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Doc improvements #4694

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16 changes: 8 additions & 8 deletions src/main/antora/modules/ROOT/pages/mongodb/mapping/mapping.adoc
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Original file line number Diff line number Diff line change
Expand Up @@ -28,13 +28,13 @@ Public `JavaBean` properties are not used.
[[mapping.conventions.id-field]]
=== How the `_id` field is handled in the mapping layer.

MongoDB requires that you have an `_id` field for all documents.If you don't provide one the driver will assign a ObjectId with a generated value.The "_id" field can be of any type the, other than arrays, so long as it is unique.The driver naturally supports all primitive types and Dates.When using the `MappingMongoConverter` there are certain rules that govern how properties from the Java class is mapped to this `_id` field.
MongoDB requires that you have an `_id` field for all documents.If you don't provide one the driver will assign a ObjectId with a generated value.The `_id` field can be of any type, other than arrays, so long as it is unique.The driver naturally supports all primitive types and Dates.When using the `MappingMongoConverter` there are certain rules that govern how properties from the Java class are mapped to the `_id` field.

The following outlines what field will be mapped to the `_id` document field:

* A field annotated with `@Id` (`org.springframework.data.annotation.Id`) will be mapped to the `_id` field.
* A field annotated with `@Id` (`org.springframework.data.annotation.Id`) will be mapped to the `_id` field. +
Additionally, the name of the document field can be customized via the `@Field` annotation, in which case the document will not contain a field `_id`.
* A field without an annotation but named `id` will be mapped to the `_id` field.
* The default field name for identifiers is `_id` and can be customized via the `@Field` annotation.

[cols="1,2",options="header"]
.Examples for the translation of `_id` field definitions
Expand All @@ -54,23 +54,23 @@ The following outlines what field will be mapped to the `_id` document field:
| `@Id` `String` x
| `_id`

| `@Field("x")` `@Id` `String` x
| `_id`
| `@Field("x")` `@Id` `String` y
| `x`
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This is incorrect, @Id takes precedence. I will update the change during the merge.

|===

The following outlines what type conversion, if any, will be done on the property mapped to the _id document field.

* If a field named `id` is declared as a String or BigInteger in the Java class it will be converted to and stored as an ObjectId if possible.
ObjectId as a field type is also valid.
If you specify a value for `id` in your application, the conversion to an ObjectId is detected to the MongoDB driver.
If the specified `id` value cannot be converted to an ObjectId, then the value will be stored as is in the document's _id field.
If you specify a value for `id` in your application, the conversion to an ObjectId is done by the MongoDB driver.
If the specified `id` value cannot be converted to an ObjectId, then the value will be stored as is in the document's `_id` field.
This also applies if the field is annotated with `@Id`.
* If a field is annotated with `@MongoId` in the Java class it will be converted to and stored as using its actual type.
No further conversion happens unless `@MongoId` declares a desired field type.
If no value is provided for the `id` field, a new `ObjectId` will be created and converted to the properties type.
* If a field is annotated with `@MongoId(FieldType.…)` in the Java class it will be attempted to convert the value to the declared `FieldType`.
If no value is provided for the `id` field, a new `ObjectId` will be created and converted to the declared type.
* If a field named `id` id field is not declared as a String, BigInteger, or ObjectID in the Java class then you should assign it a value in your application so it can be stored 'as-is' in the document's _id field.
* If a field named `id` is not declared as a String, BigInteger, or ObjectID in the Java class then you should assign it a value in your application so it can be stored 'as-is' in the document's `_id` field.
* If no field named `id` is present in the Java class then an implicit `_id` file will be generated by the driver but not mapped to a property or field of the Java class.

When querying and updating `MongoTemplate` will use the converter to handle conversions of the `Query` and `Update` objects that correspond to the above rules for saving documents so field names and types used in your queries will be able to match what is in your domain classes.
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