com.google.gson

Interface ToNumberStrategy

All Known Implementing Classes:

ToNumberPolicy

public interface ToNumberStrategy

A strategy that is used to control how numbers should be deserialized for Object and Number when a concrete type of the deserialized number is unknown in advance. By default, Gson uses the following deserialization strategies:

• Double values are returned for JSON numbers if the deserialization type is declared as Object, see ToNumberPolicy.DOUBLE;
• Lazily parsed number values are returned if the deserialization type is declared as Number, see ToNumberPolicy.LAZILY_PARSED_NUMBER.

For historical reasons, Gson does not support deserialization of arbitrary-length numbers for Object and Number by default, potentially causing precision loss. However, RFC 8259 permits this:

   This specification allows implementations to set limits on the range
   and precision of numbers accepted.  Since software that implements
   IEEE 754 binary64 (double precision) numbers [IEEE754] is generally
   available and widely used, good interoperability can be achieved by
   implementations that expect no more precision or range than these
   provide, in the sense that implementations will approximate JSON
   numbers within the expected precision.  A JSON number such as 1E400
   or 3.141592653589793238462643383279 may indicate potential
   interoperability problems, since it suggests that the software that
   created it expects receiving software to have greater capabilities
   for numeric magnitude and precision than is widely available.
 

To overcome the precision loss, use for example ToNumberPolicy.LONG_OR_DOUBLE or ToNumberPolicy.BIG_DECIMAL.

See Also:

ToNumberPolicy, GsonBuilder.setObjectToNumberStrategy(ToNumberStrategy), GsonBuilder.setNumberToNumberStrategy(ToNumberStrategy)

Method Summary

Modifier and Type	Method and Description
java.lang.Number	readNumber(JsonReader in) Reads a number from the given JSON reader.

Method Detail

readNumber

java.lang.Number readNumber(JsonReader in)
                     throws java.io.IOException

Reads a number from the given JSON reader. A strategy is supposed to read a single value from the reader, and the read value is guaranteed never to be null.

Parameters:

in - JSON reader to read a number from

Returns:

number read from the JSON reader.

Throws:

java.io.IOException