HttpUtilities.java

package com.google.refine.commands;

import java.io.IOException;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.io.Writer;
import java.util.Properties;

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

import org.apache.velocity.VelocityContext;
import org.json.JSONException;
import org.json.JSONObject;
import org.json.JSONWriter;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.google.refine.Jsonizable;
import com.google.refine.RefineServlet;
import com.google.refine.util.ParsingUtilities;

abstract public class HttpUtilities {
    final static protected Logger logger = LoggerFactory.getLogger("command");

    static public void respond(HttpServletResponse response, String content)
        throws IOException, ServletException {
    
        response.setCharacterEncoding("UTF-8");
        response.setStatus(HttpServletResponse.SC_OK);
        Writer w = response.getWriter();
        if (w != null) {
            w.write(content);
            w.flush();
            w.close();
        } else {
            throw new ServletException("response returned a null writer");
        }
    }

    static public void respond(HttpServletResponse response, String status, String message)
        throws IOException {
    
        Writer w = response.getWriter();
        try {
            JSONWriter writer = new JSONWriter(w);
            writer.object();
            writer.key("status"); writer.value(status);
            writer.key("message"); writer.value(message);
            writer.endObject();
            w.flush();
            w.close();
        } catch (JSONException e) {
            // This can never occue
        }
    }

    static public void respondJSON(HttpServletResponse response, Jsonizable o)
        throws IOException, JSONException {
    
        respondJSON(response, o, new Properties());
    }

    static public void respondJSON(
            HttpServletResponse response, Jsonizable o, Properties options)
            throws IOException, JSONException {
    
        response.setCharacterEncoding("UTF-8");
        response.setHeader("Content-Type", "application/json");
    
        Writer w = response.getWriter();
        JSONWriter writer = new JSONWriter(w);
    
        o.write(writer, options);
        w.flush();
        w.close();
    }

    static public void respondException(HttpServletResponse response, Exception e)
        throws IOException, ServletException {
    
        logger.warn("Exception caught", e);
    
        if (response == null) {
            throw new ServletException("Response object can't be null");
        }
    
        try {
            JSONObject o = new JSONObject();
            o.put("code", "error");
            o.put("message", e.getMessage());
    
            StringWriter sw = new StringWriter();
            PrintWriter pw = new PrintWriter(sw);
            e.printStackTrace(pw);
            pw.flush();
            sw.flush();
    
            o.put("stack", sw.toString());
    
            response.setCharacterEncoding("UTF-8");
            response.setHeader("Content-Type", "application/json");
            respond(response, o.toString());
        } catch (JSONException e1) {
            e.printStackTrace(response.getWriter());
        }
    }

    static public void redirect(HttpServletResponse response, String url) throws IOException {
        response.sendRedirect(url);
    }

    static public int getIntegerParameter(HttpServletRequest request, String name, int def) {
        if (request == null) {
            throw new IllegalArgumentException("parameter 'request' should not be null");
        }
        try {
            return Integer.parseInt(request.getParameter(name));
        } catch (Exception e) {
            logger.warn("Error getting integer parameter", e);
        }
        return def;
    }

    static public JSONObject getJsonParameter(HttpServletRequest request, String name) {
        if (request == null) {
            throw new IllegalArgumentException("parameter 'request' should not be null");
        }
        String value = request.getParameter(name);
        if (value != null) {
            try {
                return ParsingUtilities.evaluateJsonStringToObject(value);
            } catch (JSONException e) {
                logger.warn("Error getting json parameter", e);
            }
        }
        return null;
    }

    static public void respondWithErrorPage(
        RefineServlet servlet,
        HttpServletRequest request, 
        HttpServletResponse response, 
        String message, 
        Throwable e
    ) {
        respondWithErrorPage(servlet, request, response, message,
            HttpServletResponse.SC_INTERNAL_SERVER_ERROR, e);
    }

    static public void respondWithErrorPage(
        RefineServlet servlet,
        HttpServletRequest request, 
        HttpServletResponse response, 
        String message,
        int status,
        Throwable e
    ) {
        VelocityContext context = new VelocityContext();
        
        context.put("message", message);
        
        if (e != null) {
            StringWriter writer = new StringWriter();
            
            e.printStackTrace(new PrintWriter(writer));
            
            context.put("stack", writer.toString());
        } else {
            context.put("stack", "");
        }
        
        try {
            response.setStatus(status);
            
            servlet.getModule("core").sendTextFromTemplate(
                request, response, context, "error.vt", "UTF-8", "text/html", true);
            
        } catch (Exception e1) {
            e1.printStackTrace();
        }
    }
}