Springboot #Value not loading - spring-boot

Question

In my sample Springboot project on Github, the #Value property won't get loaded when starting the application. I cannot explain the strange behavior and hope that anyone could help me please to solve it and to avoid such stupid errors?
#RestController
public class PostClient {
#Value(value = "${target.uri}")
public String uri;
private RestTemplate restTemplate = new RestTemplate();
private HttpHeaders headers = new HttpHeaders();
public PostClient() {}
public HttpStatus postNumberPlate(CamImage camImage) {
LinkedMultiValueMap<String, Object> map = new LinkedMultiValueMap<>();
map.add("numplate", camImage.getIdentifier());
headers.setContentType(MediaType.MULTIPART_FORM_DATA);
HttpEntity<LinkedMultiValueMap<String, Object>> requestEntity = new HttpEntity<LinkedMultiValueMap<String,
Object>>(map, headers);
ByteArrayResource resource = new ByteArrayResource(camImage.getData()) {
#Override
public String getFilename() {
return camImage.getIdentifier() + ".png";
}
};
map.add("image", resource);
System.out.println(uri);
ResponseEntity<String> result = restTemplate.exchange(uri,
HttpMethod.POST,
requestEntity, String.class);
return result.getStatusCode();
}
}
The application.properties
target.uri=http://localhost:9001/postoffice
I read that the #Value is a core functionality of Springboot and should work fine. My project is so small, that I wonder what might broke the framework's behavior of automatic value replacement. I found different and similar questions regarding the #Value issue, but a real explanation cannot be found.
I tried to use a #Component Class with getters/setters and tried to #Autowire it into the shown Class, but that didn't work, too.
I'd like to go the proposed way of the Springboot reference, because any hard-coded String will result in problems, when building docker containers, where I must pass a configuration parameter. So I cannot only rely on a fixed application.properties in the classpath.
EDIT:
Running the application looks like:
shell:>one
Euro Plate # unimportant sysout
CamImage [identifier=BNAYG63, data=[B#4f4c4c4b] # generated plate
null # from sysout here should be the address!!
URI is not absolute
Details of the error have been omitted. You can use the stacktrace command to print the full stacktrace.
shell:>stacktrace
java.lang.IllegalArgumentException: URI is not absolute
at java.base/java.net.URL.fromURI(URL.java:674)
at java.base/java.net.URI.toURL(URI.java:1116)
at org.springframework.http.client.SimpleClientHttpRequestFactory.createRequest(SimpleClientHttpRequestFactory.java:145)
at org.springframework.http.client.support.HttpAccessor.createRequest(HttpAccessor.java:87)
at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:731)
at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:670)
at org.springframework.web.client.RestTemplate.exchange(RestTemplate.java:579)
at dev.semo.npgen.service.PostClient.postNumberPlate(PostClient.java:45)
at dev.semo.npgen.shell.NumberplateClientCommands.one(NumberplateClientCommands.java:62)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:566)
at org.springframework.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:282)
at org.springframework.shell.Shell.evaluate(Shell.java:180)
at org.springframework.shell.Shell.run(Shell.java:142)
at org.springframework.shell.jline.InteractiveShellApplicationRunner.run(InteractiveShellApplicationRunner.java:84)
at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:770)
at org.springframework.boot.SpringApplication.callRunners(SpringApplication.java:760)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:318)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1213)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1202)
at dev.semo.npgen.NpgenApplication.main(NpgenApplication.java:10)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:566)
at org.springframework.boot.devtools.restart.RestartLauncher.run(RestartLauncher.java:49)

Answer 1

I have pulled your source from github and tested. Initially it was throwing error as you mentioned. After I have changed like below it is working fine. You should to autowire the PostClient, because the scanning happened and loaded the defaults while you started the application.
#ShellComponent
public class NumberplateClientCommands {
#Autowired
private PostClient postClient;
.....
#ShellMethod("Sends one simple POST request.")
public String one() throws FileNotFoundException {
NumberPlateUtility np = new NumberPlateUtility();
HttpStatus response = postClient.postNumberPlate(np.completeImage());
if (response == HttpStatus.ACCEPTED) {
return "Request sent successfully.";
}
return String.format("Request failed: %s", response.getReasonPhrase());
}
.......
}

Answer 2

Follow this Code Snip
#Value("${target.uri}")
private String uri;