Google Gson：POJO 和 JSON 的字段映射规则

GsonBuilder 类的 setFieldNamingPolicy 和 setFieldNamingStrategy 方法可以定义 POJO 和 JSON 的字段映射规则

1 setFieldNamingPolicy

示例

POJO

public class User {

    private String name;

    private String phoneNumber;

    public User() {}

    public User(String name, String phoneNumber) {
        this.name = name;
        this.phoneNumber = phoneNumber;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPhoneNumber() {
        return phoneNumber;
    }

    public void setPhoneNumber(String phoneNumber) {
        this.phoneNumber = phoneNumber;
    }

    @Override
    public String toString() {
        return "User [name=" + name + ", phoneNumber=" + phoneNumber + "]";
    }

}

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测试代码：

@Test
public void test() throws IOException {
    User user = new User("UserX", "160");

    Gson gson = new GsonBuilder()
        .setFieldNamingPolicy(FieldNamingPolicy.IDENTITY)
        .create();
    System.out.println(gson.toJson(user));
    String userStr = "{\"name\":\"User1\",\"phoneNumber\":\"161\"}";
    System.out.println(gson.fromJson(userStr, User.class));

    gson = new GsonBuilder()
        .setFieldNamingPolicy(FieldNamingPolicy.LOWER_CASE_WITH_DASHES)
        .create();
    System.out.println(gson.toJson(user));
    userStr = "{\"name\":\"User1\",\"phone-number\":\"162\"}";
    System.out.println(gson.fromJson(userStr, User.class));

    gson = new GsonBuilder()
        .setFieldNamingPolicy(FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES)
        .create();
    System.out.println(gson.toJson(user));
    userStr = "{\"name\":\"User1\",\"phone_number\":\"163\"}";
    System.out.println(gson.fromJson(userStr, User.class));

    gson = new GsonBuilder()
        .setFieldNamingPolicy(FieldNamingPolicy.UPPER_CAMEL_CASE)
        .create();
    System.out.println(gson.toJson(user));
    userStr = "{\"name\":\"User1\",\"PhoneNumber\":\"164\"}";
    System.out.println(gson.fromJson(userStr, User.class));

    gson = new GsonBuilder()
        .setFieldNamingPolicy(FieldNamingPolicy.UPPER_CAMEL_CASE_WITH_SPACES)
        .create();
    System.out.println(gson.toJson(user));
    userStr = "{\"name\":\"User1\",\"Phone Number\":\"165\"}";
    System.out.println(gson.fromJson(userStr, User.class));
}

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运行结果： 

2 setFieldNamingStrategy

测试代码：

@Test
public void test() throws IOException {
    User user = new User("UserX", "160");

    Gson gson = new GsonBuilder()
        .setFieldNamingStrategy(new FieldNamingStrategy() {
            public String translateName(Field arg0) {
                if (arg0.getName().equals("name")) {
                    return "custom-name";
                } else if (arg0.getName().equals("phoneNumber")) {
                    return "custom-phone";
                }
                return null;
            }
        })
        .create();

    System.out.println(gson.toJson(user));
    String userStr = "{\"custom-name\":\"userN\",\"custom-phone\":\"168\"}";
    System.out.println(gson.fromJson(userStr, User.class));
}

运行结果：