java Spring @Value 注释方法，属性不可用时使用默认值
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Spring @Value annotated method, use default value when properties not available
提问by RenatoIvancic
Situation
情况
I am injecting properties from .propertiesfile into fields annotated with @Value. However this properties present sensitive credentials, so I remove them from repository. I still want that in case someone wants to run project and doesnt have .properties file with credentials that default values will be set to fields.
我将.properties文件中的属性注入到用@Value注释的字段中。但是，此属性提供敏感凭据，因此我将它们从存储库中删除。我仍然希望以防万一有人想要运行项目并且没有带有凭据的 .properties 文件，默认值将设置为字段。
Problem
问题
Even if I set default values to field itself I get exception when .properties file is not present:
即使我将默认值设置为字段本身，当 .properties 文件不存在时，也会出现异常：
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'xxx': Injection of autowired dependencies failed; nested exception is java.lang.IllegalArgumentException: Could not resolve placeholder 'secret' in string value "${secret}"
Here is the annotated field:
这是带注释的字段：
@Value("${secret}")
private String ldapSecret = "secret";
I expected in this case just plain String "secret" would be set.
我希望在这种情况下只设置简单的字符串“秘密”。
回答by Bernie Lenz
To answer your question exactly...
准确回答你的问题...
@Value("${secret:secret}")
private String ldapSecret;
And a few more variations are below for completeness of the examples...
为了示例的完整性，下面还有一些变化......
Default a String to null:
默认字符串为空：
@Value("${secret:#{null}}")
private String secret;
Default a number:
默认一个数字：
@Value("${someNumber:0}")
private int someNumber;
回答by Federico Peralta Schaffner
Just use:
只需使用：
@Value("${secret:default-secret-value}")
private String ldapSecret;
回答by Ahmet Karakaya
@Value and Property Examples
To set a default value for property placeholder :
${property:default value}
Few examples :
//@PropertySource("classpath:/config.properties}")
//@Configuration
@Value("${mongodb.url:127.0.0.1}")
private String mongodbUrl;
@Value("#{'${mongodb.url:172.0.0.1}'}")
private String mongodbUrl;
@Value("#{config['mongodb.url']?:'127.0.0.1'}")
private String mongodbUrl;
回答by Vinh
Actually the default value will be ALWAYS used. To overcome this, I use a String value
实际上，将始终使用默认值。为了克服这个问题，我使用了一个字符串值
@Value("${prop}")
String propValue;//if no prop defined, the propValue is set to the literal "${prop}"
....
if("${prop}".equals(propValue)) {
propValue=defaultValue
}
