Appendix B. Spring Java Configuration Tips

B.1. Spring Java Configuration Tips

Note that auto-completion in Eclipse and STS is CTRL+Space, even on a Mac.

B.2. Barebones Bean Definitions

Consider writing @Configuration classes where each bean method is defined as a skeleton, just returning null. If you do this first:

It allows you to think first about what beans you need, and only later about how to create each one
When you come to do dependency injection, auto-completion can be used to select the bean method to invoke as you write the body of each method

@Configuration
public class AppConfig {

    @Bean
    public AccountService accountService() {
        return null;
    }

    @Bean
    public AccountRepository accountRepository() {
        return null;
    }

    @Bean
    public CustomerRepository customerRepository() {
        return null;
    }
}

B.3. Dependency Injection

Dependency injection should be performed one of three ways.

Local dependency, invoke the bean method:

@Bean
public AccountService accountService() {
    return new AccountService(accountRepository(), customerRepository());
}

External dependency, defined in a different @Configuration class. Option 1: Use @Autowired:

@Configuration
public class AppConfig {

    private DataSource dataSource;

    @Autowired
    public AppConfig(DataSource dataSource) {
        this.dataSource = dataSource;
    }

    @Bean
    public CustomerRepository customerRepository() {
        return new CustomerRepository(dataSource);
    }
}

External dependency, defined in a different @Configuration class. Option 2: Use a method parameter:

@Configuration
public class AppConfig {

    @Bean
    public CustomerRepository customerRepository(DataSource dataSource) {
        return new CustomerRepository(dataSource);
    }
}

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