序列化（三）JSON

1. JSON 相关说明

  1.1 JSON 全称: JavaScript Object Notation
  1.2 Android studio 中创建JSON文件: File -> New -> Scratch File -> JSON
  1.3 transient 关键字: 不参与序列化
  1.4 @SerializedName 序列化，反序化时，自定义标记的名称

2. build.gradle 文件引入 GSON 库

 dependencies {
    implementation 'com.google.code.gson:gson:2.9.1'
 }

3. 创建两个实体类

  3.1 Student.java

public class Student {
    @SerializedName("student_name")
    private String name;
    @SerializedName("student_age")
    private int age;
    // private transient int age;//不参与序列化
    private Score score;
 
    public Student(String name, int age, Score score) {
        this.name = name;
        this.age = age;
        this.score = score;
    }
 
    public String getName() {
        return name;
    }
 
    public int getAge() {
        return age;
    }
 
    public Score getScore() {
        return score;
    }
 
    @Override
    public String toString() {
        return "Student{" + "name='" + name + '\'' + ", age=" + age + ", score=" + score + '}';
    }
}

  3.2 Score.java

public class Score {
    private int math;
    private int english;
    private int chinese;
 
    public Score(int math, int english, int chinese) {
        this.math = math;
        this.english = english;
        this.chinese = chinese;
    }
 
    public int getMath() {
        return math;
    }
 
    public int getEnglish() {
        return english;
    }
 
    public int getChinese() {
        return chinese;
    }
 
    @Override
    public String toString() {
        return "Score{" + "math=" + math + ", english=" + english + ", chinese=" + chinese + '}';
    }
}

4. 基本序列化

  4.1 对 Student 序列化

    //序列化
    private void serialize() {
        Student student1 = new Student("YuYu", 21, new Score(88, 77, 99));
        Gson gson = new Gson();
        String jsonStudent1 = gson.toJson(student1);
        Log.i("MyTag", jsonStudent1);
    }

  4.2 对 String 反序列化

    //反序列化
    private void deSerialize() {
        String str = "{\"age\":21,\"name\":\"YuYu\",\"score\":{\"chinese\":99,\"english\":77,\"math\":88}}";
        Gson gson = new Gson();
        Student student = gson.fromJson(str, Student.class);
        Log.i("MyTag", student.toString());
    }

5. 序列化数组

  5.1 Student 数组序列化

    //序列化数组/列表
    private void serializeArray() {
        Student student1 = new Student("AA", 11, new Score(88, 77, 99));
        Student student2 = new Student("BB", 22, new Score(88, 77, 99));
        Student[] students = {student1, student2};
        Gson gson = new Gson();
        String jsonArray = gson.toJson(students);
        Log.i("MyTag", jsonArray);
    }

  5.2 String 数组反序列化

    //反序列化数组/列表
    private void deSerializeArray() {
        String str = "[{\"age\":11,\"name\":\"AA\",\"score\":{\"chinese\":99,\"english\":77,\"math\":88}}," + "{\"age\":22,\"name\":\"BB\",\"score\":{\"chinese\":99,\"english\":77,\"math\":88}}]";
        Gson gson = new Gson();
        //[] 表示正列
        Student[] students = gson.fromJson(str, Student[].class);
        for (int i = 0; i < students.length; i++) {
            Log.i("MyTag", students[i].toString());
        }
        //数组转List
        List list = Arrays.asList(students);
    }

6. 序列化 List

  6.1 Student List 序列化

    //序列化列表
    private void serializeList() {
        Student student1 = new Student("AA", 11, new Score(88, 77, 99));
        Student student2 = new Student("BB", 22, new Score(88, 77, 99));
        //Arrays.asList(student1,student2);
        List students = new ArrayList<>();
        students.add(student1);
        students.add(student2);
        Gson gson = new Gson();
        String jsonArray = gson.toJson(students);
        Log.i("MyTag", jsonArray);
    }

  6.2 String 到 List 反序列化

    //反序列化列表
    private void deSerializeList() {
        String str = "[{\"age\":11,\"name\":\"AA\",\"score\":{\"chinese\":99,\"english\":77,\"math\":88}}," + "{\"age\":22,\"name\":\"BB\",\"score\":{\"chinese\":99,\"english\":77,\"math\":88}}]";
        Gson gson = new Gson();
        Type typeStudents = new TypeToken>() {
        }.getType();
        List list = gson.fromJson(str, typeStudents);
        for (int i = 0; i < list.size(); i++) {
            Log.i("MyTag", list.get(i).toString());
        }
    }

7. 序列化自定义

    //不参与序列化
    @SerializedName("student_age")
    private transient int age; 

  7.1 序列化自定义标记名称 @SerializedName，transient 不参与序列化

    private void serializedName() {
        Student student = new Student("WW", 33, new Score(88, 77, 99));
        Gson gson = new Gson();
        String str = gson.toJson(student);
        Log.i("MyTag", str);
        //打印结果
        //{"student_age":33,"student_name":"WW","score":{"chinese":99,"english":77,"math":88}}
    }

  7.2 反序列化自定义标记名称 @SerializedName，transient 不参与序列化

    private void deSerializedName() {
        String str = "{\"student_age\":33,\"student_name\":\"WW\",\"score\":{\"chinese\":99,\"english\":77,\"math\":88}}";
        Gson gson = new Gson();
        Student student = gson.fromJson(str, Student.class);
        Log.i("MyTag", student.toString());
        //打印结果 Student{name='WW', age=0, score=Score{math=88, english=77, chinese=99}}
    }