java - 如何将 Java SQL 查询转换为 Java 对象 [][]？

Question

我正在寻找一种使用 Java 查询 SQL 数据库并返回对象 [][] 的方法。这是 SQL 查询:

 private static Object result[][] = null;
 result = run.query(conn, "select * from TREEDATA", rsh);

以下是数据应该镜像的示例:

    Object[][] table = {
        {1, null, "Root"}, //i=0
        {2, 1, "Node2"}, //i=1
        {3, 2, "Node3"}, //i=2
        {4, 3, "Node4"}, //i=3
        {5, 4, "Node5"}, //i=4
        {6, 5, "Node6"}, //i=5
        {7, 6, "Node7"}, //i=6
        {8, 1, "Node8"}, //i=7
        {9, 1, "Node9"}, //i=8
        {10, 9, "Node10"},};    //i=9

这是带有我无法理解的代码的结果集处理程序:

    public Object[][] handle(ResultSet rs) throws SQLException {
        if (!rs.next()) {
            System.out.println("result set is null");
            return null;
        }
        ResultSetMetaData meta = rs.getMetaData();
        int rows = 0;
        while (rs.next()) {
            rows++;
        }
        Object[][] result = new Object[rows];
        int i = 0;
        while (rs.next()) {
 //How do I do what I need to do in order to return result[][] 
            result[i][] = rs.getObject(3);           
            System.out.println(result[i][2].toString());
        }
        return result;
}

Answer 1

这是您启动时的实现:

    public Object[][] handle(ResultSet rs) throws SQLException {
        if (!rs.last()) { //If false, the result set is empty.
            System.out.println("result set is null");
            return null;
        }
        int rowCount = rs.getRow(); // You are pointing on the last row, so this will get the row number of the last row.
        rs.beforeFirst(); // Reset your cursor.
        ResultSetMetaData meta = rs.getMetaData();
        int columnCount = meta.getColumnCount();
        Object[][] result = new Object[rowCount][columnCount];
        int i = 0;
        while (rs.next()) {
            for (int j = 0; j < columnCount; j++) {
                result[i][j] = rs.getObject(j);
            }
        }
        return result;
}

但我个人更希望函数返回 ArrayList<Object[]>甚至更好List<TreeData>但随后您需要实现并填写 TreeData手动具有行值的对象。这就是 JPA/Hibernate 的用武之地。但根据您的应用程序，这可能又是矫枉过正。