超类的Json4s序列化

Question

我在为 Json4s 编写自定义序列化程序来处理以下情况时遇到问题。我有案例类:

trait Condition
case class BasicExpression (field:String, operator:String, value:String) extends Condition
case class BooleanExpression  (val leftExpr: Condition, val logicalOperator:String, 
    val rightExpr: Condition) extends Condition

我希望能够读取 BasicExpression 和 BooleanExpression 的 JSON，例如：

var jsonStringBasic:String = """ {"field":"name","operator":"=","value":"adam"}""";
var jsonStringBoolean:String = """{"leftExpr":{"leftExpr":{"field":"field1", "operator":"=", "value":"value1"}, "logicalOperator":"AND", "rightExpr":{"field":"field2","operator":">","value":"500"}}, "logicalOperator":"AND", "rightExpr": {"field":"field3","operator":"<","value":"10000"}}""";
var jValueBasic:JValue = parse(jsonStringBasic, false);
var readCBasic = jValueBasic.extract[Condition];

我了解自定义序列化程序如何读取 BasicExpression，我可以使用 SimpleTypeHints，但最好不要为每个文件都膨胀 JSON Condition。我也可以尝试 extract[BooleanExpression]，如果失败则尝试 extract[BasicExpression]，但这看起来很难看。是否可以编写自定义序列化程序来处理 BooleanCondition 本身将递归包含另一个 Condition 这样我可以 extract[Condition]?

Answer 1

为了更好地解析 JSON 你可以试试这个 :

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;


public class GsonUtils {

public static String defaultDateTimeFormat = "yyyy-MM-dd'T'HH:mm:ssZ";
private static GsonBuilder gsonBuilder = new GsonBuilder().setDateFormat(defaultDateTimeFormat);

/***
 * Creates a GSON instance from the builder with the default date/time format
 *
 * @return the GSON instance
 */
public static Gson createGson() {
    // Create with default params
    gsonBuilder = gsonBuilder.setDateFormat(defaultDateTimeFormat);
    return gsonBuilder.create();
}

/***
 * Creates a GSON instance from the builder specifying custom date/time format
 *
 * @return the GSON instance
 */
public static Gson createGson(String dateTimeFormat) {
    // Create with the specified dateTimeFormat
    gsonBuilder = gsonBuilder.setDateFormat(dateTimeFormat);
    return gsonBuilder.create();
}

}

并像这样使用它

  var String = """ {"field":"name","operator":"=","value":"adam"}""";

  Type collectionType = new TypeToken<YOUR_CLASS>() {}.getType();
  YOUR_CLASS iii=  GsonUtils.createGson().fromJson(jsonStringBasic, collectionType);

Answer 2

设法使 CustomSerializer 正常工作，以便它可以递归调用自身，在 BooleanExpression 的情况下，如下所示：

class ConditionSerialiser extends CustomSerializer[Condition]( format => (

{
    def deserialiseCondition:PartialFunction[JValue, Condition]= {
      case JObject(List(JField("field", JString(field)), JField("operator", JString(operator)), JField("value", JString(value)))) => BasicStringExpression(field, operator, value)
      case JObject(List(JField("field", JString(field)), JField("operator", JString(operator)), JField("value", JInt(value)))) => BasicNumericExpression(field, operator, value.doubleValue)
      case JObject(List(JField("field", JString(field)), JField("operator", JString(operator)), JField("value", JDouble(value)))) => BasicNumericExpression(field, operator, value)
      case JObject(List(JField("leftExpr", leftExpr), JField("logicalOperator", JString(logicalOperator)), JField("rightExpr", rightExpr))) => BooleanExpression(deserialiseCondition(leftExpr), logicalOperator, deserialiseCondition(rightExpr))
    }
    deserialiseCondition
},
{
  case bse: BasicStringExpression => JObject(List(JField("field", JString(bse.field)), JField("operator", JString(bse.operator)), JField("value", JString(bse.value))))       
}
))

超类的Json4s序列化

Json4s serialisation of superclass

java

json

scala

json4s