select 在 while 循环中查询

Question

我在 While 循环中有一个 SELECT 查询。我期待单行。得到那一行后，我想退出 while 循环。问题是，在我执行 select 查询并检查结果集时的第一次迭代之后，出现 "Invalid Cursor" 错误。不确定我在这里做错了什么。

//looping thru hashmap

Iterator it = map.entrySet().iterator();
while (it.hasNext()) {
    int bind_index=1; 
    Map.Entry pair = (Map.Entry)it.next();
    log.debug(pair.getKey() + " = " + pair.getValue());

    String sql_main = null;
    sql_main = getSql(sb2.toString());
    ResultSet resultSet = null;
    PreparedStatement p_stmt1 = null;
    p_stmt1 = db.getPreparedStatement(sql_main);    

    p_stmt1.setString(bind_index++, (String)pair.getKey()); 
    p_stmt1.setString(bind_index++, (String)pair.getValue());   
    p_stmt1.setString(bind_index++,strGMTDate+" "+strGMTTime);
    p_stmt1.setString(bind_index++,strGMTDate+" "+strGMTTime);
    resultSet = db.executeQuery(p_stmt1);


    CachedRowSetImpl rsCopy2 = new CachedRowSetImpl();  
    rsCopy2.populate(resultSet);    
    if(rsCopy2.next()){
        rsCopy2.beforeFirst();
        grid.bind(rsCopy2);
        break;
    }
    resultSet = null;
    p_stmt1=null;
    resultSet.close();
    p_stmt1.close();
}

Answer 1

首先，由于您的 SQL 没有改变，您应该在循环外准备语句。此外，您应该使用 try-with-resources 来确保 JDBC 资源被清理。

还有，你的executeQuery错了。

String sql_main = getSql(sb2.toString());
try (PreparedStatement p_stmt1 = db.getPreparedStatement(sql_main)) {
    for (Map.Entry pair : map.entrySet()) {
        log.debug(pair.getKey() + " = " + pair.getValue());
        int bind_index = 0;
        p_stmt1.setString(++bind_index, (String)pair.getKey());
        p_stmt1.setString(++bind_index, (String)pair.getValue());
        p_stmt1.setString(++bind_index, strGMTDate + " " + strGMTTime);
        p_stmt1.setString(++bind_index, strGMTDate + " " + strGMTTime);
        try (ResultSet resultSet = p_stmt1.executeQuery()) {
            if (resultSet.next()) {

                // Capture/use values from resultSet here

                break;
            }
        }
    }
}

select 在 while 循环中查询

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