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));
}
The error trace:
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)
What am I doing wrong here?
You have to do a result.next() before you can access the result. It's a very common idiom to do
ResultSet rs = stmt.executeQuery();
while (rs.next())
{
int foo = rs.getInt(1);
...
}
You have to call next()
before you can start reading values from the first row. beforeFirst
puts the cursor before the first row, so there's no data to read.
It's better if you create a class that has all the query methods, inclusively, in a different package, so instead of typing all the process in every class, you just call the method from that class.
Every answer uses .next()
or uses .beforeFirst()
and then .next()
. But why not this:
result.first();
So You just set the pointer to the first record and go from there. It's available since java 1.2 and I just wanted to mention this for anyone whose ResultSet
exists of one specific record.
You need to move the pointer to the first row, before asking for data:
result.beforeFirst();
result.next();
String foundType = result.getString(1);
Source: Stackoverflow.com