edu.cornell.mannlib.vitro.webapp.controller.json.JsonArrayProducer.java Source code

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Here is the source code for edu.cornell.mannlib.vitro.webapp.controller.json.JsonArrayProducer.java

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/* $This file is distributed under the terms of the license in /doc/license.txt$ */

package edu.cornell.mannlib.vitro.webapp.controller.json;

import java.io.IOException;
import java.io.Writer;

import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.json.JSONArray;

import edu.cornell.mannlib.vitro.webapp.controller.VitroRequest;

/**
 * A base for classes that produce a JSON array based on the parameters in the
 * VitroRequest.
 * 
 * Catches any exceptions. Logs the error and returns an empty JSON array.
 */
public abstract class JsonArrayProducer extends JsonProducer {
    private static final Log log = LogFactory.getLog(JsonArrayProducer.class);

    protected final VitroRequest vreq;
    protected final ServletContext ctx;

    protected JsonArrayProducer(VitroRequest vreq) {
        this.vreq = vreq;
        this.ctx = vreq.getSession().getServletContext();
    }

    /**
     * Sub-classes implement this method. Given the request, produce a JSON
     * object as the result.
     */
    protected abstract JSONArray process() throws Exception;

    public final void process(HttpServletResponse resp) throws IOException {
        JSONArray jsonArray = null;
        try {
            jsonArray = process();
        } catch (Exception e) {
            log.error("Failed to create JSON response" + e);
            resp.setStatus(500 /* HttpURLConnection.HTTP_SERVER_ERROR */);
        }

        if (jsonArray == null) {
            jsonArray = new JSONArray();
        }

        log.debug("Response to JSON request: " + jsonArray.toString());

        resp.setCharacterEncoding("UTF-8");
        resp.setContentType("application/json;charset=UTF-8");
        Writer writer = resp.getWriter();
        writer.write(jsonArray.toString());
    }
}