Android 利用Gson生成或解析json

目前手機端和服務端數據交流格式一般是json，而谷歌提供了Gson來解析json。下載Gson:https://code.google.com/p/google-gson/

下載的放在lib並導入，若出現錯誤：java.lang.NoClassDefFoundError: com.google.gson.Gson

是因為沒有導入android-support-v4.jar，導入即可。

一、單個對象生成json

生成以下類，該怎么生成呢？

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

先定義一個account類,屬性有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";
	}
}

定義好這個類，就可以利用Gson生成json字符串了。

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

輸入的log如下

 二、解析json字符串為單個對象

 在上面已生成了jsonString，那如何將其解析為單個對象，很簡單。

		// 利用gson解析json字符串為單個對象
		Account account1 = gson.fromJson(jsonString, Account.class);
		Log.i("", account1.toString());

看看輸出的log

三、生成單個對象的json數組

什么事json數組，類似下面的

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

生成json數組代碼如下

		Account account2 = new Account("2", "123456", "傳說", 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的輸出為

四、由多個單個對象的json數組解析為對個單個對象

多個單個對象組成的json數組解析如下

		// 解析json數組
		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());

輸出的log

 

或者用更快捷的轉化方法

		Account[] accountArrays = new Gson().fromJson(accountArray.toString(), Account[].class);
		for(int i=0;i<accountArrays.length;i++){
			Log.i("accountArrays",accountArrays[i].toString());
		}
		// 轉化為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、生成一個對象嵌套對象的json

嵌套的json類似如下

{
    "member": {
        "id": "4", 
        "name": "我是傳說"
    }, 
    "id": "4", 
    "createDate": "2015-02-02 12:03:32", 
    "password": "888888", 
    "name": "傳說之美"
}

生成這個json有2種方法。

1、再添加一個member類，像添加account類一樣添加即可。

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";
	}
}

生成代碼如下

		// 生成對象嵌套對象的json
		Account account4 = new Account("4", "888888", "傳說之美", sdf.format(new Date()));
		Member member = new Member("4", "我是傳說");
		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());

輸出的log

六、解析對象嵌套對象的json 

		Account account5 = gson.fromJson(object.toString(), Account.class);
		Log.i("解析對象嵌套對象的json", account5.toString());
		// 這里用isNull來判斷是否存在這個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("解析對象嵌套對象的json", member5.toString());
		}

輸出的結果

 7、另外一種解析對象嵌套對象的json 

定義一個類

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並解析

		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());

打印出來的log

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

demo下載鏈接：http://files.cnblogs.com/files/liqw/LauncherActivity.zip