SpanTag (Spring Cloud Sleuth API 3.1.11 API)

```
@Retention(RUNTIME)
@Inherited
@Target(PARAMETER)
public @interface SpanTag
```
There are 3 different ways to add tags to a span. All of them are controlled by the annotation values. Precedence is: try with the TagValueResolver bean if the value of the bean wasn't set, try to evaluate a SPEL expression if there’s no SPEL expression just return a toString() value of the parameter

Since:

1.2.0

Author:

Christian Schwerdtfeger

- Optional Element Summary
  
  Optional Elements
  Modifier and Type Optional Element Description
  
  String expression
  
  String key
  
  Class<? extends TagValueResolver> resolver
  
  String value

- Element Detail
  - value
```
@AliasFor("key")
String value
```
    Returns:
    
    - The name of the key of the tag which should be created.
    
    Default:
    
    ""
- - key
```
@AliasFor("value")
String key
```
    Returns:
    
    - The name of the key of the tag which should be created.
    
    Default:
    
    ""
- - expression
```
String expression
```
    Returns:
    
    - Execute this SPEL expression to calculate the tag value. Will be analyzed if no value of the resolver() was set.
    
    Default:
    
    ""
- - resolver
```
Class<? extends TagValueResolver> resolver
```
    Returns:
    
    - Use this bean to resolve the tag value. Has the highest precedence.
    
    Default:
    
    org.springframework.cloud.sleuth.annotation.NoOpTagValueResolver.class