Spring boot 2 Converting Duration java 8 application.properties

问题

I need to define Duration value (spring.redis.timeout) by application.properties.

I was trying to use one point defined in Spring boot documentation:

Spring Boot has dedicated support for expressing durations. If you expose a java.time.Duration property, the following formats in application properties are available:

A regular long representation (using milliseconds as the default unit unless a @DurationUnit has been specified) The standard ISO-8601 format used by java.util.Duration A more readable format where the value and the unit are coupled (e.g. 10s means 10 seconds)

When i use spring.redis.timeout=3s Spring boot application throws this exception:

Cannot convert value of type 'java.lang.String' to required type 'java.time.Duration': no matching editors or conversion strategy found

Which would it be the best way to set a correct value to a Duration property in application.properties withs last Spring boot 2 release?

回答1:

It's possible to use @Value notation with Spring Expression Language

@Value("#{T(java.time.Duration).parse('${spring.redis.timeout}')}")
private Duration timeout;

回答2:

The Duration in the moment (Spring-Boot 2.0.4.RELEASE) it is not possible to use together with @Value notation, but it is possible to use with @ConfigurationProperties

For Redis, you have RedisProperties and you can use the configuration:

spring.redis.timeout=5s

And:

@SpringBootApplication
public class DemoApplication {

  @Autowired
  RedisProperties redisProperties;

  public static void main(String[] args) {
    SpringApplication.run(DemoApplication.class, args);
  }

  @PostConstruct
  void init() {
    System.out.println(redisProperties.getTimeout());
  }
}

It printed (parse as 5s):

PT5S

https://docs.oracle.com/javase/8/docs/api//java/time/Duration.html#parse-java.lang.CharSequence-

回答3:

Spring Boot attempts to coerce the external application properties to the right type when it binds to the @ConfigurationProperties beans. If you need custom type conversion, you can provide a ConversionService bean (with a bean named conversionService)

See: https://docs.spring.io/spring-boot/docs/2.0.4.RELEASE/reference/htmlsingle/#boot-features-external-config-conversion

Create new ApplicationConversionService bean (it must be named conversionService ). Here you are my code tested with Spring boot 2.0.4:

@Configuration
public class Conversion {

@Bean
public ApplicationConversionService conversionService()
{
    final ApplicationConversionService applicationConversionService = new ApplicationConversionService();
    return applicationConversionService;
}

Here you are an example project using this approach:

https://github.com/cristianprofile/spring-data-redis-lettuce

回答4:

If your Spring-Boot version or its dependencies don't put ApplicationConversionService into context (and Spring-Boot doesn't until 2.1), you can expose it explicitly

@Bean
public ConversionService conversionService() {
    return ApplicationConversionService.getSharedInstance();
}

It invokes Duration.parse, so you may use PT3S, PT1H30M, etc in properties files.

来源：https://stackoverflow.com/questions/51818137/spring-boot-2-converting-duration-java-8-application-properties

标签

spring-boot

java-8

duration