Java で JSON を逆シリアル化するときに生成されるエラーを処理する方法は何ですか?

逆シリアル化プロセス中に回復可能な可能性のある問題が発生した場合は、DeserializationProblemHandler クラスを登録して呼び出しを行うことができます。 JSON を逆シリアル化するときに生成されるエラーは、DeserializationProblemHandler クラスの handleUnknownProperty() メソッドを実装することで処理できます。

構文

public boolean handleUnknownProperty(DeserializationContext ctxt, JsonParser p, JsonDeserializer<!--?--> deserializer, Object beanOrClass, String propertyName) throws IOException

例

import java.io.*;
import com.fasterxml.jackson.core.*;
import com.fasterxml.jackson.databind.*;
import com.fasterxml.jackson.databind.deser.*;
public class DeserializationErrorTest {
   public static void main(String[] args) throws JsonMappingException, JsonGenerationException, IOException {
      String jsonString = "{\"id\":\"101\", \"name\":\"Ravi Chandra\", \"address\":\"Pune\", \"salary\":\"40000\" }";
      <strong>ObjectMapper </strong>objectMapper = new ObjectMapper();
      DeserializationProblemHandler deserializationProblemHandler = new UnMarshallingErrorHandler();
      objectMapper.addHandler(deserializationProblemHandler);
      Customer customer = objectMapper.readValue(jsonString, Customer.class);
      System.out.println(customer);
   }
}
// UnMarshallingErrorHandler class<strong>
</strong>class UnMarshallingErrorHandler extends DeserializationProblemHandler {
   @Override
   public boolean handleUnknownProperty(DeserializationContext ctxt, JsonParser jp, JsonDeserializer deserializer, Object beanOrClass, String propertyName) throws IOException, JsonProcessingException {
      boolean result = false;
      super.handleUnknownProperty(ctxt, jp, deserializer, beanOrClass, propertyName);
      System.out.println("Property with name &#39;" + propertyName + "&#39; doesn&#39;t exist in Class of type &#39;" + beanOrClass.getClass().getName() + "&#39;");
      return true; // returns true to inform the deserialization process that we can handle the error and it can continue deserializing and returns false, if we want to stop the deserialization immediately.
   }
}
// Customer class
class Customer {
   private int id;
   private String name;
   private String address;
   public int getId() {
      return id;
   }
   public void setId(int id) {
      this.id = id;
   }
   public String getName() {
      return name;
   }
   public void setName(String name) {
      this.name = name;
   }
   public String getAddress() {
      return address;
   }
   public void setAddress(String address) {
      this.address = address;
   }
   @Override
   public String toString() {
      return "Customer [id=" + id + ", name=" + name + ", address=" + address + "]";
   }
}

trueが返された場合の出力

Property with name 'salary' doesn't exist in Class of type 'Customer'
Customer [id=101, name=Ravi Chandra, address=Pune]

falseが返された場合の出力

Property with name 'salary' doesn't exist in Class of type 'Customer'
Exception in thread "main" com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "salary" (class Customer), not marked as ignorable (3 known properties: "id", "address", "name"])
at [Source: (String)"{"id":"101", "name":"Ravi Chandra", "address":"Pune", "salary":"40000" }"; line: 1, column: 65] (through reference chain: Customer["salary"]) at com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException.from(UnrecognizedPropertyException.java:61)
at com.fasterxml.jackson.databind.DeserializationContext.handleUnknownProperty(DeserializationContext.java:840)
at com.fasterxml.jackson.databind.deser.std.StdDeserializer.handleUnknownProperty(StdDeserializer.java:1179)
at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.handleUnknownProperty(BeanDeserializerBase.java:1592) at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.handleUnknownVanilla(BeanDeserializerBase.java:1570) at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:294)
at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:151)
at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4202)
at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3205)
at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3173)
at DeserializationErrorTest.main(DeserializationErrorTest.java:12)<strong>
</strong>

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