Custom data type bindings

public interface Converter<T, U> {

    // Your conversion logic goes into these two methods, that can convert
    // between the database type T and the user type U:
    U from(T databaseObject);
    T to(U userObject);

	// You need to provide Class instances for each type, too:
    Class<T> fromType();
    Class<U> toType();
}

import java.sql.Date;
import java.time.LocalDate;

import org.jooq.Converter;

public class LocalDateConverter implements Converter<Date, LocalDate> {

    @Override
    public LocalDate from(Date t) {
        return t == null ? null : LocalDate.parse(t.toString());
    }

    @Override
    public Date to(LocalDate u) {
        return u == null ? null : Date.valueOf(u.toString());
    }

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

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

DataType<LocalDate> type = DATE.asConvertedDataType(new LocalDateConverter());

DataType<LocalDate> type = DATE.asConvertedDataType(new LocalDateConverter());

// Plain SQL based
Field<LocalDate> date1 = DSL.field("my_table.my_column", type);

// Name based
Field<LocalDate> date2 = DSL.field(name("my_table", "my_column"), type);

public interface Binding<T, U> extends Serializable {

    // A converter that does the conversion between the database type T
    // and the user type U (see previous examples)
    Converter<T, U> converter();

    // A callback that generates the SQL string for bind values of this
    // binding type. Typically, just ?, but also ?::json, etc.
    void sql(BindingSQLContext<U> ctx) throws SQLException;

    // Callbacks that implement all interaction with JDBC types, such as
    // PreparedStatement, CallableStatement, SQLOutput, SQLinput, ResultSet
    void register(BindingRegisterContext<U> ctx) throws SQLException;
    void set(BindingSetStatementContext<U> ctx) throws SQLException;
    void set(BindingSetSQLOutputContext<U> ctx) throws SQLException;
    void get(BindingGetResultSetContext<U> ctx) throws SQLException;
    void get(BindingGetStatementContext<U> ctx) throws SQLException;
    void get(BindingGetSQLInputContext<U> ctx) throws SQLException;
}

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 database type), and <U> = JsonElement (user type)
public class PostgresJSONGsonBinding implements Binding<Object, JsonElement> {

    private final Gson gson = new Gson();

    // 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 : gson.fromJson("" + t, JsonElement.class);
            }

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