Java tutorial
/******************************************************************************* * =========================================================== * Ankush : Big Data Cluster Management Solution * =========================================================== * * (C) Copyright 2014, by Impetus Technologies * * This is free software; you can redistribute it and/or modify it under * the terms of the GNU Lesser General Public License (LGPL v3) as * published by the Free Software Foundation; * * This software is distributed in the hope that it will be useful, but * WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. * See the GNU Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public License * along with this software; if not, write to the Free Software Foundation, * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. ******************************************************************************/ /** * */ package com.impetus.ankush.common.utils; import java.io.File; import java.io.IOException; import java.lang.reflect.Field; import java.lang.reflect.InvocationTargetException; import java.util.ArrayList; import java.util.HashMap; import java.util.LinkedHashMap; import java.util.List; import java.util.Map; import org.apache.commons.beanutils.BeanUtils; import org.apache.commons.io.FileUtils; import org.codehaus.jackson.map.ObjectMapper; import com.impetus.ankush2.logger.AnkushLogger; /** * The Class JsonMapperUtil. * * @author hokam chauhan Utility class to convert json string into the object * and vice versa. */ public class JsonMapperUtil { /** The log. */ private static final AnkushLogger LOG = new AnkushLogger(FileNameUtils.class); /** The mapper. */ private static ObjectMapper mapper = new ObjectMapper(); /** * Method to convert a object into JSON string. * * @param object * the object * @return the string */ public static String jsonFromObject(Object object) { try { /* Generating the JSON string for the object. */ return mapper.writeValueAsString(object); } catch (Exception e) { LOG.error(e.getMessage(), e); } return null; } /** * Method to Convert the given json string into the specified class object. * * @param <S> * the generic type * @param jsonString * the json string * @param targetClass * the target class * @return Object of the class formed using the JSON string. */ public static <S> S objectFromString(String jsonString, Class<S> targetClass) { S object = null; try { /* Creating the target class object */ object = targetClass.newInstance(); } catch (InstantiationException e) { LOG.error(e.getMessage(), e); } catch (IllegalAccessException e) { LOG.error(e.getMessage(), e); } try { /* Populating the object with json string values. */ object = mapper.readValue(jsonString, targetClass); } catch (Exception e) { LOG.error(e.getMessage(), e); } return object; } /** * Object from json file. * * @param <S> * the generic type * @param filePath * the file path * @param targetClass * the target class * @return the s */ public static <S> S objectFromJsonFile(String filePath, Class<S> targetClass) { S object = null; try { File jsonFile = new File(filePath); object = objectFromString(FileUtils.readFileToString(jsonFile), targetClass); } catch (IOException e) { LOG.error(e.getMessage(), e); } return object; } /** * Object from map. * * @param <S> * the generic type * @param values * the values * @param targetClass * the target class * @return the s * @throws IllegalArgumentException * the illegal argument exception * @throws IllegalAccessException * the illegal access exception * @throws InstantiationException * the instantiation exception * @throws InvocationTargetException * the invocation target exception * @throws Exception * the exception */ public static <S> S objectFromMap(Map<String, Object> values, Class<S> targetClass) throws IllegalArgumentException, IllegalAccessException, InstantiationException, InvocationTargetException, Exception { // Creating target class object. S mainObject = targetClass.newInstance(); // Getting fields of the class. Field[] fields = targetClass.getDeclaredFields(); Map<String, Field> fieldMap = new HashMap<String, Field>(); for (Field field : fields) { // Putting fields in fieldMap fieldMap.put(field.getName(), field); } // Iterating over the key set in value map. for (String mainKey : values.keySet()) { if (values.get(mainKey) instanceof LinkedHashMap) { // Creating target object type. if (fieldMap.get(mainKey) == null) { continue; } Object subObject = fieldMap.get(mainKey).getType().newInstance(); // Casting to map. Map subValues = (Map) values.get(mainKey); // Iterating over the map keys. for (Object subKey : subValues.keySet()) { BeanUtils.setProperty(subObject, (String) subKey, subValues.get(subKey)); } // setting the sub object in bean main object. BeanUtils.setProperty(mainObject, mainKey, subObject); } else { // setting the value in bean main object. BeanUtils.setProperty(mainObject, mainKey, values.get(mainKey)); } } return mainObject; } /** * Method to get Map from the object. * * @param obj * the obj * @return the map * @throws Exception * the exception */ public static Map<String, Object> mapFromObject(Object obj) throws Exception { ObjectMapper mapper = new ObjectMapper(); return mapper.convertValue(obj, HashMap.class); } /** * Map from object. * * @param <S> * the generic type * @param obj * the obj * @param className * the class name * @return the s * @throws Exception * the exception */ public static <S> S objectFromObject(Object obj, Class<S> className) throws Exception { ObjectMapper mapper = new ObjectMapper(); return mapper.convertValue(obj, className); } /** * Gets the node info list. * * @param <S> * the generic type * @param dataMap * the monitoring info * @param key * the key * @param targetClass * the target class * @return the node info list * @throws Exception * the exception */ public static <S> List<S> getListObject(List<Map> listMapData, Class<S> targetClass) throws Exception { // checking if map is null. if (listMapData == null) { return null; } // Creating the resultant list object. List<S> result = new ArrayList<S>(listMapData.size()); // populating values in the list object from map. for (Map<String, Object> info : listMapData) { // creating target class object. S status = targetClass.newInstance(); // populating object with map values. BeanUtils.populate(status, info); // adding object in result list. result.add(status); } return result; } }