Loading value from json upon start up application - spring-boot

Question

I want to load the values from json file upon the Spring Boot Application is started.
My code for the Configuration File is like the below:
#Configuration
#Getter
public class FedexAPIConfig {
private final static String JSON_FILE = "/static/config/fedex-api-credentials.json";
private final boolean IS_PRODUCTION = false;
private FedexAPICred apiCredentials;
public FedexAPIConfig() {
try (InputStream in = getClass().getResourceAsStream(JSON_FILE);
BufferedReader reader = new BufferedReader(new InputStreamReader(in, StandardCharsets.UTF_8))) {
JSONObject json = new JSONObject();
// this.apiCredentials = new JSONObject(new JSONTokener(reader));
if (IS_PRODUCTION) {
json = new JSONObject(new JSONTokener(reader)).getJSONObject("production");
} else {
json = new JSONObject(new JSONTokener(reader)).getJSONObject("test");
}
System.out.println(json.toString());
this.apiCredentials = FedexAPICred.builder()
.url(json.optString("url"))
.apiKey(json.optString("api_key"))
.secretKey(json.optString("secret_key"))
.build();
} catch (FileNotFoundException fnfe) {
fnfe.printStackTrace();
} catch (IOException ioe) {
ioe.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
}
}
and with this, when the application is in progress of startup, values are successfully printed on the console.Startup console log
When I tried to call this value from other ordinary class, like the below:, it brings nothing but just throws NullPointerException... What are my faults and what shall I do?
public class FedexOAuthTokenManager extends OAuthToken {
private static final String VALIDATE_TOKEN_URL = "/oauth/token";
private static final String GRANT_TYPE_CLIENT = "client_credentials";
private static final String GRANT_TYPE_CSP = "csp_credentials";
#Autowired
private FedexAPIConfig fedexApiConfig;
#Autowired
private Token token;
#Override
public void validateToken() {
// This is the part where "fedexApiConfig" is null.
FedexAPICred fedexApiCred = fedexApiConfig.getApiCredentials();
Response response = null;
try {
RequestBody body = new FormBody.Builder()
.add("grant_type", GRANT_TYPE_CLIENT)
.add("client_id", fedexApiCred.getApiKey())
.add("client_secret", fedexApiCred.getSecretKey())
.build();
response = new HttpClient().post(fedexApiCred.getUrl() + VALIDATE_TOKEN_URL, body);
if (response.code() == 200) {
JSONObject json = new JSONObject(response.body().string());
token.setAccessToken(json.optString("access_token"));
token.setTokenType(json.optString("token_type"));
token.setExpiredIn(json.optInt("expires_in"));
token.setExpiredDateTime(LocalDateTime.now().plusSeconds(json.optInt("expires_in")));
token.setScope(json.optString("scope"));
}
} catch (IOException ioe) {
ioe.printStackTrace();
}
}
}
fedexApiConfg is null even though I autowired it in prior to call.
And this FedexOAuthTokenManager is called from other #Component class by new FedexOAuthTokenManager()

Answer 1

Did you try like below?
Step 1: Create one Configuration class like below
public class DemoConfig implements ApplicationListener<ApplicationPreparedEvent> {
#Override
public void onApplicationEvent(ApplicationPreparedEvent event) {
//Load the values from the JSON file and populate the application
//properties dynamically
ConfigurableEnvironment environment = event.getApplicationContext().getEnvironment();
Properties props = new Properties();
props.put("spring.datasource.url", "<my value>");
//Add more properties
environment.getPropertySources().addFirst(new PropertiesPropertySource("myProps", props));
}
To listen to a context event, a bean should implement the ApplicationListener interface which has just one method onApplicationEvent().The ApplicationPreparedEvent is invoked very early in the lifecycle of the application
Step 2: Customize in src/main/resources/META-INF/spring.factories
org.springframework.context.ApplicationListener=com.example.demo.DemoConfig
Step 3: #Value in spring boot is commonly used to inject the configuration values into the spring boot application. Access the properties as per your wish.
#Value("${spring.datasource.url}")
private String valueFromJSon;
Try this sample first in your local machine and then modify your changes accordingly.
Refer - https://www.baeldung.com/spring-value-annotation
Refer - https://www.knowledgefactory.net/2021/02/aws-secret-manager-service-as.html