Imagine having a tool that can automatically detect if you are using JPA and Hibernate properly. Hypersistence Optimizer is that tool!
As already explained, the hibernate-types open-source project allows you to map JSON, ARRAY, PostgreSQL ENUM types and provides a simple way of adding immutable Hibernate Types.
After adding support for customizing the Jackson ObjectMapper, the next most-wanted issue was to provide a way to customize the JSON serializing mechanism.
In this article, you are going to see how you can customize the JSON serializer using hibernate-types.
How to customize the #JSON Serializer used by #Hibernate-Types - @vlad_mihalcea https://t.co/HD2OJJnl1S pic.twitter.com/zNBslsftIt
— Java (@java) March 31, 2018
The easiest way to achieve this goal is to set the hibernate.types.json.serializer configuration property in the hibernate.properties file:
hibernate.types.json.serializer=com.vladmihalcea.hibernate.type.json.configuration.CustomJsonSerializerSupplier
This property takes the fully-qualified class name of an implementation of the CustomJsonSerializerSupplier interface:
What’s nice about customizing the hibernate-types project is that you can use either the Hibernate-specific hibernate.properties or you can provide a hibernate-types.properties file if you cannot alter hibernate.properties.
You can even supply a different Java properties file via the hibernate-types.properties.path System property,
The CustomJsonSerializerSupplier can look as follows:
public class CustomJsonSerializerSupplier
implements JsonSerializerSupplier {
@Override
public JsonSerializer get() {
return new CustomJsonSerializer();
}
}
Here, for testing sake, we are using a custom CustomJsonSerializer that implements the JsonSerializer interface:
public class CustomJsonSerializer
implements JsonSerializer {
private static boolean called;
public static boolean isCalled() {
return called;
}
public static void reset() {
called = false;
}
@Override
public <T> T clone(T value) {
called = true;
return JacksonUtil.clone(value);
}
}
We are going to use the called static variable to check in our unit test if this method is called by hibernate-types.
assertFalse(CustomJsonSerializer.isCalled());
doInJPA(entityManager -> {
Location location = new Location();
location.setCountry("Romania");
location.setCity("Cluj-Napoca");
location.setReference(
BigDecimal.valueOf(2.25262562526626D)
);
Event event = new Event();
event.setId(1L);
event.setLocation(location);
entityManager.persist(event);
});
assertTrue(CustomJsonSerializer.isCalled());
CustomJsonSerializer.reset();
assertFalse(CustomJsonSerializer.isCalled());
doInJPA(entityManager -> {
Event event = entityManager.find(Event.class, 1L);
assertEquals(
"2.25262562526626",
event.getLocation().getReference().toString()
);
});
assertTrue(CustomJsonSerializer.isCalled());
As you can see, the CustomJsonSerializer is being used, so you can easily customize the way a given JSON object is serialized by hibernate-types.
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Because of the configuration mechanism, I introduced for customizing the ObjectMapper, it is very easy to add new configuration options, like this one which allows you to change the way a given JSON object is serialized by hibernate-types.
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