前言

MongoDB是面向集合存儲的文檔型數據庫，其涉及到的基本概念與關系型數據庫比有所不同。本文主要介紹關于mongo數據集合屬性存在點號(.)的相關內容，下面話不多說了，來一起看看詳細的介紹吧

基本知識點：

1.似乎mongo3.6之前不允許插入帶點（.）或美元符號（$）的鍵，但是當我使用mongoimport工具導入包含點的JSON文件時，它工作正常。

2.在使用spring-data-mongodb處理mongodb的增刪改查時會通過一個MappingMongoConverter(Document和Modle轉換類)轉換數據

3.具體對點號的轉換在DBObjectAccessor(spring-data-mongodb-1.10.13)或者DocumentAccessor(spring-data-mongodb-2.0.9)，如下：

//插入時轉換
public void put(MongoPersistentProperty prop, Object value) {
Assert.notNull(prop, “MongoPersistentProperty must not be null!”);
String fieldName = prop.getFieldName();
if (!fieldName.contains(“.”)) {
dbObject.put(fieldName, value);
return;
}
Iterator<String> parts = Arrays.asList(fieldName.split(“\.”)).iterator();
DBObject dbObject = this.dbObject;
while (parts.hasNext()) {
String part = parts.next();
if (parts.hasNext()) {
dbObject = getOrCreateNestedDbObject(part, dbObject);
} else {
dbObject.put(part, value);
}
}
}

//查詢時轉換
public Object get(MongoPersistentProperty property) {
String fieldName = property.getFieldName();
if (!fieldName.contains(“.”)) {
return this.dbObject.get(fieldName);
}
Iterator<String> parts = Arrays.asList(fieldName.split(“\.”)).iterator();
Map<String, Object> source = this.dbObject;
Object result = null;
while (source != null && parts.hasNext()) {
result = source.get(parts.next());
if (parts.hasNext()) {
source = getAsMap(result);
}
}
return result;
}

//判斷值是否為空
public boolean hasValue(MongoPersistentProperty property) {
Assert.notNull(property, “Property must not be null!”);
String fieldName = property.getFieldName();
if (!fieldName.contains(“.”)) {
return this.dbObject.containsField(fieldName);
}
String[] parts = fieldName.split(“\.”);
Map<String, Object> source = this.dbObject;
Object result = null;
for (int i = 1; i < parts.length; i++) {
result = source.get(parts[i – 1]);
source = getAsMap(result);
if (source == null) {
return false;
}
}
return source.containsKey(parts[parts.length – 1]);
}