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，但不是详细信息。这很好用。但我看到getUserAsJsonForAdmin也一样，也没有细节。如果我删除@JsonIgnore注释 - 我确实在两个调用中都看到了详细信息。

我错了什么，有好的方法吗？谢谢！

Answer 1

您可能会发现使用the dynamic Jackson filtering稍微优雅一点的用例。以下是基于共享一个对象映射器实例的自定义注释过滤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"
}

Answer 2

看起来像杰克逊在像@JsonView这样很酷的功能上有一个可怕的概念。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);
    }
}

也许它帮助了一个人。但我希望找到更好的解决方案，因为我不接受自己的答案。

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})

jackson：忽略getter，但不能使用@JsonView

2 个答案: