Create Hibernate Type to save JSONObject with PostgreSQL

Question

I'm using Postgres 9 and Hibernate 4 as ORM.

In Postgres there is an option of creating a table with json type column.

I would like in my Java code to be able to send JSONObject in queries so they would be transformed\converted to Postgres type.

How can I do that?

I need to Object:

1. The first object extends from UserType.
2. The 2nd object extends: extends AbstractSingleColumnStandardBasicType implements DiscriminatorType.

Is there any example for that??

Answer 1

You don’t have to create all these types manually, you can simply get them via Maven Central using the following dependency:

<dependency>
 <groupId>com.vladmihalcea</groupId>
 <artifactId>hibernate-types-52</artifactId>
 <version>1.0.0</version>
</dependency>

For more info, check out the Hibernate Types open-source project.

Now, your mapping can use the JsonType, like this:

@Entity(name = "Book")
@Table(name = "book")
@TypeDef(
 name = "json", 
 typeClass = JsonType.class
)
public class Book {
 
 @Id
 @GeneratedValue
 private Long id;
 
 @NaturalId
 private String isbn;
 
 @Type( type = "json" )
 @Column(columnDefinition = "jsonb")
 private JsonNode properties;
 
 //Getters and setters omitted for brevity
}

That's it!

Answer 2

Just had to spend some time on this and this worked for me:

 public class JSONUserType implements UserType {
 private static final int[] SQL_TYPES = { Types.LONGVARCHAR };
 @Override
 public Object assemble(Serializable cached, Object owner)
 throws HibernateException {
 return deepCopy(cached);
 }
 @Override
 public Object deepCopy(Object value) throws HibernateException {
 if (value == null)
 return value;
 try {
 return new JSONObject(((JSONObject) value).toString());
 } catch (JSONException e) {
 throw new RuntimeException(e);
 }
 }
 @Override
 public Serializable disassemble(Object value) throws HibernateException {
 return ((JSONObject) value).toString();
 }
 @Override
 public boolean equals(Object x, Object y) throws HibernateException {
 if (x == null)
 return (y != null);
 return (x.equals(y));
 }
 @Override
 public int hashCode(Object x) throws HibernateException {
 return ((JSONObject) x).toString().hashCode();
 }
 @Override
 public boolean isMutable() {
 return true;
 }
 @Override
 public Object replace(Object original, Object target, Object owner)throws HibernateException {
 return deepCopy(original);
 }
 @Override
 @SuppressWarnings("unchecked")
 public Class returnedClass() {
 return JSONObject.class;
 }
 @Override
 public int[] sqlTypes() {
 return SQL_TYPES;
 }
 @Override
 public Object nullSafeGet(ResultSet rs, String[] names,SessionImplementor session, Object owner)throws HibernateException, SQLException {
 String jsonString = rs.getString(names[0]);
 if (jsonString == null)
 return null;
 try {
 return new JSONObject(jsonString);
 } catch (JSONException e) {
 throw new RuntimeException(e);
 }
 }
 @Override
 public void nullSafeSet(PreparedStatement st, Object value, int index,SessionImplementor session) throws HibernateException, SQLException {
 if (value == null) {
 st.setNull(index, Types.OTHER);
 } else {
 st.setObject(index, ((JSONObject) value).toString(),Types.OTHER);
 }
 }
}