Java遍历json字符串取值的实例

java遍历json字符串，取得相应KV值时，各种麻烦，比如将json中的list取出来转为JSONArray，再将list中的object转化为map，再取值（之前的做法），仙子啊通过阿里的fastjson，可以很方便的直接将str转化为JSONArray，再将里面的object强转为JSONObject，然后再通过obj.getInteger(“key”)和obj.getString(“key”)等取值。

JSonArray json = (JSONArray) JSONArray.parse(str);
for (Object obj : json) {
  JSonObject jo = (JSONObject)obj;
  int status = jo.getInteger("status");
  String message= jo.getString("message");
  System.out.println("status---" + status + "---message---" + message);
}

1.当json字符串中有数组和map对象，遍历数据，数据格式如下：

[
  {
    "status":0,
    "tags":[
      "check:ntp"
    ],
    "timestamp":1492151922.198,
    "check":"datadog.agent.check_status",
    "host_name":"song-2",
    "message":null,
    "id":2
  },
  {
    "status":0,
    "tags":null,
    "timestamp":1492151922.2325,
    "check":"datadog.agent.up",
    "host_name":"song-2",
    "message":null,
    "id":5
  }
]

解析上面json字符串数据，如果不使用如fastjson或者Gson时，解析方法如下：

方法一

  private List> operStr(String str) throws Exception{
    List> mList = new ArrayList>();//探针开启的服务名list
    JSonArray json = (JSONArray) JSONArray.parse(str);
    Map objMap = null;
    Map resMap = null;
    for (Object obj : json) {
      objMap = Obj2Map(obj);
      @SuppressWarnings("unchecked")
      Map mObj = (Map) objMap.get("map");
      int status = (Integer) mObj.get("status");
      if(status != 0){
 resMap = new HashMap();
 switch (status) {
 case 1:
   resMap.put("status","WARNING");
   break;
 case 2:
   resMap.put("status","ERROR");
   break;
 case 3:
   resMap.put("status","CRIT");
   break;
 default:
   break;
 }
 resMap.put("serviceName", ((String) mObj.get("check")).split("\.")[0]);
 resMap.put("msg", (String)mObj.get("message"));
 mList.add(resMap);
      }
    }
    return mList;
  }
  
  public Map Obj2Map(Object obj) throws Exception{
    if(obj == null){  
      return null;  
    }
    Map map=new HashMap();
    Field[] fields = obj.getClass().getDeclaredFields();
    for(Field field:fields){
      field.setAccessible(true);
      map.put(field.getName(), field.get(obj));
    }
    return map;
  }

方法二

  private List> operStr(String str) throws Exception{
    List> mList = new ArrayList>();//探针开启的服务名list
    JSonArray json = (JSONArray) JSONArray.parse(str);
    Map resMap = null;
    for (Object obj : json) {
      JSonObject jo = (JSONObject)obj;
      int status = jo.getInteger("status");
      if(status != 0){
 resMap = new HashMap();
 switch (status) {
 case 1:
   resMap.put("status","WARNING");
   break;
 case 2:
   resMap.put("status","ERROR");
   break;
 case 3:
   resMap.put("status","CRIT");
   break;
 default:
   break;
 }
 resMap.put("serviceName", (jo.getString("check")).split("\.")[0]);
 resMap.put("msg", jo.getString("message"));
 mList.add(resMap);
      }
    }
    return mList;
  }

2.当json字符串中是数组包含数组时候，遍历数据，数据格式如下：

[
  [
    "haproxy",
    "haproxy",
    0,
    "ERROR",
    "swdfghyjuikl",
    {
    }
  ],
  [
    "gearmand",
    "gearmand",
    0,
    "ERROR",
    "'Found no valid connections in list: []'",
    {
      "version":"[8, 4, 20]"
    }
  ]
]

方法一

  private List> getExceptInfoFromAgentChecks(String agentChecksStr){
    List> mList = new ArrayList>();//探针开启的服务名list
    //mList 主机详情中，异常错误信息的报错的平台服务状态和message
    Object jsonArray = JSONArray.parse(agentChecksStr);
    @SuppressWarnings("unchecked")
    List> list= (List>) jsonArray;
    Map map = null;
    for(int i=0;i();
      String status = list.get(i).get(3).toString();
      if(!status.equals("OK")){
 String serviceName = list.get(i).get(0).toString();
 String msg = list.get(i).get(4).toString();
 map.put("serviceName", serviceName);
 map.put("status", status);
 map.put("msg", msg);
 mList.add(map);
      }
    }
    return mList;
  }

方法二

  private List> getExceptInfoFromAgentChecks(String agentChecksStr){
    //探针开启的服务名list
    List> mList = new ArrayList>();
    JSonArray jsonArray = (JSONArray) JSONArray.parse(agentChecksStr);
    Map map = null;
    for (Object obj : jsonArray) {
      map = new HashMap();
      JSonArray ja = (JSONArray)obj;
      String status = ja.getString(3);
      if(!status.equals("OK")){
 String serviceName = ja.getString(0);
 String msg = ja.getString(4);
 map.put("serviceName", serviceName);
 map.put("status", status);
 map.put("msg", msg);
 mList.add(map);
      }
    }
    return mList;
  }

Gson将json字符串转化为json对象：

import com.google.gson.Gson;
import com.google.gson.JsonArray;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonParser;
public class MainTest {
  public static void main(String[] args) throws Exception{
    String jsonstr0 = "{"alarmDetails":{"conditionDetails":{"alarmId":7,"alarmNodataNotifyTime":1,"alarmNowSeriesWaitTime":2},"conditionStatic":{"alarmId":7,"conditionAggregate":"avg","conditionOperator":1,"conditionThresholdTime":5,"conditionThresholdValue":"123"},"metricDetails":{"alarmId":7,"metricAggregater":"avg","metricBy":"host","metricExcludeTag":"host:paas-177","metricName":"system.cpu.user","metricQ":"avg:system.cpu.user{#address:wuhan,!host:paas-177}by{host}","metricTag":"#address:wuhan"},"notify":[{"alarmId":7,"notifyChannel":5,"notifyUserId":1},{"alarmId":7,"notifyChannel":5,"notifyUserId":2}],"view":{"alarmexpression":"avg(last_5m)avg:system.cpu.user{#address:wuhan,!host:paas-177}by{host}>123.0","alarmId":7,"alarmLastValue":"UP","alarmName":"static_metric","alarmStatus":1,"alarmType":2,"alarmTypeJoin":3,"createTime":"2017-06-28 17:25:52.0","createUserId":1,"isDisable":false,"lastAlarmTime":"2017-06-28 17:25:27.0","metricName":"system.cpu.user","metricTag":"#address:wuhan","updateTime":"2017-06-29 15:49:18.0"}},"alarmId":7,"allMark":{"avg:system.cpu.user{host:cfeng-4,#address:wuhan,!host:paas-177}":{"changePutTime":true,"lastPutTsdbTime":1499655343,"lastSuccessCheckTime":1499655349,"series":"avg:system.cpu.user{host:cfeng-4,#address:wuhan,!host:paas-177}","tagMap":{"host":"cfeng-4","#address":"wuhan","!host":"paas-177"}}},"joinType":3,"useMetricUnit":"percent","validataDetails":{"status":0,"validataMerges":[{"alarmMarkDto":{"changePutTime":true,"lastPutTsdbTime":1499655343,"lastSuccessCheckTime":1499655349,"series":"avg:system.cpu.user{host:cfeng-4,#address:wuhan,!host:paas-177}","tagMap":{"host":"cfeng-4","#address":"wuhan","!host":"paas-177"}},"status":0,"tag":"host:cfeng-4","validataNodata":{"currentTime":1499655349,"isNodata":false,"lastSuccessCheckTime":1499655349,"series":"avg:system.cpu.user{host:cfeng-4,#address:wuhan,!host:paas-177}","tag":{"host":"cfeng-4","#address":"wuhan","!host":"paas-177"},"thresholdTime":60},"validataStatic":{"converToThresholdValue":123.0,"end":1499655343,"intervalAggregator":"avg","isAlart":true,"operator":1,"series":"avg:system.cpu.user{host:cfeng-4,#address:wuhan,!host:paas-177}","start":1499655043,"sysUnit":"percent","tag":{"#address":"wuhan","host":"cfeng-4","!host":"paas-177"},"thresholdTime":300,"thresholdValue":"123","value":5.715769243240357}}],"validataTimeSeconds":1499655349}}";
    String jsonstr1 = "{"alarmDetails":{"conditionDetails":{"alarmId":7,"alarmNodataNotifyTime":1,"alarmNowSeriesWaitTime":2},"conditionStatic":{"alarmId":7,"conditionAggregate":"avg","conditionOperator":1,"conditionThresholdTime":5,"conditionThresholdValue":"123"},"metricDetails":{"alarmId":7,"metricAggregater":"avg","metricBy":"host","metricExcludeTag":"host:paas-177","metricName":"system.cpu.user","metricQ":"avg:system.cpu.user{#address:wuhan,!host:paas-177}by{host}","metricTag":"#address:wuhan"},"notify":[{"alarmId":7,"notifyChannel":5,"notifyUserId":1},{"alarmId":7,"notifyChannel":5,"notifyUserId":2}],"view":{"alarmexpression":"avg(last_5m)avg:system.cpu.user{#address:wuhan,!host:paas-177}by{host}>123.0","alarmId":7,"alarmLastValue":"UP","alarmName":"static_metric","alarmStatus":1,"alarmType":2,"alarmTypeJoin":3,"createTime":"2017-06-28 17:25:52.0","createUserId":1,"isDisable":false,"lastAlarmTime":"2017-06-28 17:25:27.0","metricName":"system.cpu.user","metricTag":"#address:wuhan","updateTime":"2017-06-29 15:49:18.0"}},"alarmId":7,"allMark":{"avg:system.cpu.user{host:cfeng-4,#address:wuhan,!host:paas-177}":{"changePutTime":true,"lastPutTsdbTime":1499655374,"lastSuccessCheckTime":1499655379,"series":"avg:system.cpu.user{host:cfeng-4,#address:wuhan,!host:paas-177}","tagMap":{"host":"cfeng-4","#address":"wuhan","!host":"paas-177"}}},"joinType":3,"useMetricUnit":"percent","validataDetails":{"status":0,"validataMerges":[{"alarmMarkDto":{"changePutTime":true,"lastPutTsdbTime":1499655374,"lastSuccessCheckTime":1499655379,"series":"avg:system.cpu.user{host:cfeng-4,#address:wuhan,!host:paas-177}","tagMap":{"host":"cfeng-4","#address":"wuhan","!host":"paas-177"}},"status":0,"tag":"host:cfeng-4","validataNodata":{"currentTime":1499655379,"isNodata":false,"lastSuccessCheckTime":1499655379,"series":"avg:system.cpu.user{host:cfeng-4,#address:wuhan,!host:paas-177}","tag":{"host":"cfeng-4","#address":"wuhan","!host":"paas-177"},"thresholdTime":60},"validataStatic":{"converToThresholdValue":123.0,"end":1499655374,"intervalAggregator":"avg","isAlart":true,"operator":1,"series":"avg:system.cpu.user{host:cfeng-4,#address:wuhan,!host:paas-177}","start":1499655074,"sysUnit":"percent","tag":{"#address":"wuhan","host":"cfeng-4","!host":"paas-177"},"thresholdTime":300,"thresholdValue":"123","value":5.089640821729388}}],"validataTimeSeconds":1499655379}}";
    Set set = new HashSet();
    set.add(jsonstr0);
    set.add(jsonstr1);
    Gson gs = new Gson();
    List