DefaultAttribute (IBM InfoSphere Streams Java Operator API)

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Summary:
Required |
Optional

Detail:
Element

```
@Target(value=METHOD)
@Retention(value=RUNTIME)
@Documented
public @interface DefaultAttribute
```
Declare a default attribute to be used as the value for an optional 'Attribute' parameter.
The name of the attribute to be used as the default must be specified as the value of the annotation. If an attribute by the specified name exists in more than one input port's schema then the matching attribute in the first such port will be used as the parameter value.
This annotation must be used in conjunction with the com.ibm.streams.operator.model.Parameter annotation on a setter method of a Java bean of type com.ibm.streams.operator.TupleAttribute. For example, to specify that the 'jsonAttribute' optional parameter will pick up the 'jsonString' attribute from the stream by default (unless specified otherwise), you would specify the following:
```
        @Parameter
        @DefaultAttribute("jsonString")
        public void setJsonAttribute(TupleAttribute ta) {...}
 
```
When the DefaultAttribute parameter is used for the parameter, the parameter defaults to be being optional and having a cardinality of 1.
Since:

InfoSphere® Streams Version 4.0

See Also:
Parameter, TupleAttribute

- Required Element Summary
  
  Required Elements
  Modifier and Type Required Element and Description
  
  java.lang.String value
  Name of the attribute to be used as the default

- Element Detail
  - value
```
public abstract java.lang.String value
```
    Name of the attribute to be used as the default