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/introspect/SimpleMixInResolver.java

package com.fasterxml.jackson.databind.introspect;

import java.util.HashMap;
import java.util.Map;

import com.fasterxml.jackson.databind.type.ClassKey;

/**
 * Simple implementation of {@link ClassIntrospector.MixInResolver}
 * that just uses a {@link java.util.Map} for containing mapping
 * from target to mix-in classes.
 *<p>
 * Implementation is only thread-safe after initialization (that is,
 * when underlying Map is not modified but only read).
 * 
 * @since 2.6
 */
public class SimpleMixInResolver
    implements ClassIntrospector.MixInResolver,
        java.io.Serializable
{
    private static final long serialVersionUID = 1L;

    /**
     * External resolver that gets called before looking at any locally defined
     * mix-in target classes.
     */
    protected final ClassIntrospector.MixInResolver _overrides;

    /**
     * Simple mix-in targets defined locally.
     */
    protected Map<ClassKey,Class<?>> _localMixIns;

    public SimpleMixInResolver(ClassIntrospector.MixInResolver overrides) {
        _overrides = overrides;
    }

    protected SimpleMixInResolver(ClassIntrospector.MixInResolver overrides,
            Map<ClassKey,Class<?>> mixins) {
        _overrides = overrides;
        _localMixIns = mixins;
    }

    /**
     * Mutant factory for constructor a new resolver instance with given
     * mix-in resolver override.
     */
    public SimpleMixInResolver withOverrides(ClassIntrospector.MixInResolver overrides) {
        return new SimpleMixInResolver(overrides, _localMixIns);
    }

    /**
     * Mutant factory method that constructs a new instance that has no locally
     * defined mix-in/target mappings.
     */
    public SimpleMixInResolver withoutLocalDefinitions() {
        return new SimpleMixInResolver(_overrides, null);
    }

    public void setLocalDefinitions(Map<Class<?>, Class<?>> sourceMixins) {
        if (sourceMixins == null || sourceMixins.isEmpty()) {
            _localMixIns = null;
        } else {
            Map<ClassKey,Class<?>> mixIns = new HashMap<ClassKey,Class<?>>(sourceMixins.size());
            for (Map.Entry<Class<?>,Class<?>> en : sourceMixins.entrySet()) {
                mixIns.put(new ClassKey(en.getKey()), en.getValue());
            }
            _localMixIns = mixIns;
        }
    }

    public void addLocalDefinition(Class<?> target, Class<?> mixinSource) {
        if (_localMixIns == null) {
            _localMixIns = new HashMap<ClassKey,Class<?>>();
        }
        _localMixIns.put(new ClassKey(target), mixinSource);
    }

    @Override
    public SimpleMixInResolver copy() {
        ClassIntrospector.MixInResolver overrides = (_overrides == null)
                ? null : _overrides.copy();
        Map<ClassKey,Class<?>> mixIns = (_localMixIns == null)
                ? null : new HashMap<ClassKey,Class<?>>(_localMixIns);
        return new SimpleMixInResolver(overrides, mixIns);
    }

    @Override
    public Class<?> findMixInClassFor(Class<?> cls)
    {
        Class<?> mixin = (_overrides == null) ? null : _overrides.findMixInClassFor(cls);
        if (mixin == null && (_localMixIns != null)) {
            mixin = _localMixIns.get(new ClassKey(cls));
        }
        return mixin;
    }

    public int localSize() {
        return (_localMixIns == null) ? 0 : _localMixIns.size();
    }

    /**
     * Method that may be called for optimization purposes, to see if calls to
     * mix-in resolver may be avoided. Return value of {@code true} means that
     * it is possible that a mix-in class will be found; {@code false} that no
     * mix-in will ever be found. In latter case caller can avoid calls altogether.
     *<p>
     * Note that the reason for "empty" resolvers is to use "null object" for simplifying
     * code.
     *
     * @return True, if this resolver MAY have mix-ins to apply; false if not (it
     *   is "empty")
     *
     * @since 2.10.1
     */
    public boolean hasMixIns() {
        if (_localMixIns == null) {
            // if neither local mix-ins nor overrides, no mix-ins
            if (_overrides == null) {
                return false;
            }
            // or, if no local mix-ins and can delegate to resolver
            if (_overrides instanceof SimpleMixInResolver) {
                return ((SimpleMixInResolver) _overrides).hasMixIns();
            }
        }
        // cannot rule out the possibility, so...
        return true;
    }
}

⏎ com/fasterxml/jackson/databind/introspect/SimpleMixInResolver.java

 

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