QueryDSL:如何编写表达式来查找日期的秒差？

import com.querydsl.core.types.dsl.Expressions;
import com.querydsl.core.types.dsl.DateTimeExpression;
import com.querydsl.jpa.impl.JPAQueryFactory;

import javax.persistence.EntityManager;
import java.time.LocalDateTime;

public class QueryDSLExample {
    public static void main(String[] args) {
        EntityManager entityManager = // 获取EntityManager对象
        JPAQueryFactory queryFactory = new JPAQueryFactory(entityManager);

        // 定义查询表达式
        DateTimeExpression<LocalDateTime> startDate = Expressions
                .dateTimePath(LocalDateTime.class, "startDate");
        DateTimeExpression<LocalDateTime> endDate = Expressions
                .dateTimePath(LocalDateTime.class, "endDate");

        // 计算秒差
        long secondsDiff = queryFactory.select(startDate
                .second().subtract(endDate.second()))
                .from(/* 表名 */)
                .where(/* 查询条件 */)
                .fetchOne();

        System.out.println("秒差：" + secondsDiff);
    }
}