Type conversion in Spring Boot CommandLineRunner app

Question

I have been happily using @Value to inject command line parameters into Spring Boot CommandLineRunner based programs. i.e.

 java -jar myJar.jar --someParm=foo

... works just fine with classes containing:

 @Autowired
 public MyBean(@Value("someParm") String someParm) { ... }

However I'm now seeing this fail when the parm is not a String.

Here is my bean:

@Component
class MyBean {

    private final LocalDate date;

    @Autowired
    public MyBean (@Value("date") @DateTimeFormat(iso=ISO.DATE) LocalDate date) {
        this.date = date;
    }

    public void hello() {
        System.out.println("Hello on " + date);
    }

}

... and my application class:

@SpringBootApplication
public class MyApp implements CommandLineRunner {

    @Autowired
    private MyBean myBean;

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

    @Override
    public void run(String... args) throws IOException {
        myBean.hello();
    }
}

When I run it as java -jar MyApp.java --date=2016-12-10, I get a stack trace ending:

 java.lang.IllegalStateException: Cannot convert value of type
 [java.lang.String] to required type [java.time.LocalDate]: 
 no matching editors or conversion strategy found
at org.springframework.beans.TypeConverterDelegate.convertIfNecessary(TypeConverterDelegate.java:302)

Although the docs state that there is a standard converter for String->Date, I have experimented with registering my own, and hit the same NullPointerException as this post: How to register custom converters in spring boot?

What can I do to make this work?

Java 8, Spring Boot 1.3.5-RELEASE

score 0 · Answer 1 · answered Jun 08 '16 at 11:23

0

Did you try using java.util.Date instead of java.time.LocalDate? I suspect that the conversion would work automatically.

answered Jun 08 '16 at 11:23

fkleedorfer

525
4
8

I did try that -- same exception, apart from the type. – slim Jun 08 '16 at 12:08

score 0 · Answer 2 · answered Oct 10 '17 at 09:52

Normally (when @EnableWebMvc or something like that is used) Spring registers conversion service automatically, but there are situations (such as command-line application), when you should register it manually:

@Bean
public static ConversionService conversionService() {
    return new DefaultFormattingConversionService();
}

Type conversion in Spring Boot CommandLineRunner app

2 Answers2