Adapt field to store to database - grails

Question

Say I have a field content that is a json. I would like to store it in database so that my domain class keeps only the 1 field only. (It's more of a brain task ;-)
class MyDomain{
def content
static constraints = {
content nullable: false, blank: false, sqlType: "text" // adapter from JSON to String??
}
def beforeInsert(){
content = content.toString()
}
def beforeUpdate(){
content = content.toString()
}
def afterInsert(){
content = JSON.parse(content) as JSON
}
def afterUpdate(){
content = JSON.parse(content) as JSON
}
def onLoad(){
content = JSON.parse(content) as JSON
}
}
I want my domain object to expose only content so I don't want to use another field like String contentAsText because it would be visible outside.
In the whole GORM documentation I haven't found a thing how to manage it. I've tried beforeValidate()/beforeInsert() and onLoad() methods but no luck...
How can I adapt the value before it gets persisted?

Answer 1

You can define a custom hibernate user-type for JSONElement as described here: https://stackoverflow.com/a/28655708/607038
In domain class constraints:
static constraints = {
content type: JSONObjectUserType
}
User Type Class:
import org.grails.web.json.JSONObject
import org.hibernate.HibernateException
import org.hibernate.engine.spi.SessionImplementor
import org.hibernate.type.StandardBasicTypes
import org.hibernate.usertype.EnhancedUserType
import java.sql.PreparedStatement
import java.sql.ResultSet
import java.sql.SQLException
import java.sql.Types
class JSONObjectUserType implements EnhancedUserType, Serializable {
private static final int[] SQL_TYPES = [Types.VARCHAR]
#Override
public int[] sqlTypes() {
return SQL_TYPES
}
#Override
public Class returnedClass() {
return JSONObject.class
}
#Override
public boolean equals(Object x, Object y) throws HibernateException {
if (x == y) {
return true
}
if (x == null || y == null) {
return false
}
JSONObject zx = (JSONObject) x
JSONObject zy = (JSONObject) y
return zx.equals(zy)
}
#Override
public int hashCode(Object object) throws HibernateException {
return object.hashCode()
}
#Override
public Object nullSafeGet(ResultSet resultSet, String[] names, SessionImplementor session, Object owner)
throws HibernateException, SQLException {
Object jsonObject = StandardBasicTypes.STRING.nullSafeGet(resultSet, names, session, owner)
if (jsonObject == null) {
return null
}
return new JSONObject((String) jsonObject)
}
#Override
public void nullSafeSet(PreparedStatement preparedStatement, Object value, int index, SessionImplementor session)
throws HibernateException, SQLException {
if (value == null) {
StandardBasicTypes.STRING.nullSafeSet(preparedStatement, null, index, session)
} else {
JSONObject jsonObject = (JSONObject) value
StandardBasicTypes.STRING.nullSafeSet(preparedStatement, jsonObject.toString(), index, session)
}
}
#Override
public Object deepCopy(Object value) throws HibernateException {
return value
}
#Override
public boolean isMutable() {
return false
}
#Override
public Serializable disassemble(Object value) throws HibernateException {
return (Serializable) value
}
#Override
public Object assemble(Serializable cached, Object value) throws HibernateException {
return cached
}
#Override
public Object replace(Object original, Object target, Object owner) throws HibernateException {
return original
}
#Override
public String objectToSQLString(Object object) {
throw new UnsupportedOperationException()
}
#Override
public String toXMLString(Object object) {
return object.toString()
}
#Override
public Object fromXMLString(String string) {
return new JSONObject(string)
}
}

Answer 2

class MyDomain{
JSONElement content
static constraints = {
content nullable: false, blank: false, sqlType: "text" // adapter from Map to String??
}
def setContent(String textContent){
content = JSON.parse(textContent)
}
}
I had to do 2 things.
replace def content with JSON content so that it gets persisted, see Grails Domain Constructor is not Groovy Constructor
Convert a json string back to json via def setContent().
As content is JSONElement use JSONObject and JSONArray as concrete classes.