cannot convert from String to HashMap Spring Boot application

Question

I have below code and issue. I am running a Spring boot application to test application.properties file usage.

application.properties file,

server.port=8080
server.servlet.context-path=/HelloWorldBoot

myMap={key1:'value1',key2:'value2'}

Controller code below,

@RestController
public class MyController {

    @Autowired
    Environment env;

    @Value("#{${myMap}}")  
    private HashMap<String,String> myMapUsingValue;

    @GetMapping("/hello")
    public String hello() {
        System.out.println("myMapUsingValue : "+myMapUsingValue);

        HashMap<String, String> myMapUsingEnv = env.getProperty("myMap", HashMap.class);
        System.out.println("myMapUsingEnv : "+myMapUsingEnv);

        return "Hello World";
    }
}

Now when I hit the URL: http://localhost:8080/HelloWorldBoot/hello

Map details using @Value gets printed successfully,

myMapUsingValue : {key1=value1, key2=value2} 

But I get error like below while accessing the same Map using Environment API,

No converter found capable of converting from type [java.lang.String] to type [java.util.HashMap<?, ?>]]

How can I resolve this? How can I read the Map directly from application properties file using the Environment variable API?

Any help is appreciated on this. Thanks in advance.

Answer 1

Environment variables are always strings. The fact that the Spring value injector knows how to convert them to a map is super nice, but when using the java environment api you are going to have to parse that string yourself and convert it into a Map.

Something like Jackson might make this easier. Otherwise you might write a utility method that does this. You might look in the spring source.