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Convert Java POJO to Map without JSON serialization

I'd like to convert a Java POJO into a Map without using JSON serialization for the properties (e.g. that Date's are converted to a long or a ISO8601 String). I just want the fields to be retained as they are.
For example if I have a POJO defined like this:
public class MyPojo {
private Date date;
private String x;
public MyPojo(Date date, String x) {
this.date = date;
this.x = x;
}
public Date getDate() {
return date;
}
public void setDate(Date date) {
this.date = date;
}
public String getX() {
return x;
}
public void setX(String x) {
this.x = x;
}
}
I know I can use Jackson as described in this Stackoverflow question but the result is not what I want. For example if I do:
Map<String, Object> x = new ObjectMapper().convertValue(new MyPojo(new Date(), "x"), new TypeReference<Map<String, Object>>() {});
System.out.println(x);
I get this result:
{date=1528521584984, x=x}
whereas I would simply like a Map retaining the java.util.Date instance without being serialized.
Note that I obviously would like this work for nested Pojo's such as:
public class MyPojo {
private MyOtherPojo otherPojo;
...
}
How can I achieve this?

First off, going from a POJO to a Map seems like a bad idea. But I guess that you have reasons for wanting to do it ...
The simple approach is to just create a HashMap and populate it using a sequence of put calls. That gives you a map that contains the same information as the original POJO, but is not "connected" to is.
If you want the Map to be a view of the original POJO, there are 3rd-party libraries that can be used to do this. For example, org.apache.commons.beanutils has classes for wrapping an POJO that follows the JavaBeans conventions as a DynaBean. You can then adapt that as a Map using DynaBeanMapDecorator.
Mapping nested POJOs to nested maps would require more work. (And it contradicts your requirement that you can get the value of getData() as a Date POJO rather than as a Map!)

Jackson will serialize the Date to a timestamp format by default (number of milliseconds since January 1st, 1970, UTC). #JsonFormat annotation can be used to control the date format on individual classes.
#JsonFormat(shape = JsonFormat.Shape.STRING, pattern = "dd-MM-yyyy hh:mm:ss")
private Date date;

Mapping from java.time.MonthDay to java.sql.*

We have a case, where we require only the day and the month and thus would use the java.time.MonthDay (Javadocs) to represent that information.
We are aware that we could create our own JPA object for persistence or just use the java.sql.Date object, but that generally requires an unrequired year information.
Another way is to call the method .atYear(int) (Javadoc) (with a fictitious year) on it and receive a java.time.LocalDate (Javadoc), which can be easily converted to java.sql.Date. But this is prone to missunderstandings in the future (and also persist the year information).
Is there some "elegant"/supposed solution for this case? Or is there a replacement for SQL that supports the whole new date and time API for Persistence.
Another case would be java.time.YearMonth (Javadoc).
Thanks for reading!

Since SQL databases don't have a type compatible with MonthDay, use a VARCHAR columns, and simply use toString() and MonthDay.parse().
Or use a custom DateTimeFormatter, if you don't like the --12-03 format.
The default format will correctly sort, as a string.

here are the code snippets:
// column define:
#Column(name = "date", columnDefinition = "mediumint", nullable = false)
#Convert(converter = MonthDayIntegerAttributeConverter.class)
protected MonthDay date;
// converter define:
public class MonthDayIntegerAttributeConverter implements AttributeConverter<MonthDay, Integer> {
#Override
public Integer convertToDatabaseColumn(MonthDay attribute) {
return (attribute.getMonthValue() * 100) + attribute.getDayOfMonth();
}
#Override
public MonthDay convertToEntityAttribute(Integer dbData) {
int month = dbData / 100;
int day = dbData % 100;
return MonthDay.of(month, day);
}
}

How to change default date formats in Struts2?

I am developing a multilingual Struts2 application, and I have quite a few actions which are dealing with Calendar properties. The default type conversion works most of the time, however in some locales I would like to change the default format used.
Specifically I would like to have the dates in English locale to follow the yyyy-MM-dd format. However, this does not work (strangely yyyy-MM-dd HH:mm works fine, but in this case I do not want to have a time part), as Struts2 expect dates in English locale to look different.
So, I would like to change the expected format of the conversion. I am looking for a sane solution for this. The options I have already tried:
A) Own StrutsTypeConverter. This should work, but I could not inject the format specified in the package.properties file into it.
B) Changing the getter/setter pair, to use String instead - works, but this is not a sane solution.
How to fix the solution A? Or is there an alternative approach? Of course, if this can be done entirely in configuration, that would be the best.

Okay, I found a solution for my problem at hand, still, I think this could done in a saner way. Anyway, I am posting my own type converter:
public class DateConverter extends StrutsTypeConverter {
private DateFormat dateFormat;
{
ActionContext ctx = ActionContext.getContext();
ActionSupport action = (ActionSupport) ctx.getActionInvocation().getAction();
String formatString = action.getText("dateformat.ui");
dateFormat = new SimpleDateFormat(formatString);
}
public Object convertFromString(Map context, String[] values, Class toClass) {
String input = values[0];
try {
Date date = dateFormat.parse(input);
Calendar cal = Calendar.getInstance();
cal.setTime(date);
return cal;
} catch (ParseException e) {
return null;
}
}
public String convertToString(Map context, Object object) {
Calendar cal = (Calendar) object;
return dateFormat.format(cal.getTime());
}
}
I removed the non-essential parts of the code, but this is a working solution.

How to persist Joda Date to sql database?

How can I persist a jodatime YearMonth object to a sql database?
#Entity
public class MyEntity {
private YearMonth date; //how to persist?
//some more properties
}
I want later to be able to pick all entities by a specific month.

The better question is how do you intend to use the data in the database? Generally you want to store dates in databases using data types supported by the target database as opposed to strings or composite integers. That would allow you to use the built in database date/time functions and validations as opposed to needing to implement that logic in your application.
You can certainly add methods to your entity to convert to/from jodatime values to your entity for the parts of your application that need it.

You need a javax.persistence.Converter for this (see How to convert java.util.Date to Java8 java.time.YearMonth):
#Entity
public class MyEntity {
#Convert(converter = YearMonthConverter.class)
private YearMonth date; //how to persist?
//some more properties
}
The following is an example converter for Java8 java.time.YearMonth to java.utilDate. You need to change java.time.YearMonth to org.joda.time.YearMonth and use the appropriate methods to convert to/from the desired type:
(imports omitted):
#Converter(autoApply = true)
public class YearMonthConverter implements AttributeConverter<YearMonth, Date> {
#Override
public Date convertToDatabaseColumn(YearMonth attribute) {
// uses default zone since in the end only dates are needed
return attribute == null ? null : Date.from(attribute.atDay(1).atStartOfDay(ZoneId.systemDefault()).toInstant());
}
#Override
public YearMonth convertToEntityAttribute(Date dbData) {
// TODO: check if Date -> YearMonth can't be done in a better way
if (dbData == null) return null;
Calendar calendar = Calendar.getInstance();
calendar.setTime(dbData);
return YearMonth.of(calendar.get(Calendar.YEAR), calendar.get(Calendar.MONTH) + 1);
}
}

How to return from JavaScript object with type java.util.Date?

I'm calling in JS some javaMethod(java.util.Date date).
I can't change code on java-side. How can I create java.util.Date object from JS-side (at least empty date)?

There is no way to use java date in javascript use javascript Date
var date = new Date();
Just get the long value from javascript date and pass to java.
in javascript get time in milliseconds as
var timeinmillis = new Date().getTime();
and pass this to java.
in java , look at the constructor
public Date(long date)

Solved it in a not very good way, but still..
So now I'm just added to that method with JS just one more Date arg.
Now it looks like
native void doSomething(Object object, Date date) /*-{
.....
.....::setDate(Ljava/util/Date;)(date);
.....
}-*/;
and calling it like doSomething(var1, new Date());