GSON方式生成和解析json数据

客户端与服务器进行数据交互时，常常需要将数据在服务器端将数据转化成字符串并在客户端对json数据进行解析生成对象。但是用jsonObject和jsonArray解析相对麻烦。利用Gson和阿里的fastjson可以很方便的将下面四种常用的数据转换成json字符串，并能够将其解析成原数据对象。

类型一：JavaBean

类型二：List<JavaBean>

类型三:List<String>

类型四:List<Map<String,Object>>

一.Gson将上面的四种数据对象转换成json字符串的方法都是一样的

Gson gson = new Gson();

String jsonString = gson.toJson(obj);

二.Gson将json字符串转化成JavaBean对象

1.类型一：JavaBean

Person person = new Person("香港","刘德华",1001);

Gson gson = new Gson();

//这里将javabean转化成json字符串

String jsonString = gson.toJson(person);

System.out.println(jsonString);

//这里将json字符串转化成javabean对象,

person = gson.fromJson(jsonString,Person.class);

2.类型二：List<JavaBean>

将json字符串转化成List<JavaBean>对象

Person person1 = new Person("香港","刘德华",1001);

Person person2 = new Person("韩国","宋慧乔",1002);

List<Person> persons = new ArrayList<Person>();

persons.add(person1);

persons.add(person2);

Gson gson = new Gson();

//这里将lsit<javabean>转化成json字符串

String jsonString = gson.toJson(persons);

//解析json字符串

List<Person> persons2 = gson.fromJson(jsonString, new TypeToken<List<Person>>(){}.getType()) ;

3.类型三:List<String>

将json字符串转化成List<String>对象

List<String> list = new ArrayList<String>();

list.add("gson1");

list.add("gson2");

list.add("gson3");

Gson gson = new Gson();

String jsonString = gson.toJson(list);

System.out.println("json字符串:"+jsonString);

//解析json字符串

List<String> list2 = gson.fromJson(jsonString, new TypeToken<List<String>>(){}.getType());

4.类型四:List<Map<String,Object>>

将json字符串转化成List<Map<String,Object>>对象

Map<String,Object> map = new HashMap<String,Object>();

map.put("key1", "value1");

map.put("key2", "value2");

Map<String,Object> map2 = new HashMap<String,Object>();

map2.put("key1", 1);

map2.put("key2", 2);

List<Map<String,Object>> list = new ArrayList<Map<String,Object>>();

list.add(map);

list.add(map2);

Gson gson =  new Gson();

String jsonString = gson.toJson(list);

System.out.println("json字符串:"+jsonString);

//解析json字符串

List<Map<String,Object>> list2 = gson.fromJson(jsonString, new TypeToken<List<Map<String,Object>>>(){}.getType());

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本程序服务器端通过Gson生成json字符串数据，客户端用Gson将从服务器端接收的json字符串分别转换为<Person>,List<Person>,List<String>,List<Map<String,Object>>4种类型，程序思路和过程跟前篇  android
Intent传递 object , list<object>,list<Map<String,Object>>   相同，唯一区别就是：生成json用Gson方式，解析json用Gson方式。

程序结果截图：



1.点击“解析Person数据”按钮



3.点击“解析Persons”数据按钮



4.点击“解析listString数据”按钮



5.点击“解析listMap数据”按钮



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客户端eclipse android工程目录（左边）服务器端myeclipse web工程目录（右边）


     


服务器端

1.Person.java

package com.gson.data;

public class Person {
private int id;
private String name;
private String address;

public Person() {
// TODO Auto-generated constructor stub
}

public int getId() {
return id;
}

public void setId(int id) {
this.id = id;
}

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

public String getAddress() {
return address;
}

public void setAddress(String address) {
this.address = address;
}

public Person(int id, String name, String address) {
super();
this.id = id;
this.name = name;
this.address = address;
}

@Override
public String toString() {
return "Person [id=" + id + ", name=" + name + ", address=" + address
+ "]";
}

}

2.GsonService.java

package com.gson.service;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import com.gson.data.Person;

public class GsonService {

public static Person getPerson() {

Person person = new Person(1001, "刘德华", "香港");
return person;

}

public static List<Person> getListPersons() {
List<Person> persons = new ArrayList<Person>();
Person person1 = new Person(1001, "刘德华", "香港");
Person person2 = new Person(1002, "宋慧乔", "韩国");
persons.add(person1);
persons.add(person2);
return persons;

}

public static List<String> getListString(){

List<String> list = new ArrayList<String>();
list.add("美国");
list.add("中国");
list.add("俄罗斯");

return list;
}

public static List<java.util.Map<String, Object>> getListMap(){
List<java.util.Map<String, Object>> list = new ArrayList<Map<String,Object>>();
java.util.Map<String,Object> map1 = new HashMap<String,Object>();
map1.put("id",1001);
map1.put("name","刘德华");
map1.put("address","香港");

java.util.Map<String,Object> map2 = new HashMap<String,Object>();
map2.put("id",1002);
map2.put("name","宋慧乔");
map2.put("address","韩国");

list.add(map1);
list.add(map2);

return list;

}
}

3.GsonTools.java

package com.gson.tools;

import com.google.gson.Gson;

public class GsonTools {

public static String creatJsonString(Object object) {

Gson gson = new Gson();
String jsonString = gson.toJson(object); // 用Gson方式 把object 保存为 json字符串
return jsonString;
}
}

4.GsonAction.java

package com.gson.action;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.gson.service.GsonService;
import com.gson.tools.GsonTools;

public class GsonAction extends HttpServlet {

/**
* Destruction of the servlet. <br>
*/
public void destroy() {
super.destroy(); // Just puts "destroy" string in log
// Put your code here
}

/**
* The doGet method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to get.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doPost(request, response);
}

/**
* The doPost method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to post.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

response.setContentType("text/html;charset=utf-8");
request.setCharacterEncoding("utf-8");
response.setCharacterEncoding("utf-8");

String action_flag = request.getParameter("action_flag");
PrintWriter out = response.getWriter();
if ("person".equals(action_flag)) {
String person = GsonTools.creatJsonString(GsonService.getPerson());
out.println(person);

} else if("persons".equals(action_flag)) {
String persons = GsonTools.creatJsonString(GsonService.getListPersons());
out.println(persons);
}else if("listString".equals(action_flag)) {
String listString = GsonTools.creatJsonString(GsonService.getListString());
out.println(listString);
}else if("listMap".equals(action_flag)) {
String listMap = GsonTools.creatJsonString(GsonService.getListMap());
out.println(listMap);
}

out.flush();
out.close();
}

/**
* Initialization of the servlet. <br>
*
* @throws ServletException if an error occurs
*/
public void init() throws ServletException {
// Put your code here
}

}

5. TestGson.java

package com.gson.test;

import com.gson.service.GsonService;
import com.gson.tools.GsonTools;

public class TestGson {

/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub

//Test1 Person
System.out.println("Gson数据格式测试结果：\n");
String person = GsonTools.creatJsonString(GsonService.getPerson()) ;
//Test2 persons
String listPerson =  GsonTools.creatJsonString(GsonService.getListPersons()) ;
//Test3 listString
String listString =  GsonTools.creatJsonString(GsonService.getListString()) ;
//Test 4 listMap
String listMap = GsonTools.creatJsonString(GsonService.getListMap()) ;

System.out.println("测试结果1："+person+"\n");
System.out.println("测试结果2："+listPerson+"\n");
System.out.println("测试结果3："+listString+"\n");
System.out.println("测试结果4："+listMap);
}

}

1.Person.java

package com.gson.data;

import java.io.Serializable;

public class Person implements Serializable{

private int id;
private String name;
private String address;

public Person() {
// TODO Auto-generated constructor stub
}

public int getId() {
return id;
}

public void setId(int id) {
this.id = id;
}

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

public String getAddress() {
return address;
}

public void setAddress(String address) {
this.address = address;
}

public Person(int id, String name, String address) {
super();
this.id = id;
this.name = name;
this.address = address;
}

@Override
public String toString() {
return "Person [id=" + id + ", name=" + name + ", address=" + address
+ "]";
}

}

2.HttpUtils.java

package com.gson.http;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

import android.annotation.SuppressLint;
import android.os.StrictMode;

/** 接收path服务器端返回的 InputStream, 转换为 json字符串
* @author ben
*
*/
public class HttpUtils {

public static String getJsonContent(String url_path ,String encode){

String jsonString = "";
try {
URL url = new URL(url_path);
HttpURLConnection connection = (HttpURLConnection)url.openConnection();

connection.setConnectTimeout(3000);
connection.setRequestMethod("GET");
connection.setDoInput(true);  //从服务器获得数据

int responseCode = connection.getResponseCode();

if (200 == responseCode) {
jsonString = changeInputStream(connection.getInputStream(),encode);

}

} catch (Exception e) {
// TODO: handle exception
}

//
return jsonString;
}

private static String changeInputStream(InputStream inputStream , String encode) throws IOException {
// TODO Auto-generated method stub
String  jsonString = null;

ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
byte[] data = new byte[1024];
int len = 0;
while((len=inputStream.read(data))!=-1){
outputStream.write(data, 0, len);
}

jsonString = new String(outputStream.toByteArray(), encode);

inputStream.close();

return jsonString;
}

}

3.MainActivity.java

package com.android.mygson;

import java.io.Serializable;
import java.util.List;
import java.util.Map;

import com.google.gson.Gson;
import com.gson.data.Person;
import com.gson.http.HttpUtils;
import android.os.Bundle;
import android.os.StrictMode;
import android.annotation.SuppressLint;
import android.app.Activity;
import android.content.Intent;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import com.google.gson.reflect.TypeToken;

;

public class MainActivity extends Activity implements OnClickListener {
private Button person, persons, listString, listMap;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
closeStrictMode();

// closeStrictMode(); //关闭严苛模式

person = (Button) findViewById(R.id.person);
persons = (Button) findViewById(R.id.persons);
listString = (Button) findViewById(R.id.listString);
listMap = (Button) findViewById(R.id.listMap);
person.setOnClickListener(this);
persons.setOnClickListener(this);
listString.setOnClickListener(this);
listMap.setOnClickListener(this);

}

@Override
public void onClick(View v) {
// TODO Auto-generated method stub
switch (v.getId()) {
case R.id.person:

String url_path = "http://192.168.0.102:8080/gsonProject/servlet/GsonAction?action_flag=person";
String jsonString = HttpUtils.getJsonContent(url_path, "utf-8");
Gson gson = new Gson();
Person person = gson.fromJson(jsonString, Person.class);

Intent intent = new Intent(MainActivity.this, OtherActivity.class);
intent.putExtra("click_flag", "person");
intent.putExtra("person", (Serializable) person);
startActivity(intent);
// Log.i(TAG, person.toString());

break;

case R.id.persons:
String url_path2 = "http://192.168.0.102:8080/gsonProject/servlet/GsonAction?action_flag=persons";
String jsonString2 = HttpUtils.getJsonContent(url_path2, "utf-8");
Gson gson2 = new Gson();
// 用GSON 将json字符串转换成 List<Person>
List<Person> listPerson = gson2.fromJson(jsonString2,new TypeToken<List<Person>>(){}.getType());
Intent intent2 = new Intent(MainActivity.this, OtherActivity.class);
intent2.putExtra("click_flag", "persons");
intent2.putExtra("persons", (Serializable) listPerson); // 用Intent传递 List<Person>数据类型
startActivity(intent2);
break;

case R.id.listString:
String url_path3 = "http://192.168.0.102:8080/gsonProject/servlet/GsonAction?action_flag=listString";
String jsonString3 = HttpUtils.getJsonContent(url_path3, "utf-8");
Gson gson3 = new Gson();
// 用GSON 将json字符串转换成 List<String>
List<String> listString = gson3.fromJson(jsonString3,new TypeToken<List<String>>(){}.getType());
Intent intent3 = new Intent(MainActivity.this, OtherActivity.class);
intent3.putExtra("click_flag", "listString");
intent3.putExtra("listString", (Serializable) listString); // 用Intent传递 List<Person>数据类型
startActivity(intent3);
break;
case R.id.listMap:
String url_path4 = "http://192.168.0.102:8080/gsonProject/servlet/GsonAction?action_flag=listMap";
String jsonString4 = HttpUtils.getJsonContent(url_path4, "utf-8");
Gson gson4 = new Gson();
// 用GSON 将json字符串转换成 List<Map<String,Object>>
List<Map<String, Object>> listMap = gson4.fromJson(jsonString4,	new TypeToken<List<Map<String, Object>>>() {}.getType());
Intent intent4 = new Intent(MainActivity.this, OtherActivity.class);
intent4.putExtra("click_flag", "listMap");
intent4.putExtra("listMap", (Serializable) listMap); // 用Intent传递 List<Map<Sting,Object>>数据类型
intent4.putExtra("jsonString", jsonString4);
startActivity(intent4);
break;

}

}

@SuppressLint("NewApi")
public static void closeStrictMode() {
StrictMode.setThreadPolicy(new StrictMode.ThreadPolicy.Builder()
.detectAll().penaltyLog().build());
}

}

4.OtherActvity.java

package com.android.mygson;

import java.util.List;
import java.util.Map;

import com.gson.data.Person;

import android.R.integer;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.widget.TextView;

public class OtherActivity extends Activity {

private TextView textView;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_other);

textView = (TextView) findViewById(R.id.msg);
Intent intent = getIntent();
String click_flag = intent.getStringExtra("click_flag");
if ("person".equals(click_flag)) { // 如果是点击 person按钮
// 接收Intent传递的Person对象
Person person =(Person) intent.getSerializableExtra("person");
textView.setText(person.toString());

} else if ("persons".equals(click_flag)) {// 如果是点击 persons按钮

// 接收Intent传递的List<Person>参数
@SuppressWarnings("unchecked")
List<Person> list = (List<Person>) intent
.getSerializableExtra("persons");
String persons = "";
for (Person person : list) {
persons += person.toString() + "\n";
}
textView.setText(persons);

}else if ("listString".equals(click_flag)) {
List<String> list = (List<String>) intent
.getStringArrayListExtra("listString");

String listString = "";
for (String s : list) {
listString += s + "\n";
}
textView.setText(listString);
} else if ("listMap".equals(click_flag)) {
//接收Intent传递的List<Map<String,Object>>参数
@SuppressWarnings("unchecked")
List<Map<String, Object>> list = (List<Map<String, Object>>) intent
.getSerializableExtra("listMap");

String listMapString = "";
for (Map<String, Object> map : list) {
// 遍历一个Map
for (Map.Entry<String, Object> entry : map.entrySet()) {
String key = entry.getKey();
Object value = entry.getValue();
listMapString += " " + key + " : " + value + " ";
}
listMapString += "\n";
}

textView.setText(listMapString+intent.getStringExtra("jsonString"));
}

}

}

5.AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.android.mygson"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="19" />

<!-- 添加访问网络的授权 -->
<uses-permission android:name="android.permission.INTERNET" />

<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.android.mygson.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".OtherActivity"></activity>
</application>
</manifest>

6.activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<Button
android:id="@+id/person"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="解析Person数据" />
<Button
android:id="@+id/persons"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="解析Persons数据" />
<Button
android:id="@+id/listString"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="解析listString数据" />
<Button
android:id="@+id/listMap"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="解析listMap数据" />
</LinearLayout>

7.activity_other.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >

<TextView
android:id="@+id/msg"
android:layout_width="match_parent"
android:layout_height="wrap_content"

/>

</LinearLayout>

注意三点：

1. AndroidManifest.xml 加上访问网络权限，和注册<activity> OtherActivity.java

2. List<Map<String,Object>> list 被Gson生成的json字符串int 类型1001 和 1002 没问题，但再次解析成 List<Map<String,Object>> list是，int 型 id 变成了 1001.0 ， 1002.0 。

即Gson 将 Object类型的 1001默认转成Double 的1001.0,所以设计接口时要注意，这里设计时应该把Map<String,Object>设计成一个Person类，变成List<Person>，即第4个按钮应该设计第2个按钮的数据保存和解析方式。

3. 客户端和服务器端都要导入Gson jar包。本例中用gson-2.2.4.jar。