com.threewks.thundr.view.jsonp.JsonpViewResolver.java Source code

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Here is the source code for com.threewks.thundr.view.jsonp.JsonpViewResolver.java

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/*
 * This file is a component of thundr, a software library from 3wks.
 * Read more: http://3wks.github.io/thundr/
 * Copyright (C) 2014 3wks, <thundr@3wks.com.au>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *         http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.threewks.thundr.view.jsonp;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.lang3.StringUtils;

import com.atomicleopard.expressive.Cast;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.JsonElement;
import com.threewks.thundr.json.GsonSupport;
import com.threewks.thundr.view.BaseView;
import com.threewks.thundr.view.ViewResolutionException;
import com.threewks.thundr.view.ViewResolver;

public class JsonpViewResolver implements ViewResolver<JsonpView> {
    private GsonBuilder gsonBuilder;

    public JsonpViewResolver() {
        this(GsonSupport.createBasicGsonBuilder());
    }

    public JsonpViewResolver(GsonBuilder gsonBuilder) {
        this.gsonBuilder = gsonBuilder;
    }

    /**
     * Exposes the underlying gson builder, allowing modification of the properties controlling how json is serialized.
     * 
     * @return
     */
    public GsonBuilder getGsonBuilder() {
        return gsonBuilder;
    }

    @Override
    public void resolve(HttpServletRequest req, HttpServletResponse resp, JsonpView viewResult) {
        Object output = viewResult.getOutput();
        try {
            Gson create = gsonBuilder.create();
            JsonElement jsonElement = Cast.as(output, JsonElement.class);
            String json = jsonElement == null ? create.toJson(output) : create.toJson(jsonElement);
            String jsonp = wrapJsonInCallback(req, json);

            String encoding = viewResult.getCharacterEncoding();
            resp.setContentLength(jsonp.getBytes(encoding).length);
            BaseView.applyToResponse(viewResult, resp);
            resp.getWriter().write(jsonp);
        } catch (Exception e) {
            throw new ViewResolutionException(e, "Failed to generate JSONP output for object '%s': %s",
                    output.toString(), e.getMessage());
        }
    }

    public static String wrapJsonInCallback(HttpServletRequest req, String json) {
        return getCallback(req) + "(" + json + ");";
    }

    public static String getCallback(HttpServletRequest req) {
        Object callback = req.getParameter("callback");
        String callbackStr = callback == null ? null : StringUtils.trimToNull(callback.toString());
        callbackStr = callbackStr == null ? "callback" : callbackStr;
        return callbackStr;
    }

    @Override
    public String toString() {
        return this.getClass().getSimpleName();
    }
}