How to Resolve @Value Annotation Issues in Spring 3.2 with Pure Java Configuration?

Why does the @Value annotation not work with pure Java configuration in Spring 3.2, while Environment.getProperty works?

@Configuration
@PropertySource("classpath:app.properties")
public class Config {
    @Value("${my.prop}") 
    String name;

    @Autowired
    Environment env;

    @Bean(name = "myBean", initMethod = "print")
    public MyBean getMyBean(){
         MyBean myBean = new MyBean();
         myBean.setName(name);
         System.out.println(env.getProperty("my.prop"));
         return myBean;
    }
}

The @Value annotation in Spring is used for injecting property values into beans, but when using pure Java configuration in Spring 3.2, developers can encounter issues that prevent this behavior from functioning as expected. Understanding the configuration process and ensuring that the property sources are properly loaded is crucial for resolving these issues.

@Bean
public static PropertySourcesPlaceholderConfigurer propertySourcesPlaceholderConfigurer() {
    return new PropertySourcesPlaceholderConfigurer();
}

Causes

• The @Value annotation can fail to inject values if the PropertySource is not correctly configured or accessible.
• @Value annotations rely on the Spring context to process and resolve values, which might not be set up correctly in certain configurations.
• The context may not have read the properties file by the time the @Value injection occurs.

Solutions

• Ensure that the @PropertySource annotation correctly points to the properties file and that the file is present in the classpath.
• To verify property loading, print debug statements or use Environment.getProperty to ensure properties are accessible before the bean is initialized.
• Consider using Spring's PropertySourcesPlaceholderConfigurer to ensure that property placeholder processing is handled by Spring.

Mistake: Assuming @Value will work without configuring property sources correctly.

Solution: Always ensure that @PropertySource is set correctly and that properties are loaded in the correct context.

Mistake: Not checking the classpath for the properties file.

Solution: Verify that your properties file is in the resources folder and is included in the classpath during runtime.