://start.spring.io
    • 配置好依赖后，下载得到一个demo.zip
    • $ ./mvnw clean install
      • 靠！当时我就震惊了。话说我之前用brew安装的maven似乎没派上用场啊？？
    • $ ./mvnw spring-boot:run
      • 默认8080端口，但是怎么需要登录？fuck
    • 接下来完成对应的DemoApplication类及其tests类（靠！陡峭的学习曲线）
      • 虽然Spring提供了代码模板，但是实际上也给Java开发人员强制了一堆编码规范...
      • REST直接处理url path与对象／服务的映射（感觉我还是更怀念Node.js/express里简单的方式...）
  • The Spring Tool Suite is an Eclipse-based IDE that packages up ...
    • IDE用IntelliJ？还是Eclipse／NetBeans？当然也可以用Sublime，但那样没有代码自动完成功能...
    • Spring guides？？
  • configuration类
    • class ApplicationConfiguration（我觉得这里倒是可以和AngularJs的DI进行对比？）
      • @Configuration
      • @Bean(destroyMethod = "shutdown") //import org.springframework.context.annotation.Bean;
    • “By default, a Spring bean is singleton scoped.”
    • 提升：@ComponentScan：扫描所有标记了@Component的bean类（servive）
    • 把DataSource转换为JdbcTemplate？
     @Bean
 JdbcTemplate jdbcTemplate(DataSource dataSource) {
 	return new JdbcTemplate(dataSource);
 }
  • AOP
  • 自动配置
    • revisit之前的DemoApplication类实现代码：...
      • @RestController（相当于struts2里面的Action类）
      • JdbcTemplateAutoConfiguration？
  • Pivotal Cloud Foundry：AWS上架设的PaaS？
    • cf create-service p-mysql 100mb bootcamp-customers-mysql
    • ...
    • manifest.yml
     The Cloud Foundry Java client is built on the Pivotal Reactor 3.0 project. Reactor, in turn, underpins the reactive web runtime in Spring Framework 5.
    • “almost entirely non-blocking”？Java的nio是非阻塞的吗？异步的？？
    • Mono／Flux？
     import org.reactivestreams.Publisher;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;

总的来说，信息量有点大啊？不知道Spring Boot的使用现在流行否？要是升级到5.0 Reactive Streams呢？

Twelve-Factor Application Style Configuration

  • PropertyPlaceholderConfigurer: 把XML中的配置替换为.properties
  • 环境抽象与@Value
    • @PropertySource("some.properties") 类标注
    • 需要注入PropertySourcesPlaceholderConfigurer as static bean（因为它作为BeanFactoryPostProcessor，需要在bean实例化之前执行）
    • @Value("${configuration.projectName}") 可以标注到构造函数、属性、setter
  • Profiles：依据不同环境分组的beans
  • Spring Boot will automatically load properties from a hierarchy of well-known places by default.（但问题是记住所有的先后顺序也很费脑～～）
  • @EnableConfigurationProperties 与 @ConfigurationProperties("configuration") //把.properties映射到一个Java类
  • The Spring Cloud Config Server（依据REST API来加载配置？registry服务器？）、
    • 用 @EnableConfigServer 标注 Application类
    • Spring Cloud Config Clients：
      • 从“src/main/resources/bootstrap.(properties,yml)”加载spring.application.name（服务名称）
    • 验证config server：http://localhost:8888/SERVICE/master
    • 安全：包含org.springframework.boot: spring-boot-starter-security，并定义security.user.name／password
    • 可refresh的配置
      • @RefreshScope：当bean收到“ApplicationContext event of the type RefreshScopeRefreshedEvent”
      • Actuator endpoints？？

Testing

  • 单元测试
    • ApplicationTests.java
      • 类标注：@SpringBootTest
      • 类标注：@RunWith(SpringRunner.class) 特定于JUnit
      • 方法标注：@Test，Assert.assertXxx(...)
  • 集成测试
    • Test Slices：选择性激活，不必整个ApplicationContext
      • @JsonTest 测试json序列化反序列化
      • @WebMvcTest 测试单个的controller
        • @Autowired private MockMvc mvc; //模仿一个web客户端？
      • @DataJpaTest 测试repository
      • @RestClientTest 测试某个service类
    • Mocking
      • @MockBean
      • @Autowired用于constructor注入吗
      • Optional.ofNullable ？（Java8里的容器类？和Streams API结合使用）
      • servlet容器：@SpringBootTest’s webEnvironment attribute
  • End-to-End Testing
    • 从最终用户的角度测试，确保release组件的替换不会引发问题
    • 分布式系统下的状态维护：“The key concern is to design testing conditions that make sure that state is always eventually consistent”
    • Consumer-Driven Contract Testing（CDC-T）*
    • Spring Cloud Contract
      • stub：用Groovy DSL编写？通常在“src/main/test/java/resources” //生成假数据？不如用Node.js/express做一个mock server好了
      • consumer测试类标注：@AutoConfigureStubRunner(ids = { "cnj:user-microservice:+:stubs:8081" }, workOffline = true)

The Forklifted Application

  • Buildpacks
  • 容器化应用
    • 不够安全，docker允许指定完全的root fs？（buildpack运行在trusted环境？）
  • backing services：provisioning（服务的creation？）
  • 迁移遗留的JavaEE系统：Spring’s HTTP Invoker：tunneling RMI over HTTP
  • Spring Session：依赖于SPI处理同步：backend包括“Redis, Apache Geode, and Hazelcast”
    • add org.springframework.boot:spring-boot-starter-redis and org.springframework.session:spring-session（groupId：artifactId）to Boot app
    • UUID uid = Optional.ofNullable(UUID.class.cast(session.getAttribute("uid"))).orElse(UUID.randomUUID()); ...
  • 发邮件：SendGrid？
  • 身份管理*
    • “Technologies like Okta are important because they are fully hosted and managed for you”

REST APIs

  • Leonard Richardson put forth his REST maturity model to help grade an API’s compliance with REST’s principles:
    • Level 0: The swamp of POX
    • Level 1: Resources
    • Level 2: HTTP verbs
    • Level 3: Hypermedia controls (HATEOAS, for Hypermedia as the Engine of Application State)
  • Simple REST APIs with Spring MVC: 
     @RestController
 @RequestMapping("/v1/customers")
 public class CustomerRestController {
 	...

 	@GetMapping(value = "/{id}")
  	ResponseEntity<Customer> get(@PathVariable Long id) {
   		return this.customerRepository.findById(id).map(ResponseEntity::ok)
    			.orElseThrow(() -> new CustomerNotFoundException(id));
  	}
  • 内容协商
    • 处理上传：返回一个Callable<ResponseEntity<?>>
     File uploads may block and monopolize the Servlet container’s threadpool. Spring MVC backgrounds Callable<T> handler method returns values to a configured Executor thread pool and frees up the container’s thread until the response is ready.
    • 其他异步返回：WebAsyncTask、DeferredResult
    • Google Protocol Buffers
      • 定制的HttpMessageConverter
  • 错误处理
    • 中心化处理：use a @ControllerAdvice component.
      • @ExceptionHandler
  • Hypermedia
  • API Versioning

Routing

  • DiscoveryClient抽象（由service registry实现）
    • 服务注册：Netflix Eureka（作者怎么老是在强调CF的自动化clustering operations？）
    • 客户端LB：Netflix Ribbon
      • @Autowired public LoadBalancedRestTemplateCLR(@LoadBalanced RestTemplate restTemplate) { ... } //用起来倒是蛮简单的
    • CF Route服务（skip for now）

Edge Services

  • API Gateway
    • “Netflix Feign is a library that makes deriving service clients as simple as an interface definition and some conventions.”
  • Filtering and Proxying with Netflix Zuul（为什么不直接用Nginx呢）
    • “the /routes Actuator endpoint”
    • HTML5 client：CORS（基于clientId判断是否允许，唉？这让人想起了Zero-Trust模型...）
    • filters：pre、routing、post、error
  • 安全：OAuth（skip for now）
    • Build an OAuth-Secured SPA

管理Data

  • JPA provides the abstraction and implementations for vendor-specific ORM technologies, such as Hibernate and DataNucleus.
    • 你不必一定要用JPA：MyBatis、JOOQ
    • Auditing with JPA：BaseEntity：记录创建时间和每次的更新时间（？）
  • Spring Data MongoDB
  • Spring Data Neo4j
  • Spring Data Redis

这一部分许多内容及代码示例只能暂时忽略了。注意：JPA的例子似乎没有考虑后端数据如何做水平切分。不过对于一家公司的业务容量来说，可能没这个必要？

Messageing

  • Message brokers like Apache Kafka, RabbitMQ, ActiveMQ, or MQSeries act as the repository and hub for messages.
  • 事件驱动的架构 with Spring Integration
    • MessageChannel & Message
  • The centerpiece of Spring Cloud Stream is a binding.

批处理与任务

  • Spring Batch：工业标准？真扯淡

本章内容还挺多的，但不太有什么兴趣。skip。

数据集成

  • CAP
  • 隔离失败和优雅降级
    • circuit breaks
      • Netflix Hystrix
      • Spring Retry
  • Saga模式（乐观事务模型？）
    • 事务：至多1次；补偿事务：至少1次。？
  • CQRS（不就是读写分离嘛）
  • Spring Cloud Data Flow
    • SEDA
    • Streams：source、processor、sink
    • Tasks

The Observable System

  • Actuator endpoints：/info /metrics /beans /health ...
  • Metrics
    • TSDB: “Ganglia, Graphite, OpenTSDB, InfluxDB, and Prometheus”
      • 图形显示：“Graphite Composer, and Grafana”
  • Health Checks
  • Audit Events
  • Application Logging
  • Distributed Tracing
    • OpenZipkin
  • Dashboards
  • Remediation

Service Brokers

  • Releasing with BOSH

连续交付

  • Pivotal Concourse

附录

  • Spring Boot用于Java EE
    • Dependency Injection with JSR 330 (and JSR 250)
      • ... “so Spring founder Rod Johnson and Guice founder Bob Lee proposed JSR 330”
    • Building REST APIs with JAX-RS (Jersey)