Spring bean not being picked up?

Question

I have a java spring project with the below service:

@Slf4j
public class DialogFlowService {

    private String projectId;
    private String sessionId;
    private String languageCode;

    public DialogFlowService(DialogFlowConfig dialogFlowConfig) {
        log.info("aaa" + dialogFlowConfig.languageCode);
        this.projectId = dialogFlowConfig.projectId;
        this.sessionId = dialogFlowConfig.sessionId;
        this.languageCode = dialogFlowConfig.languageCode;
    }
}

The constructor takes the below class as an argument:

@Configuration
@ConfigurationProperties(prefix = "dialog-flow")
public class DialogFlowConfig {

    @NotNull
    public String projectId;

    @NotNull
    public String sessionId;

    @NotNull
    public String languageCode;
}

In theory, this should be instantiated by the below bean:

@Bean
public DialogFlowService dialogFlowService() {
   return new DialogFlowService(new DialogFlowConfig());
}

However in practice, when I try to log one of the constructor arguments, it comes up as null. Am I missing something?

have you print this object `dialogFlowConfig` under `DialogFlowService` — Kiran Mistry, Apr 12 '20 at 14:02
You need to autowire `DialogFlowConfig` in the parameters for `DialogFlowService` bean. You also need to add `@Setter` (as you are using lombok), or manually add setters for the fields in `DialogFlowConfig`. Probably best to add getters as well and set the fields to private. — 123, Apr 12 '20 at 14:12
Where is that `@Bean`? Also, it is not usually a good idea to mix `@Configuration` and `@ConfigurationProperties` on the same class; `@ConfigurationProperties` should be a simple record class. — chrylis -cautiouslyoptimistic-, Apr 12 '20 at 14:26
@chrylis-onstrike- what makes you say that, official spring packages use `@Configuration` and `@ConfigurationProperties` in the same class — 123, Apr 12 '20 at 14:36
@123 It is _extremely_ easy to accidentally end up with multiple copies of the `@ConfigurationProperties` bean, which leads to errors with applying the values and with bean resolution. — chrylis -cautiouslyoptimistic-, Apr 12 '20 at 14:40

score 2 · Answer 1 · edited Apr 12 '20 at 14:54

2

I think changing your third code snippet like this would do the trick.

@Bean
public DialogFlowService dialogFlowService(DialogFlowConfig  dialogFlowConfig) {
    return new DialogFlowService(dialogFlowConfig);
}

The DialogFlowConfig class is already marked as @Configuration. Hence it is managed by the Spring Application context. So you dont have to explicitly make an object using the new keyword. You can just take it as a parameter

Try putting @EnableConfigurationProperties(DialogFlowConfig.class) into you Spring Application class.

edited Apr 12 '20 at 14:54

Zack

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answered Apr 12 '20 at 14:20

Dilini Peiris

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Still won't work, since the config class has no setters. – 123 Apr 12 '20 at 14:22
1

are you sure @123 that he needs setters? Because he has used the @ConfigurationProperties(prefix = "dialog-flow") in order to get those from any properties file there in his project right? – Dilini Peiris Apr 12 '20 at 14:38
They still need to be set though. – 123 Apr 12 '20 at 14:39
1

This should be the accepted answer. OP should wire up the bean and add getters/setters to the @ConfigurationProperties class. – Zack Apr 12 '20 at 14:56
@123 No you dont have to set any setters when using this way. If you have any answer kindly post it. – Ramindu Samarawickrama Apr 12 '20 at 15:21

Savior · Answer 2 · 2020-04-12T18:10:46.627

This is similar to what's being described here: Why is my Spring @Autowired field null?

Essentially, by instantiating the DialogFlowConfig instance yourself and not handing it over to Spring, you're preventing Spring from post processing it and injecting ConfigurationProperties property values.

Instead create a @Bean method for DialogFlowConfig and use the corresponding Spring bean to create your DialogFlowService. For example

@Bean
public DialogFlowService dialogFlowService(DialogFlowConfig dialogFlowConfig) {
    return new DialogFlowService(dialogFlowConfig);
}

@Bean
public DialogFlowConfig dialogFlowConfig() {
    return new DialogFlowConfig();
}

Spring will use the @Bean annotated dialogFlowConfig() factory bean method to instantiate and process the corresponding instance (setting its fields). It'll then use it with the dialogFlowService() factory method.

Note: If you do it this way, you'll need to remove @Configuration annotation from DialogFlowConfig, assuming you were previously component scanning it. Alternatively, if you were correctly component scanning, you don't even need the additional @Bean annotated dialogFlowConfig() factory method I proposed. Just inject the DialogFlowConfig bean declared by its @Configuration annotation in the dialogFlowService method.

@123 I missed the `@Configuration`, but it won't break. One bean will overwrite the other, since they have the same implicit bean name. Still, I left a note to clarify things. — Savior, Apr 12 '20 at 18:11

score -1 · Answer 3 · answered Apr 12 '20 at 16:22

-1

First of all you need to use either setter getter in DialogFlowConfig or @Value annotation on all properties. You also need to annotate your service class DialogFlowService with @Service stereotype

answered Apr 12 '20 at 16:22

roushan kumar Singh

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12

Spring bean not being picked up?

3 Answers3