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Spring学习笔记

书籍参考： Spring in action，跟随书中项目Taco Cloud

  • IDEA无法自动更新的解决办法

    • 打开Build project automatically
    • CTRL+SHIFT+A
    • 输入Registry
    • 勾选compiler.automake.allow.when.app.running
    • 勾选ide.windowSystem.autoShowProcessPopup，含义不明
    • 参考

  • LiveReload插件安装

    • Firefox插件链接失效
    • Chrome安装，需要点击使图标中心变为实心点
      • Site Access需要设置为On all sites或者On specific sites，On Click会报错

  • 应用的classpath的根目录下有schema.sql/data.sql文件，会在应用开始时被执行

    • 应该将schema.sql和data.sql放在src/main/resources

  • http://localhost:8080/h2-console

    • JDBC URL: jdbc:h2:mem:testdb
    • 其他默认

  • 输入符合信用卡Credit Card Number验证的值比较麻烦，可以用 http://www.getcreditcardnumbers.com/ 生成

  • 书中很多地方讲解不完整需要自行解决才能顺利运行

  • JPA domain-specific language (DSL)

    • verb+[subject]+By+predicate
    • findByDeliveryZip()
    • readOrdersByDeliveryZipAndPlacedAtBetween()
    • many operators

  • JdbcTemplate切换到JPA注意事项

    • 需要删除schema.sql和data.sql
    • 需要执行clean，否则构建后的sql文件不会被清除，会导致执行错误

  • Spring Security

    • User store
      • in memory
      • database
      • LDAP, TODO: LDAP暂时忽略
    • register
    • login
    • logout
    • WebSecurityConfigurerAdapter
    • User & UserRepository
    • UserDetailsService
    • Controller中确定User
      • Authentication @AuthenticationPrincipal Principal

  • JPA utf-8 设置

    • MySQL charset需要设置为utf-8，见start-mysql.sh
    • spring.datasource.url需要设置为jdbc:mysql://localhost:13306/tacocloud?useUnicode=yes&characterEncoding=utf-8
    • MySQL charset设置为utf8mb4会报错，字符串类型的primary key提示key too long，最大为767bytes，待解决
      • 原因varchar(255)，utf8mb4为4字节

  • Configuration

    • application.yml/application.properties
    • properties metadata: src/resource/META-INF/additional-spring-configuration-metadata.json
    • 生产环境和开发环境配置
      • 环境变量 
        export SPRING_DATASOURCE_URL=jdbc:mysql://localhost/tacocloud
export SPRING_DATASOURCE_USRERNAME=tacouser
export SPRING_DATASOURCE_PASSWORD=tacopassword
      • profile
        • 使用application-{profile name}.yml or application-{profile name}.properties文件
          • application-prod.yml
        • yml文件特有方法，使用---分隔，并指定spring.profiles 
          ---
spring:
  profiles: prod
        • activating profiles
          • spring.profiles.active (worst way) 
            spring:
  profiles:
    active:
      - prod
      - audit
      - ha
          • 环境变量 SPRING_PROFILES_ACTIVE=prod,audit,ha
          • 命令行参数 java -jar taco-cloud.jar --spring.profiles.active=prod
          • Cloud Foundry会自动激活cloud profile
      • 根据profile有条件地创建bean
        • @Profile
        • @Profile("dev")
        • @Profile("dev", "qa") dev或qa
        • @Profile("!prod", "!qa") prod与qa都没有被激活

  • REST API

    • @GetMapping @PostMapping @PutMapping @PatchMapping @DeleteMapping @RequestMapping
    • @RequestMapping(path="/", produces="application/json") @RequestMapping(path="/", produces={"application/json","text/xml"})
    • @CrossOrigin(origins="*")
    • @PathVariable @RequestBody
    • consumes="application/json"

  • HATEOAS(Hypermedia as the Engine of Application State)

    • 书中不一致的地方，参考Migrating to Spring HATEOAS 1.0
      • ResourceSupport -> RepresentationModel
      • Resource -> EntityModel
      • Resources -> CollectionModel
      • PagedResources -> PagedModel
    • Deprecated
      • ControllerLinkBuilder -> WebMvcLinkBuilder
    • Resource Assembler
      • hateoas版本更新导致的书中不一致
        • ResourceAssemblerSupport -> RepresentationModelAssemblerSupport
        • toResource -> toModel
    • @Relation(value="taco", collectionRelation="tacos")

  • Spring Data REST

    • spring.data.rest.base-path: /api
    • 直接访问base path可以查看可用的url
    • RepositoryRestController
    • ResourceProcessor -> RepresentationModelProcessor

  • RestTemplate

    • 41 methods: delete getForEntity getForObject headForHeaders optionsForAllow patchForObject postForEntity postForLocation postForObject put
      • Object/Entity(ResponseEntity)
    • 三种方式
      • url+按顺序给定placeholder
      • ulr+Map
      • UriComponents

  • Traverson

    • follow toObject asLink getHref
    • ParameterizedTypeReference
    • 只能浏览不能POST/PUT/DELETE，如果需要，需要使用RestTemplate
    • TODO: Traverson如何处理通过ResourceAssembler保证的嵌套数据
    • TODO: linkTo/methodOn如何处理RepositoryRestController的base url

  • asynchronous message

    • ActiveMQ/Artemis
      • spring.artemis.host/port/user/password
      • spring.activemq.broker-url/user/password/in-memory
      • 打开 http://127.0.0.1:8161 查看Management Console
    • JmsTemplate
      • 发送消息
        • send MessageCreator
        • convertAndSend Object MessagePostProcessor
        • 指定目标 default/Destination/String
      • spring.jms.template.default-destination: tacocloud.order.queue
      • MessageConverter (toMessage fromMessage)
        • MappingJackson2MessageConverter
          • 从org.springframework.jms.support.converter而不是org.springframework.messaging.converter导入
          • setTypeIdPropertyName setTypeIdMappings
        • MarshallingMessageConverter
        • MessagingMessageConverter
        • SimpleMessageConverter，default，需要对象实现Serializable
      • MessagePostProcessor
      • 接收消息
        • model: pull model/push model
        • pull model
          • receive Message
          • receiveAndConvert Object
        • push model @JmsListener
    • RabbitMQ/AMQP
      • exchange / routing key
      • Sender Exchange Binding Queue Receiver
      • Default/Direct/Topic/Fanout/Headers/Dead letter
      • RabbitMQ in Action by Alvaro Videla & Jason J.W. Williams
      • spring.rabbitmq.addresses/host/port/username/password
      • RabbitTemplate
      • 发送消息
        • send convertAndSend
        • Message exchange routingKey MessagePostProcessor
      • @Qualifier
      • 接收消息
        • pulling(RabbitTemplate) listener(@RabbitListener)
        • RabbitTemplate receiving
          • receive Message
          • receiveAndConvert Object/ParameterizedTypeReference
          • 参数：queueName/timeoutMillis
      • 如何处理同时使用Jms和RabbitMQ时，都需要注入MessageConverter，但Bean不能重名的问题
        • 没有问题，只是jms和rabbitmq配置时都使用了同名的MessagingConfig的Configuration导致的Bean重复
    • Kafka
      • Kafka启动，见start-kafka.sh和docker-compose.kafka.yml，采用单broker，多broker端口会变化需要修改配置文件
      • 通用配置 spring.kafka.bootstrap-servers/template.default-topic
      • 发送消息
        • ListenableFuture<SendResult<K,V>> send(String topic, Integer partition, Long timestamp, K key, V data) & 去除部分参数
        • ListenableFuture<SendResult<K,V>> send(ProducerRecord<K,V> record)
        • ListenableFuture<SendResult<K,V>> send(Message<?> message)
        • ListenableFuture<SendResult<K,V>> sendDefault(Integer partition, Long timestamp, K key, V data) & 去除部分参数
        • 配置 producer.keySerializer/valueSerializer
      • 接收消息
        • @KafkaListener
        • Order ConsumerRecord<Order> Message<Order>
        • 配置 consumer.group-id/value-deserializer/properties(spring.json.trusted.packages)

  • Spring Integration

    • Enterprise Integration Patterns by Gregor Hohpe and Bobby Woolf
    • File System
    • @MessagingGateway @Header(FileHeaders.FILENAME)
    • 3中配置方法
      • XML @ImportResource("classpath:/filewriter-config.xml")
      • Java @Transformer @ServiceActivator 会自动创建channel
      • Java with a DSL IntegrationFlow IntegrationFlows
    • Channels, Filters, Transformers, Routers, Splitters, Aggregators, Service activators, Channel adapters, Gateways
      • Channel: PublishSubscribeChannel QueueChannel PriorityChannel RendezvousChannel DirectChannel ExecutorChannel FluxMessageChannel
    • Endpoint Modules: AMQP, Spring application events, RSS and Atom, FileSystem, FTP/FTPS, GemFire, HTTP, JDBC, JMS, Email, MongoDB, MQTT, Redis, RMI, SFTP, STOMP, Stream, Syslog, TCP/UDP, Twitter, Web Services, WebFlux, WebSocket, XMPP, ZooKeeper
    • 需要引入javax.mail
    • org.apache.commons.text.similarity.LevenshteinDistance
    • AbstractMailMessageTransfomer AbstractIntegrationMessageBuilder GenericHandler
    • spring.main.web-application-type: none/servlet/reactive
    • 需要邮箱中有未读邮件，且收取后会设为已读

  • Reactive Spring

    • Imperative vs Reactive
    • Reactive Stream
      • Publisher Subscriber Subscription Processor
      • public interface Publisher<T> {
    void subscribe(Subscriber<? super T> subscriber);
}
public interface Subscriber<T> {
    void onSubscribe(Subscription sub);
    void onNext(T item);
    void onError(Throwable ex);
    void onComplete();
}
public interface Subscription{
    void request(long n);
    void cancel();
}
public interface Processor<T,R> extends Subscriber<T>, Publisher<R> {}
    • Reactor
      • 2 Core types: （都实现了Publisher）
        • Mono：不超过1个数据，just() map() subscribe()
        • Flux：0或1或多个（可能无限个）数据
      • RxJava/ReactiveX (Flux Mono 对应 Observable Single)
      • Mable Diagram
      • operations分类
        • Creation operations
          • just()
          • fromArray()
          • fromIterable()
          • fromStream() Java Stream
          • range()
          • interval()
        • Combination operations
          • mergeWith()
          • zip() Tuple2/Object(传入函数，如(c,f)-> c+" eats " + f)
          • first() 选择先产生数据的Flux
        • Transformation operations
          • skip() 跳过前n个数据，或若干时间
          • take() 取前n个数据，或若干时间
          • filter()
          • distinct()
          • map() 同步转换
          • flatMap() 可以实现异步转换
            • subscribeOn()
              • Schedulers
                • immediate()
                • single()
                • newSingle()
                • elastic()
                • parallel()
          • buffer(n)
          • buffer() collectList()
          • collectMap()
        • Logic operations
          • all()
          • any()
        • log()
      • 没有Subscriber，数据不会flow
      • StepVerifier

  • WebFlux (a reactive web framework for Spring) (参考webflux分支)

    • asynchronous web framework, event looping
    • Spring MVC Stack WebFlux Stack
      @Controller, @RequestMapping, etc Router functions
      Spring MVC Spring WebFlux
      Servlet API Reactive HTTP
      Servlet Container Tomcat, Jetty, Serverlet 3.1+, Netty, UnderTow
    • RxJava: Observable Single Completable(=Mono) Flowable
    • functional programming model
      • RequestPredicate
      • RouterFunction
      • ServerRequest
      • ServerResponse
    • route() ok() body() addRoute()
    • test
      • WebTestClient get/post/put/patch/delete/head
      • 集成测试 @RunWIth @SpringBootTest
    • Consuming
      • WebClient
    • Security
      • Spring Security从5.0.0开始，不依赖于servlet API
      • @EnableWebFluxSecurity SecurityWebFilterChain
      • ReactiveUserDetailService

  • Persisting data reactively

    • Cassandra MongoDB Couchbase Redis
    • reactive不支持JPA/关系型数据库
    • Flux<Ingredient> findByType (Ingredient.Type type)
    • <Taco> Flux<Taco> saveAll(Publisher<Taco> tacoPublisher)
    • reactive/non-reactive 转换
      • Flux.fromIterable() Mon.just() mono.block() flux.toIterable()
      • subscribe()
    • Spring Data Cassandra
      • spring-boot-starter-data-cassandra/spring-boot-starter-data-cassandra-reactive
      • spring.data.cassandra.keyspace-name/schema-action/contact-points/port/username/password
    • Spring Data MongoDB
      • spring-boot-starter-data-mongodb/spring-boot-starter-data-mongodb-reactive
      • spring.data.mongodb.host/port/username/password/database
      • @Id @Document @Field
      • ReactiveCrudRepository/ReactiveMongoRepository

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