Managing the Application Availability State

@Component
public class ReadinessStateExporter {
  @EventListener
  public void onStateChange(AvailabilityChangeEvent<ReadinessState> event) {
  switch (event.getState()) {
  case ACCEPTING_TRAFFIC:
  // create file /tmp/healthy
  break;
  case REFUSING_TRAFFIC:
  // remove file /tmp/healthy
  break;
  }
  }
}

@Component
public class LocalCacheVerifier {
  private final ApplicationEventPublisher eventPublisher;
  public LocalCacheVerifier(ApplicationEventPublisher eventPublisher) {
  this.eventPublisher = eventPublisher;
  }
  public void checkLocalCache() {
  try {
  //...
  }
  catch (CacheCompletelyBrokenException ex) {
  AvailabilityChangeEvent.publish(this.eventPublisher, ex,
LivenessState.BROKEN);
  }
  }
}

Application Events and Listeners

• ApplicationContext初始化之前不能注册监听器, 但可以使用SpringApplication.addListeners(…) , SpringApplicationBuilder.listeners(…)

• Listener: 长任务可能不执行,使用CommandLineRunner

  • ApplicationStartingEvent
  • ApplicationEnvironmentPreparedEvent
  • ApplicationContextInitializedEvent

  • ApplicationPreparedEvent

    • WebServerInitializedEvent
    • ServletWebServerInitializedEvent,ReactiveWebServerInitializedEvent
    • A ContextRefreshedEvent
  • ApplicationStartedEvent
  • AvailabilityChangeEvent
  • ApplicationReadyEvent
  • AvailabilityChangeEvent
  • ApplicationFailedEvent

Accessing Application Arguments

import org.springframework.boot.*;
import org.springframework.beans.factory.annotation.*;
import org.springframework.stereotype.*;
@Component
public class MyBean {
  @Autowired
  public MyBean(ApplicationArguments args) {
  boolean debug = args.containsOption("debug");
  List<String> files = args.getNonOptionArgs();
  // if run with "--debug logfile.txt" debug=true, files=["logfile.txt"]
  }
}

Using the ApplicationRunner or CommandLineRunner

• 在SpringApplication.run()结束前运行

  import org.springframework.boot.*;
  import org.springframework.stereotype.*;
  @Component
  public class MyBean implements CommandLineRunner {
    public void run(String... args) {
    // Do something...
    }
  }

Application Exit

@SpringBootApplication
public class ExitCodeApplication {
  @Bean
  public ExitCodeGenerator exitCodeGenerator() {
  return () -> 42;
  }
  public static void main(String[] args) {
System.exit(SpringApplication.exit(SpringApplication.run(ExitCodeApplication.class,
args)));
  }
}

Application Startup

public static void main(String[] args) {
  SpringApplication app = new SpringApplication(MySpringConfiguration.class);
  app.setApplicationStartup(new BufferingApplicationStartup(2048));
  app.run(args);
}

@Value

• Java properties files, YAML files, environment variables, and command-line arguments

• $--$server.port=9000

  • SpringApplication.setAddCommandLineProperties(false) 设置命令行参数后不生效
• SPRING_APPLICATION_JSON='{"acme":{"name":"test"}}' 环境变量
• java -Dspring.application.json='{"acme":{"name":"test"}}' -jar myapp.jar 系统变量
• java -jar myapp.jar --spring.application.json='{"acme":{"name":"test"}}' 命令行参数

默认配置文件位置

• classpath
• classpath:/config
• current directory
• current directory/config
• 环境变量:spring.config.name可以自定义配置文件名称

• spring.config.location 配置文件位置 需要以"/"结尾

  • spring.config.additional-location

• java -jar myproject.jar --spring.config.name=myproject
  java -jar myproject.jar --spring.config.location=optional:classpath:/default.properties,optional:classpath:/ov
  erride.properties,optional:file:./custom-config/
  # Use the prefix optional: if the locations are optional and you don’t mind if they don’t exist.

• optional:classpath:/
• optional:classpath:/config/
• optional:file:./
• optional:file:./config/
• optional:file:./config/*/
• optional:classpath:custom-config/

• optional:file:./custom-config/

  @Random Value

  my.secret=${random.value}
  my.number=${random.int}
  my.bignumber=${random.long}
  my.uuid=${random.uuid}
  my.number-less-than-ten=${random.int(10)}
  my.number-in-range=${random.int[1024,65536]}

  @ConstructorBinding

• 2.2之前的属性绑定需要setter方法,之后使用该注解可以使用构造方法绑定

• 松散绑定,不区分大小写,可已添加连字符

  Map绑定

• Map<String，String>

• acme.map.[/key1]=value1
  acme.map.[/key2]=value2
  acme.map./key3=value3

Logging

• logging.file.name
• logging.file.path
• logging.level.root=warn
• logging.level.org.springframework.web=debug
• logging.level.org.hibernate=error
• $logging.register-shutdown-hook=true$

国际化

spring.messages.basename=messages,config.i18n.messages
spring.messages.fallback-to-system-locale=false

响应式webflux

• spring-boot-starter-webflux
• 异步springmvc

MVC

• @EnableWebMvc
• DelegatingWebMvcConfiguration

• 自定义对象转json

  import java.io.*;
  import com.fasterxml.jackson.core.*;
  import com.fasterxml.jackson.databind.*;
  import org.springframework.boot.jackson.*;
  @JsonComponent
  public class Example {
    public static class Serializer extends JsonSerializer<SomeObject> {
    // ...
    }
    public static class Deserializer extends JsonDeserializer<SomeObject> {
    // ...
    }
  }

static content

• /static ,/public, /resources, /META-INF/resources
• WebMvcConfigurer and overriding the addResourceHandlers