a5dcbf043a
We now use the springDocsUrl attribute provided via spring-projects/spring-data-build#1895 to resolve links to framework documentation. Original Pull Request: #4267
106 lines
3.5 KiB
Plaintext
106 lines
3.5 KiB
Plaintext
[[mongo.custom-converters]]
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== Custom Conversions - Overriding Default Mapping
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The most trivial way of influencing the mapping result is by specifying the desired native MongoDB target type via the
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`@Field` annotation. This allows to work with non MongoDB types like `BigDecimal` in the domain model while persisting
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values in native `org.bson.types.Decimal128` format.
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.Explicit target type mapping
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====
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[source,java]
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----
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public class Payment {
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@Id String id; <1>
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@Field(targetType = FieldType.DECIMAL128) <2>
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BigDecimal value;
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Date date; <3>
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}
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----
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[source,java]
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----
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{
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"_id" : ObjectId("5ca4a34fa264a01503b36af8"), <1>
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"value" : NumberDecimal(2.099), <2>
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"date" : ISODate("2019-04-03T12:11:01.870Z") <3>
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}
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----
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<1> String _id_ values that represent a valid `ObjectId` are converted automatically. See <<mongo-template.id-handling>>
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for details.
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<2> The desired target type is explicitly defined as `Decimal128` which translates to `NumberDecimal`. Otherwise the
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`BigDecimal` value would have been truned into a `String`.
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<3> `Date` values are handled by the MongoDB driver itself an are stored as `ISODate`.
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====
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The snippet above is handy for providing simple type hints. To gain more fine-grained control over the mapping process,
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you can register Spring converters with the `MongoConverter` implementations, such as the `MappingMongoConverter`.
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The `MappingMongoConverter` checks to see if any Spring converters can handle a specific class before attempting to map the object itself. To 'hijack' the normal mapping strategies of the `MappingMongoConverter`, perhaps for increased performance or other custom mapping needs, you first need to create an implementation of the Spring `Converter` interface and then register it with the `MappingConverter`.
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NOTE: For more information on the Spring type conversion service, see the reference docs link:{springDocsUrl}/core.html#validation[here].
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[[mongo.custom-converters.writer]]
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=== Saving by Using a Registered Spring Converter
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The following example shows an implementation of the `Converter` that converts from a `Person` object to a `org.bson.Document`:
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[source,java]
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----
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import org.springframework.core.convert.converter.Converter;
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import org.bson.Document;
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public class PersonWriteConverter implements Converter<Person, Document> {
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public Document convert(Person source) {
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Document document = new Document();
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document.put("_id", source.getId());
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document.put("name", source.getFirstName());
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document.put("age", source.getAge());
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return document;
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}
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}
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----
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[[mongo.custom-converters.reader]]
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=== Reading by Using a Spring Converter
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The following example shows an implementation of a `Converter` that converts from a `Document` to a `Person` object:
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[source,java]
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----
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public class PersonReadConverter implements Converter<Document, Person> {
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public Person convert(Document source) {
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Person p = new Person((ObjectId) source.get("_id"), (String) source.get("name"));
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p.setAge((Integer) source.get("age"));
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return p;
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}
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}
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----
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[[mongo.custom-converters.xml]]
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=== Registering Spring Converters with the `MongoConverter`
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[source,java]
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----
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class MyMongoConfiguration extends AbstractMongoClientConfiguration {
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@Override
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public String getDatabaseName() {
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return "database";
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}
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@Override
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protected void configureConverters(MongoConverterConfigurationAdapter adapter) {
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adapter.registerConverter(new com.example.PersonReadConverter());
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adapter.registerConverter(new com.example.PersonWriteConverter());
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}
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}
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----
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include::../{spring-data-commons-docs}/custom-conversions.adoc[leveloffset=+3]
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