I have a class that looks like
class MyClass {
private byte[] payload;
public MyClass(){}
@JsonCreator
public MyClass(@JsonProperty("payload") final byte[] payload) {
this.payload = payload;
}
public byte[] getPayload() {
return this.payload;
}
}
I am using Jackson so serialize and then to deserialize. Serialization works fine, but during deserialization, I am getting this error message -
Cannot construct instance of `mypackage.MyClass` (no Creators, like default construct, exist): cannot deserialize from Object value (no delegate- or property-based Creator)
I was reading about this problem online, and came across several texts recommending to have a default constructor or a constructor with @JsonCreator
annotation. I tried adding both, but still getting that exception. What am I missing here?
EDIT:
I just found a much better solution, add the ParanamerModule to the ObjectMapper
:
mapper.registerModule(new ParanamerModule());
Maven:
<dependency>
<groupId>com.fasterxml.jackson.module</groupId>
<artifactId>jackson-module-paranamer</artifactId>
<version>${jackson.version}</version>
</dependency>
The advantage against the ParameterNamesModule seems to be that the classes do not need to be compiled with the -parameters
argument.
END EDIT
With Jackson 2.9.9 I tried to deserialize this simple POJO and came accros the same exception, adding a default constructor solved the problem:
POJO:
public class Operator {
private String operator;
public Operator(String operator) {
this.operator = operator;
}
public String getOperator() {
return operator;
}
}
ObjectMapper and Serialize/Deserialize:
ObjectMapper mapper = new ObjectMapper();
mapper.setVisibility(PropertyAccessor.ALL, Visibility.NONE);
mapper.setVisibility(PropertyAccessor.FIELD, Visibility.ANY);
mapper.setVisibility(PropertyAccessor.CREATOR, Visibility.ANY);
String value = mapper.writeValueAsString(new Operator("test"));
Operator result = mapper.readValue(value, Operator.class);
JSON:
{"operator":"test"}
Exception:
com.fasterxml.jackson.databind.exc.MismatchedInputException:
Cannot construct instance of `...Operator` (although at least one Creator exists): cannot deserialize from Object value (no delegate- or property-based Creator)
at [Source: (String)"{"operator":"test"}"; line: 1, column: 2]
Solution (POJO with default constructor):
public class Operator {
private String operator;
private Operator() {
}
public Operator(String operator) {
this();
this.operator = operator;
}
public String getOperator() {
return operator;
}
}