问题描述
我需要对存储在面向文档的数据库 (MongoDB) 中的(简单)Java 对象图进行版本控制.对于关系数据库和 Hibernate,我发现了 Envers 并对这些可能性感到非常惊讶.是否有类似的东西可以与 Spring Data Documents 一起使用?
I need to do versioning on (simple) Java object graphs stored in a document-oriented database (MongoDB). For relational databases and Hibernate, I discovered Envers and am very amazed about the possibilities. Is there something similar that can be used with Spring Data Documents?
我发现 这篇文章概述了我的想法(以及更多...)关于存储对象版本,我当前的实现工作类似,因为它将对象的副本存储在带有时间戳的单独历史集合中,但我想改进它以节省存储空间.因此,我认为我需要在对象树上实现差异"操作和重构旧对象的合并"操作.有没有图书馆可以帮助解决这个问题?
I found this post outlining the thoughts I had (and more...) about storing the object versions, and my current implementation works similar in that it stores copies of the objects in a separate history collection with a timestamp, but I would like to improve this to save storage space. Therefore, I think I need to implement both a "diff" operation on object trees and a "merge" operation for reconstructing old objects. Are there any libraries out there helping with this?
编辑:任何使用 MongoDB 和版本控制的经验都非常感谢!我认为很可能不会有 Spring Data 解决方案.
Edit: Any experiences with MongoDB and versioning highly appreciated! I see most probably there won't be a Spring Data solution.
推荐答案
我们正在使用一个基础实体(我们在其中设置 Id、创建 + 上次更改日期......).在此基础上,我们使用了一个通用的持久化方法,看起来像这样:
We're using a base entity (where we set the Id, creation + last change dates,...). Building upon this we're using a generic persistence method, which looks something like this:
@Override public <E extends BaseEntity> ObjectId persist(E entity) { delta(entity); mongoDataStore.save(entity); return entity.getId(); }
delta 方法看起来像这样(我会尽量使它尽可能通用):
The delta method looks like this (I'll try to make this as generic as possible):
protected <E extends BaseEntity> void delta(E newEntity) { // If the entity is null or has no ID, it hasn't been persisted before, // so there's no delta to calculate if ((newEntity == null) || (newEntity.getId() == null)) { return; } // Get the original entity @SuppressWarnings("unchecked") E oldEntity = (E) mongoDataStore.get(newEntity.getClass(), newEntity.getId()); // Ensure that the old entity isn't null if (oldEntity == null) { LOG.error("Tried to compare and persist null objects - this is not allowed"); return; } // Get the current user and ensure it is not null String email = ...; // Calculate the difference // We need to fetch the fields from the parent entity as well as they // are not automatically fetched Field[] fields = ArrayUtils.addAll(newEntity.getClass().getDeclaredFields(), BaseEntity.class.getDeclaredFields()); Object oldField = null; Object newField = null; StringBuilder delta = new StringBuilder(); for (Field field : fields) { field.setAccessible(true); // We need to access private fields try { oldField = field.get(oldEntity); newField = field.get(newEntity); } catch (IllegalArgumentException e) { LOG.error("Bad argument given"); e.printStackTrace(); } catch (IllegalAccessException e) { LOG.error("Could not access the argument"); e.printStackTrace(); } if ((oldField != newField) && (((oldField != null) && !oldField.equals(newField)) || ((newField != null) && !newField .equals(oldField)))) { delta.append(field.getName()).append(": [").append(oldField).append("] -> [") .append(newField).append("] "); } } // Persist the difference if (delta.length() == 0) { LOG.warn("The delta is empty - this should not happen"); } else { DeltaEntity deltaEntity = new DeltaEntity(oldEntity.getClass().toString(), oldEntity.getId(), oldEntity.getUuid(), email, delta.toString()); mongoDataStore.save(deltaEntity); } return; }
我们的 delta 实体看起来像这样(没有 getter + setter、toString、hashCode 和 equals):
Our delta entity looks like that (without the getters + setters, toString, hashCode, and equals):
@Entity(value = "delta", noClassnameStored = true) public final class DeltaEntity extends BaseEntity { private static final long serialVersionUID = -2770175650780701908L; private String entityClass; // Do not call this className as Morphia will // try to work some magic on this automatically private ObjectId entityId; private String entityUuid; private String userEmail; private String delta; public DeltaEntity() { super(); } public DeltaEntity(final String entityClass, final ObjectId entityId, final String entityUuid, final String userEmail, final String delta) { this(); this.entityClass = entityClass; this.entityId = entityId; this.entityUuid = entityUuid; this.userEmail = userEmail; this.delta = delta; }
希望这可以帮助您入门:-)
Hope this helps you getting started :-)