java - 多层 Spring 应用程序依赖解析

Question

我正在尝试使用Spring创建一个三层应用程序，view，logic，data，或多或少。 View 取决于逻辑，而逻辑又取决于数据。

如何在 view 项目中配置 Spring 应用程序，以便能够解析依赖关系图？

例如:

在 View 层中:

@Controller
public class SomeView {
  private final SomeService someService;

  @Autowired
  public SomeView(SomeService someService) {
    this.someService = someService;
  }
}

@Configuration
@EnableAutoConfiguration
@SpringBootApplication
public class Application {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

}

在逻辑层:

@Component
public class SomeService {

  private final SomeData someData;

  @Autowired
  public SomeService(SomeData someData){
    this.someData = someData;
  }

}

在数据层:

@Component
public class SomeData {

}

此配置无法启动，因为SomeService无法解析SomeData，因为SomeData未在 View 中扫描 层 Application.java

Answer 1

当使用@SpringBootApplication时 Spring boot 使用默认值。如果你看一下@SpringBootApplication定义你会看到:

Many Spring Boot developers always have their main class annotated with @Configuration, @EnableAutoConfiguration and @ComponentScan. Since these annotations are so frequently used together (especially if you follow the best practices above), Spring Boot provides a convenient @SpringBootApplication alternative.

The @SpringBootApplication annotation is equivalent to using @Configuration, @EnableAutoConfiguration and @ComponentScan with their default attributes: [...]

这意味着:

@SpringBootApplication // same as @Configuration    @EnableAutoConfiguration @ComponentScan
public class Application {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

}

此外，这意味着当使用 @ComponentScan 的默认值时，您的包结构应如下所示:

• com.example.model -> 您的实体
• com.example.repositoriy -> 您的存储库
• com.example.controller -> Controller
• com.example -> MainApplication 类

如果不遵循此结构，您应该告诉 @ComponentScan 包在哪里可以找到组件:

示例 1:

@Configuration
@EnableAutoConfiguration
@ComponentScan({"com.my.package.controller","com.my.package.domain"})
public class Application {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

}

示例 2:

    @Configuration
@EnableAutoConfiguration
@ComponentScan(basePackageClasses = {SomeService.class, SomeData.class})
public class Application {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

}

另外，我建议您检查一下这个guide关于如何在 Spring Boot 应用程序中构建代码。