Google Gson 字段过滤：基于 Gson 版本

本文内容大多基于官方文档和网上前辈经验总结，经过个人实践加以整理积累，仅供参考。

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当为生成的 Google Gson 对象指定版本信息时，可以使用 @Since 和 @Until 注释实现字段过滤。@Since 和 @Until 都接收一个 double 类型参数。

@Since 当设置的 Gson 对象版本大于或等于其所接收的参数时导出该字段

@Until 当设置的 Gson 对象版本小于其所接收的参数时导出该字段

示例

(1) POJO 对象

public class User {    private String account;    @Since(2)    private String password;    private String name;    @Until(4)    private int age;    public User() {}    public User(String account, String password, String name, int age) {        this.account = account;        this.password = password;        this.name = name;        this.age = age;    }    public String getAccount() {        return account;    }    public void setAccount(String account) {        this.account = account;    }    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 int getAge() {        return age;    }    public void setAge(int age) {        this.age = age;    }    @Override    public String toString() {        return "User [account=" + account + ", password=" + password + ", name=" + name + ", age=" + age + "]";    }}

(2) 测试代码

@Testpublic void test() throws IOException {    User user = new User("admin", "123456", "John", 30);    String userStr = "{\"account\":\"normal\",\"password\":\"xyz123\",\"name\":\"Normal\",\"age\":25}";    Gson gson = new GsonBuilder()        .setVersion(1)        .create();    System.out.println(gson.toJson(user));    System.out.println(gson.fromJson(userStr, User.class));    gson = new GsonBuilder()        .setVersion(2)        .create();    System.out.println(gson.toJson(user));    System.out.println(gson.fromJson(userStr, User.class));    gson = new GsonBuilder()        .setVersion(3)        .create();    System.out.println(gson.toJson(user));    System.out.println(gson.fromJson(userStr, User.class));    gson = new GsonBuilder()        .setVersion(4)        .create();    System.out.println(gson.toJson(user));    System.out.println(gson.fromJson(userStr, User.class));    gson = new GsonBuilder()        .setVersion(5)        .create();    System.out.println(gson.toJson(user));    System.out.println(gson.fromJson(userStr, User.class));}

运行结果：