Custom data type binding

import static org.jooq.tools.Convert.convert;
import java.sql.*;
import org.jooq.*;
import org.jooq.impl.DSL;
import com.google.gson.*;

// We're binding <T> = Object (unknown JDBC type), and <U> = JsonElement (user type)
public class PostgresJSONGsonBinding implements Binding<Object, JsonElement> {

    // The converter does all the work
    @Override
    public Converter<Object, JsonElement> converter() {
        return new Converter<Object, JsonElement>() {
            @Override
            public JsonElement from(Object t) {
                return t == null ? JsonNull.INSTANCE : new Gson().fromJson("" + t, JsonElement.class);
            }

            @Override
            public Object to(JsonElement u) {
                return u == null || u == JsonNull.INSTANCE ? null : new Gson().toJson(u);
            }

            @Override
            public Class<Object> fromType() {
                return Object.class;
            }

            @Override
            public Class<JsonElement> toType() {
                return JsonElement.class;
            }
        };
    }

    // Rending a bind variable for the binding context's value and casting it to the json type
    @Override
    public void sql(BindingSQLContext<JsonElement> ctx) throws SQLException {
        // Depending on how you generate your SQL, you may need to explicitly distinguish
        // between jOOQ generating bind variables or inlined literals.
        if (ctx.render().paramType() == ParamType.INLINED)
            ctx.render().visit(DSL.inline(ctx.convert(converter()).value())).sql("::json");
        else
            ctx.render().sql("?::json");
    }

    // Registering VARCHAR types for JDBC CallableStatement OUT parameters
    @Override
    public void register(BindingRegisterContext<JsonElement> ctx) throws SQLException {
        ctx.statement().registerOutParameter(ctx.index(), Types.VARCHAR);
    }

    // Converting the JsonElement to a String value and setting that on a JDBC PreparedStatement
    @Override
    public void set(BindingSetStatementContext<JsonElement> ctx) throws SQLException {
        ctx.statement().setString(ctx.index(), Objects.toString(ctx.convert(converter()).value(), null));
    }

    // Getting a String value from a JDBC ResultSet and converting that to a JsonElement
    @Override
    public void get(BindingGetResultSetContext<JsonElement> ctx) throws SQLException {
        ctx.convert(converter()).value(ctx.resultSet().getString(ctx.index()));
    }

    // Getting a String value from a JDBC CallableStatement and converting that to a JsonElement
    @Override
    public void get(BindingGetStatementContext<JsonElement> ctx) throws SQLException {
        ctx.convert(converter()).value(ctx.statement().getString(ctx.index()));
    }

    // Setting a value on a JDBC SQLOutput (useful for Oracle OBJECT types)
    @Override
    public void set(BindingSetSQLOutputContext<JsonElement> ctx) throws SQLException {
        throw new SQLFeatureNotSupportedException();
    }

    // Getting a value from a JDBC SQLInput (useful for Oracle OBJECT types)
    @Override
    public void get(BindingGetSQLInputContext<JsonElement> ctx) throws SQLException {
        throw new SQLFeatureNotSupportedException();
    }
}

<database>
  <forcedTypes>
    <forcedType>

      <!-- Specify the Java type of your custom type. This corresponds to the Binding's <U> type. -->
      <userType>com.google.gson.JsonElement</userType>

      <!-- Associate that custom type with your binding. -->
      <binding>com.example.PostgresJSONGsonBinding</binding>

      <!-- Add a Java regular expression matching fully-qualified columns. Use the pipe to separate several expressions.
           
           If provided, both "expressions" and "types" must match. -->
      <expression>.*JSON.*</expression>
      
      <!-- Add a Java regular expression matching data types to be forced to
           have this type.
      
           Data types may be reported by your database as:
           - NUMBER              regexp suggestion: NUMBER
           - NUMBER(5)           regexp suggestion: NUMBER\(5\)
           - NUMBER(5, 2)        regexp suggestion: NUMBER\(5,\s*2\)
           - any other form
           
           It is thus recommended to use defensive regexes for types.
           
           If provided, both "expressions" and "types" must match. -->
      <types>.*</types>
    </forcedType>
  </forcedTypes>
</database>

public class TAuthor extends TableImpl<TAuthorRecord> {

    // [...]
    public final TableField<TAuthorRecord, JsonElement> CUSTOM_DATA_JSON =    // [...]
    // [...]

}