How correctly and thread safe reuse Jackson ObjectReader?

Question

Jackson have ObjectReader and documentation says that you need to use it for thread safety. But I can't understand how to do it correctly

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.ObjectReader;

import java.io.IOException;
import java.util.Map;

public class JsonParser {
    private ObjectMapper OBJECT_MAPPER = new ObjectMapper();
    private ObjectReader OBJECT_READER = new ObjectMapper().readerFor(Map.class);

    public Map<String, String> parseJson1(String json) throws IOException {
        ObjectReader objectReader = OBJECT_MAPPER.readerFor(Map.class);
        return objectReader.readValue(json);
    }

    public Map<String, String> parseJson2(String json) throws IOException {
        return OBJECT_READER.readValue(json);
    }
}

I wrote two samples

1. parseJson1() - creates ObjectReader from ObjectMapper on each parsing
2. parseJson2() - reuses single instance on ObjectReader

Which of them is right?

Answer 1

Documentation said it's "fully thread-safe" it means you can use parseJson2 safely without worring about invoking this method in concurrent threads.

https://fasterxml.github.io/jackson-databind/javadoc/2.5/com/fasterxml/jackson/databind/ObjectReader.html

Uses "fluent" (or, kind of, builder) pattern so that instances are immutable (and thus fully thread-safe with no external synchronization); new instances are constructed for different configurations. Instances are initially constructed by ObjectMapper and can be reused, shared, cached; both because of thread-safety and because instances are relatively light-weight.