如何在Spring MongoDB中将两个整数值连接成一个字符串

import org.springframework.data.mongodb.core.aggregation.Aggregation;
import org.springframework.data.mongodb.core.aggregation.ConcatenationOperators.Concat;
import org.springframework.data.mongodb.core.aggregation.StringOperators.Substr;
import org.springframework.data.mongodb.core.aggregation.StringOperators.Value;

Aggregation aggregation = Aggregation.newAggregation(
    Aggregation.project()
        .and(Concat.valueOf(Value.valueOf("num1")).concatValue(Value.valueOf("num2"))).as("concatenatedValue")
);

List<Document> results = mongoTemplate.aggregate(aggregation, "collectionName", Document.class).getMappedResults();