java - 在循环 JDBC 结果集时，如果我们失去网络会发生什么？

Question

如果您从通过 wi-fi 连接到办公室网络的笔记本电脑运行 JDBC 程序。如果在循环 ( JDBC ) 结果集时网络丢失会发生什么？我注意到 java.sql.Connection 和 Statement 对象超时。但结果集没有超时设置。

ResultSet rs = st.getResultSet();
while (rs.next()) {
    int id = rs.getInt(1);
    // use this and run some biz logic.
}

我注意到程序一直在等待下一个结果。如何让它抛出异常？有人经历过吗？你做了什么？

Answer 1

ResultSet 将不再可用，但您可以做的是:

您有两个选择:

首先:(我建议)使用交易，如 Oracle doc说:

When a connection is created, it is in auto-commit mode. This means that each individual SQL statement is treated as a transaction and is automatically committed right after it is executed. (To be more precise, the default is for a SQL statement to be committed when it is completed, not when it is executed. A statement is completed when all of its result sets and update counts have been retrieved. In almost all cases, however, a statement is completed, and therefore committed, right after it is executed.)

在您的情况下，您应该在所有语句完成后执行一次，如果网络故障或一条语句中出现任何错误，您的所有语句都将回滚

示例:reference

public void updateCoffeeSales(HashMap<String, Integer> salesForWeek)
    throws SQLException {
    PreparedStatement updateSales = null;
    PreparedStatement updateTotal = null;
    String updateString =
        "update " + dbName + ".COFFEES " +
        "set SALES = ? where COF_NAME = ?";
    String updateStatement =
        "update " + dbName + ".COFFEES " +
        "set TOTAL = TOTAL + ? " +
        "where COF_NAME = ?";
    try {
        con.setAutoCommit(false);
        updateSales = con.prepareStatement(updateString);
        updateTotal = con.prepareStatement(updateStatement);
        for (Map.Entry<String, Integer> e : salesForWeek.entrySet()) {
            updateSales.setInt(1, e.getValue().intValue());
            updateSales.setString(2, e.getKey());
            updateSales.executeUpdate();
            updateTotal.setInt(1, e.getValue().intValue());
            updateTotal.setString(2, e.getKey());
            updateTotal.executeUpdate();
            con.commit();
        }
    } catch (SQLException e ) {
        JDBCTutorialUtilities.printSQLException(e);
        if (con != null) {
            try {
                System.err.print("Transaction is being rolled back");
                con.rollback();
            } catch(SQLException excep) {
                JDBCTutorialUtilities.printSQLException(excep);
            }
        }
    } finally {
        if (updateSales != null) {
            updateSales.close();
        }
        if (updateTotal != null) {
            updateTotal.close();
        }
        con.setAutoCommit(true);
    }
}

第二:您可能必须在连接丢失之前缓冲所有结果，但要注意关闭结果集、语句和连接