Wie kann mit Fehlern umgegangen werden, die bei der Deserialisierung von JSON in Java entstehen?

Wenn Sie während des Deserialisierungsprozesses auf ein potenziell behebbares Problem stoßen, können Sie die Klasse DeserializationProblemHandler registrieren, um einen Anruf zu tätigen. Wir können Fehler behandeln, die beim Deserialisieren von JSON entstehen, indem wir die Methode handleUnknownProperty() der Klasse DeserializationProblemHandler implementieren.

Syntax

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

Beispiel

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 + "]";
   }
}

Ausgabe, wenn true zurückgegeben wird

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

Ausgabe, wenn false zurückgegeben wird

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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