com.fasterxml.jackson.databind.deser
Class DeserializerCache

java.lang.Object
  com.fasterxml.jackson.databind.deser.DeserializerCache

public final class DeserializerCache
extends Object

Class that defines caching layer between callers (like ObjectMapper, DeserializationContext) and classes that construct deserializers (DeserializerFactory).

Field Summary

protected ConcurrentHashMap<JavaType,JsonDeserializer<Object>>	_cachedDeserializers We will also cache some dynamically constructed deserializers; specifically, ones that are expensive to construct.
protected HashMap<JavaType,JsonDeserializer<Object>>	_incompleteDeserializers During deserializer construction process we may need to keep track of partially completed deserializers, to resolve cyclic dependencies.

Constructor Summary

DeserializerCache()

Method Summary

protected JsonDeserializer<Object>	_createAndCache2(DeserializationContext ctxt, DeserializerFactory factory, JavaType type) Method that handles actual construction (via factory) and caching (both intermediate and eventual)
protected JsonDeserializer<Object>	_createAndCacheValueDeserializer(DeserializationContext ctxt, DeserializerFactory factory, JavaType type) Method that will try to create a deserializer for given type, and resolve and cache it if necessary
protected JsonDeserializer<Object>	_createDeserializer(DeserializationContext ctxt, DeserializerFactory factory, JavaType type) Method that does the heavy lifting of checking for per-type annotations, find out full type, and figure out which actual factory method to call.
protected JsonDeserializer<Object>	_findCachedDeserializer(JavaType type)
protected KeyDeserializer	_handleUnknownKeyDeserializer(JavaType type)
protected JsonDeserializer<Object>	_handleUnknownValueDeserializer(JavaType type)
int	cachedDeserializersCount() Method that can be used to determine how many deserializers this provider is caching currently (if it does caching: default implementation does) Exact count depends on what kind of deserializers get cached; default implementation caches only dynamically constructed deserializers, but not eagerly constructed standard deserializers (which is different from how serializer provider works).
protected JsonDeserializer<Object>	findDeserializerFromAnnotation(DeserializationContext ctxt, Annotated ann) Helper method called to check if a class or method has annotation that tells which class to use for deserialization.
KeyDeserializer	findKeyDeserializer(DeserializationContext ctxt, DeserializerFactory factory, JavaType type) Method called to get hold of a deserializer to use for deserializing keys for Map.
JsonDeserializer<Object>	findValueDeserializer(DeserializationContext ctxt, DeserializerFactory factory, JavaType propertyType) Method called to get hold of a deserializer for a value of given type; or if no such deserializer can be found, a default handler (which may do a best-effort generic serialization or just simply throw an exception when invoked).
void	flushCachedDeserializers() Method that will drop all dynamically constructed deserializers (ones that are counted as result value for cachedDeserializersCount()).
boolean	hasValueDeserializerFor(DeserializationContext ctxt, DeserializerFactory factory, JavaType type) Method called to find out whether provider would be able to find a deserializer for given type, using a root reference (i.e.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

_cachedDeserializers

protected final ConcurrentHashMap<JavaType,JsonDeserializer<Object>> _cachedDeserializers

We will also cache some dynamically constructed deserializers; specifically, ones that are expensive to construct. This currently means bean and Enum deserializers; array, List and Map deserializers will not be cached.

Given that we don't expect much concurrency for additions (should very quickly converge to zero after startup), let's explicitly define a low concurrency setting.

_incompleteDeserializers

protected final HashMap<JavaType,JsonDeserializer<Object>> _incompleteDeserializers

During deserializer construction process we may need to keep track of partially completed deserializers, to resolve cyclic dependencies. This is the map used for storing deserializers before they are fully complete.

Constructor Detail

DeserializerCache

public DeserializerCache()

Method Detail

cachedDeserializersCount

public int cachedDeserializersCount()

Method that can be used to determine how many deserializers this provider is caching currently (if it does caching: default implementation does) Exact count depends on what kind of deserializers get cached; default implementation caches only dynamically constructed deserializers, but not eagerly constructed standard deserializers (which is different from how serializer provider works).

The main use case for this method is to allow conditional flushing of deserializer cache, if certain number of entries is reached.

flushCachedDeserializers

public void flushCachedDeserializers()

Method that will drop all dynamically constructed deserializers (ones that are counted as result value for cachedDeserializersCount()). This can be used to remove memory usage (in case some deserializers are only used once or so), or to force re-construction of deserializers after configuration changes for mapper than owns the provider.

findValueDeserializer

public JsonDeserializer<Object> findValueDeserializer(DeserializationContext ctxt,
                                                      DeserializerFactory factory,
                                                      JavaType propertyType)
                                               throws JsonMappingException

Method called to get hold of a deserializer for a value of given type; or if no such deserializer can be found, a default handler (which may do a best-effort generic serialization or just simply throw an exception when invoked).

Note: this method is only called for value types; not for keys. Key deserializers can be accessed using findKeyDeserializer(com.fasterxml.jackson.databind.DeserializationContext, com.fasterxml.jackson.databind.deser.DeserializerFactory, com.fasterxml.jackson.databind.JavaType).

Note also that deserializer returned is guaranteed to be resolved (if it is of type ResolvableDeserializer), but not contextualized (wrt ContextualDeserializer): caller has to handle latter if necessary.

Parameters:

ctxt - Deserialization context

propertyType - Declared type of the value to deserializer (obtained using 'setter' method signature and/or type annotations

Throws:

JsonMappingException - if there are fatal problems with accessing suitable deserializer; including that of not finding any serializer

findKeyDeserializer

public KeyDeserializer findKeyDeserializer(DeserializationContext ctxt,
                                           DeserializerFactory factory,
                                           JavaType type)
                                    throws JsonMappingException

Method called to get hold of a deserializer to use for deserializing keys for Map.

Throws:

JsonMappingException - if there are fatal problems with accessing suitable key deserializer; including that of not finding any serializer

hasValueDeserializerFor

public boolean hasValueDeserializerFor(DeserializationContext ctxt,
                                       DeserializerFactory factory,
                                       JavaType type)

Method called to find out whether provider would be able to find a deserializer for given type, using a root reference (i.e. not through fields or membership in an array or collection)

_findCachedDeserializer

protected JsonDeserializer<Object> _findCachedDeserializer(JavaType type)

_createAndCacheValueDeserializer

protected JsonDeserializer<Object> _createAndCacheValueDeserializer(DeserializationContext ctxt,
                                                                    DeserializerFactory factory,
                                                                    JavaType type)
                                                             throws JsonMappingException

Method that will try to create a deserializer for given type, and resolve and cache it if necessary

Parameters:

ctxt - Currently active deserialization context

type - Type of property to deserialize

Throws:

JsonMappingException

_createAndCache2

protected JsonDeserializer<Object> _createAndCache2(DeserializationContext ctxt,
                                                    DeserializerFactory factory,
                                                    JavaType type)
                                             throws JsonMappingException

Method that handles actual construction (via factory) and caching (both intermediate and eventual)

Throws:

JsonMappingException

_createDeserializer

protected JsonDeserializer<Object> _createDeserializer(DeserializationContext ctxt,
                                                       DeserializerFactory factory,
                                                       JavaType type)
                                                throws JsonMappingException

Method that does the heavy lifting of checking for per-type annotations, find out full type, and figure out which actual factory method to call.

Throws:

JsonMappingException

findDeserializerFromAnnotation

protected JsonDeserializer<Object> findDeserializerFromAnnotation(DeserializationContext ctxt,
                                                                  Annotated ann)
                                                           throws JsonMappingException

Helper method called to check if a class or method has annotation that tells which class to use for deserialization. Returns null if no such annotation found.

Throws:

JsonMappingException

_handleUnknownValueDeserializer

protected JsonDeserializer<Object> _handleUnknownValueDeserializer(JavaType type)
                                                            throws JsonMappingException

Throws:

JsonMappingException

_handleUnknownKeyDeserializer

protected KeyDeserializer _handleUnknownKeyDeserializer(JavaType type)
                                                 throws JsonMappingException

Throws:

JsonMappingException