我需要對存儲在面向文檔的數據庫（MongoDB）中的（簡單）Java對象圖進行版本控制。對於關係數據庫和Hibernate，我發現了Envers，並對可能性感到非常驚訝。是否有類似的東西可以用於Spring Data Documents？Java MongoDB對象版本控制
我發現this post勾勒出的想法我有（更多...）有關存儲對象的版本，和我目前的執行工作在它存儲的對象的副本在一個單獨的歷史收集與時間戳類似，但我想要改善這一點以節省存儲空間。因此，我認爲我需要在對象樹上執行「差異」操作和爲重建舊對象執行「合併」操作。有沒有圖書館在這方面提供幫助？
編輯： 任何有關MongoDB和版本的經驗都非常感謝！我認爲很可能不會有Spring Data解決方案。
我們正在使用一個基礎實體（我們在這裏設置標識，創建+最後更改日期，...）。基於這一點，我們使用一個通用的持久性方法，它看起來是這樣的：
@Override
public <E extends BaseEntity> ObjectId persist(E entity) {
delta(entity);
mongoDataStore.save(entity);
return entity.getId();
}
增量方法看起來像這樣（我會盡力使這一儘可能通用）：
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;
}
我們三角洲實體看起來像這樣（不幹將+ setter方法，的toString，hashCode時和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;
}
希望這有助於你入門:-)
非常感謝您的示例。我還發現一篇關於java對象差異的文章（http://stackoverflow.com/questions/8001400/is-there-a-java-library-that-can-diff-two-objects）提到這個庫：https：// github.com/SQiShER/java-object-diff - 也許我可以用這個差異算法「激發」你的解決方案。我想留下這個問題更多的時間，也許還有其他的想法。 –
有趣的項目，期待您的解決方案。在此期間仍然讚賞upvote ;-) – xeraa
這就是我最終如何實現MongoDB實體的版本控制。感謝StackOverflow社區的幫助！
equals方法，以便它測試數據庫主鍵而不是子屬性。 （否則，JavaObjectDiff將無法識別收集元素中的屬性更改。）這裏是我用於版本控制的實體（getters/setters等）去掉）：
// This entity is stored once (1:1) per entity that is to be versioned
// in an own collection
public class MongoDiffHistoryEntry {
/* history id */
private String id;
/* reference to original entity */
private String objectId;
/* copy of original entity (first version) */
private Object originalObject;
/* differences collection */
private List<MongoDiffHistoryChange> differences;
/* delete flag */
private boolean deleted;
}
// changeset for a single version
public class MongoDiffHistoryChange {
private Date historyDate;
private List<MongoDiffHistoryChangeItem> items;
}
// a single property change
public class MongoDiffHistoryChangeItem {
/* path to changed property (PropertyPath) */
private String path;
/* change state (NEW, CHANGED, REMOVED etc.) */
private Node.State state;
/* original value (empty for NEW) */
private Object base;
/* new value (empty for REMOVED) */
private Object modified;
}
這裏是saveChangeHistory操作：
private void saveChangeHistory(Object working, Object base) {
assert working != null && base != null;
assert working.getClass().equals(base.getClass());
String baseId = ObjectUtil.getPrimaryKeyValue(base).toString();
String workingId = ObjectUtil.getPrimaryKeyValue(working).toString();
assert baseId != null && workingId != null && baseId.equals(workingId);
MongoDiffHistoryEntry entry = getObjectHistory(base.getClass(), baseId);
if (entry == null) {
//throw new RuntimeException("history not found: " + base.getClass().getName() + "#" + baseId);
logger.warn("history lost - create new base history record: {}#{}", base.getClass().getName(), baseId);
saveNewHistory(base);
saveHistory(working, base);
return;
}
final MongoDiffHistoryChange change = new MongoDiffHistoryChange();
change.setHistoryDate(new Date());
change.setItems(new ArrayList<MongoDiffHistoryChangeItem>());
ObjectDiffer differ = ObjectDifferFactory.getInstance();
Node root = differ.compare(working, base);
root.visit(new MongoDiffHistoryChangeVisitor(change, working, base));
if (entry.getDifferences() == null)
entry.setDifferences(new ArrayList<MongoDiffHistoryChange>());
entry.getDifferences().add(change);
mongoTemplate.save(entry, getHistoryCollectionName(working.getClass()));
}
這是怎麼看起來像在MongoDB中：
{
"_id" : ObjectId("5040a9e73c75ad7e3590e538"),
"_class" : "MongoDiffHistoryEntry",
"objectId" : "5034c7a83c75c52dddcbd554",
"originalObject" : {
BLABLABLA, including sections collection etc.
},
"differences" : [{
"historyDate" : ISODate("2012-08-31T12:11:19.667Z"),
"items" : [{
"path" : "/sections[[email protected]]",
"state" : "ADDED",
"modified" : {
"_class" : "LetterSection",
"_id" : ObjectId("5034c7a83c75c52dddcbd556"),
"letterId" : "5034c7a83c75c52dddcbd554",
"sectionIndex" : 2,
"stringContent" : "BLABLA",
"contentMimetype" : "text/plain",
"sectionConfiguration" : "BLUBB"
}
}, {
"path" : "/sections[[email protected]]",
"state" : "REMOVED",
"base" : {
"_class" : "LetterSection",
"_id" : ObjectId("5034c7a83c75c52dddcbd556"),
"letterId" : "5034c7a83c75c52dddcbd554",
"sectionIndex" : 2,
"stringContent" : "BLABLABLA",
"contentMimetype" : "text/plain",
"sectionConfiguration" : "BLUBB"
}
}]
}, {
"historyDate" : ISODate("2012-08-31T13:15:32.574Z"),
"items" : [{
"path" : "/sections[[email protected]]/stringContent",
"state" : "CHANGED",
"base" : "blub5",
"modified" : "blub6"
}]
},
}],
"deleted" : false
}
編輯：這裏是遊客代碼：
public class MongoDiffHistoryChangeVisitor implements Visitor {
private MongoDiffHistoryChange change;
private Object working;
private Object base;
public MongoDiffHistoryChangeVisitor(MongoDiffHistoryChange change, Object working, Object base) {
this.change = change;
this.working = working;
this.base = base;
}
public void accept(Node node, Visit visit) {
if (node.isRootNode() && !node.hasChanges() ||
node.hasChanges() && node.getChildren().isEmpty()) {
MongoDiffHistoryChangeItem diffItem = new MongoDiffHistoryChangeItem();
diffItem.setPath(node.getPropertyPath().toString());
diffItem.setState(node.getState());
if (node.getState() != State.UNTOUCHED) {
diffItem.setBase(node.canonicalGet(base));
diffItem.setModified(node.canonicalGet(working));
}
if (change.getItems() == null)
change.setItems(new ArrayList<MongoDiffHistoryChangeItem>());
change.getItems().add(diffItem);
}
}
}
看起來像Javers是r該作業飛行工具，見http://javers.org/documentation/features/#javers-repository
Javers是概念上的域對象的版本一個VCS，通過JSON和MongoDB
不完整的版本的支持，但我們已經實現了一個很小的審計系統 - 記錄誰改變了舊值到新的。我們使用Morphia的''prePersist（）''方法（它只適用於完整的實體保存，而不是特定的更新）。可以提供一些代碼示例，但它沒有什麼複雜的... – xeraa
感謝您的評論！我會對展示您的解決方案的更多細節非常感興趣。只有跟蹤完整的實體保存才能確定：這也是我們的主要用例。一個非常有趣的觀點是你比較舊實體和新實體的方式，確定已更改的屬性。我在這裏查看了圖形比較框架，但沒有找到快速簡單的解決方案。 –