How to place @Bean factory method in the bean class itself?

Question

I have a class that shall contain data which is de-serialized from a JSON file. This data shall be available in my application, so I want to bind it as bean.

To keep the de-serialization logic and and the data structure together, I wanted to put the @Bean annotated factory method into the data class itself – like this:

@Configuration
public class MyData {

    // factory method
    @Bean
    public static MyData loadMyData(ResourceLoader resourceLoader) throws IOException {
        try (InputStream input = resourceLoader.getResource("classpath:data.json").getInputStream()) {
            return new ObjectMapper().readValue(input, MyData.class);
        } 
    }

    // data structure
    private Map<String, DataDetail> details;

    // ...
}

However this fails because @ComponentScan finds two bean definitions now:

org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type 'org.example.MyData' available: expected single matching bean but found 2: myData,loadMyData

I also tried to replace the @Configuration with @Component, but the result is the same.

Am I just missing the right annotation on the class, or is it just not possible to place the @Bean method in the bean class itself?

take a look at [Best way to load some JSON files into a Spring Boot application](https://stackoverflow.com/q/34277392/217324) — Nathan Hughes, Mar 18 '19 at 14:05
do you need two beans of same type? you can name them unique and `Autowire` the corresponding one — Ryuzaki L, Mar 18 '19 at 14:40
No, I only want one bean. But so far I haven't figured out how to get this in the described scenario. — oberlies, Mar 18 '19 at 15:11

score 0 · Answer 1 · answered Mar 18 '19 at 15:19

Basically i prefer layered architecture with spring boot, so with two different layers for Configuration and model, for example

package app.config

@Configuration
public class MyDataConfig {

// factory method
@Bean
public static MyData loadMyData(ResourceLoader resourceLoader) throws IOException {
    try (InputStream input = resourceLoader.getResource("classpath:data.json").getInputStream()) {
        return new ObjectMapper().readValue(input, MyData.class);
    } 
 }

}

package com.model

public class MyData {

// data structure
private Map<String, DataDetail> details;

    // ...
}

score 0 · Answer 2 · answered Mar 18 '19 at 18:53

As Deadpool answered, you should separate the MyData class from the @Configurtion class.
@Configuration is meta-annotated with @Component so once you annotate MyData with @Configuration, Spring also relate it as a regular bean, and that makes the double defenition of the MyData beans.

How to place @Bean factory method in the bean class itself?

2 Answers2