1

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

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

以下是数据应反映的示例:

    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

这是结果集处理程序,其中包含我无法弄清楚的代码:

    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;
}
4

3 回答 3

2

这是您开始时的实现:

    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;
}

但就我个人而言,我宁愿让函数返回ArrayList<Object[]>甚至更好List<TreeData>,但是你需要TreeData手动实现并用行值填充对象。这就是 JPA/Hibernate 的用武之地。但根据您的应用程序,这可能又有点过头了。

于 2012-04-08T09:22:52.680 回答
1

这是你想要的吗?您需要在循环获取数据之前重置结果集。

Object[][] result = new Object[rows];
rs.first();
int i = 0;
while (rs.next()) {
  result[i] = new Object[3];
  result[i][0] = rs.getObject(1);
  result[i][1] = rs.getObject(2);
  result[i][2] = rs.getObject(3);
  i++;
}
于 2012-04-08T09:01:28.540 回答
1

在您的函数中,从使用 anArrayList而不是Object[][]. 所以你不需要计算行数。

然后对于每一行

while(rs.next()) {
  Object[] row = new Object[meta.getColumnCount()];
  for (int i = 0 ; i < row.length ; ++i) {
    row[i] = rs.getObject(i+1); // remember thet on ResultSet object first column is 1
  }
  rows.add(row); // add row to the ArrayList
}

最后,您可以ArrayList使用toArray().

于 2012-04-08T09:00:45.713 回答