com.lazyloading.tag.handler.LazyHandler.java Source code

Introduction

Here is the source code for com.lazyloading.tag.handler.LazyHandler.java

Source

/*
 * Copyright 2014 the original author or authors.
 * 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 com.lazyloading.tag.handler;

import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.jsp.JspException;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.lazyloading.tag.LazyLoading;
import com.lazyloading.tag.form.Template;
import com.lazyloading.tag.util.EncDec;

/**
 * 
 * @author Sahil Shaikh
 *
 */
@Controller
public class LazyHandler {
    /**
     * Default request handler of the Ajax requests made by the Lazy Loading table
     * Change the Enc/Dec secret key in production environment
     * 
     * @param json    Request parameters which keep track of Lazy Loading table
     * @param request HttpServletRequest 
     * @param response HttpServletResponse
     * @return List<?> List of ? Objects
     * @throws Exception
     */
    @RequestMapping(value = "/lazyLoading.htm")
    public @ResponseBody List<?> lazyLoading(@RequestBody String json, HttpServletRequest request,
            HttpServletResponse response) throws Exception {
        try {

            Gson gson = new GsonBuilder().create();

            Template template = gson.fromJson(json, Template.class);
            if (template.getGetPage() == null)
                throw new JspException("Reuested page no cannot be null");

            Long requestedPage = template.getGetPage();
            Long end = new Long(template.getGetPage()) * new Long(template.getRecordsPerPage());
            Long begin = end - new Long(template.getRecordsPerPage());

            //DECRYPT THE REQUESTED ATTRS. Change the Secret key in production deployment
            String decryptedReqyestAttr = EncDec.decrypt("L!A@Z#Y$L%O^A*D(I)N_G", template.getRequestAttr());

            //CONVERT REUEST ATTRIBUTES IN HASHMAP
            HashMap<String, String> requestMap = new HashMap<String, String>();
            try {
                for (String keyVal : decryptedReqyestAttr.split(",")) {
                    String[] split = keyVal.split("=");
                    if (split.length > 1) {
                        split[1] = split[1].equals("null") ? null : split[1];

                        requestMap.put(split[0], split[1]);
                    } else {
                        requestMap.put(split[0], null);
                    }

                }
            } catch (Exception e) {
                throw new JspException("ERROR: lazyLoading 'requestAttrs' should be in attribute=value pair");
            }

            List<?> requestedList = new ArrayList();
            requestedList = LazyLoading.lazyLoadData(begin, end, template.getModelClass(), request, requestMap);

            List<Object> paginatedList = new ArrayList<Object>();

            Long indexCounter = 0L;
            try {

                for (Object obj : requestedList) {

                    Method lazyMethod = obj.getClass().getMethod("setLazyPageNo", Long.class);
                    lazyMethod.invoke(obj, new Long(template.getGetPage()));

                    //Searchable page numbers helps Angular Filter to paginate records
                    //records are coupled with commas to differentiate between 1, 11, 2, 22, 23 ... so on
                    lazyMethod = obj.getClass().getMethod("setSearchablePageNo", String.class);
                    lazyMethod.invoke(obj, "," + template.getGetPage() + ",");

                    //CALCLCULATE INDEX
                    Long index = (template.getGetPage() - 1) * new Long(template.getRecordsPerPage())
                            + indexCounter;
                    indexCounter++;

                    lazyMethod = obj.getClass().getMethod("set$index", Long.class);
                    lazyMethod.invoke(obj, index);

                    paginatedList.add(obj);

                }

            } catch (NullPointerException e) {
                throw new JspException("ERROR: Lazy loading. The load method returned null as a list.");
            }

            return (paginatedList);

        } catch (Exception e) {
            throw new Exception(e);
        }
    }

}