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• DeserializerCache.java

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com.fasterxml.jackson.databind.deser.DeserializerCache Maven / Gradle / Ivy

package com.fasterxml.jackson.databind.deser;

import java.util.HashMap;

import com.fasterxml.jackson.annotation.JsonFormat;
import com.fasterxml.jackson.databind.*;
import com.fasterxml.jackson.databind.deser.std.StdDelegatingDeserializer;
import com.fasterxml.jackson.databind.introspect.Annotated;
import com.fasterxml.jackson.databind.type.*;
import com.fasterxml.jackson.databind.util.ClassUtil;
import com.fasterxml.jackson.databind.util.Converter;
import com.fasterxml.jackson.databind.util.LRUMap;

/**
 * Class that defines caching layer between callers (like
 * {@link ObjectMapper},
 * {@link com.fasterxml.jackson.databind.DeserializationContext})
 * and classes that construct deserializers
 * ({@link com.fasterxml.jackson.databind.deser.DeserializerFactory}).
 */
public final class DeserializerCache
    implements java.io.Serializable // since 2.1
{
    private static final long serialVersionUID = 1L;

    /*
    /**********************************************************
    /* Caching
    /**********************************************************
     */

    /**
     * We will also cache some dynamically constructed deserializers;
     * specifically, ones that are expensive to construct.
     * This currently means bean, Enum and container deserializers.
     */
    final protected LRUMap> _cachedDeserializers;

    /**
     * During deserializer construction process we may need to keep track of partially
     * completed deserializers, to resolve cyclic dependencies. This is the
     * map used for storing deserializers before they are fully complete.
     */
    final protected HashMap> _incompleteDeserializers
        = new HashMap>(8);

    /*
    /**********************************************************
    /* Life-cycle
    /**********************************************************
     */

    public DeserializerCache() {
        this(2000); // see [databind#1995]
    }

    public DeserializerCache(int maxSize) {
        int initial = Math.min(64, maxSize>>2);
        _cachedDeserializers = new LRUMap<>(initial, maxSize);
    }

    /*
    /**********************************************************
    /* JDK serialization handling
    /**********************************************************
     */

    Object writeReplace() {
        // instead of making this transient, just clear it:
        _incompleteDeserializers.clear();
        return this;
    }
    
    /*
    /**********************************************************
    /* Access to caching aspects
    /**********************************************************
     */

    /**
     * Method that can be used to determine how many deserializers this
     * provider is caching currently 
     * (if it does caching: default implementation does)
     * Exact count depends on what kind of deserializers get cached;
     * default implementation caches only dynamically constructed deserializers,
     * but not eagerly constructed standard deserializers (which is different
     * from how serializer provider works).
     *

     * The main use case for this method is to allow conditional flushing of
     * deserializer cache, if certain number of entries is reached.
     */
    public int cachedDeserializersCount() {
        return _cachedDeserializers.size();
    }

    /**
     * Method that will drop all dynamically constructed deserializers (ones that
     * are counted as result value for {@link #cachedDeserializersCount}).
     * This can be used to remove memory usage (in case some deserializers are
     * only used once or so), or to force re-construction of deserializers after
     * configuration changes for mapper than owns the provider.
     */
    public void flushCachedDeserializers() {
        _cachedDeserializers.clear();       
    }

    /*
    /**********************************************************
    /* General deserializer locating method
    /**********************************************************
     */

    /**
     * Method called to get hold of a deserializer for a value of given type;
     * or if no such deserializer can be found, a default handler (which
     * may do a best-effort generic serialization or just simply
     * throw an exception when invoked).
     *

     * Note: this method is only called for value types; not for keys.
     * Key deserializers can be accessed using {@link #findKeyDeserializer}.
     *

     * Note also that deserializer returned is guaranteed to be resolved
     * (if it is of type {@link ResolvableDeserializer}), but
     * not contextualized (wrt {@link ContextualDeserializer}): caller
     * has to handle latter if necessary.
     *
     * @param ctxt Deserialization context
     * @param propertyType Declared type of the value to deserializer (obtained using
     *   'setter' method signature and/or type annotations
     *
     * @throws JsonMappingException if there are fatal problems with
     *   accessing suitable deserializer; including that of not
     *   finding any serializer
     */
    public JsonDeserializer