动态条件配置，使用泛型"T"作为实体类标识，在使用过程中替换成自己的实体类

/**
* 部分import引用
*/
import org.springframework.data.jpa.domain.Specification;

import javax.persistence.criteria.*;
import java.util.ArrayList;
import java.util.List;

public class MessageSpec {

    public static Specification<T> messageSpec(MessageJson messageJson){
            return new Specification<T>() {
                @Override
                public Predicate toPredicate(Root<T> root, CriteriaQuery<?> query, CriteriaBuilder cb) {
                    List<Predicate> whereList = new ArrayList<>();
                    if(EmptyUtil.isNotEmpty(messageJson.getUserId())) {
                        whereList.add(cb.equal(root.get("userId"), messageJson.getUserId()));
                    }

                    whereList.add(cb.between(root.get("notificationTime"), messageJson.getStartTime(), messageJson.getEndTime()));
                    Predicate[] pre = new Predicate[whereList.size()];
                    return query.where(whereList.toArray(pre)).getRestriction();
                }
            };
        }
}

方法调用示例

Page<T> Messagepage = messageDao.findAll(MessageSpec.messageSpec(message),pageable);

pom.xml配置依赖

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