Google Gson 字段过滤：@Expose

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。

---

Google Gson 使用 @Expose 注解实现字段过滤，该注解必须和 com.google.gson.GsonBuilder 类配合使用，如果使用 com.google.gson.Gson 类则不会产生任何作用。

(1) @Expose(serialize = true, deserialize = true)：序列化和反序列化时都生效，即序列化和反序列化都会处理

(2) @Expose(serialize = false, deserialize = false)：序列化和反序列化时都不生效，即序列化和反序列化都忽略，和不加 @Expose 注解效果一样

(3) @Expose(serialize = true, deserialize = false)：只有序列化时生效，即序列化时处理，反序列化时忽略

(4) @Expose(serialize = false, deserialize = true)：只有反序列化时生效，即反序列化时处理，序列化时忽略

示例

(1) POJO 类

public class User {    @Expose(serialize = true, deserialize = true)    private String account;    @Expose(serialize = false, deserialize = false)    private String password;    @Expose(serialize = true, deserialize = false)    private String name;    @Expose(serialize = false, deserialize = true)    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 {    Gson gson = new GsonBuilder()        .excludeFieldsWithoutExposeAnnotation()        .create();    User user = new User("admin", "123456", "John", 30);    System.out.println(gson.toJson(user));    String userStr = "{\"account\":\"normal\",\"password\":\"xyz123\",\"name\":\"Normal\",\"age\":25}";    User normalUser = gson.fromJson(userStr, User.class);    System.out.println(normalUser);}

运行测试结果：