json转换工具类

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.URL;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;

import javax.servlet.http.HttpServletResponse;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.fasterxml.jackson.databind.ObjectMapper;

import net.sf.json.JSONArray;
import net.sf.json.JSONObject;

/**
* @author leon
* @createDate 2018年5月14日 下午3:21:06
* @version v1.0
* @classRemarks json工具类
*/
public class JsonUtils {

	private static final ObjectMapper objectMapper = new ObjectMapper();
	/*** 编码 */
	private static final String CHAR_ENCODING = "UTF-8";

	private static Logger logger = LoggerFactory.getLogger(JsonUtils.class);

	/**
	 * 将 Java 对象转为 JSON 字符串
	 */
	public static String obj2JSON(Object obj) {
		String jsonStr;
		try {
			jsonStr = objectMapper.writeValueAsString(obj);
		} catch (Exception e) {
			logger.error("Java 转 JSON 出错！", e);
			throw new RuntimeException(e);
		}
		return jsonStr;
	}

	/**
	 * 将 JSON 字符串转为 Java 对象
	 */
	@SuppressWarnings({ "rawtypes", "unchecked" })
	public static  T json2Object(String json, Class type) {
		T obj;
		try {
			obj = (T) objectMapper.readValue(json, type);
		} catch (Exception e) {
			logger.error("JSON 转 Java 出错！", e);
			throw new RuntimeException(e);
		}
		return obj;
	}

	/**
	 * json串 转map
	 * 
	 * @param jsonStr
	 * @return
	 */
	public static Map parseJSON2Map(String jsonStr) {
		Map map = new HashMap();
		JSONObject json = JSONObject.fromObject(jsonStr);
		for (Object k : json.keySet()) {
			Object v = json.get(k);
			if (v instanceof JSONArray) {
				List> list = new ArrayList>();
				Iterator it = ((JSONArray) v).iterator();
				while (it.hasNext()) {
					JSONObject json2 = it.next();
					list.add(parseJSON2Map(json2.toString()));
				}
				map.put(k.toString(), list);
			} else {
				map.put(k.toString(), v);
			}
		}
		return map;
	}
	
	/**
	 * Json转map和List>
	 * 
	 * @param jsonStr
	 * @return
	 * @throws Exception
	 */
	@SuppressWarnings("unchecked")
	public static List> parseJSON2Listmap(String jsonStr) {
		// Gson gson = new Gson();
		ObjectMapper objectMapper = new ObjectMapper();
		List> newMap = null;
		try {
			newMap = objectMapper.readValue(jsonStr, List.class);
		} catch (Exception e) {
			logger.error("系统错误:",e);
		}
		//System.out.println(newMap);
		return newMap;
	}

	/**
	 *
	 * 通过HTTP获取JSON数据. 

	 * 通过HTTP获取JSON数据返回list
	 * 
	 * @param url
	 *            链接
	 * @return
	 * @return List> list
	 * @throws @author
	 *             slj
	 */
	public static List> getListByUrl(String url) {
		try {
			// 通过HTTP获取JSON数据
			InputStream in = new URL(url).openStream();
			BufferedReader reader = new BufferedReader(new InputStreamReader(in));
			StringBuilder sb = new StringBuilder();
			String line;
			while ((line = reader.readLine()) != null) {
				sb.append(line);
			}
			return parseJSON2Listmap(sb.toString());
		} catch (Exception e) {
			logger.error("系统错误:",e);
		}
		return null;
	}

	/**
	 *
	 * 通过HTTP获取JSON数据. 

	 * 通过HTTP获取JSON数据返回map
	 * 
	 * @param url
	 *            链接
	 * @return
	 * @return Map 集合
	 * @throws @author
	 *             slj
	 */
	public static Map getMapByUrl(String url) {
		try {
			// 通过HTTP获取JSON数据
			InputStream in = new URL(url).openStream();
			BufferedReader reader = new BufferedReader(new InputStreamReader(in));
			StringBuilder sb = new StringBuilder();
			String line;
			while ((line = reader.readLine()) != null) {
				sb.append(line);
			}
			return parseJSON2Map(sb.toString());
		} catch (Exception e) {
			logger.error("系统错误:",e);
		}
		return null;
	}

	/**
	 *
	 * map转换json.
	 * @param map 集合
	 * @return
	 */
	public static String mapToJson(Map map) {
		Set keys = map.keySet();
		String key = "";
		String value = "";
		StringBuffer jsonBuffer = new StringBuffer();
		jsonBuffer.append("{");
		for (Iterator it = keys.iterator(); it.hasNext();) {
			key = (String) it.next();
			value = map.get(key);
			jsonBuffer.append(key + ":" + "\"" + value + "\"");
			if (it.hasNext()) {
				jsonBuffer.append(",");
			}
		}
		jsonBuffer.append("}");
		return jsonBuffer.toString();
	}
	
	/**
	 * 返回json格式的数据
	 * 
	 * @param response
	 * @param jsonObject
	 */
	public static void doJsonResponse(HttpServletResponse response,
			final JSONObject jsonObject) {
		response.setCharacterEncoding(CHAR_ENCODING);
		response.setContentType("application/json; charset=utf-8");  
		try {
			response.getWriter().print(jsonObject);
		} catch (IOException e) {
			logger.error(e.getMessage());
			logger.error("系统错误:",e);
		}
	}

}