Spring：如何向静态字段注入值？
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Spring: How to inject a value to static field?
提问by Whiteship
With this class
有了这个班
@Component
public class Sample {
@Value("${my.name}")
public static String name;
}
If I try Sample.name, it is always 'null'. So I tried this.
如果我尝试Sample.name，它总是“空”。所以我尝试了这个。
public class Sample {
public static String name;
@PostConstruct
public void init(){
name = privateName;
}
@Value("${my.name}")
private String privateName;
public String getPrivateName() {
return privateName;
}
public void setPrivateName(String privateName) {
this.privateName = privateName;
}
}
This code works. Sample.nameis set properly. Is this good way or not? If not, is there something more good way? And how to do it?
此代码有效。Sample.name设置正确。这是好方法还是坏方法？如果没有，有什么更好的方法吗？以及怎么做？
回答by Tomasz Nurkiewicz
First of all, public staticnon-finalfields are evil. Spring does not allow injecting to such fields for a reason.
首先，public static非final字段是邪恶的。由于某种原因，Spring 不允许注入这些字段。
Your workaroundis valid, you don't even need getter/setter, privatefield is enough. On the other hand try this:
您的解决方法是有效的，您甚至不需要 getter/setter，private字段就足够了。另一方面试试这个：
@Value("${my.name}")
public void setPrivateName(String privateName) {
Sample.name = privateName;
}
(works with @Autowired/@Resource). But to give you some constructive advice: Create a second class with privatefield and getter instead of public staticfield.
（与@Autowired/ 一起使用@Resource）。但是给你一些建设性的建议：用private字段和吸气剂而不是public static字段创建第二个类。
回答by Vitalii Shramko
Spring uses dependency injection to populate the specific value when it finds the @Value annotation. However, instead of handing the value to the instance variable, it's handed to the implicit setter instead. This setter then handles the population of our NAME_STATIC value.
Spring 使用依赖注入在找到 @Value 注释时填充特定值。但是，它不是将值传递给实例变量，而是传递给隐式 setter。然后这个 setter 处理我们的 NAME_STATIC 值的填充。
@RestController
//or if you want to declare some specific use of the properties file then use
//@Configuration
//@PropertySource({"classpath:application-${youeEnvironment}.properties"})
public class PropertyController {
@Value("${name}")//not necessary
private String name;//not necessary
private static String NAME_STATIC;
@Value("${name}")
public void setNameStatic(String name){
PropertyController.NAME_STATIC = name;
}
}
