Jackson is "the Java JSON library" or "the best JSON parser for Java". Or simply as "JSON for Java".

Jackson Annotations Source Code files are provided in the source packge (jackson-annotations-2.12.4-sources.jar). You can download it at Jackson Maven Website.

You can also browse Jackson Annotations Source Code below:

⏎ com/fasterxml/jackson/databind/deser/impl/JDKValueInstantiators.java

package com.fasterxml.jackson.databind.deser.impl;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.Map;

import com.fasterxml.jackson.core.JsonLocation;
import com.fasterxml.jackson.databind.DeserializationConfig;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.deser.ValueInstantiator;
import com.fasterxml.jackson.databind.deser.std.JsonLocationInstantiator;

/**
 * Container for a set of {@link ValueInstantiator}s used for certain critical
 * JDK value types, either as performance optimization for initialization time observed
 * by profiling, or due to difficulty in otherwise finding constructors.
 *
 * @since 2.10
 */
public abstract class JDKValueInstantiators
{
    public static ValueInstantiator findStdValueInstantiator(DeserializationConfig config,
            Class<?> raw)
    {
        if (raw == JsonLocation.class) {
            return new JsonLocationInstantiator();
        }
        // [databind#1868]: empty List/Set/Map
        // [databind#2416]: optimize commonly needed default creators
        if (Collection.class.isAssignableFrom(raw)) {
            if (raw == ArrayList.class) {
                return ArrayListInstantiator.INSTANCE;
            }
            if (Collections.EMPTY_SET.getClass() == raw) {
                return new ConstantValueInstantiator(Collections.EMPTY_SET);
            }
            if (Collections.EMPTY_LIST.getClass() == raw) {
                return new ConstantValueInstantiator(Collections.EMPTY_LIST);
            }
        } else if (Map.class.isAssignableFrom(raw)) {
            if (raw == LinkedHashMap.class) {
                return LinkedHashMapInstantiator.INSTANCE;
            }
            if (raw == HashMap.class) {
                return HashMapInstantiator.INSTANCE;
            }
            if (Collections.EMPTY_MAP.getClass() == raw) {
                return new ConstantValueInstantiator(Collections.EMPTY_MAP);
            }
        }
        return null;
    }

    private static class ArrayListInstantiator
        extends ValueInstantiator.Base
        implements java.io.Serializable
    {
        private static final long serialVersionUID = 2L;

        public final static ArrayListInstantiator INSTANCE = new ArrayListInstantiator();
        public ArrayListInstantiator() {
            super(ArrayList.class);
        }

        @Override
        public boolean canInstantiate() { return true; }

        @Override
        public boolean canCreateUsingDefault() {  return true; }

        @Override
        public Object createUsingDefault(DeserializationContext ctxt) throws IOException {
            return new ArrayList<>();
        }
    }

    private static class HashMapInstantiator
        extends ValueInstantiator.Base
        implements java.io.Serializable
    {
        private static final long serialVersionUID = 2L;

        public final static HashMapInstantiator INSTANCE = new HashMapInstantiator();

        public HashMapInstantiator() {
            super(HashMap.class);
        }

        @Override
        public boolean canInstantiate() { return true; }

        @Override
        public boolean canCreateUsingDefault() {  return true; }

        @Override
        public Object createUsingDefault(DeserializationContext ctxt) throws IOException {
            return new HashMap<>();
        }
    }

    private static class LinkedHashMapInstantiator
        extends ValueInstantiator.Base
        implements java.io.Serializable
    {
        private static final long serialVersionUID = 2L;

        public final static LinkedHashMapInstantiator INSTANCE = new LinkedHashMapInstantiator();

        public LinkedHashMapInstantiator() {
            super(LinkedHashMap.class);
        }

        @Override
        public boolean canInstantiate() { return true; }

        @Override
        public boolean canCreateUsingDefault() {  return true; }

        @Override
        public Object createUsingDefault(DeserializationContext ctxt) throws IOException {
            return new LinkedHashMap<>();
        }
    }

    private static class ConstantValueInstantiator
        extends ValueInstantiator.Base
        implements java.io.Serializable
    {
        private static final long serialVersionUID = 2L;

        protected final Object _value;

        public ConstantValueInstantiator(Object value) {
            super(value.getClass());
            _value = value;
        }

        @Override // yes, since default ctor works
        public boolean canInstantiate() { return true; }

        @Override
        public boolean canCreateUsingDefault() {  return true; }

        @Override
        public Object createUsingDefault(DeserializationContext ctxt) throws IOException {
            return _value;
        }
    }

}

⏎ com/fasterxml/jackson/databind/deser/impl/JDKValueInstantiators.java

 

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⇐ Jackson Data Binding Source Code

⇑ Downloading and Reviewing jackson-*.jar

⇑⇑ Jackson - Java JSON library