Develop Reference

Best validation method for a dynamic class in java (Micronaut)

I have a class A (listed below) which can have many different types of attributes saved to it. Naturally these attributes can be of different types. Based on the type of attribute I want to apply some validations to it.
What would be the best way of doing it in Micronaut?
Here is an example of what I want to achieve:
public class A {
private String type;
private String value;
// getter/setter omitted…
}
Some example instances of class A:
{type: "type1", value: "examplevalue1"}
{type: "type2", value: "examplevalue2"}
{type: "type2", value: "examplevalue3"}
Then I have some set of validation rules which are relevant to the respective types. Each type (type1, type2, type3) have separate set of validation rules. These rules are not just restricted to String validation but also semantic and business validation.

I would solve this using specific class per type. You can introduce an interface A
interface A {
String getType();
}
and then implement the concrete types.
public class Type1 implements A {
#NotBlank
private String value;
#Override
public String getValue() { return this.value; }
public void setValue(String v) { this.value = v; }
}
public class Type2 implements A {
#YourCustomValidator
private String value;
#Override
public String getValue() { return this.value; }
public void setValue(String v) { this.value = v; }
}
and then implement a custom Jackson Deserializer which is able to build an instance of A by inspecting the JSON string field type.
I don't think that Drools has anything to do with this question.

Jackson: Serializing Map<Object, BigDecimal> yields undesired object reference

Suppose I am trying to serialize the following with Jackson:
public class Investment implements Serializable{
private String shortName;
private MutualFund mutualFund;
public String getShortName() {
return shortName;
}
public void setShortName(String shortName) {
this.shortName = shortName;
}
public MutualFund getMutualFund() {
return mutualFund;
}
public void setMutualFund(MutualFund mutualFund) {
this.mutualFund = mutualFund;
}
}
That in turn refers to:
public class MutualFund implements Serializable{
private BigDecimal expenseRatio;
private Map<Investment, BigDecimal> underlyingInvestments;
public BigDecimal getExpenseRatio() {
return BigDecimalHelper.guard(expenseRatio);
}
public void setExpenseRatio(BigDecimal expenseRatio) {
this.expenseRatio = expenseRatio;
}
public Map<Investment, BigDecimal> getUnderlyingInvestments() {
return underlyingInvestments;
}
public void setUnderlyingInvestments(Map<Investment, BigDecimal>
underlyingFunds) {
this.underlyingInvestments = underlyingFunds;
}
}
When I try to serialize this with Jackson, everything else is fine except that I end up with an Investment object reference instead of the string with attributes like I was expecting:
"underlyingInvestments":{"com.financial.detail.Investment#5d465e4b":1}}
I've tried to fashion some custom serializers, but without success as I always get an object reference for the nested Investment(s). So, I have a two part question:
Can this problem be addressed simply with Jackson annotations?
If I have to build a custom serializer, could someone kindly point me in the right direction on how to best
approach this issue given the nested nature of this (e.g. an Investment could contain a Mutual Fund, which in turn has an Investment with a Mutual Fund...)

The problem is that you are using the object Investment as keys of a Map, so the question here is, what keys do you expect the json to have? Json keys cand only be strings so the mapper is executing the toString() method of the Investment class. If you know what that key should be, then you can implement the method, like this:
public class Investment implements Serializable {
private String shortName;
private MutualFund mutualFund;
// ...
#Override
public String toString() {
return shortName;
}
}
This will create a json object like this:
{
"expenseRatio": 1,
"underlyingInvestments": {
"shortName": 10
}
}
Also, as #chrylis-cautiouslyoptimistic suggested, another option is to use #JsonValue to indicate which method to use when serializing, like this:
public class Investment implements Serializable{
private String shortName;
private MutualFund mutualFund;
#JsonValue
public String getShortName() {
return shortName;
}
// ...
}

Assign an enum element to an annotation

I would like to use an enum element as a value of an annotation attribute (which requires a string value). Hence, I have created an interface holding the String constants:
public interface MyStringConstants {
public static final String COMPANY_LOGIN = "Company Login";
public static final String COMPANY_LOGOUT = "Company Logout";
...
}
Furthermore I created the enum:
public enum MyEnumType implements MyStringConstants {
COMPANY_CONFIGURATION_READ(MyStringConstants.COMPANY_CONFIGURATION_READ),
COMPANY_CONFIGURATION_WRITE(MyStringConstants.COMPANY_CONFIGURATION_WRITE),
...;
private final String value;
private MyEnumType(final String myStringConstant) {
this.value = myStringConstant;
}
public String getValue() {
return this.value.toString();
}
public static MyEnumType getByValue(final String value){
for(final MyEnumType type : values()){
if( type.getValue().equals(value)){
return type;
}
}
return null;
}
}
There exists an annotation:
#DeviceValidatorOperation(operationType=MyStringConstants.COMPANY_CONFIGURATION_READ)
I would like to define the enum as mentioned above to put as a value for the annotation's operationType attribute. Using my enum from above results in this way:
#DeviceValidatorOperation(operationType=MyEnumType.COMPANY_CONFIGURATION_READ.getValue())
results in Eclipse complaining:
The value for annotation attribute DeviceValidatorOperation.operationType must be a constant expression
How can I achieve to use an enum element as a value for an annotation's attribute?

How could I change java.lang.Enum's ordinal when using JPA and Spring?

The Entity:
#Entity
#Table(name = "table_name")
public class MyClass extends IdEntity {
private MyEnumType enumType;
#Enumerated(EnumType.ORDINAL)
public MyEnumType getEnumType() {
return enumType;
}
public void setEnumType(MyEnumType enumType) {
this.enumType= enumType;
}
}
The Enum:
public enum MyEnumType {
DOG(11),CAT(13),BULL(20);
private int value;
private MyEnumType (int value) {
this.value= value;
}
public int getValue() {
return value;
}
public void setValue(int value) {
this.value= value;
}
}
The Main Code:
//any code then ...
entity.setsEnumType(MyEnumType.CAT);
//...persist API
I want to persist the cat's int value(13) in the database(e.g. mysql).But in mysql,the enumType is （1）,what is the ORDINAL value.I wonder is there a way to store my custom value by JPA and spring???
There is a way like this:
change "private MyEnumType enumType;" to "private **int** enumType;"
Then:
entity.setsEnumType(MyEnumType.CAT.getValue());
But I don't like this.

JPA 2.1 allows defining custom types in a standard way. Using the #Convert annotation. See http://www.thoughts-on-java.org/2013/10/jpa-21-how-to-implement-type-converter.html for an explanation, is the javadoc is not sufficient.
If you're still using JPA 2.0, then Hibernate has a proprietary way of defining custom types.

Jackson enum Serializing and DeSerializer

I'm using JAVA 1.6 and Jackson 1.9.9 I've got an enum
public enum Event {
FORGOT_PASSWORD("forgot password");
private final String value;
private Event(final String description) {
this.value = description;
}
#JsonValue
final String value() {
return this.value;
}
}
I've added a #JsonValue, this seems to do the job it serializes the object into:
{"event":"forgot password"}
but when I try to deserialize I get a
Caused by: org.codehaus.jackson.map.JsonMappingException: Can not construct instance of com.globalrelay.gas.appsjson.authportal.Event from String value 'forgot password': value not one of declared Enum instance names
What am I missing here?

The serializer / deserializer solution pointed out by #xbakesx is an excellent one if you wish to completely decouple your enum class from its JSON representation.
Alternatively, if you prefer a self-contained solution, an implementation based on #JsonCreator and #JsonValue annotations would be more convenient.
So leveraging on the example by #Stanley the following is a complete self-contained solution (Java 6, Jackson 1.9):
public enum DeviceScheduleFormat {
Weekday,
EvenOdd,
Interval;
private static Map<String, DeviceScheduleFormat> namesMap = new HashMap<String, DeviceScheduleFormat>(3);
static {
namesMap.put("weekday", Weekday);
namesMap.put("even-odd", EvenOdd);
namesMap.put("interval", Interval);
}
#JsonCreator
public static DeviceScheduleFormat forValue(String value) {
return namesMap.get(StringUtils.lowerCase(value));
}
#JsonValue
public String toValue() {
for (Entry<String, DeviceScheduleFormat> entry : namesMap.entrySet()) {
if (entry.getValue() == this)
return entry.getKey();
}
return null; // or fail
}
}

Note that as of this commit in June 2015 (Jackson 2.6.2 and above) you can now simply write:
public enum Event {
#JsonProperty("forgot password")
FORGOT_PASSWORD;
}
The behavior is documented here: https://fasterxml.github.io/jackson-annotations/javadoc/2.11/com/fasterxml/jackson/annotation/JsonProperty.html
Starting with Jackson 2.6 this annotation may also be used to change serialization of Enum like so:
public enum MyEnum {
#JsonProperty("theFirstValue") THE_FIRST_VALUE,
#JsonProperty("another_value") ANOTHER_VALUE;
}
as an alternative to using JsonValue annotation.

You should create a static factory method which takes single argument and annotate it with #JsonCreator (available since Jackson 1.2)
#JsonCreator
public static Event forValue(String value) { ... }
Read more about JsonCreator annotation here.

Actual Answer:
The default deserializer for enums uses .name() to deserialize, so it's not using the #JsonValue. So as #OldCurmudgeon pointed out, you'd need to pass in {"event": "FORGOT_PASSWORD"} to match the .name() value.
An other option (assuming you want the write and read json values to be the same)...
More Info:
There is (yet) another way to manage the serialization and deserialization process with Jackson. You can specify these annotations to use your own custom serializer and deserializer:
#JsonSerialize(using = MySerializer.class)
#JsonDeserialize(using = MyDeserializer.class)
public final class MyClass {
...
}
Then you have to write MySerializer and MyDeserializer which look like this:
MySerializer
public final class MySerializer extends JsonSerializer<MyClass>
{
#Override
public void serialize(final MyClass yourClassHere, final JsonGenerator gen, final SerializerProvider serializer) throws IOException, JsonProcessingException
{
// here you'd write data to the stream with gen.write...() methods
}
}
MyDeserializer
public final class MyDeserializer extends org.codehaus.jackson.map.JsonDeserializer<MyClass>
{
#Override
public MyClass deserialize(final JsonParser parser, final DeserializationContext context) throws IOException, JsonProcessingException
{
// then you'd do something like parser.getInt() or whatever to pull data off the parser
return null;
}
}
Last little bit, particularly for doing this to an enum JsonEnum that serializes with the method getYourValue(), your serializer and deserializer might look like this:
public void serialize(final JsonEnum enumValue, final JsonGenerator gen, final SerializerProvider serializer) throws IOException, JsonProcessingException
{
gen.writeString(enumValue.getYourValue());
}
public JsonEnum deserialize(final JsonParser parser, final DeserializationContext context) throws IOException, JsonProcessingException
{
final String jsonValue = parser.getText();
for (final JsonEnum enumValue : JsonEnum.values())
{
if (enumValue.getYourValue().equals(jsonValue))
{
return enumValue;
}
}
return null;
}

I've found a very nice and concise solution, especially useful when you cannot modify enum classes as it was in my case. Then you should provide a custom ObjectMapper with a certain feature enabled. Those features are available since Jackson 1.6. So you only need to write toString() method in your enum.
public class CustomObjectMapper extends ObjectMapper {
#PostConstruct
public void customConfiguration() {
// Uses Enum.toString() for serialization of an Enum
this.enable(WRITE_ENUMS_USING_TO_STRING);
// Uses Enum.toString() for deserialization of an Enum
this.enable(READ_ENUMS_USING_TO_STRING);
}
}
There are more enum-related features available, see here:
https://github.com/FasterXML/jackson-databind/wiki/Serialization-Features
https://github.com/FasterXML/jackson-databind/wiki/Deserialization-Features

Try this.
public enum Event {
FORGOT_PASSWORD("forgot password");
private final String value;
private Event(final String description) {
this.value = description;
}
private Event() {
this.value = this.name();
}
#JsonValue
final String value() {
return this.value;
}
}

I like the accepted answer. However, I would improve it a little (considering that there is now Java higher than version 6 available).
Example:
public enum Operation {
EQUAL("eq"),
NOT_EQUAL("ne"),
LESS_THAN("lt"),
GREATER_THAN("gt");
private final String value;
Operation(String value) {
this.value = value;
}
#JsonValue
public String getValue() {
return value;
}
#JsonCreator
public static Operation forValue(String value) {
return Arrays.stream(Operation.values())
.filter(op -> op.getValue().equals(value))
.findFirst()
.orElseThrow(); // depending on requirements: can be .orElse(null);
}
}

You can customize the deserialization for any attribute.
Declare your deserialize class using the annotationJsonDeserialize (import com.fasterxml.jackson.databind.annotation.JsonDeserialize) for the attribute that will be processed. If this is an Enum:
#JsonDeserialize(using = MyEnumDeserialize.class)
private MyEnum myEnum;
This way your class will be used to deserialize the attribute. This is a full example:
public class MyEnumDeserialize extends JsonDeserializer<MyEnum> {
#Override
public MyEnum deserialize(JsonParser jsonParser, DeserializationContext deserializationContext) throws IOException {
JsonNode node = jsonParser.getCodec().readTree(jsonParser);
MyEnum type = null;
try{
if(node.get("attr") != null){
type = MyEnum.get(Long.parseLong(node.get("attr").asText()));
if (type != null) {
return type;
}
}
}catch(Exception e){
type = null;
}
return type;
}
}

Here is another example that uses string values instead of a map.
public enum Operator {
EQUAL(new String[]{"=","==","==="}),
NOT_EQUAL(new String[]{"!=","<>"}),
LESS_THAN(new String[]{"<"}),
LESS_THAN_EQUAL(new String[]{"<="}),
GREATER_THAN(new String[]{">"}),
GREATER_THAN_EQUAL(new String[]{">="}),
EXISTS(new String[]{"not null", "exists"}),
NOT_EXISTS(new String[]{"is null", "not exists"}),
MATCH(new String[]{"match"});
private String[] value;
Operator(String[] value) {
this.value = value;
}
#JsonValue
public String toStringOperator(){
return value[0];
}
#JsonCreator
public static Operator fromStringOperator(String stringOperator) {
if(stringOperator != null) {
for(Operator operator : Operator.values()) {
for(String operatorString : operator.value) {
if (stringOperator.equalsIgnoreCase(operatorString)) {
return operator;
}
}
}
}
return null;
}
}

There are various approaches that you can take to accomplish deserialization of a JSON object to an enum. My favorite style is to make an inner class:
import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonFormat;
import com.fasterxml.jackson.annotation.JsonProperty;
import org.hibernate.validator.constraints.NotEmpty;
import java.util.Arrays;
import java.util.Map;
import java.util.function.Function;
import java.util.stream.Collectors;
import static com.fasterxml.jackson.annotation.JsonFormat.Shape.OBJECT;
#JsonFormat(shape = OBJECT)
public enum FinancialAccountSubAccountType {
MAIN("Main"),
MAIN_DISCOUNT("Main Discount");
private final static Map<String, FinancialAccountSubAccountType> ENUM_NAME_MAP;
static {
ENUM_NAME_MAP = Arrays.stream(FinancialAccountSubAccountType.values())
.collect(Collectors.toMap(
Enum::name,
Function.identity()));
}
private final String displayName;
FinancialAccountSubAccountType(String displayName) {
this.displayName = displayName;
}
#JsonCreator
public static FinancialAccountSubAccountType fromJson(Request request) {
return ENUM_NAME_MAP.get(request.getCode());
}
#JsonProperty("name")
public String getDisplayName() {
return displayName;
}
private static class Request {
#NotEmpty(message = "Financial account sub-account type code is required")
private final String code;
private final String displayName;
#JsonCreator
private Request(#JsonProperty("code") String code,
#JsonProperty("name") String displayName) {
this.code = code;
this.displayName = displayName;
}
public String getCode() {
return code;
}
#JsonProperty("name")
public String getDisplayName() {
return displayName;
}
}
}

In the context of an enum, using #JsonValue now (since 2.0) works for serialization and deserialization.
According to the jackson-annotations javadoc for #JsonValue:
NOTE: when use for Java enums, one additional feature is that value returned by annotated method is also considered to be the value to deserialize from, not just JSON String to serialize as. This is possible since set of Enum values is constant and it is possible to define mapping, but can not be done in general for POJO types; as such, this is not used for POJO deserialization.
So having the Event enum annotated just as above works (for both serialization and deserialization) with jackson 2.0+.

Besides using #JsonSerialize #JsonDeserialize, you can also use SerializationFeature and DeserializationFeature (jackson binding) in the object mapper.
Such as DeserializationFeature.READ_UNKNOWN_ENUM_VALUES_USING_DEFAULT_VALUE, which give default enum type if the one provided is not defined in the enum class.

In my case, this is what resolved:
import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonFormat;
import com.fasterxml.jackson.annotation.JsonProperty;
#JsonFormat(shape = JsonFormat.Shape.OBJECT)
public enum PeriodEnum {
DAILY(1),
WEEKLY(2),
;
private final int id;
PeriodEnum(int id) {
this.id = id;
}
public int getId() {
return id;
}
public String getName() {
return this.name();
}
#JsonCreator
public static PeriodEnum fromJson(#JsonProperty("name") String name) {
return valueOf(name);
}
}
Serializes and deserializes the following json:
{
"id": 2,
"name": "WEEKLY"
}
I hope it helps!

#JsonFormat(shape = JsonFormat.Shape.OBJECT)
public enum LoginOptionType {
PHONE(1, "Phone"), MAIL(2, "mail"), PERSONAL_EMAIL(3, "Personal email");
private static List<LoginOptionType> all;
static {
all = new ArrayList<LoginOptionType>() {
{
add(LoginOptionType.PHONE);
add(LoginOptionType.MAIL);
add(LoginOptionType.PERSONAL_EMAIL);
}
};
}
private final Integer viewValue;
private final String name;
LoginOptionType(Integer viewValue, String name) {
this.viewValue = viewValue;
this.name = name;
}
public Integer getViewValue() {
return viewValue;
}
public String getName() {
return name;
}
public static List<LoginOptionType> getAll() {
return all;
}
}
Response
[
{
"viewValue": 1,
"name": "Phone"
},
{
"viewValue": 2,
"name": "mail"
},
{
"viewValue": 3,
"name": "Personal email"
}
]

Here, 'value' acts as a deserialiser and 'namespace' acts as a serialiser. Hence, you can pass in value "Student Absent" to API while saving, and in DB it will be saved as "STUDENT_ABSENT". On the other hand, while retrieving data in your class, your API will return "Student Absent"
import com.fasterxml.jackson.annotation.JsonProperty;
public enum AttendanceEnums {
STUDENT_PRESENT,
#JsonProperty(value = "Student Absent", namespace = "Student Absent")
STUDENT_ABSENT;
}

I had been looking for a solution to enum serialization and I finally made a solution.
https://github.com/sirgilligan/EnumerationSerialization
https://digerati-illuminatus.blogspot.com/2022/10/java-enum-generic-serializer-and.html
It uses a new annotation and two new classes, EnumerationSerializer and EnumerationDeserializer. You can subclass the EnumerationDeserializer and make a class that sets the enum Class (typical approach) or you can annotate the enum and you don't have to have a subclass of EnumerationDeserializer.
#JsonSerialize(using = EnumerationSerializer.class)
#JsonDeserialize(using = EnumerationDeserializer.class)
#EnumJson(serializeProjection = Projection.NAME, deserializationClass = RGB.class)
enum RGB {
RED,
GREEN,
BLUE
}
Notice how the implementation of ContextualDeserializer pulls the class from the annotation.
https://github.com/sirgilligan/EnumerationSerialization/blob/main/src/main/java/org/example/EnumerationDeserializer.java
There is a lot of good code in this that might give insights.
For your specific question you could do this:
#JsonSerialize(using = EnumerationSerializer.class)
#JsonDeserialize(using = EnumerationDeserializer.class)
#EnumJson(serializeProjection = Projection.NAME, deserializationClass = Event.class)
public enum Event {
FORGOT_PASSWORD("forgot password");
//This annotation is optional because the code looks for value or alias.
#EnumJson(serializeProjection = Projection.VALUE)
private final String value;
private Event(final String description) {
this.value = description;
}
}
Or you could do this:
#JsonSerialize(using = EnumerationSerializer.class)
#JsonDeserialize(using = EnumerationDeserializer.class)
#EnumJson(serializeProjection = Projection.NAME, deserializationClass = Event.class)
public enum Event {
FORGOT_PASSWORD("forgot password");
private final String value;
private Event(final String description) {
this.value = description;
}
}
That's all you have to do.
Then if you have a class that "has a" event you can annotate each occurance to serialize the way you want.
class EventHolder {
#EnumJson(serializeProjection = Projection.NAME)
Event someEvent;
#EnumJson(serializeProjection = Projection.ORDINAL)
Event someOtherEvent;
#EnumJson(serializeProjection = Projection.VALUE)
Event yetAnotherEvent;
}

The simplest way I found is using #JsonFormat.Shape.OBJECT annotation for the enum.
#JsonFormat(shape = JsonFormat.Shape.OBJECT)
public enum MyEnum{
....
}

I did it like this :
// Your JSON
{"event":"forgot password"}
// Your class to map
public class LoggingDto {
#JsonProperty(value = "event")
private FooEnum logType;
}
//Your enum
public enum FooEnum {
DATA_LOG ("Dummy 1"),
DATA2_LOG ("Dummy 2"),
DATA3_LOG ("forgot password"),
DATA4_LOG ("Dummy 4"),
DATA5_LOG ("Dummy 5"),
UNKNOWN ("");
private String fullName;
FooEnum(String fullName) {
this.fullName = fullName;
}
public String getFullName() {
return fullName;
}
#JsonCreator
public static FooEnum getLogTypeFromFullName(String fullName) {
for (FooEnum logType : FooEnum.values()) {
if (logType.fullName.equals(fullName)) {
return logType;
}
}
return UNKNOWN;
}
}
So the value of the property "logType" for class LoggingDto will be DATA3_LOG

This post is old, but if it can help someone, use JsonFormat.Shape.STRING
#JsonFormat(shape = JsonFormat.Shape.STRING)
public enum SomeEnum{
#JsonProperty("SOME_PROPERTY")
someProperty,
...
}
Code results is like this
{"someenum":"SOME_PROPERTY"}