@Override
    public void init(StreamDefinition streamDefinition, OptionHolder optionHolder,
                     List<AttributeMapping> attributeMappingList, ConfigReader configReader,
                     SiddhiAppContext siddhiAppContext) {
        this.streamDefinition = streamDefinition;
        this.optionHolder = optionHolder;
        this.attributeMappingList = attributeMappingList;
        this.configReader = configReader;
        this.siddhiAppContext = siddhiAppContext;
    }
Test String Mapper implementation to is used for testing purposes.
modules/siddhi-core/src/test/java/io/siddhi/core/transport/TestTrpSourceMapper.java