8. Spring Boot Service

8.1. 理解 Service

Service Components are the class file which contains @Service annotation. These class files are used to write business logic in a different layer.

8.2. @Autowired

Inject list of all beans with a certain interface

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
@Component
public class SomeComponent {

    interface SomeInterface {

    }

    @Component
    class Impl1 implements SomeInterface {

    }

    @Component
    class Impl2 implements SomeInterface {

    }

    @Autowired
    private List<SomeInterface> listOfImpls;
}

8.3. 类中获取属性数据

8.3.1. @ConfigurationProperties

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
@PropertySource("classpath:dbconfig.properties")
@ConfigurationProperties("database")
public class DatabaseConfiguration {

    @Length(min=2, max=10)
    private String name;

    @NotEmpty
    private String url;

    @Length(min=5, max=10)
    @Pattern(regexp = "[a-z-A-Z]*", message = "Username can not contain invalid characters")
    private String username;

    @Length(min=8, max=16)
    private String password;

}
  • @PropertySource 标签是指定属性文件，默认是application.yml 或 application.properties
  • @ConfigurationProperties 标签指定属性文件中的属性前缀

8.3.2. @Value

This annotation can be used for injecting values into fields in Spring-managed beans and it can be applied at the field or constructor/method parameter level.

https://www.baeldung.com/spring-value-annotation

8.4. Error Handling for REST

@ResponseStatus(code = HttpStatus.NOT_FOUND, reason = "Actor Not Found")
public class ActorNotFoundException extends Exception {
}

@GetMapping("/actor/{id}")
public String getActorName(@PathVariable("id") int id) {
    try {
        return actorService.getActor(id);
    } catch (ActorNotFoundException ex) {
        throw new ResponseStatusException(
          HttpStatus.NOT_FOUND, "Actor Not Found", ex);
    }
}

8.5. Spring boot自定义注解

1
2
3
4
5
<!-- AOP依赖模块 -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-aop</artifactId>
</dependency>

8.5.1. 使用自定义注解来统计方法的执行时间

8.5.1.1. 创建@AnalysisActuator

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
package com.example.demo.aop;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface AnalysisActuator {
    String note() default "";
}

8.5.1.2. 创建Aspect

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
package com.example.demo.aop;

import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.After;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.annotation.Pointcut;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;

@Aspect
@Component
public class AnalysisActuatorAspect {
    final static Logger log = LoggerFactory.getLogger(AnalysisActuatorAspect.class);

    ThreadLocal<Long> beginTime = new ThreadLocal<>();

    @Pointcut("@annotation(analysisActuator)")
    public void serviceStatistics(AnalysisActuator analysisActuator) {
    }

    @Before("serviceStatistics(analysisActuator)")
    public void doBefore(JoinPoint joinPoint, AnalysisActuator analysisActuator) {
        // 记录请求到达时间
        beginTime.set(System.currentTimeMillis());
        log.info("------ note:{}", analysisActuator.note());
    }

    @After("serviceStatistics(analysisActuator)")
    public void doAfter(AnalysisActuator analysisActuator) {
        log.info("------ statistic time:{}, note:{}", System.currentTimeMillis() - beginTime.get(),
                analysisActuator.note());
    }

}

8.5.1.3. 使用

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
package com.example.demo.controller;

import java.util.Optional;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

import com.example.demo.aop.AnalysisActuator;

@RestController
public class HelloWorldController {

    @GetMapping("/")
    @AnalysisActuator(note = "HelloWorldController中的hello方法")
    public String hello(String name) {
        return "Hello " + Optional.ofNullable(name).orElse("World!");
    }
}

调用地址：http://localhost:8080/?name=Java 屏幕打印：

2019-10-22 15:21:18.512  INFO 22521 --- [nio-8080-exec-1] c.e.demo.aop.AnalysisActuatorAspect
      : ------ note:HelloWorldController中的hello方法
2019-10-22 15:21:18.550  INFO 22521 --- [nio-8080-exec-1] c.e.demo.aop.AnalysisActuatorAspect
      : ------ statistic time:38, note:HelloWorldController中的hello方法