如何在spring-boot应用程序中从application.yml文件中读取属性

Question

我的应用程序有存储在applicaion.yml文件中的嵌套属性。
我希望在应用程序启动时将这些属性映射到POJO。

application.yml:

    demo:
     - A:
       - type: A
         prop1: 1
         prop2: 2
         proop3: 3
       - type: B
         prop1: 1
         prop2: 2
         proop3: 3
     - B:
       - type: A
         prop1: 1
         prop2: 2
         proop3: 3
       - type: B
         prop1: 1
         prop2: 2
         proop3: 3

为了实现这一点，我使用了以下注释:

@configuration
@enableConfigurationProperties
@configurationProperties（“demo”）

类演示:

@Configuration
@EnableConfigurationProperties
@ConfigurationProperties("demo")
public class Demo {
    @JsonProperty("A")
    private List<A> a = null;
    @JsonProperty("B")
    private List<B> b = null;

    @JsonProperty("A")
    public List<A> getA() {
        return a;
    }

    @JsonProperty("A")
    public void setA(List<A> a) {
        this.a = a;
    }

    @JsonProperty("B")
    public List<B> getB() {
        return b;
    }

    @JsonProperty("B")
    public void setB(List<B> b) {
        this.b = b;
    }

    @Override
    public String toString() {
        return "Demo [a=" + a + ", b=" + b + "]";
    }   
}

public class A {

    @JsonProperty("type")
    private String type;
    @JsonProperty("prop1")
    private Integer prop1;
    @JsonProperty("prop2")
    private Integer prop2;
    @JsonProperty("proop3")
    private Integer proop3;

    @JsonProperty("type")
    public String getType() {
        return type;
    }

    @JsonProperty("type")
    public void setType(String type) {
        this.type = type;
    }

    @JsonProperty("prop1")
    public Integer getProp1() {
        return prop1;
    }

    @JsonProperty("prop1")
    public void setProp1(Integer prop1) {
        this.prop1 = prop1;
    }

    @JsonProperty("prop2")
    public Integer getProp2() {
        return prop2;
    }

    @JsonProperty("prop2")
    public void setProp2(Integer prop2) {
        this.prop2 = prop2;
    }

    @JsonProperty("proop3")
    public Integer getProop3() {
        return proop3;
    }

    @JsonProperty("proop3")
    public void setProop3(Integer proop3) {
        this.proop3 = proop3;
    }

    @Override
    public String toString() {
        return "A [type=" + type + ", prop1=" + prop1 + ", prop2=" + prop2 + ", proop3=" + proop3 + "]";
    }
}

public class B {

    @JsonProperty("type")
    private String type;
    @JsonProperty("prop1")
    private Integer prop1;
    @JsonProperty("prop2")
    private Integer prop2;
    @JsonProperty("proop3")
    private Integer proop3;

    @JsonProperty("type")
    public String getType() {
        return type;
    }

    @JsonProperty("type")
    public void setType(String type) {
        this.type = type;
    }

    @JsonProperty("prop1")
    public Integer getProp1() {
        return prop1;
    }

    @JsonProperty("prop1")
    public void setProp1(Integer prop1) {
        this.prop1 = prop1;
    }

    @JsonProperty("prop2")
    public Integer getProp2() {
        return prop2;
    }

    @JsonProperty("prop2")
    public void setProp2(Integer prop2) {
        this.prop2 = prop2;
    }

    @JsonProperty("proop3")
    public Integer getProop3() {
        return proop3;
    }

    @JsonProperty("proop3")
    public void setProop3(Integer proop3) {
        this.proop3 = proop3;
    }

    @Override
    public String toString() {
        return "B [type=" + type + ", prop1=" + prop1 + ", prop2=" + prop2 + ", proop3=" + proop3 + "]";
    }
}

主类

@SpringBootApplication
@ComponentScan(basePackages = {"com.microservice.*"})
@EnableJpaRepositories("com.microservice.*")
@EntityScan("com.microservice.*")
public class MainApplication {  
    public static void main(String[] args) {
         SpringApplication app = new SpringApplication(MainApplication.class);
            app.run();
            System.out.println("step 1");
            Demo config = new Demo();
            System.out.println("name: " + config);
        }

        public void run(String... args) throws Exception {
            System.out.println("step 2");

        }
}

但是我在O/P下面:
步骤1
名称:Demo[a=null,b=null]

Answer 1

当您手动创建属性POJO的实例时，Spring并不知道它，并且不会进行属性绑定。

 SpringApplication app = new SpringApplication(MainApplication.class);
    app.run();
    System.out.println("step 1");
    Demo config = new Demo(); // Not a Spring managed bean!
    System.out.println("name: " + config);
}

与使用@enableConfigurationProperties注释配置不同，您可以将demo设置为bean，如类型安全配置属性中所示。

@Component
@ConfigurationProperties("demo")
public class Demo {
    ...
}

然后您可以从上下文中获得demobean：

@SpringBootApplication
public class MainApplication {
    public static void main(String[] args) {
        ConfigurableApplicationContext context = SpringApplication.run(MainApplication.class, args);
        Demo demo = (Demo) context.getBean("demo");
        System.out.println(demo.getName());
    }
}

demo:
  a:
    - type: A
      prop1: 1
      prop2: 2
      proop3: 3
    - type: B
      prop1: 1
      prop2: 2
      proop3: 3
  b:
    - type: B
      prop1: 1
      prop2: 2
      proop3: 3

@SpringBootApplication
public class MainApplication {

    @Bean
    public ObjectMapper objectMapper() {
        return new ObjectMapper();
    }

    public static void main(String[] args) throws JsonProcessingException {
        ...
        ObjectMapper objectMapper = (ObjectMapper) context.getBean("objectMapper");
        System.out.println(objectMapper.writeValueAsString(demo));
    }
}

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.0.1</version>
</dependency>