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

Jackson Databind Source Code files are provided in the source packge (jackson-databind-2.14.0-sources.jar). You can download it at Jackson Maven Website.

You can also browse Jackson Databind Source Code below:

⏎ com/fasterxml/jackson/databind/ext/OptionalHandlerFactory.java

package com.fasterxml.jackson.databind.ext;

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

import com.fasterxml.jackson.databind.*;
import com.fasterxml.jackson.databind.deser.Deserializers;
import com.fasterxml.jackson.databind.ser.Serializers;
import com.fasterxml.jackson.databind.ser.std.DateSerializer;
import com.fasterxml.jackson.databind.util.ClassUtil;

/**
 * Helper class used for isolating details of handling optional+external types
 * (javax.xml classes) from standard factories that offer them.
 *<p>
 * Note that 2.7 changed handling to slightly less dynamic, to avoid having to
 * traverse class hierarchy, which turned to be a performance issue in
 * certain cases. Since DOM classes are assumed to exist on all Java 1.6
 * environments (yes, even on Android/GAE), this part could be simplified by
 * slightly less dynamic lookups.
 *<p>
 * Also with 2.7 we are supporting JDK 1.7/Java 7 type(s).
 */
public class OptionalHandlerFactory implements java.io.Serializable
{
    private static final long serialVersionUID = 1;

    /* To make 2 main "optional" handler groups (javax.xml.stream)
     * more dynamic, we better only figure out handlers completely dynamically, if and
     * when they are needed. To do this we need to assume package prefixes.
     */
    private final static String PACKAGE_PREFIX_JAVAX_XML = "javax.xml.";

    private final static String SERIALIZERS_FOR_JAVAX_XML = "com.fasterxml.jackson.databind.ext.CoreXMLSerializers";
    private final static String DESERIALIZERS_FOR_JAVAX_XML = "com.fasterxml.jackson.databind.ext.CoreXMLDeserializers";

    // Plus we also have a single serializer for DOM Node:
//    private final static String CLASS_NAME_DOM_NODE = "org.w3c.dom.Node";
//    private final static String CLASS_NAME_DOM_DOCUMENT = "org.w3c.dom.Document";
    private final static String SERIALIZER_FOR_DOM_NODE = "com.fasterxml.jackson.databind.ext.DOMSerializer";
    private final static String DESERIALIZER_FOR_DOM_DOCUMENT = "com.fasterxml.jackson.databind.ext.DOMDeserializer$DocumentDeserializer";
    private final static String DESERIALIZER_FOR_DOM_NODE = "com.fasterxml.jackson.databind.ext.DOMDeserializer$NodeDeserializer";

    // // Since 2.7, we will assume DOM classes are always found, both due to JDK 1.6 minimum
    // // and because Android (and presumably GAE) have these classes

    // // 02-Nov-2020, Xakep_SDK: java.xml module classes may be missing
    // // in actual runtime, if module java.xml is not present
    private final static Class<?> CLASS_DOM_NODE;
    private final static Class<?> CLASS_DOM_DOCUMENT;

    static {
        Class<?> doc = null, node = null;
        try {
            node = org.w3c.dom.Node.class;
            doc = org.w3c.dom.Document.class;
        } catch (Throwable e) {
            // not optimal but will do
            // 02-Nov-2020, Xakep_SDK: Remove java.logging module dependency
//            Logger.getLogger(OptionalHandlerFactory.class.getName())
//                .log(Level.INFO, "Could not load DOM `Node` and/or `Document` classes: no DOM support");
        }
        CLASS_DOM_NODE = node;
        CLASS_DOM_DOCUMENT = doc;
    }

    // // But Java7 type(s) may or may not be; dynamic lookup should be fine, still
    // // (note: also assume it comes from JDK so that ClassLoader issues with OSGi
    // // can, I hope, be avoided?)

    private static final Java7Handlers _jdk7Helper;
    static {
        Java7Handlers x = null;
        try {
            x = Java7Handlers.instance();
        } catch (Throwable t) { }
        _jdk7Helper = x;
    }
    
    public final static OptionalHandlerFactory instance = new OptionalHandlerFactory();

    // classes from java.sql module, this module may or may not be present at runtime
    // (is included on Java 8, but not part of JDK core for Java 9 and beyond)
    private final Map<String, String> _sqlDeserializers;
    private final Map<String, Object> _sqlSerializers;

    private final static String CLS_NAME_JAVA_SQL_TIMESTAMP = "java.sql.Timestamp";
    private final static String CLS_NAME_JAVA_SQL_DATE = "java.sql.Date";
    private final static String CLS_NAME_JAVA_SQL_TIME = "java.sql.Time";
    private final static String CLS_NAME_JAVA_SQL_BLOB = "java.sql.Blob";
    private final static String CLS_NAME_JAVA_SQL_SERIALBLOB = "javax.sql.rowset.serial.SerialBlob";

    protected OptionalHandlerFactory() {
        _sqlDeserializers = new HashMap<>();
        _sqlDeserializers.put(CLS_NAME_JAVA_SQL_DATE,
                "com.fasterxml.jackson.databind.deser.std.DateDeserializers$SqlDateDeserializer");
        _sqlDeserializers.put(CLS_NAME_JAVA_SQL_TIMESTAMP,
                "com.fasterxml.jackson.databind.deser.std.DateDeserializers$TimestampDeserializer");
        // 09-Nov-2020, tatu: No deserializer for `java.sql.Blob` yet; would require additional
        //    dependency and not yet requested by anyone. Add if requested

        _sqlSerializers = new HashMap<>();
        // 09-Jan-2015, tatu: As per [databind#1073], let's try to guard against possibility
        //   of some environments missing `java.sql.` types

        // note: timestamps are very similar to java.util.Date, thus serialized as such
        _sqlSerializers.put(CLS_NAME_JAVA_SQL_TIMESTAMP, DateSerializer.instance);
        _sqlSerializers.put(CLS_NAME_JAVA_SQL_DATE, "com.fasterxml.jackson.databind.ser.std.SqlDateSerializer");
        _sqlSerializers.put(CLS_NAME_JAVA_SQL_TIME, "com.fasterxml.jackson.databind.ser.std.SqlTimeSerializer");

        // 09-Nov-2020, tatu: Not really optimal way to deal with these, problem  being that
        //   Blob is interface and actual instance we get is usually different. So may
        //   need to improve if we reported bugs. But for now, do this
        
        _sqlSerializers.put(CLS_NAME_JAVA_SQL_BLOB, "com.fasterxml.jackson.databind.ext.SqlBlobSerializer");
        _sqlSerializers.put(CLS_NAME_JAVA_SQL_SERIALBLOB, "com.fasterxml.jackson.databind.ext.SqlBlobSerializer");
    }

    /*
    /**********************************************************
    /* Public API
    /**********************************************************
     */
    
    public JsonSerializer<?> findSerializer(SerializationConfig config, JavaType type,
            BeanDescription beanDesc)
    {
        final Class<?> rawType = type.getRawClass();

        if (_IsXOfY(rawType, CLASS_DOM_NODE)) {
            return (JsonSerializer<?>) instantiate(SERIALIZER_FOR_DOM_NODE, type);
        }

        if (_jdk7Helper != null) {
            JsonSerializer<?> ser = _jdk7Helper.getSerializerForJavaNioFilePath(rawType);
            if (ser != null) {
                return ser;
            }
        }

        String className = rawType.getName();
        Object sqlHandler = _sqlSerializers.get(className);

        if (sqlHandler != null) {
            if (sqlHandler instanceof JsonSerializer<?>) {
                return (JsonSerializer<?>) sqlHandler;
            }
            // must be class name otherwise
            return (JsonSerializer<?>) instantiate((String) sqlHandler, type);
        }

        String factoryName;
        if (className.startsWith(PACKAGE_PREFIX_JAVAX_XML) || hasSuperClassStartingWith(rawType, PACKAGE_PREFIX_JAVAX_XML)) {
            factoryName = SERIALIZERS_FOR_JAVAX_XML;
        } else {
            return null;
        }

        Object ob = instantiate(factoryName, type);
        if (ob == null) { // could warn, if we had logging system (j.u.l?)
            return null;
        }
        return ((Serializers) ob).findSerializer(config, type, beanDesc);
    }

    public JsonDeserializer<?> findDeserializer(JavaType type, DeserializationConfig config,
            BeanDescription beanDesc)
        throws JsonMappingException
    {
        final Class<?> rawType = type.getRawClass();

        if (_jdk7Helper != null) {
            JsonDeserializer<?> deser = _jdk7Helper.getDeserializerForJavaNioFilePath(rawType);
            if (deser != null) {
                return deser;
            }
        }
        if (_IsXOfY(rawType, CLASS_DOM_NODE)) {
            return (JsonDeserializer<?>) instantiate(DESERIALIZER_FOR_DOM_NODE, type);
        }
        if (_IsXOfY(rawType, CLASS_DOM_DOCUMENT)) {
            return (JsonDeserializer<?>) instantiate(DESERIALIZER_FOR_DOM_DOCUMENT, type);
        }
        String className = rawType.getName();
        final String deserName = _sqlDeserializers.get(className);
        if (deserName != null) {
            return (JsonDeserializer<?>) instantiate(deserName, type);
        }
        String factoryName;
        if (className.startsWith(PACKAGE_PREFIX_JAVAX_XML)
                || hasSuperClassStartingWith(rawType, PACKAGE_PREFIX_JAVAX_XML)) {
            factoryName = DESERIALIZERS_FOR_JAVAX_XML;
        } else {
            return null;
        }
        Object ob = instantiate(factoryName, type);
        if (ob == null) { // could warn, if we had logging system (j.u.l?)
            return null;
        }
        return ((Deserializers) ob).findBeanDeserializer(type, config, beanDesc);
    }

    public boolean hasDeserializerFor(Class<?> valueType) {
        if (_IsXOfY(valueType, CLASS_DOM_NODE)) {
            return true;
        }
        if (_IsXOfY(valueType, CLASS_DOM_DOCUMENT)) {
            return true;
        }
        String className = valueType.getName();
        if (className.startsWith(PACKAGE_PREFIX_JAVAX_XML)
                || hasSuperClassStartingWith(valueType, PACKAGE_PREFIX_JAVAX_XML)) {
            return true;
        }
        // 06-Nov-2020, tatu: One of "java.sql" types?
        return _sqlDeserializers.containsKey(className);
    }

    // @since 2.12.1
    private boolean _IsXOfY(Class<?> valueType, Class<?> expType) {
        return (expType != null) && expType.isAssignableFrom(valueType);
    }

    /*
    /**********************************************************
    /* Internal helper methods
    /**********************************************************
     */

    private Object instantiate(String className, JavaType valueType)
    {
        try {
            return instantiate(Class.forName(className), valueType);
        } catch (Throwable e) {
            throw new IllegalStateException("Failed to find class `"
+className+"` for handling values of type "+ClassUtil.getTypeDescription(valueType)
+", problem: ("+e.getClass().getName()+") "+e.getMessage());
        }
    }

    private Object instantiate(Class<?> handlerClass, JavaType valueType)
    {
        try {
            return ClassUtil.createInstance(handlerClass, false);
        } catch (Throwable e) {
            throw new IllegalStateException("Failed to create instance of `"
+handlerClass.getName()+"` for handling values of type "+ClassUtil.getTypeDescription(valueType)
+", problem: ("+e.getClass().getName()+") "+e.getMessage());
        }
    }

    /**
     * Since 2.7 we only need to check for class extension, as all implemented
     * types are classes, not interfaces. This has performance implications for
     * some cases, as we do not need to go over interfaces implemented, just
     * superclasses
     * 
     * @since 2.7
     */
    private boolean hasSuperClassStartingWith(Class<?> rawType, String prefix)
    {
        for (Class<?> supertype = rawType.getSuperclass(); supertype != null; supertype = supertype.getSuperclass()) {
            if (supertype == Object.class) {
                return false;
            }
            if (supertype.getName().startsWith(prefix)) {
                return true;
            }
        }
        return false;
    }
}

⏎ com/fasterxml/jackson/databind/ext/OptionalHandlerFactory.java

Or download all of them as a single archive file:

File name: jackson-databind-2.14.0-sources.jar
File size: 1187952 bytes
Release date: 2022-11-05
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