使用Spring-Data-Mongo如何限制搜索？

Question

Using Spring-Data-Mongo how do I limit search?

I am trying to find everyone over 19 but under 50 years old? the field is called "age". The following code is NOT working

public void countUnderAge()
{
    List<Person> results = null;

    Query query = new Query();
    Criteria criteria = new Criteria();
    criteria = criteria.lte("21");

    query.addCriteria(criteria);
    results = mongoTemplate.find(query, Person.class);

    logger.info("Total number of under age in database: {}", results.size());
}

Answer 1

Use this:

Query query= new Query();
query.addCriteria(where("age").lte(21)); 
List<Person> results = mongoTemplate.find(query, Person.class);

You are missing the field name of the where clause. You can also do:

Query query = new Query();
Criteria criteria = new Criteria();
criteria = where("age").lte("21");
query.addCriteria(criteria);

To use "where" you need to add this import:

import static org.springframework.data.mongodb.core.query.Criteria.where;