Java配置

Java配置是Spring 4.x和SpringBoot推荐的方式。 Java配置是通过@Configuration和@Bean来实现的：

• @Configuration声明当前类是一个配置类，相当于一个Spring配置的xml文件。
• @Bean注解在方法上，声明当前方法的返回值是一个Bean。

java config的demo

项目结构

Main

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class Main {
    
    public static void main(String[] args) {
        AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(JavaConfig.class); //1
        UseFunctionService useFunctionService = applicationContext.getBean(UseFunctionService.class); //2
        System.out.println(useFunctionService.SayHello("JavaConfig"));
        applicationContext.close();
    }

}

JavaConfig

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class JavaConfig {

    @Bean
    public FunctionService functionService(){
        return new FunctionService();
    }

    @Bean
    public UseFunctionService userFunctionService(){
        UseFunctionService useFunctionService = new UseFunctionService();
        useFunctionService.setFunctionService(functionService());//3
        return useFunctionService;
    }

}

FunctionService

public class FunctionService {

    public String sayHello(String word){

        return "Hello " + word + "!";

    }
}

UseFunctionService

public class UseFunctionService {

    FunctionService functionService;

    public FunctionService getFunctionService() {
        return functionService;
    }

    public void setFunctionService(FunctionService functionService) {
        this.functionService = functionService;
    }

    public String SayHello(String word) {
        return functionService.sayHello(word);
    }

}