json学习

2017.7.25更

json简介

这里给出一个json示例

{  "beans" : [ {    "name" : "Hadoop:service=NameNode,name=FSNamesystem",    "modelerType" : "FSNamesystem",    "tag.Context" : "dfs",    "tag.HAState" : "standby",    "tag.Hostname" : "master",    "BlocksTotal" : 58,    "MissingBlocks" : 0,    "MissingReplOneBlocks" : 0,    "ExpiredHeartbeats" : 0,    "TransactionsSinceLastCheckpoint" : 73,    "TransactionsSinceLastLogRoll" : 0,    "LastWrittenTransactionId" : 3583,    "LastCheckpointTime" : 1501029386291,    "UnderReplicatedBlocks" : 0,    "CorruptBlocks" : 0,    "CapacityTotal" : 115360407552,    "CapacityTotalGB" : 107.0,    "CapacityUsed" : 265039872,    "CapacityUsedGB" : 0.0,    "CapacityRemaining" : 82021745387,    "CapacityRemainingGB" : 76.0,    "CapacityUsedNonDFS" : 33073622293,    "TotalLoad" : 24,    "SnapshottableDirectories" : 0,    "Snapshots" : 0,    "FilesTotal" : 200,    "PendingReplicationBlocks" : 0,    "ScheduledReplicationBlocks" : 0,    "PendingDeletionBlocks" : 0,    "ExcessBlocks" : 0,    "PostponedMisreplicatedBlocks" : 0,    "PendingDataNodeMessageCount" : 0,    "MillisSinceLastLoadedEdits" : 42018,    "BlockCapacity" : 2097152,    "StaleDataNodes" : 0,    "TotalFiles" : 200  } ]}

遇见”{” 就是json对象，遇见”[” 就是json数组。

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下面是使用org.json包（下载地址），java解析json数据的部分代码。

String result = "[{\"username\": \"your name\", \"user_json\": {\"username\": \"your name\", \"nickname\": \"your nickname\"}}]"; 5  6 //根据字符串生成JSON对象 7 JSONArray resultArray = new JSONArray(result); 8 JSONObject resultObj = resultArray.optJSONObject(0); 9 10 //获取数据项11 String username = resultObj.getString("username");12 13 //获取数据对象14 JSONObject user = resultObj.getJSONObject("user_json");15 String nickname = user.getString("nickname");