java - 使用 JDBI 将二维数组插入 PostreSQL DB？

Question

我可以使用 SQL 对象 API 将 Game 映射到 GAMES 数据库中的一行吗？这是我的尝试:

数据类:

public class Game {
    protected int id; 
    protected int whoseTurn;
    protected int winner;
    protected char[][] board;

    public Game(int id, int turn, int winner, char[][] board ) {
        this.id=id;
        this.whoseTurn=turn;
        this.winner=winner;
        this.board=board;
    }

    @JsonProperty
    public int getId() {
        return id;
    }

    @JsonInclude(Include.NON_NULL)
    public int getWhoseTurn() {
        return whoseTurn;
    }

    @JsonInclude(Include.NON_NULL)
    public int getWinner() {
        return winner;
    }

    public char[][] getBoard() {
        return board;
    }   
}

道:

@RegisterMapper(GameMapper.class)
public interface GameDAO {

    @SqlUpdate("create table if not exists GAMES (ID integer, WHOSE_TURN varchar(10), WINNER varchar(10), BOARD char(1)[][])")
    void createTableIfNotExists();

    @SqlUpdate("insert into GAMES (ID, WHOSE_TURN, WINNER, BOARD) values (:id, :whoseTurn, :winner, :board)")
    void insert(@BindBean Game game);
}

当 insert 被调用时，我得到这个错误:

org.postgresql.util.PSQLException: Can't infer the SQL type to use for an instance of [[C. Use setObject() with an explicit Types value to specify the type to use.

什么是[[C？我能以某种方式完成这项工作吗？如果没有，我真的很感激一个替代方案。

Answer 1

JDBI 不知道如何转换数组类型。所以我们需要像这样为 char[][] 定义 ArgumentFactory。

import org.skife.jdbi.v2.StatementContext;
import org.skife.jdbi.v2.tweak.Argument;
import org.skife.jdbi.v2.tweak.ArgumentFactory;

import java.sql.Array;
import java.sql.PreparedStatement;
import java.sql.SQLException;

public class CharArrayArgument implements ArgumentFactory<char[][]> {
    @Override
    public boolean accepts(Class<?> expectedType, Object value, StatementContext ctx) {
        return value != null && char[][].class.isAssignableFrom(value.getClass());
    }

    @Override
    public Argument build(Class<?> expectedType, final char[][] value, StatementContext ctx) {
        return new Argument() {
            @Override
            public void apply(int position, PreparedStatement statement, StatementContext ctx) throws SQLException {
                Array values = statement.getConnection().createArrayOf("char", value);
                statement.setArray(position, values);
            }
        };
    }
}

将此 argumentFactory 注册到 dbi。它应该有效。

    dbi.registerArgumentFactory(new CharArrayArgument());
    GameDao gameDao = dbi.open(GameDao.class);
    Game game = new Game(1, 2, 3, new char[][]{{'a'}, {'b'}});

    gameDao.createTableIfNotExists();
    gameDao.insert(game);