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LogGraph is an application for viewing and filtering zookeeper logs. It can handle transaction logs and message logs.

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/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.zookeeper.graph.servlets;

import java.io.IOException;

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

import org.json.simple.JSONObject;
import org.json.simple.JSONValue;

import java.util.Map;

abstract public class JsonServlet extends HttpServlet {
    abstract String handleRequest(JsonRequest request) throws Exception;

    protected class JsonRequest {
	private Map map;

	public JsonRequest(ServletRequest request) {
	    map = request.getParameterMap();
	}
	
	public long getNumber(String name, long defaultnum) {
	    String[] vals = (String[])map.get(name);
	    if (vals == null || vals.length == 0) {
		return defaultnum;
	    }

	    try {
		return Long.valueOf(vals[0]);
	    } catch (NumberFormatException e) {
		return defaultnum;
	    }
	}
	
	public String getString(String name, String defaultstr) {
	    String[] vals = (String[])map.get(name);
	    if (vals == null || vals.length == 0) {
		return defaultstr;
	    } else {
		return vals[0];
	    }
	}
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
    {
        response.setContentType("text/plain;charset=utf-8");
        response.setStatus(HttpServletResponse.SC_OK);
	
	try {
	    String req = request.getRequestURI().substring(request.getServletPath().length());

	    response.getWriter().println(handleRequest(new JsonRequest(request)));
	} catch (Exception e) {
	    JSONObject o = new JSONObject();
	    o.put("error", e.toString());
	    response.getWriter().println(JSONValue.toJSONString(o));
	} catch (java.lang.OutOfMemoryError oom) {
	    JSONObject o = new JSONObject();
	    o.put("error", "Out of memory. Perhaps you've requested too many logs. Try narrowing you're filter criteria.");
	    response.getWriter().println(JSONValue.toJSONString(o));
	}
    }
}