附加 QueryDSL 谓词或基于过滤器值构建谓词答案

【问题标题】：Append QueryDSL Predicate or building predicate based on filter values附加 QueryDSL 谓词或基于过滤器值构建谓词
【发布时间】：2021-04-13 16:58:39
【问题描述】：

我是 Querydsl 的新手，我正在寻找一种基于过滤器附加/构建谓词的方法。您可以在示例中看到，如果过滤器中的某个字段没有值，则不应进入谓词。

如果这样的事情是不可能的，那么最好的方法是什么？

例如过滤器（GetPaintingRequest）包含这些字段（过滤器中有更多，但不重要）：

public class GetPaintingsRequest {
    private String author;
    private Integer style;
    private String paintingName;

    //.....getters and setters
}

所以在服务类中我想像这样过滤绘画

public List<Painting> getFilteredPaintings(GetPaintingsRequest request) {
        
        QPainting painting = QPainting.painting;
        
        //predicate for all paintings that are not deleted and not sold
        Predicate query = painting.deleted.isFalse().and(painting.isSold.isFalse());
        
        if (!request.getAuthor().equals("")) {
            //append to existing predicate name of the author
            query.and.painting.autor.eq(request.getAuthor()); //obviously not working - just as an example what I want
            
        }

        if (!request.getPaintingName().equals("")) {
            //append to existing predicate painting name
            query.and.painting.paintingName.eq(request.getPaintingName()); //obviously not working - just as an example what I want
        }
        
        var paintingList = paintingRepository.findAll(query);

}

【问题讨论】：

标签： java spring-data-jpa filtering querydsl predicate

【解决方案1】：

我找到了解决办法！

QPainting painting = QPainting.painting;
        
        BooleanBuilder booleanBuilder = new BooleanBuilder();
        
        booleanBuilder.and(painting.deleted.isFalse().and(painting.isSold.isFalse()));      
        

        if (!request.getAuthor().equals("")) {
            booleanBuilder.and(painting.author.eq(request.getAuthor()));

        }

        if (!request.getPaintingName().equals("")) {
            booleanBuilder.and(painting.paintingName.eq(request.getPaintingName()));
        }
        
        
        
        Predicate predicate = booleanBuilder;
        var paintingList = paintingRepository.findAll(predicate);

【讨论】：