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法律研究如何在 Java 中處理反序列化 JSON 時產生的錯誤？
DeserializationProblemHandler 類可註冊為在反序列化過程中遇到潛在可恢復的問題時呼叫。我們可以透過實現 DeserializationProblemHandler 類的 handleUnknownProperty() 方法來處理反序列化 JSON 時產生的錯誤。
語法
public boolean handleUnknownProperty(DeserializationContext ctxt, JsonParser p, JsonDeserializer deserializer, Object beanOrClass, String propertyName) throws IOException
示例
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\" }";
ObjectMapper objectMapper = new ObjectMapper();
DeserializationProblemHandler deserializationProblemHandler = new UnMarshallingErrorHandler();
objectMapper.addHandler(deserializationProblemHandler);
Customer customer = objectMapper.readValue(jsonString, Customer.class);
System.out.println(customer);
}
}
// UnMarshallingErrorHandler class
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 '" + propertyName + "' doesn't exist in Class of type '" + beanOrClass.getClass().getName() + "'");
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 + "]";
}
}返回 true 時的輸出
Property with name 'salary' doesn't exist in Class of type 'Customer' Customer [id=101, name=Ravi Chandra, address=Pune]
返回 false 時的輸出
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)
更新於： 07-07-2020
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