mongotemplate聚合查询

您好！对于MongoTemplate的聚合查询，您可以使用Aggregation类来构建聚合查询管道。以下是一个简单的示例：

import org.springframework.data.mongodb.core.MongoTemplate;
import org.springframework.data.mongodb.core.aggregation.Aggregation;
import org.springframework.data.mongodb.core.aggregation.TypedAggregation;
import org.springframework.data.mongodb.core.aggregation.AggregationResults;

import static org.springframework.data.mongodb.core.aggregation.Aggregation.*;

public class AggregationExample {
    private MongoTemplate mongoTemplate;

    public AggregationExample(MongoTemplate mongoTemplate) {
        this.mongoTemplate = mongoTemplate;
    }

    public void performAggregation() {
        TypedAggregation aggregation = newAggregation(
                // 添加聚合操作
                match(Criteria.where("fieldName").is("value")),
                group("groupField").count().as("count"),
                sort(Sort.Direction.DESC, "count")
        );

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

        // 处理结果
        for (AggregateResultClass result : resultList) {
            // 进行相应的操作
            // result.getGroupField();
            // result.getCount();
        }
    }
}

// 聚合结果的POJO类
class AggregateResultClass {
    private String groupField;
    private int count;

    // 省略构造函数、getter和setter
}

请根据您的具体需求修改上述示例中的字段和条件。希望对您有所帮助！如果您有任何其他问题，请随时提问。