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问题描述
我无法从 ResultSet
对象.这是我的代码:
I'm having trouble getting data from a ResultSet
object. Here is my code:
String sql = "SELECT type FROM node WHERE nid = ?";
PreparedStatement prep = conn.prepareStatement(sql);
int meetNID = Integer.parseInt(node.get(BoutField.field_meet_nid));
prep.setInt(1, meetNID);
ResultSet result = prep.executeQuery();
result.beforeFirst();
String foundType = result.getString(1);
if (! foundType.equals("meet")) {
throw new IllegalArgumentException(String.format("Node %d must be of type 'meet', but was %s", meetNID, foundType));
}
错误跟踪:
Exception in thread "main" java.sql.SQLException: Before start of result set
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1072)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:986)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:981)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:926)
at com.mysql.jdbc.ResultSetImpl.checkRowPos(ResultSetImpl.java:841)
at com.mysql.jdbc.ResultSetImpl.getStringInternal(ResultSetImpl.java:5656)
at com.mysql.jdbc.ResultSetImpl.getString(ResultSetImpl.java:5576)
at nth.cumf3.nodeImport.Validator.validate(Validator.java:43)
at nth.cumf3.nodeImport.Main.main(Main.java:38)
我在这里做错了什么?
推荐答案
基本上,您将光标定位在第一行之前,然后请求数据.您需要将光标移动到第一行.
Basically you are positioning the cursor before the first row and then requesting data. You need to move the cursor to the first row.
result.next();
String foundType = result.getString(1);
通常在 if 语句或循环中执行此操作.
It is common to do this in an if statement or loop.
if(result.next()){
foundType = result.getString(1);
}
这篇关于结果集异常 - 在结果集开始之前的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持!