java - 当我在枚举中使用属性值时出现 Spring Boot 错误

Question

我有一个 Spring Boot 项目，我正在尝试恢复 .properties 文件的值并在枚举中使用它。

我遵循接下来的步骤。

• 我有一个application.properties带有value = 000. 我通过以下方式恢复此值：

  @RestController
  public class ReadProperty {
  
      @Value("${value}")
      public String value;
  
      public String getValueProperty() {
          return this.value;
      }
  
      @GetMapping(value = "/get")
      public String getValue() {
          System.out.println("read value is " + value);
          return value;
      }
  
      @GetMapping(value = "/getEnum")
      public String getValueEnum() {
  
          String response = EnumInsideAClass.TEST.toString();
  
          System.out.println("response value is " + response);
          return response;
      }
  }
  

如果我在类中使用值，我会毫无问题地得到值 000。

• 我在这样的类中创建了一个枚举

  public class EnumTest {
  
      @Autowired
      static ReadProperty readProperty;
  
      public final static String VAL = readProperty.getValueProperty();
  
      public enum EnumInsideAClass {
  
          TEST(VAL);
  
          private String value;
  
          private EnumInsideAClass(String value) {
              this.value = value;
          }
  
          @Override
          public String toString() {
              return this.value;
          }
      }
  }
  

问题是在枚举类内部我需要一个静态变量。如果我使用

@Value("${value}")
public static String value;

值更改为 null。

所以我尝试通过 get 方法访问该值，但该值仍然为空。

我没有想法，我该怎么办？可以在枚举中使用属性值吗？

非常感谢

标签： javaspring-bootenumsproperties

Answer 1

The problem you're describing has nothing to do with the @Value being in the enum but rather it has to do with your attempt to inject the property's value on a static variable.

Spring will let you inject values directly on non-static and not on static fields. If you want to do this in your case, you could potentially proxy the injection through a setter method e.g:

public static String value;

@Value("${value}")
public void setValue(String someValue) {
    SomeClass.value = someValue;
}

But I would advise you to be very aware of what you're doing. Since this is going to be a non-final field that is also public and static you need to be aware of who's allowed to access it and also who's allowed to change it's value.