默认情况下,Jackson 只使用 public
的字段进行序列化和反序列化。没有 public
字段时,会使用 public
的 getters/setters。可以通过 @JsonAutoDetect
自定义这种行为,指定字段、方法的可见性规则。
@Target({ElementType.ANNOTATION_TYPE, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@JacksonAnnotation
public @interface JsonAutoDetect
{
public enum Visibility {
ANY,
NON_PRIVATE,
PROTECTED_AND_PUBLIC,
PUBLIC_ONLY,
NONE,
DEFAULT;
}
Visibility getterVisibility() default Visibility.DEFAULT;
Visibility isGetterVisibility() default Visibility.DEFAULT;
Visibility setterVisibility() default Visibility.DEFAULT;
Visibility creatorVisibility() default Visibility.DEFAULT;
Visibility fieldVisibility() default Visibility.DEFAULT;
}
Example
Java Object
@JsonAutoDetect(fieldVisibility = JsonAutoDetect.Visibility.ANY)
public class Employee {
private String name;
private String dept;
private String address;
public static Employee of(String name, String dept, String address) {
Employee e = new Employee();
e.name = name;
e.dept = dept;
e.address = address;
return e;
}
@Override
public String toString() {
return "Employee{" +
"name='" + name + '\'' +
", dept='" + dept + '\'' +
", address='" + address + '\'' +
'}';
}
}
Main class
public class ExampleMain {
public static void main(String[] args) throws IOException {
Employee employee = Employee.of("Trish", "Admin", "421 Moon Hill");
ObjectMapper om = new ObjectMapper();
String jsonString = om.writeValueAsString(employee);
System.out.println(jsonString);
Employee e = om.readValue(jsonString, Employee.class);
System.out.println(e);
}
}
{"name":"Trish","dept":"Admin","address":"421 Moon Hill"}
Employee{name='Trish', dept='Admin', address='421 Moon Hill'}
不使用 @JsonAutoDetect
删除 @JsonAutoDetect
将抛出异常,因为 Employee
中没有可用的字段或 getter/setters:
Exception in thread "main" com.fasterxml.jackson.databind.exc.InvalidDefinitionException: No serializer found for class org.example.c22.Employee and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS)
at com.fasterxml.jackson.databind.exc.InvalidDefinitionException.from(InvalidDefinitionException.java:77)
at com.fasterxml.jackson.databind.SerializerProvider.reportBadDefinition(SerializerProvider.java:1276)
at com.fasterxml.jackson.databind.DatabindContext.reportBadDefinition(DatabindContext.java:400)
at com.fasterxml.jackson.databind.ser.impl.UnknownSerializer.failForEmpty(UnknownSerializer.java:71)
at com.fasterxml.jackson.databind.ser.impl.UnknownSerializer.serialize(UnknownSerializer.java:33)
at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider._serialize(DefaultSerializerProvider.java:480)
at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:319)
at com.fasterxml.jackson.databind.ObjectMapper._writeValueAndClose(ObjectMapper.java:4487)
at com.fasterxml.jackson.databind.ObjectMapper.writeValueAsString(ObjectMapper.java:3742)
at org.example.c22.ExampleMain.main(ExampleMain.java:17)
Disconnected from the target VM, address: '127.0.0.1:64172', transport: 'socket'
Process finished with exit code 1
原文链接
Jackson JSON - Using @JsonAutoDetect to define fields/methods access visibility rules
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