Custom expression in JPA CriteriaBuilder

Question

I have an Entity with a String field (storing JSON), and need to compare value from its database column with another value. Problem is that type of this database column is TEXT, but in fact it contains JSON. So, is there a way to write something like this? I.e. I need to compare my value with some field of JSON from TEXT column.

criteriaBuilder.equal(root.get("json_column").customExpressionn(new Expression{
   Object handle(Object data){
    return ((Object)data).get("json_field")
}
}), value)

Answer 1

Assuming, you have a MySQL server with version > 5.7.x

I just had the same issue. I wanted to find all entities of a class that had a JSON field value inside a JSON object column.

The solution that worked for me was something along the lines (sorry typing from a phone)

(root, query, builder)->{
    return builder.equal(
        builder.function("JSON_EXTRACT", String.class, root.get("myEntityJsonAttribute"), builder.literal("$.json.path.to.json.field")),
        "searchedValueInJsonFieldOfJsonAttribute"
    )
}