Spring Data Conversion

Spring3 introduces a more general type conversion system, which defines the SPI interface (converter, etc.) and the corresponding runtime execution type conversion API (Conversionservice, etc.), which in spring is similar to the PropertyEditor function, You can substitute PropertyEditor to convert the value of an external bean property to the type required by the Bean property.

The type conversion system is spring-generic and is defined in the Org.springframework.core.convert package, not just in the spring Web MVC scenario. The goal is to completely replace the propertyeditor, providing a stateless, strongly typed type conversion system that can be converted between any type, and can be used wherever needed, such as spel, data binding.

1. Type converter: provides implementation support for type conversions.

2. Type converter registrar, type Conversion Service: provides type converter registration support, runtime type conversion API support.

Defaultconversionservice: The default type conversion service implementation;

Defaultformattingconversionservice: A type conversion service implementation with data formatting support that is typically implemented with this service.

3. The spring built-in type converter is as follows:

Class name	Description
First group: Scalar converters
Stringtobooleanconverter	String----->boolean TRUE:TRUE/ON/YES/1; false:false/off/no/0
Objecttostringconverter	Object----->string Call the ToString Method transformation
Stringtonumberconverterfactory	String----->number (such as Integer, Long, and so on)
Numbertonumberconverterfactory	Number subtype (integer, long, double, etc.) <--> number subtype (integer, long, double, etc.)
Stringtocharacterconverter	String----->java.lang.character Takes the first character of a string
Numbertocharacterconverter	Number subtype (Integer, Long, double, and so on)-Java.lang.Character
Charactertonumberfactory	Java.lang.character-->number subtype (Integer, Long, double, etc.)
Stringtoenumconverterfactory	String----->enum Type Convert a string to the required enum type by enum.valueof
Enumtostringconverter	Enum type----->string Returns the name () value of an Enum object
Stringtolocaleconverter	String----->java.util.local
Propertiestostringconverter	Java.util.Properties----->string Default decoding via Iso-8859-1
Stringtopropertiesconverter	String----->java.util.properties Use ISO-8859-1 encoding by default
Second group: sets, array-dependent converters
Arraytocollectionconverter	Arbitrary s array----> arbitrary t Set (List, set)
Collectiontoarrayconverter	Any t set (List, set)----> arbitrary s array
Arraytoarrayconverter	Arbitrary s Array <----> arbitrary t array
Collectiontocollectionconverter	Any t set (list, set) <----> Any T collection (list, set) That is, type conversions between collections
Maptomapconverter	Conversion between map<---->map
Arraytostringconverter	Arbitrary s array---->string type
Stringtoarrayconverter	String-----> Array The default is split by "," and the whitespace (trim) is removed from both sides of the string.
Arraytoobjectconverter	Arbitrary s array----> conversion of any object (returns the source object directly if the target type is compatible with the source type; otherwise returns the first element of the S array and casts the type)
Objecttoarrayconverter	Object-----> Unit Prime Group
Collectiontostringconverter	Any t set (List, set)---->string type
Stringtocollectionconverter	String-----> collection (List, set) The default is split by "," and the whitespace (trim) is removed from both sides of the string.
Collectiontoobjectconverter	Any t set----> Conversion of any object (returns the source object directly if the target type is compatible with the source type; otherwise returns the first element of the S array and casts the type)
Objecttocollectionconverter	Object-----> Single Element collection
Third group: Default (Fallback) Converter: The previous converter cannot be converted when called
Objecttoobjectconverter	Object (S)----->object (T) First try valueof for conversion, no then try new constructor (S)
Idtoentityconverter	Id (S)----->entity (T) Find and call public static T Find[entityname] (S) Gets the target object, EntityName is a simple type of type T
Fallbackobjecttostringconverter	Object----->string Conversionservice called (The ToString () method of the executing object) as a recovery use, that is, when other converters cannot be converted

S: Represents the source Type, T: Represents the target type

The converters above are automatically registered when using the transform service to implement Defaultconversionservice and Defaultformattingconversionservice.

Spring Data Conversion