melnorme.lang.utils.gson.GsonHelper.java Source code

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Here is the source code for melnorme.lang.utils.gson.GsonHelper.java

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/*******************************************************************************
 * Copyright (c) 2016 Bruno Medeiros and other Contributors.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     Bruno Medeiros - initial API and implementation
 *******************************************************************************/
package melnorme.lang.utils.gson;

import com.google.gson.JsonArray;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;

import melnorme.utilbox.core.CommonException;

public class GsonHelper {

    protected CommonException wrongTypeException(String key, String expectedType) throws CommonException {
        return CommonException.fromMsgFormat("Member `{0}` is not a {1}.", key, expectedType);
    }

    public JsonObject getObject(JsonObject jsonObject, String key) throws CommonException {
        JsonElement element = jsonObject.get(key);
        if (element != null && element.isJsonObject()) {
            return element.getAsJsonObject();
        } else {
            throw wrongTypeException(key, "Object");
        }
    }

    public JsonArray getArray(JsonObject jsonObject, String key) throws CommonException {
        JsonElement element = jsonObject.get(key);
        if (element != null && element.isJsonArray()) {
            return element.getAsJsonArray();
        } else {
            throw wrongTypeException(key, "Array");
        }
    }

    public String getString(JsonObject jsonObject, String key) throws CommonException {
        JsonElement element = jsonObject.get(key);
        if (element != null && element.isJsonPrimitive() && element.getAsJsonPrimitive().isString()) {
            return element.getAsString();
        } else {
            throw wrongTypeException(key, "String");
        }
    }

    public boolean getBoolean(JsonObject jsonObject, String key) throws CommonException {
        JsonElement element = jsonObject.get(key);
        if (element != null && element.isJsonPrimitive() && element.getAsJsonPrimitive().isBoolean()) {
            return element.getAsBoolean();
        } else {
            throw wrongTypeException(key, "boolean");
        }
    }

    public Number getNumber(JsonObject jsonObject, String key) throws CommonException {
        JsonElement element = jsonObject.get(key);
        if (element != null && element.isJsonPrimitive() && element.getAsJsonPrimitive().isNumber()) {
            return element.getAsNumber();
        } else {
            throw wrongTypeException(key, "Number");
        }
    }

    public int getInteger(JsonObject jsonObject, String key) throws CommonException {
        Number number = getNumber(jsonObject, key);

        int intValue = number.intValue();

        // This check is not 100% precise, but good enough for now.
        if ((double) intValue != number.doubleValue()) {
            throw CommonException.fromMsgFormat("Number `{0}` cannot be represente as an Integer.", key, number);
        }
        return intValue;
    }

    /* ----------------- optional ----------------- */

    public boolean isPresent(JsonObject jsonObject, String key) {
        JsonElement jsonElement = jsonObject.get(key);
        return jsonElement != null && !jsonElement.isJsonNull();
    }

    public JsonObject getOptionalObject(JsonObject jsonObject, String key) throws CommonException {
        if (!isPresent(jsonObject, key)) {
            return null;
        }
        return getObject(jsonObject, key);
    }

    public JsonArray getOptionalArray(JsonObject jsonObject, String key) throws CommonException {
        if (!isPresent(jsonObject, key)) {
            return null;
        }
        return getArray(jsonObject, key);
    }

    public String getOptionalString(JsonObject jsonObject, String key) throws CommonException {
        return getOptionalString(jsonObject, key, null);
    }

    public String getOptionalString(JsonObject jsonObject, String key, String defaultValue) throws CommonException {
        if (!isPresent(jsonObject, key)) {
            return defaultValue;
        }
        return getString(jsonObject, key);
    }

    public Number getOptionalNumber(JsonObject jsonObject, String key) throws CommonException {
        if (!isPresent(jsonObject, key)) {
            return null;
        }
        return getNumber(jsonObject, key);
    }

    public boolean getOptionalBoolean(JsonObject jsonObject, String key, boolean defaultValue)
            throws CommonException {
        if (!isPresent(jsonObject, key)) {
            return defaultValue;
        }
        return getBoolean(jsonObject, key);
    }

    public int getOptionalInteger(JsonObject jsonObject, String key, int defaultValue) throws CommonException {
        if (!isPresent(jsonObject, key)) {
            return defaultValue;
        }
        return getInteger(jsonObject, key);
    }

}