在Springboot mongo聚合中将ObjectID转换为字符串

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-mongodb</artifactId>
</dependency>

import org.bson.types.ObjectId;
import org.springframework.data.annotation.Id;
import org.springframework.data.mongodb.core.mapping.Document;
import org.springframework.data.mongodb.core.mapping.Field;

@Document(collection = "your_collection")
public class YourEntity {
    @Id
    private ObjectId id;

    @Field("your_field_name")
    private String yourField;

    // 其他属性和方法
}

import org.springframework.data.mongodb.core.aggregation.Aggregation;
import org.springframework.data.mongodb.core.aggregation.Fields;
import org.springframework.data.mongodb.core.aggregation.TypedAggregation;
import org.springframework.data.mongodb.core.query.Criteria;

TypedAggregation<YourEntity> aggregation = Aggregation.newAggregation(
    YourEntity.class,
    Aggregation.match(Criteria.where("your_field_name").is("your_value")),
    Aggregation.project()
        .and(Fields.field("id").toString()).as("idAsString")
        .and("yourField")
);

List<YourResultClass> results = mongoTemplate.aggregate(aggregation, YourResultClass.class).getMappedResults();