com.fasterxml.jackson.databind.deser.std

Class FromStringDeserializer<T>

java.lang.Object

com.fasterxml.jackson.databind.JsonDeserializer<T>

com.fasterxml.jackson.databind.deser.std.StdDeserializer<T>

com.fasterxml.jackson.databind.deser.std.StdScalarDeserializer<T>

com.fasterxml.jackson.databind.deser.std.FromStringDeserializer<T>

All Implemented Interfaces:

NullValueProvider, ValueInstantiator.Gettable, java.io.Serializable

Direct Known Subclasses:

CoreXMLDeserializers.Std, DOMDeserializer, FromStringDeserializer.Std, UUIDDeserializer

public abstract class FromStringDeserializer<T>
extends StdScalarDeserializer<T>

Base class for simple deserializers that serialize values from String representation: this includes JSON Strings and other Scalar values that can be coerced into text, like Numbers and Booleans). Simple JSON String values are trimmed using String.trim(). Partial deserializer implementation will try to first access current token as a String, calls _deserialize(String,DeserializationContext) and returns return value. If this does not work (current token not a simple scalar type), attempts are made so that:

• Embedded values (JsonToken.VALUE_EMBEDDED_OBJECT) are returned as-is if they are of compatible type
• Arrays may be "unwrapped" if (and only if) DeserializationFeature.UNWRAP_SINGLE_VALUE_ARRAYS is enabled, and array contains just a single scalar value that can be deserialized (for example, JSON Array with single JSON String element).

Special handling includes:

• Null values (JsonToken.VALUE_NULL) are handled by returning value returned by JsonDeserializer.getNullValue(DeserializationContext): default implementation simply returns Java `null` but this may be overridden.
• Empty String (after trimming) will result in _deserializeFromEmptyString() getting called, and return value being returned as deserialization: default implementation simply returns `null`.

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	FromStringDeserializer.Std "Chameleon" deserializer that works on simple types that are deserialized from a simple String.

Nested classes/interfaces inherited from class com.fasterxml.jackson.databind.JsonDeserializer

JsonDeserializer.None

Method Summary

Modifier and Type	Method and Description
T	deserialize(JsonParser p, DeserializationContext ctxt) Method that can be called to ask implementation to deserialize JSON content into the value type this serializer handles.
static FromStringDeserializer<?>	findDeserializer(java.lang.Class<?> rawType) Factory method for trying to find a deserializer for one of supported types that have simple from-String serialization.
LogicalType	logicalType() Method for accessing logical type of values this deserializer produces.
static java.lang.Class<?>[]	types()

Methods inherited from class com.fasterxml.jackson.databind.deser.std.StdScalarDeserializer

deserialize, deserializeWithType, getEmptyAccessPattern, getNullAccessPattern, supportsUpdate

Methods inherited from class com.fasterxml.jackson.databind.deser.std.StdDeserializer

getValueClass, getValueInstantiator, getValueType, getValueType, handledType

Methods inherited from class com.fasterxml.jackson.databind.JsonDeserializer

deserializeWithType, findBackReference, getAbsentValue, getDelegatee, getEmptyValue, getEmptyValue, getKnownPropertyNames, getNullValue, getNullValue, getObjectIdReader, isCachable, replaceDelegatee, unwrappingDeserializer

Methods inherited from class java.lang.Object

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

Method Detail

types

public static java.lang.Class<?>[] types()

findDeserializer

public static FromStringDeserializer<?> findDeserializer(java.lang.Class<?> rawType)

Factory method for trying to find a deserializer for one of supported types that have simple from-String serialization.

logicalType

public LogicalType logicalType()

Description copied from class: JsonDeserializer

Method for accessing logical type of values this deserializer produces. Typically used for further configuring handling of values, for example, to find which coercions are legal.

Overrides:

logicalType in class StdScalarDeserializer<T>

Returns:

Logical type of values this deserializer produces, if known; null if not

deserialize

public T deserialize(JsonParser p,
                     DeserializationContext ctxt)
              throws java.io.IOException

Description copied from class: JsonDeserializer

Method that can be called to ask implementation to deserialize JSON content into the value type this serializer handles. Returned instance is to be constructed by method itself.

Pre-condition for this method is that the parser points to the first event that is part of value to deserializer (and which is never JSON 'null' literal, more on this below): for simple types it may be the only value; and for structured types the Object start marker or a FIELD_NAME.

The two possible input conditions for structured types result from polymorphism via fields. In the ordinary case, Jackson calls this method when it has encountered an OBJECT_START, and the method implementation must advance to the next token to see the first field name. If the application configures polymorphism via a field, then the object looks like the following.

      {
          "@class": "class name",
          ...
      }
  

Jackson consumes the two tokens (the @class field name and its value) in order to learn the class and select the deserializer. Thus, the stream is pointing to the FIELD_NAME for the first field after the @class. Thus, if you want your method to work correctly both with and without polymorphism, you must begin your method with:

       if (p.currentToken() == JsonToken.START_OBJECT) {
         p.nextToken();
       }
  

This results in the stream pointing to the field name, so that the two conditions align.

Post-condition is that the parser will point to the last event that is part of deserialized value (or in case deserialization fails, event that was not recognized or usable, which may be the same event as the one it pointed to upon call).

Note that this method is never called for JSON null literal, and thus deserializers need (and should) not check for it.

Specified by:

deserialize in class JsonDeserializer<T>

Parameters:

p - Parsed used for reading JSON content

ctxt - Context that can be used to access information about this deserialization activity.

Returns:

Deserialized value

Throws:

java.io.IOException