de.cgarbs.lib.json.JSONAdapter.java Source code

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Here is the source code for de.cgarbs.lib.json.JSONAdapter.java

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/*
 * Copyright 2015 (C)  Christian Garbs <mitch@cgarbs.de>
 * Licensed under GNU GPL 3 (or later)
 */
package de.cgarbs.lib.json;

import java.util.LinkedHashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;

import org.json.simple.JSONAware;
import org.json.simple.parser.ContainerFactory;
import org.json.simple.parser.JSONParser;

import de.cgarbs.lib.exception.JSONException;
import de.cgarbs.lib.json.type.JSONType;
import de.cgarbs.lib.json.type.JSONTypeFactory;

/**
 * JSON adapter for various classes.
 * Allows conversion from and to JSON.
 *
 * @author Christian Garbs <mitch@cgarbs.de>
 * @since 0.3.0
 */
public abstract class JSONAdapter {
    private static ContainerFactory orderedContainerFactory;
    private static JSONParser jsonParser;

    /**
     * Prepares a given Object for JSON conversion.
     * <br>
     * Native data types like {@link String}, {@link Number} and {@link Boolean}
     * as well as the <code>null</code> value are returned unchanged as they can
     * be directly converted to JSON.
     * <br>
     * Other data types are converted to special wrapper objects
     * (subclasses of {@link JSONType} implementing {@link JSONAware} to
     * allow JSON conversion.
     *
     * @param o the Object to be converted
     * @return either the unchanged Object or a wrapped version ready for JSON conversion
     * @throws JSONException when no conversion exists for the given Object
     */
    protected static Object prepareForJSON(final Object o) throws JSONException {
        // no wrapping needed
        if (o instanceof String || o instanceof Number || o instanceof Boolean || o == null) {
            return o;
        }

        return JSONTypeFactory.wrapJavaObject(o);
    }

    /**
     * Prepares a given decoded JSON Object for usage in the Java world.
     * <br>
     * Native data types like {@link String}, {@link Number} and {@link Boolean}
     * as well as the <code>null</code> value are already mapped correctly and can
     * simply be returned for further usage as Java values.
     * <br>
     * {@link Maps} are considered to be special wrapper objects
     * (subclasses of {@link JSONType} and are  decoded into a proper Java class.
     *
     * @param o the Object to be converted
     * @return either the unchanged Object or a wrapped Java type
     * @throws JSONException when no conversion exists for the given Object
     */
    protected static Object prepareForJava(final Object o) throws JSONException {
        // no wrapping needed
        if (o instanceof String || o instanceof Number || o instanceof Boolean || o == null) {
            return o;
        }

        JSONType wrappedJSON = JSONTypeFactory.unwrapJSONObject(o);
        return wrappedJSON.toJavaValue();
    }

    /**
     * Returns a cached instance of a {@link JSONParser}.
     *
     * @return a JSONParser ready for use
     */
    protected static JSONParser getJSONParser() {
        if (jsonParser == null) {
            jsonParser = new JSONParser();
        }
        return jsonParser;
    }

    /**
     * Returns a JSON {@link ContainerFactors} that keeps the ordering
     * from the JSON String for Maps and Lists by using {@link LinkedHashMap}
     * and {@link LinkedList}.
     *
     * @return a ContainerFactory providing ordered results
     */
    @SuppressWarnings("rawtypes")
    protected static ContainerFactory getOrderedContainerFactory() {
        if (orderedContainerFactory == null) {
            orderedContainerFactory = new ContainerFactory() {

                @Override
                public Map createObjectContainer() {
                    return new LinkedHashMap();
                }

                @Override
                public List creatArrayContainer() {
                    return new LinkedList();
                }
            };
        }
        return orderedContainerFactory;

    }
}