[简单]代码片段_java合并userId相同数据

       工作中遇到需要合并相同用户的内容，数据如下:

      

      代码如下:

      

import java.text.ParseException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;

import org.apache.commons.lang3.StringUtils;
import org.apache.commons.lang3.time.DateUtils;
import org.codehaus.jackson.JsonParser;
import org.codehaus.jackson.map.ObjectMapper;

public class 相同数据合并_S3_Test {
	public static void main(String[] args) throws Exception {
		相同数据合并_S3_Test t=new 相同数据合并_S3_Test();
		t.testMerge();
	}
	
   public void testMerge() throws Exception{
	   String str="[ { \"createDate\": \"2015-05-04 17:05:20\", \"content\": \"测试\", \"userId\": \"545271289\" }, { \"createDate\": \"2015-05-04 19:05:20\", \"content\": \"测试5\", \"userId\": \"545271209\" }, { \"createDate\": \"2015-05-04 16:05:20\", \"content\": \"测试2\", \"userId\": \"545271289\" }, { \"createDate\": \"2015-05-04 19:05:20\", \"content\": \"测试7\", \"userId\": \"545271219\" }, { \"createDate\": \"2015-05-04 15:05:20\", \"content\": \"测试3\", \"userId\": \"545271289\" }, { \"createDate\": \"2015-05-04 11:05:20\", \"content\": \"测试4\", \"userId\": \"545271289\" }, { \"createDate\": \"2015-05-04 18:05:20\", \"content\": \"测试6\", \"userId\": \"545271219\" }, { \"createDate\": \"2015-05-04 19:05:20\", \"content\": \"测试5\", \"userId\": \"545271289\" } ] ";
	   List<Map<String,String>> srcDataList=JacksonHelper.json2Class(str, List.class);
	   System.out.println(JacksonHelper.obj2Json(srcDataList));
	   if(srcDataList.isEmpty()){
		   return ;
	   }
	   testMergeDataMethod(srcDataList);
	   testMergeDataMethod2(srcDataList);
   }

   /**
    * @Description: 按userId合并,按createDate排序
    */
	public void testMergeDataMethod( List<Map<String,String>> srcDataList) throws Exception {
		// 按userId createDate排序
		Collections.sort(srcDataList, new Comparator<Map<String, String>>() {
			public int compare(Map<String, String> m1, Map<String, String> m2) {
				int destCmp = StringUtils.trimToEmpty(m1.get("userId")).compareTo(StringUtils.trimToEmpty(m2.get("userId")));
				if (destCmp == 0) {
					try {
						return DateUtils.parseDate(StringUtils.trim(m1.get("createDate")),"yyyy-MM-dd HH:mm:ss").compareTo(
								   DateUtils.parseDate(StringUtils.trim(m2.get("createDate")),"yyyy-MM-dd HH:mm:ss"));
					} catch (ParseException e) {
						return 0;
					}
				}
				return destCmp;
			}
		});
		List<Map<String, String>> allMsgList = new ArrayList<Map<String, String>>();
		List<Map<String, Object>> rtnList = new ArrayList<Map<String, Object>>();
		Map<String, Object> firstMap = new HashMap<String, Object>();
		String userId = srcDataList.get(0).get("userId");
		String lastCreateDateStr = srcDataList.get(0).get("createDate");
		firstMap.put("userId", userId);
		firstMap.put("startDate", srcDataList.get(0).get("createDate"));
		allMsgList.add(getMsgContent(srcDataList.get(0)));
		for (int i = 1, len = srcDataList.size(); i < len; i++) {
			String currDestId = srcDataList.get(i).get("userId");
			if (currDestId.equals(userId)) {
				allMsgList.add(getMsgContent(srcDataList.get(i)));
				lastCreateDateStr = srcDataList.get(i).get("createDate");
			} else {
				firstMap.put("endDate", lastCreateDateStr);
				firstMap.put("msg", allMsgList);
				rtnList.add(firstMap);

				firstMap = new HashMap<String, Object>();
				allMsgList = new ArrayList<Map<String, String>>();
				userId = srcDataList.get(i).get("userId");
				lastCreateDateStr = srcDataList.get(i).get("createDate");
				firstMap.put("userId", userId);
				firstMap.put("startDate", lastCreateDateStr);
				allMsgList.add(getMsgContent(srcDataList.get(i)));
			}
		}
		firstMap.put("endDate", lastCreateDateStr);
		firstMap.put("msg", allMsgList);
		rtnList.add(firstMap);
		System.out.println(JacksonHelper.obj2Json(rtnList));
	}
	
	public Map<String, String> getMsgContent(Map<String, String> msgMap) {
		Map<String, Object> rtnMap = new HashMap<String, Object>();
		rtnMap.put("createDate", msgMap.get("createDate"));
		rtnMap.put("content", msgMap.get("content"));
		return msgMap;
	}
	
	/**
	 * @Description: 按userId合并
	 */
	public void testMergeDataMethod2( List<Map<String,String>> srcDataList) throws Exception {
		List<Map<String, Object>> rtnList = new ArrayList<Map<String, Object>>();
		Map<String,List<Map<String, String>>> dataMap=new HashMap<String, List<Map<String,String>>>();
		for (Map<String, String> map : srcDataList) {
			String key=map.get("userId");
			if(dataMap.containsKey(key)){
				List<Map<String, String>> dataList = dataMap.get(key);
				dataList.add(getMsgContent(map));
			}else{
				List<Map<String, String>> dataList =new ArrayList<Map<String,String>>();
				dataList.add(getMsgContent(map));
				dataMap.put(key, dataList);
			}
		}
		for (Entry<String, List<Map<String, String>>> entry: dataMap.entrySet()) {
			Map<String, Object> firstMap = new HashMap<String, Object>();
			firstMap.put("userId", entry.getKey());
			firstMap.put("msg", entry.getValue());
			rtnList.add(firstMap);
		}
		System.out.println(JacksonHelper.obj2Json(rtnList));
	}
}

class JacksonHelper {
	private static ObjectMapper mapper = new ObjectMapper();
	static{
		mapper.configure(JsonParser.Feature.ALLOW_UNQUOTED_CONTROL_CHARS,true);
	}
	
	public static String obj2Json(Object obj) throws Exception {
		return mapper.writeValueAsString(obj);
	}

	public static <T> T json2Class(String json, Class<T> cls) throws Exception {
		ObjectMapper mapper = new ObjectMapper();
		return mapper.readValue(json, cls);
	}
	
}

   方法一使用了排序,可以得到合并的时间段。结果如下:

  

     方法二简单易于理解，结果如下:

    

        欢迎提出更好的方法。

        全文完。