使用java query dsl进行“查询+聚合”elasticsearch

<dependency>
    <groupId>com.querydsl</groupId>
    <artifactId>querydsl-core</artifactId>
    <version>4.4.0</version>
</dependency>

<dependency>
    <groupId>com.querydsl</groupId>
    <artifactId>querydsl-apt</artifactId>
    <version>4.4.0</version>
    <scope>provided</scope>
</dependency>

@Entity
public class Product {
    @Id
    private Long id;
    private String name;
    private String description;
    private BigDecimal price;
    // getters and setters
}

public class QProduct extends EntityPathBase<Product> {
    public QProduct(String variable) {
        super(Product.class, variable);
    }
    
    public QProduct(Path<? extends Product> path) {
        super(path.getType(), path.getMetadata());
    }
    
    public QProduct(PathMetadata metadata) {
        super(Product.class, metadata);
    }
    
    // define query properties
    public final StringPath name = createString("name");
    public final StringPath description = createString("description");
    public final NumberPath<BigDecimal> price = createNumber("price", BigDecimal.class);
}

QProduct qProduct = QProduct.product; // 创建查询模型实例
JPAQueryFactory queryFactory = new JPAQueryFactory(entityManager); // 创建查询工厂
List<Product> result = queryFactory
    .selectFrom(qProduct)
    .where(qProduct.name.eq("iPhone"))
    .orderBy(qProduct.price.desc())
    .fetch();

QProduct qProduct = QProduct.product; // 创建查询模型实例
JPAQueryFactory queryFactory = new JPAQueryFactory(entityManager); // 创建查询工厂
BigDecimalExpression maxPrice = queryFactory
    .select(qProduct.price.max())
    .from(qProduct)
    .fetchOne();