详解Gson使用(一)简单对象转化

JSON是一种轻量级的数据交换格式。 易于人阅读和编写，同时也易于机器解析和生成(一般用于提升网络传输速率)。

在之前我写过一篇文章，《Android解析json数据》

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介绍了json和用JSONObject、JSONArray解析json数据的方法，接下来几篇文章将会介绍解析json数据的更好的方法：使用Gson解析。

Gson是Google推出的用来解析json数据以及将对象转换成json数据的框架。可以很方便地实现json数据与对象的相互转换，还可以自定义需要序列化或反序列化的字段。

使用Gson需要先导入jar，我这里用到的是gson-2.3.1.jar

项目和jar下载地址：

Github：https://github.com/smileysx/GsonTest

Oschina：https://git.oschina.net/ysx_xx/GsonText

详解Gson使用(一)简单对象转化

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详解Gson使用(二)带泛型的List转化

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详解Gson使用(三)使用注解

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详解Gson使用(四)Map对象转化

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详解Gson使用(五)实现百度翻译功能

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其中gson-2.3.1.jar在项目lib目录下

下面先来介绍简单对象的转换：

注意：以下所有实体类的变量名要跟json数据中的key相同

1.普通json数据对象实体类：

public class ToJsonBeanOne {
private int id;
private String name;
private int age;

public ToJsonBeanOne(int id, String name, int age) {
super();
this.id = id;
this.name = name;
this.age = age;
}

public int getId() {
return id;
}

public String getName() {
return name;
}

public int getAge() {
return age;
}

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

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

public void setAge(int age) {
this.age = age;
}

@Override
public String toString() {
String resultString = "";
resultString += "id:" + id + "\nname:" + name + "\nage:" + age + "\n";

return resultString;
}
}

可以看出来，上面对象中三个数据都是String类型，这是最简单的。

看看如何把该对象序列化：

public class ToJsonTest extends Activity {

private TextView show;
private Button start;
private Gson gson;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

initData();
}

private void initData() {

gson = new Gson();
show = (TextView) findViewById(R.id.showtext);
start = (Button) findViewById(R.id.send);
start.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View v) {
showData();
}
});
}

private void showData() {

String resultString = "";

resultString = one() + "\n\n";

show.setText(resultString);
}

private String one() {
//创建对象
ToJsonBeanOne toJsonBeanOne = new ToJsonBeanOne(1, "小熊", 21);
//将对象转换为json数据
return gson.toJson(toJsonBeanOne);
}
}

结果为：



接下来看看如何把json数据转换为该对象：

public class FromJsonTest extends Activity {

/**
* 显示数据的textview
*/
private TextView show;
/**
* 按钮
*/
private Button start;
/**
* gson
*/
private Gson gson;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

initData();
}

private void initData() {

gson = new Gson();
show = (TextView) findViewById(R.id.showtext);
start = (Button) findViewById(R.id.send);
start.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View v) {
showData();
}
});

}

private void showData() {
String showString = "";

showString += one();

show.setText(showString);

}

private String one() {
//这里创建个对象，是为了得到json数据，实际中json数据可能是由网络请求得到等
ToJsonBeanOne toJsonBeanOne = new ToJsonBeanOne(1, "小熊", 21);
String jsonString = gson.toJson(toJsonBeanOne);

//将json数据转换为对象
ToJsonBeanOne beanOne = gson.fromJson(jsonString, ToJsonBeanOne.class);

String showString = "";
showString += "json:" + jsonString + "\n解析结果为：\n" + beanOne.toString();

showString += "----------------------\n";
return showString;
}
}

结果为：



2.带对象的对象实体类：

public class ToJsonBeanTwo {
private String school;
private String classroom;
private ToJsonBeanOne toJsonBeanOne;

public ToJsonBeanTwo(String school, String classroom,
ToJsonBeanOne toJsonBeanOne) {
super();
this.school = school;
this.classroom = classroom;
this.toJsonBeanOne = toJsonBeanOne;
}

public String getSchool() {
return school;
}

public String getClassroom() {
return classroom;
}

public ToJsonBeanOne getToJsonBeanOne() {
return toJsonBeanOne;
}

public void setSchool(String school) {
this.school = school;
}

public void setClassroom(String classroom) {
this.classroom = classroom;
}

public void setToJsonBeanOne(ToJsonBeanOne toJsonBeanOne) {
this.toJsonBeanOne = toJsonBeanOne;
}

@Override
public String toString() {
String resultString = "";
resultString += "school:" + school + "\nclassroom:" + classroom
+ "\ntoJsonBeanOne:\nid:" + toJsonBeanOne.getId() + "\nname:"
+ toJsonBeanOne.getName() + "\nage:" + toJsonBeanOne.getAge()
+ "\n";
return resultString;
}
}

可以看出该对象中不仅有String类型数据，还有ToJsonBeanOne对象数据。

看看如何把该对象序列化：

public class ToJsonTest extends Activity {

private TextView show;
private Button start;
private Gson gson;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

initData();
}

private void initData() {

gson = new Gson();
show = (TextView) findViewById(R.id.showtext);
start = (Button) findViewById(R.id.send);
start.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View v) {
showData();
}
});
}

private void showData() {

String resultString = "";

resultString += three() + "\n\n";

show.setText(resultString);
}

private String three() {

ToJsonBeanTwo toJsonBeanTwo = new ToJsonBeanTwo("华软", "软工五班",
new ToJsonBeanOne(1, "小熊", 21));

return gson.toJson(toJsonBeanTwo);
}
}

结果为：



接下来看看如何把json数据转换为该对象：

public class FromJsonTest extends Activity {

/**
* 显示数据的textview
*/
private TextView show;
/**
* 按钮
*/
private Button start;
/**
* gson
*/
private Gson gson;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

initData();
}

private void initData() {

gson = new Gson();
show = (TextView) findViewById(R.id.showtext);
start = (Button) findViewById(R.id.send);
start.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View v) {
showData();
}
});

}

private void showData() {
String showString = "";

showString += three();

show.setText(showString);

}

private String three() {

ToJsonBeanTwo toJsonBeanTwo = new ToJsonBeanTwo("华软", "软工五班",
new ToJsonBeanOne(1, "小熊", 21));
String jsonString = gson.toJson(toJsonBeanTwo);

ToJsonBeanTwo beanTwo = gson.fromJson(jsonString, ToJsonBeanTwo.class);

String showString = "";
showString += "json:" + jsonString + "\n解析后的数据：\n" + beanTwo.toString();

showString += "----------------------\n";

return showString;
}
}

结果为：



3.既带对象又带List数据的对象(相当与json数据中有数组)实体类:

public class ToJsonBeanThree {
private String number;
private ToJsonBeanTwo toJsonBeanTwo;
private List<Book> books;

public ToJsonBeanThree(String number, ToJsonBeanTwo toJsonBeanTwo,
List<Book> books) {
super();
this.number = number;
this.toJsonBeanTwo = toJsonBeanTwo;
this.books = books;
}

public ToJsonBeanTwo getToJsonBeanTwo() {
return toJsonBeanTwo;
}

public List<Book> getBooks() {
return books;
}

public void setToJsonBeanTwo(ToJsonBeanTwo toJsonBeanTwo) {
this.toJsonBeanTwo = toJsonBeanTwo;
}

public void setBooks(List<Book> books) {
this.books = books;
}

public String getNumber() {
return number;
}

public void setNumber(String number) {
this.number = number;
}

@Override
public String toString() {

String resultString = "";
resultString += "number:" + number + "\n";
ToJsonBeanOne toJsonBeanOne = toJsonBeanTwo.getToJsonBeanOne();
resultString += "toJsonBeanTwo:\nschool:" + toJsonBeanTwo.getSchool()
+ "\nclassroom:" + toJsonBeanTwo.getClassroom() + "\n";
resultString += "toJsonBeanOne:\nid:" + toJsonBeanOne.getId()
+ "\nname:" + toJsonBeanOne.getName() + "\nage:"
+ toJsonBeanOne.getAge() + "\n";
resultString += "books:\n";

for (int i = 0; i < books.size(); ++i) {
resultString += "bookName:" + books.get(i).getBookName()
+ "\nprice:" + books.get(i).getPrice() + "\n";
}

return resultString;
}

/**
*
* @ClassName: Book
* @Description: 内部类
* @author smile
* @date 2016年5月12日 上午12:23:42
*
*/
public static class Book {
private String bookName;
private float price;

public Book(String bookName, float price) {
super();
this.bookName = bookName;
this.price = price;
}

public String getBookName() {
return bookName;
}

public float getPrice() {
return price;
}

public void setBookName(String bookName) {
this.bookName = bookName;
}

public void setPrice(float price) {
this.price = price;
}

}
}

可以看出该对象里不仅有String类型，还有ToJsonBeanTwo对象类型，还有List<Book>类型，Book对象我写成内部类，如果有多个类共用则写成外部类，这里要注意：写成内部类要写为静态内部类，不然解析会出错。

看看如何把该对象序列化：

public class ToJsonTest extends Activity {

private TextView show;
private Button start;
private Gson gson;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

initData();
}

private void initData() {

gson = new Gson();
show = (TextView) findViewById(R.id.showtext);
start = (Button) findViewById(R.id.send);
start.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View v) {
showData();
}
});
}

private void showData() {

String resultString = "";

resultString += five() + "\n\n";

show.setText(resultString);
}

private String five() {

ToJsonBeanTwo toJsonBeanTwo = new ToJsonBeanTwo("华软", "软工五班",
new ToJsonBeanOne(1, "小熊", 21));
List<Book> books = new ArrayList<Book>();
for (int i = 1; i < 5; ++i) {
books.add(new Book("第" + i + "本书", 25f * i));
}
ToJsonBeanThree toJsonBeanThree = new ToJsonBeanThree("1",
toJsonBeanTwo, books);

return gson.toJson(toJsonBeanThree);
}
}

结果为：



可以看出对象中List数据books转换成json数据变为数组

接下来看看如何把json数据转换为该对象：

public class FromJsonTest extends Activity {

/**
* 显示数据的textview
*/
private TextView show;
/**
* 按钮
*/
private Button start;
/**
* gson
*/
private Gson gson;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

initData();
}

private void initData() {

gson = new Gson();
show = (TextView) findViewById(R.id.showtext);
start = (Button) findViewById(R.id.send);
start.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View v) {
showData();
}
});

}

private void showData() {
String showString = "";

showString += five();

show.setText(showString);

}

private String five() {

ToJsonBeanTwo toJsonBeanTwo = new ToJsonBeanTwo("华软", "软工五班",
new ToJsonBeanOne(1, "小熊", 21));
List<Book> books = new ArrayList<Book>();
for (int i = 1; i < 5; ++i) {
books.add(new Book("第" + i + "本书", 25f * i));
}
ToJsonBeanThree toJsonBeanThree = new ToJsonBeanThree("1",
toJsonBeanTwo, books);

String jsonString = gson.toJson(toJsonBeanThree);

ToJsonBeanThree beanThree = gson.fromJson(jsonString,
ToJsonBeanThree.class);

String showString = "";
showString += "json:" + jsonString + "\n解析后的数据：\n"
+ beanThree.toString();

showString += "----------------------\n";
return showString;
}
}

结果为：