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

@Test
public 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：