How to return a list of tuples in a Custom Java Function using the StreamBase Client API
Article ID: KB0076355
Updated On:
| Products | Versions |
|---|---|
| TIBCO Streaming | - |
Description
What code is needed to return a list of tuples in a Custom Java Function using the StreamBase Client API?
Issue/Introduction
How to return a list of tuples in a Custom Java Function using the StreamBase Client API
Resolution
To define a schema with a list of tuples in a Custom Java Function, do the following:
1. Create a member variable to hold the list's tuple schema (example):
3. Create a function that builds the list of tuples (example):
1. Create a member variable to hold the list's tuple schema (example):
public class TheClass {
private static Schema OutputSchema = null;
2. Create a custom function resolver that defines the schema (example)
public static CompleteDataType CombineWithListCustomFunctionResolver0(
CompleteDataType arg0,
CompleteDataType arg1,
CompleteDataType arg2) {
ArrayList<Schema.Field> Fields = new ArrayList<Schema.Field>();
Fields.add(Schema.createListField("theList",CompleteDataType.forString()));
Fields.add(Schema.createField(DataType.DOUBLE, "theDouble"));
Fields.add(Schema.createField(DataType.INT, "theInt"));
OutputSchema = new Schema(null,Fields);
return CompleteDataType.forList(CompleteDataType.forTuple(OutputSchema));
}
Note that this doesn't show the input value typechecking logic.3. Create a function that builds the list of tuples (example):
@CustomFunctionResolver("CombineWithListCustomFunctionResolver0")
public static List<?> CombineWithList(List<String> arg0, Double arg1, Integer arg2) {
Tuple dataTuple = OutputSchema.createTuple(); // create the tuple
ArrayList<Tuple> dataList = new ArrayList<Tuple>(); // create the list to be emitted
try { // load the tuple
dataTuple.setList(0, arg0);
dataTuple.setDouble(1, arg1);
dataTuple.setInt(2, arg2);
} catch (NullValueException e) {
e.printStackTrace();
} catch (TupleException e) {
e.printStackTrace();
}
dataList.add(dataTuple); // add the tuple to the list, repeat as necessary with different values
return dataList;
}
Feedback
Yes
No
Powered by
