• JacksonBestPracticeThreadSafety

Jackson Best Practices: Thread Safety

Jackson follows thread-safety rules typical for modern factory-based Java data format handlers (similar to what, say, Stax or JAXP implementations do). For example:

• Factories (ObjectMapper, JsonFactory) are thread-safe once configured: so ensure that all configuration is done from a single thread, and before instantiating anything with factory.

• Reader/writer instances (like JsonParser and JsonParser) are not thread-safe -- there is usually no need for them to be, but if for some reason you need to access them from multiple threads, external synchronization is needed

• All transformer objects (custom serializers, deserializers) are expected to be stateless, and thereby thread safe -- state has to be stored somewhere outside instances (in ThreadLocal or context objects passed in, like DeserializationContext).

So... ?

Basically, following usage pattern is perfectly fine, regarding thread-safety:

class MyJsonProcessingClass
{
   protected final static ObjectMapper defaultMapper = new ObjectMapper();
   static { // if you need to change default configuration:
     defaultMapper.configure(SerializationConfig.Feature.USE_STATIC_TYPING, true); // faster this way, not default
   }

   public String doJson(MyData dataObject) throws IOException
   {
      return defaultMapper.writeValueAsString(dataObject);
   }
}

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