Gson 简明教程
Gson - Serialization Examples
在本章中，我们将讨论数组、集合和泛型的序列化/反序列化。
Array Example
int[] marks = {100,90,85};
//Serialization
System.out.println("marks:" + gson.toJson(marks));
//De-serialization
marks = gson.fromJson("[100,90,85]", int[].class);
System.out.println("marks:" + Arrays.toString(marks));Example
让我们看看 Array 序列化/反序列化如何发挥作用。在 C:\>GSON_WORKSPACE 中创建一个名为 GsonTester 的 Java 类文件。
File − GsonTester.java
import java.util.Arrays;
import com.google.gson.Gson;
public class GsonTester {
public static void main(String args[]) {
Gson gson = new Gson();
int[] marks = {100,90,85};
String[] names = {"Ram","Shyam","Mohan"};
//Serialization
System.out.print("{");
System.out.print("marks:" + gson.toJson(marks) + ",");
System.out.print("names:" + gson.toJson(names));
System.out.println("}");
//De-serialization
marks = gson.fromJson("[100,90,85]", int[].class);
names = gson.fromJson("[\"Ram\",\"Shyam\",\"Mohan\"]", String[].class);
System.out.println("marks:" + Arrays.toString(marks));
System.out.println("names:" + Arrays.toString(names));
}
}Collections Example
List marks = new ArrayList();
//Serialization
System.out.println("marks:" + gson.toJson(marks));
//De-serialization
//get the type of the collection.
Type listType = new TypeToken<list>(){}.getType();
//pass the type of collection
marks = gson.fromJson("[100,90,85]", listType);
System.out.println("marks:" +marks);</list>Example
让我们看看 Collection 序列化/反序列化如何发挥作用。在 C:\>GSON_WORKSPACE 中创建一个名为 GsonTester 的 Java 类文件。
File − GsonTester.java
import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.Collection;
import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;
public class GsonTester {
public static void main(String args[]) {
Gson gson = new Gson();
Collection<Integer> marks = new ArrayList<Integer>();
marks.add(100);
marks.add(90);
marks.add(85);
//Serialization
System.out.print("{");
System.out.print("marks:" + gson.toJson(marks));
System.out.println("}");
//De-serialization
Type listType = new TypeToken<Collection<Integer>>(){}.getType();
marks = gson.fromJson("[100,90,85]", listType);
System.out.println("marks:" +marks);
}
}Generics Example
Gson 使用 Java 反射 API 来获取 Json 文本要映射到的对象的类型。但是对于泛型，此信息会在序列化期间丢失。为了解决这个问题，Gson 提供了一个名为 com.google.gson.reflect.TypeToken 的类来存储泛型对象的类型。
Example
让我们看看 Generics 序列化/反序列化如何发挥作用。在 C:\>GSON_WORKSPACE 中创建一个名为 GsonTester 的 Java 类文件。
File − GsonTester.java
import java.lang.reflect.Type;
import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;
public class GsonTester {
public static void main(String args[]) {
// create a shape class of type circle.
Shape<Circle> shape = new Shape<Circle>();
// Create a Circle object
Circle circle = new Circle(5.0);
//assign circle to shape
shape.setShape(circle);
Gson gson = new Gson();
// Define a Type shapeType of type circle.
Type shapeType = new TypeToken<Shape<Circle>>() {}.getType();
//Serialize the json as ShapeType
String jsonString = gson.toJson(shape, shapeType);
System.out.println(jsonString);
Shape shape1 = gson.fromJson(jsonString, Shape.class);
System.out.println(shape1.get().getClass());
System.out.println(shape1.get().toString());
System.out.println(shape1.getArea());
Shape shape2 = gson.fromJson(jsonString, shapeType);
System.out.println(shape2.get().getClass());
System.out.println(shape2.get().toString());
System.out.println(shape2.getArea());
}
}
class Shape <T> {
public T shape;
public void setShape(T shape) {
this.shape = shape;
}
public T get() {
return shape;
}
public double getArea() {
if(shape instanceof Circle) {
return ((Circle) shape).getArea();
} else {
return 0.0;
}
}
}
class Circle {
private double radius;
public Circle(double radius){
this.radius = radius;
}
public String toString() {
return "Circle";
}
public double getRadius() {
return radius;
}
public void setRadius(double radius) {
this.radius = radius;
}
public double getArea() {
return (radius*radius*3.14);
}
}