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[操作系统]Android 利用Gson生成或解析json


目前手机端和服务端数据交流格式一般是json,而谷歌提供了Gson来解析json。下载Gson:https://code.google.com/p/google-gson/

下载的放在lib并导入,若出现错误:java.lang.NoClassDefFoundError: com.google.gson.Gson

是因为没有导入android-support-v4.jar,导入即可。

一、单个对象生成json

生成以下类,该怎么生成呢?

{  "createDate": "2015-02-01 10:39:50",   "id": "1",   "name": "传说之美",   "password": "123456"}

先定义一个account类,属性有id、name、password、createDate。

public class Account {	private String id;	private String password;	private String name;	private String createDate;	public Account() {		super();	}	public Account(String id, String password, String name, String createDate) {		super();		this.id = id;		this.password = password;		this.name = name;		this.createDate = createDate;	}	public String getId() {		return id;	}	public void setId(String id) {		this.id = id;	}	public String getPassword() {		return password;	}	public void setPassword(String password) {		this.password = password;	}	public String getName() {		return name;	}	public void setName(String name) {		this.name = name;	}	public String getCreateDate() {		return createDate;	}	public void setCreateDate(String createDate) {		this.createDate = createDate;	}	@Override	public String toString() {		return "Account [id=" + id + ", password=" + password + ", name=" + name + ", createDate=" + createDate + "]\n\n";	}}

定义好这个类,就可以利用Gson生成json字符串了。

		// 生成account对象		SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");		Account account = new Account("1", "123456", "传说之美", sdf.format(new Date()));				// 利用gson对象生成json字符串		Gson gson = new Gson();		String jsonString = gson.toJson(account);        Log.i("", jsonString);

输入的log如下

 二、解析json字符串单个对象

 在上面已生成了jsonString,那如何将其解析为单个对象,很简单。

		// 利用gson解析json字符串为单个对象		Account account1 = gson.fromJson(jsonString, Account.class);		Log.i("", account1.toString());

看看输出的log

三、生成单个对象的json数组

什么事json数组,类似下面的

[  {    "id": "2",     "createDate": "2015-02-01 11:21:27",     "password": "123456",     "name": "传说"  },   {    "id": "2",     "createDate": "2015-02-01 11:21:27",     "password": "123456",     "name": "之美"  }]

生成json数组代码如下

		Account account2 = new Account("2", "123456", "传说", sdf.format(new Date()));		Account account3 = new Account("2", "123456", "之美", sdf.format(new Date()));		List<Account> accountList = new ArrayList<Account>();		accountList.add(account2);		accountList.add(account3);						JSONArray accountArray = new JSONArray();		for (int i = 0; i < accountList.size(); i++) {			String accountStr = gson.toJson(accountList.get(i));			JSONObject accountObject;			try {				accountObject = new JSONObject(accountStr);				accountArray.put(i, accountObject);			} catch (JSONException e) {				e.printStackTrace();			}		}		Log.i("", accountArray.toString());

log的输出为

四、由多个单个对象的json数组解析为对个单个对象

多个单个对象组成的json数组解析如下

		// 解析json数组		List<Account> accountList2 = new ArrayList<Account>();		for(int i=0;i<accountArray.length(); i++){			JSONObject jsonObject = null;			try {				jsonObject = accountArray.getJSONObject(i);			} catch (JSONException e) {				e.printStackTrace();			}			if(jsonObject != null){				Account tempAccount = gson.fromJson(jsonObject.toString(), Account.class);				accountList2.add(tempAccount);			}		}		Log.i("accountList2", accountList2.toString());

输出的log

 

或者用更快捷的转化方法

		Account[] accountArrays = new Gson().fromJson(accountArray.toString(), Account[].class);		for(int i=0;i<accountArrays.length;i++){			Log.i("accountArrays",accountArrays[i].toString());		}		// 转化为List		List<Account> foosList = Arrays.asList(accountArrays);

更快捷地解析成List

		// 更快捷地解析成List		Type listType = new TypeToken<ArrayList<Account>>(){}.getType();		ArrayList<Account> accsList = new Gson().fromJson(accountArray.toString(), listType);		Log.i("accsList",accsList.toString());

五、生成一个对象嵌套对象的json

嵌套的json类似如下

{  "member": {    "id": "4",     "name": "我是传说"  },   "id": "4",   "createDate": "2015-02-02 12:03:32",   "password": "888888",   "name": "传说之美"}

生成这个json有2种方法。

1、再添加一个member类,像添加account类一样添加即可。

public class Member {	private String id;	private String name;	public Member() {		super();	}	public Member(String id, String name) {		super();		this.id = id;		this.name = name;	}	public String getId() {		return id;	}	public void setId(String id) {		this.id = id;	}	public String getName() {		return name;	}	public void setName(String name) {		this.name = name;	}	@Override	public String toString() {		return "Member [id=" + id + ", name=" + name + "]\n\n";	}}

生成代码如下

		// 生成对象嵌套对象的json		Account account4 = new Account("4", "888888", "传说之美", sdf.format(new Date()));		Member member = new Member("4", "我是传说");		String accountStr = gson.toJson(account4);		String memberStr = gson.toJson(member);		JSONObject object = null;		try {			JSONObject memberObject = new JSONObject(memberStr);			object = new JSONObject(accountStr);			object.put("member", memberObject);				} catch (JSONException e) {			e.printStackTrace();		}		Log.i("", object.toString());

输出的log

六、解析对象嵌套对象的json 

		Account account5 = gson.fromJson(object.toString(), Account.class);		Log.i("解析对象嵌套对象的json", account5.toString());		// 这里用isNull来判断是否存在这个object,存在就拿出member的JSONObject		JSONObject memberObject = null;		if(!object.isNull("member")){			try {				memberObject = object.getJSONObject("member");			} catch (JSONException e) {				e.printStackTrace();			}		}		Member member5 = null;		if(null != memberObject){			member5 = gson.fromJson(memberObject.toString(), Member.class);			Log.i("解析对象嵌套对象的json", member5.toString());		}

输出的结果

 7、另外一种解析对象嵌套对象的json 

定义一个类

public class AccountObject {	private String id;	private String password;	private String name;	private String createDate;	private MemberObject memberObject = new MemberObject();		public class MemberObject {		private String id;		private String name;		@Override		public String toString() {			return "MemberObject [id=" + id + ", name=" + name+ "]\n\n";		}	}	@Override	public String toString() {		return "AccountObject [id=" + id + ", password=" + password + ", name=" + name + ", createDate=" + createDate + ","+ memberObject.toString() + "]\n\n";	}}

生成json并解析

		try {			JSONObject mObject = new JSONObject(memberStr);			object = new JSONObject(accountStr);			object.put("memberObject", mObject);				} catch (JSONException e) {			e.printStackTrace();		}		AccountObject accountObject = gson.fromJson(object.toString(), AccountObject.class);		Log.i("accountObject", accountObject.toString());

打印出来的log

本文博客原创地址:http://www.cnblogs.com/liqw/p/4266209.html

demo下载链接:http://files.cnblogs.com/files/liqw/LauncherActivity.zip