杰克逊地图序列化模块

Question

我有一个包含Map(带非String键)和其他一些字段的Class.

public class MyClass() {
    private Map<KeyObject, OtherObject> map;
    private String someField;

    public MyClass(Map<KeyObject, OtherObject> map, String someField) {
        this.map = map;
        this.someField = someField;
    }

    // Getters & Setters
}

我想使用Jackson对这个类进行序列化和反序列化.我看到了不同的方法,并决定尝试使用jackson模块.

我按照这篇文章并扩展了JsonDeserializer和JsonSerializer.问题是应该键入这些类,所以看起来应该是这样的

public class keyDeserializer extends JsonDeserializer<Map<KeyObject, OtherObject>> {
...
}

KeySerializer也是如此.

然后添加到模块:

module.addSerializer(new keySerializer());
module.addDeserializer(Map.class, new keyDeserializer());

但这显然是错误的,因为我得到了一个例外:

keySerializer does not define valid handledType() -- must either register with method that takes type argument  or make serializer extend 'org.codehaus.jackson.map.ser.std.SerializerBase'

我可以将我的序列化器和反序列化器输入MyClass,但后来我必须手动解析所有这些,这是不合理的.

更新:

我设法通过使用注释绕过代码中的模块创建

@JsonDeserialize(using = keyDeserializer.class)
@JsonSerialize(using = keySerializer.class)
private Map<KeyObject, OtherObject> map;

但是我必须自己从toString()输出序列化/反序列化整个地图结构.所以尝试了不同的注释:

@JsonDeserialize(keyUsing = MyKeyDeserializer.class)
private Map<KeyObject, OtherObject> map;

MyKeyDeserializer扩展org.codehaus.jackson.map.KeyDeserializer并覆盖该方法的位置

public Object deserializeKey(String key, DeserializationContext ctxt) throws IOException, JsonProcessingException {...}

然后手动反序列化我的密钥,但再次从我的密钥类的toString()输出.

这不是最佳的(这种依赖于toString()方法).有没有更好的办法？

Answer 1

结束使用此序列化程序:

public class MapKeySerializer extends SerializerBase<Object> {
    private static final SerializerBase<Object> DEFAULT = new StdKeySerializer();
    private static final ObjectMapper mapper = new ObjectMapper();

    protected MapKeySerializer() {
    super(Object.class);
    }

    @Override
    public JsonNode getSchema(SerializerProvider provider, Type typeHint) throws JsonMappingException {
    return DEFAULT.getSchema(provider, typeHint);
    }

    @Override
    public void serialize(Object value, JsonGenerator jgen, SerializerProvider provider) throws IOException, JsonGenerationException {
    if (null == value) {
        throw new JsonGenerationException("Could not serialize object to json, input object to serialize is null");
    }
    StringWriter writer = new StringWriter();
    mapper.writeValue(writer, value);
    jgen.writeFieldName(writer.toString());
    }
}

而这个解串器:

public class MapKeyDeserializer extends KeyDeserializer {

    private static final ObjectMapper mapper = new ObjectMapper();

    @Override
    public Object deserializeKey(String key, DeserializationContext ctxt) throws IOException, JsonProcessingException {
    return mapper.readValue(key, MyObject.class);
    }
}

注释我的地图:

@JsonDeserialize(keyUsing = MapKeyDeserializer.class)
@JsonSerialize(keyUsing = MapKeySerializer.class)
private Map<KeyObject, OtherObject> map;

这是对我有用的解决方案,希望这有助于其他人.