Java ResultSet复制到通用对象或列表

Question

我知道使用ResultSet的问题,并且已经看到了将数据提取到对象(或列表)中的示例,但是,我想以通用方式执行此操作,即无需了解类.

有没有办法做到这一点,结果将是一个对象或列表,然后我可以使用反射迭代？

我检查过的解决方案似乎无法工作或要求目标类的类认知包括:

• 如何将结果集复制到对象中？
• 复制Java ResultSet

我也尝试过ResultSetMapper(http://resultsetmapper.sourceforge.net/),它似乎也需要这个类.我真的只想要一个我可以采取行动的对象或列表.

Answer 1

这非常通用:

Statement st = con.createStatement();
ResultSet rs = st.executeQuery("SELECT * FROM Clients WHERE ID <= 2");

// collect column names
List<String> columnNames = new ArrayList<>();
ResultSetMetaData rsmd = rs.getMetaData();
for (int i = 1; i <= rsmd.getColumnCount(); i++) {
    columnNames.add(rsmd.getColumnLabel(i));
}

int rowIndex = 0;
while (rs.next()) {
    rowIndex++;
    // collect row data as objects in a List
    List<Object> rowData = new ArrayList<>();
    for (int i = 1; i <= rsmd.getColumnCount(); i++) {
        rowData.add(rs.getObject(i));
    }
    // for test purposes, dump contents to check our results
    // (the real code would pass the "rowData" List to some other routine)
    System.out.printf("Row %d%n", rowIndex);
    for (int colIndex = 0; colIndex < rsmd.getColumnCount(); colIndex++) {
        String objType = "null";
        String objString = "";
        Object columnObject = rowData.get(colIndex);
        if (columnObject != null) {
            objString = columnObject.toString() + " ";
            objType = columnObject.getClass().getName();
        }
        System.out.printf("  %s: %s(%s)%n",
                columnNames.get(colIndex), objString, objType);
    }
}

对于我的测试数据(在SQL Server中),它将以下内容输出到控制台:

Row 1
  ID: 1 (java.lang.Integer)
  LastName: Thompson (java.lang.String)
  FirstName: Gord (java.lang.String)
  DOB: (null)
Row 2
  ID: 2 (java.lang.Integer)
  LastName: Loblaw (java.lang.String)
  FirstName: Bob (java.lang.String)
  DOB: 1966-09-12 16:03:00.0 (java.sql.Timestamp)