@Data
@AllArgsConstructor
@NoArgsConstructor
public static class GItem {
    private String user;
    // @IgnoreField
    private transient String pwd;
}

public void testPrint() {
    GItem item = new GItem("一灰灰", "yihui");
    String ans = new Gson().toJson(item);
    System.out.println(ans);
}

@Data
@AllArgsConstructor
@NoArgsConstructor
public static class GItem {
    @Expose
    private String user;
    // @IgnoreField
    private String pwd;
}

@Test
public void testPrint() {
    GItem item = new GItem("一灰灰", "yihui");
    String ans = new GsonBuilder().excludeFieldsWithoutExposeAnnotation().create().toJson(item);
    System.out.println(ans);
}

@Target({ElementType.ANNOTATION_TYPE, ElementType.FIELD, ElementType.TYPE})
    @Retention(RetentionPolicy.RUNTIME)
    @Documented
    public @interface IgnoreField {
}


@Test
public void testExclude() {
    Gson gson = new GsonBuilder().setExclusionStrategies(new ExclusionStrategy() {
        @Override
        public boolean shouldSkipField(FieldAttributes fieldAttributes) {
            if (fieldAttributes.getAnnotation(IgnoreField.class) != null) {
                // 包含這個注解的，直接忽略
                return true;
            }

            // 成員白名單
            if (fieldAttributes.getName().equalsIgnoreCase("pwd")) {
                return true;
            }
            return false;
        }

        @Override
        public boolean shouldSkipClass(Class<?> aClass) {
            if (aClass.isAnnotationPresent(IgnoreField.class)) {
                return true;
            }
            return false;
        }
    }).registerTypeAdapterFactory(new MyMapTypeAdapterFactory(new ConstructorConstructor(new HashMap<>()), false)).create();

    GItem item = new GItem();
    item.setUser("一灰灰");
    item.setPwd("123456");

    System.out.println(gson.toJson(item));
}