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字符串为单个对象
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：https://files.cnblogs.com/files/liqw/LauncherActivity.zip
