Spring Data + JPA 如何避免加载列 [英] Spring Data + JPA how to avoid loading a column

问题描述

我有一个包含 6 列的表，其中一个是 CLOB 列，在针对该表进行搜索时，我不想携带此列数据，但是当用户请求详细信息时，我将无法加载它，我该如何实现使用 Spring Data JPA，我尝试在没有帮助的情况下使用 Projections + MetaModel Object

i have a table with 6 columns and one of them is a CLOB column, during search against this table i don't want to bring this column data but when user requests for the details then ill load it, how do i achieve this with Spring Data JPA, I try to use Projections + MetaModel Object with no help

推荐答案

我是通过将两列移动到一个单独的表中来做到这一点的，但是即使您无法接触到数据库，您始终可以将两个不同的实体映射到不同的列同一张桌子.

I did this by moving two columns into a separate table, but even if you can't touch the database, you can always map two different entities to different columns of the same table.

重量级子实体:

@Entity
public class RawImage implements Serializable {
    // other properties
    private String type;
    private byte[] data;
}

轻量级父实体:

@Entity
public class Model implements Serializable {
    // other properties (ID etc.)

    @OneToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "fk_image_id")
    private RawImage image;

    @OneToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "fk_thumb_id")
    private RawImage thumb;
}

这意味着默认情况下不加载图像/拇指数据，我只是在需要它们时添加了一个获取，如下所示:

This means the image/thumb data isn't loaded by default, and I just added a fetch when I do need them with something like the following:

String jpql = "select m from Model m join fetch m.image i";

有本答案中描述的其他技术，但它们并不像我认为的这个简单的解决方案那么干净.

There are other techniques described in this answer but they weren't as clean as I think this simple solution is.

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