杰克逊：忽略getter，但不使用@JsonView

Question

我正在寻找仅在某些情况下序列化瞬态信息的可能性：

@JsonInclude(Include.NON_NULL)
@Entity
public class User {

    public static interface AdminView {}

    ... id, email and others ...

    @Transient
    private transient Details details;

    @JsonIgnore                  // Goal: ignore all the time, except next line
    @JsonView(AdminView.class)   // Goal: don't ignore in AdminView
    public Details getDetails() {
        if (details == null) {
            details = ... compute Details ...
        }
        return details;
    }
}

public class UserDetailsAction {
    private static final ObjectWriter writer = new ObjectMapper();
    private static final ObjectWriter writerAdmin = writer
        .writerWithView(User.AdminView.class);

    public String getUserAsJson(User user) {
        return writer.writeValueAsString(user);
    }

    public String getUserAsJsonForAdmin(User user) {
        return writerAdmin.writeValueAsString(user);
    }
}

如果我调用 getUserAsJson，我希望看到 id、email 和其他字段，但看不到详细信息。这工作正常。但我对 getUserAsJsonForAdmin 也看到了同样的情况，也没有详细说明。如果我删除 @JsonIgnore 注释 - 我确实会在两个调用中看到详细信息。

我做错了什么，有什么好的方法吗？谢谢！

Answer 1

看起来杰克逊对@JsonView 等非常酷的功能有可怕的概念。我发现解决问题的唯一方法是：

@JsonInclude(Include.NON_NULL)
@Entity
public class User {

    public static interface BasicView {}
    public static interface AdminView {}

    ... id and others ...

    @JsonView({BasicView.class, AdminView.class}) // And this for EVERY field
    @Column
    private String email;

    @Transient
    private transient Details details;

    @JsonView(AdminView.class)
    public Details getDetails() {
        if (details == null) {
            details = ... compute Details ...
        }
        return details;
    }
}

public class UserDetailsAction {
    private static final ObjectWriter writer = new ObjectMapper()
        .disable(MapperFeature.DEFAULT_VIEW_INCLUSION)
        .writerWithView(User.BasicView.class);
    private static final ObjectWriter writerAdmin = new ObjectMapper()
        .disable(MapperFeature.DEFAULT_VIEW_INCLUSION)
        .writerWithView(User.AdminView.class);

    public String getUserAsJson(User user) {
        return writer.writeValueAsString(user);
    }

    public String getUserAsJsonForAdmin(User user) {
        return writerAdmin.writeValueAsString(user);
    }
}

也许它对某人有帮助。但我希望找到更好的解决方案，因为不接受我自己的答案。

编辑：因为接口可以扩展（多个）接口，我可以使用：

public static interface AdminView extends BasicView {}

只是

@JsonView(BasicView.class)

而不是

@JsonView({BasicView.class, AdminView.class})

Answer 2

对于您的用例，您可能会发现使用 the dynamic Jackson filtering 稍微优雅一些​​。下面是一个基于共享一个对象映射器实例的自定义注解过滤 POJO 字段的示例：

public class JacksonFilter {
    static private boolean shouldIncludeAllFields;

    @Retention(RetentionPolicy.RUNTIME)
    public static @interface Admin {}

    @JsonFilter("admin-filter")
    public static class User {
        public final String email;
        @Admin
        public final String details;

        public User(String email, String details) {
            this.email = email;
            this.details = details;
        }
    }

    public static class AdminPropertyFilter extends SimpleBeanPropertyFilter {

        @Override
        protected boolean include(BeanPropertyWriter writer) {
            // deprecated since 2.3
            return true;
        }

        @Override
        protected boolean include(PropertyWriter writer) {
            if (writer instanceof BeanPropertyWriter) {
                return shouldIncludeAllFields || ((BeanPropertyWriter) writer).getAnnotation(Admin.class) == null;
            }
            return true;
        }
    }

    public static void main(String[] args) throws JsonProcessingException {
        User user = new User("email", "secret");
        ObjectMapper mapper = new ObjectMapper();
        mapper.setFilters(new SimpleFilterProvider().addFilter("admin-filter", new AdminPropertyFilter()));
        System.out.println(mapper.writerWithDefaultPrettyPrinter().writeValueAsString(user));
        shouldIncludeAllFields = true;
        System.out.println(mapper.writerWithDefaultPrettyPrinter().writeValueAsString(user));
    }

}

输出：

{
  "email" : "email"
}
{
  "email" : "email",
  "details" : "secret"
}