使用jackson序列化时有条件地跳过对象

我有一个类似的课程

interface IHideable { boolean isHidden(); } class Address implements IHideable { private String city; private String street; private boolean hidden; } class PersonalInfo implements IHideable { private String name; private int age; private boolean hidden; } 

我想在我的网络服务中序列化IHideable列表; 但过滤掉隐藏字段设置为true的任何对象。

基本上给出一个像对象的列表

 [ {'city 1','street 1',false}, {'city 2','street 2',true}, {'city 3','street 3',false} ] 

我希望输出为

 [ { city:'city 1', street:'street 1' }, { city:'city 3', street:'street 3' } ] 

我尝试了以下实现

 class ItemSerializer extends JsonSerializer { @Override public void serialize(IHideable value, JsonGenerator jgen, SerializerProvider provider) throws IOException, JsonProcessingException { if (!value.isHidden()) { jgen.writeStartObject(); jgen.writeString("city", value.city); jgen.writeString("street", value.street); jgen.writeEndObject(); } } } 

但是编写的writeString方法特定于Address类。 当我使用writeObject时，它会抛出stackoverflowexception。 我可以使用一些通用的writeObject方法，它可以写任何实现IHideable（）的对象吗？ 这是否可以使用jackson默认/自定义序列化？

Answer 1

您可以使用BeanSerializerModifier为IHideable类型注册序列化程序，并获得对此问题中讨论的默认bean序列化程序的引用。

在序列化程序中，检查isHidden标志，如果未设置，则使用默认序列化程序序列化实例。 这个技巧应该适用于任何实现IHideable接口的类型。 这是一个例子：

 public class JacksonHide { @JsonIgnoreProperties("hidden") public static interface IHideable { boolean isHidden(); } public static class Address implements IHideable { public final String city; public final String street; public final boolean hidden; public Address(String city, String street, boolean hidden) { this.city = city; this.street = street; this.hidden = hidden; } @Override public boolean isHidden() { return hidden; } } public static class PersonalInfo implements IHideable { public final String name; public final int age; public final boolean hidden; public PersonalInfo(String name, int age, boolean hidden) { this.name = name; this.age = age; this.hidden = hidden; } @Override public boolean isHidden() { return hidden; } } private static class MyBeanSerializerModifier extends BeanSerializerModifier { @Override public JsonSerializer modifySerializer(SerializationConfig config, BeanDescription beanDesc, JsonSerializer serializer) { if (IHideable.class.isAssignableFrom(beanDesc.getBeanClass())) { return new MyIHideableJsonSerializer((JsonSerializer) serializer); } return super.modifySerializer(config, beanDesc, serializer); } private static class MyIHideableJsonSerializer extends JsonSerializer { private final JsonSerializer serializer; public MyIHideableJsonSerializer(JsonSerializer serializer) { this.serializer = serializer; } @Override public void serialize(IHideable value, JsonGenerator jgen, SerializerProvider provider) throws IOException { if (!value.isHidden()) { serializer.serialize(value, jgen, provider); } } } } public static void main(String[] args) throws JsonProcessingException { ObjectMapper mapper = new ObjectMapper(); SimpleModule module = new SimpleModule(); module.setSerializerModifier(new MyBeanSerializerModifier()); mapper.registerModule(module); PersonalInfo p1 = new PersonalInfo("John", 30, false); PersonalInfo p2 = new PersonalInfo("Ivan", 20, true); Address a1 = new Address("A", "B", false); Address a2 = new Address("C", "D", true); System.out.println(mapper.writerWithDefaultPrettyPrinter().writeValueAsString (Arrays.asList(p1, p2, a1, a2))); } } 

输出：

 [ { "name" : "John", "age" : 30 }, { "city" : "A", "street" : "B" } ]