現在我正在學習java中的ResultSet類型。在這裏,我編碼以不同的方式查看記錄。起初,我顯示了emp4表中的全部記錄,然後我開始以不同的方式查看這些記錄(最後一個,下一個)。這正是我正在尋找的內容,但它不會顯示提交的所有記錄在emp4表中。看到第一個程序它不起作用,但如果我記錄了第41行(見第二個程序),它只是工作真棒。有什麼問題 ?有沒有我的代碼錯了?在JDBC中查看ResultSet時不檢索記錄
代碼示例1
package demojdbc;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.Statement;
import java.sql.ResultSet;
import java.sql.SQLException;
public class MysqlCon{
private static final String DB_DRIVER = "com.mysql.jdbc.Driver";
private static final String DB_CONNECTION = "jdbc:mysql://localhost:3306/vinoth";
private static final String DB_USER = "root";
private static final String DB_PASSWORD = "vino";
public static void main(String args[])throws SQLException{
//Creating statement and connection
Connection dbConnection = null;
Statement stmt = null;
try{
//Creating class driver
Class.forName(DB_DRIVER);
//Creating Database Connection
dbConnection = DriverManager.getConnection(DB_CONNECTION,DB_USER,DB_PASSWORD);
//Creating statement
stmt = dbConnection.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY);
//Creating query
String sql = "SELECT id,gmail,yahoo from emp4";
//Creating ResultSet
ResultSet rs = stmt.executeQuery(sql);
//Displaying database
System.out.println("Displaying records before doing some operations");
System.out.println(rs.getInt(1)+" "+rs.getString(2)+" "+rs.getString(3));
System.out.println("Displaying records for last row");
rs.last();
int id = rs.getInt("id");
String gmail = rs.getString("gmail");
String yahoo = rs.getString("yahoo");
//Displaying records in last row
System.out.println("ID : "+id);
System.out.println("GMAIL : "+gmail);
System.out.println("YAHOO : "+yahoo);
System.out.println();
rs.first();
System.out.println("Displaying records for first row");
id = rs.getInt("id");
gmail = rs.getString("gmail");
yahoo = rs.getString("yahoo");
//Displaying records in last row
System.out.println("ID : "+id);
System.out.println("GMAIL : "+gmail);
System.out.println("YAHOO : "+yahoo);
System.out.println();
rs.next();
System.out.println("Displaying records for next row");
id = rs.getInt("id");
gmail = rs.getString("gmail");
yahoo = rs.getString("yahoo");
//Displaying records in last row
System.out.println("ID : "+id);
System.out.println("GMAIL : "+gmail);
System.out.println("YAHOO : "+yahoo);
}catch(SQLException e){
e.printStackTrace();
}catch(ClassNotFoundException e){
System.out.println("Plese check the driver class path "+e.getMessage());
}finally{
if(stmt != null){
stmt.close();
}
if(dbConnection != null){
dbConnection.close();
}
}
}
}
在這裏,將能正常工作的代碼.....
代碼示例2
package demojdbc;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.Statement;
import java.sql.ResultSet;
import java.sql.SQLException;
public class MysqlCon{
private static final String DB_DRIVER = "com.mysql.jdbc.Driver";
private static final String DB_CONNECTION = "jdbc:mysql://localhost:3306/vinoth";
private static final String DB_USER = "root";
private static final String DB_PASSWORD = "vino";
public static void main(String args[])throws SQLException{
//Creating statement and connection
Connection dbConnection = null;
Statement stmt = null;
try{
//Creating class driver
Class.forName(DB_DRIVER);
//Creating Database Connection
dbConnection = DriverManager.getConnection(DB_CONNECTION,DB_USER,DB_PASSWORD);
//Creating statement
stmt = dbConnection.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY);
//Creating query
String sql = "SELECT id,gmail,yahoo from emp4";
//Creating ResultSet
ResultSet rs = stmt.executeQuery(sql);
//Displaying database
System.out.println("Displaying records before doing some operations");
//System.out.println(rs.getInt(1)+" "+rs.getString(2)+" "+rs.getString(3));
System.out.println("Displaying records for last row");
rs.last();
int id = rs.getInt("id");
String gmail = rs.getString("gmail");
String yahoo = rs.getString("yahoo");
//Displaying records in last row
System.out.println("ID : "+id);
System.out.println("GMAIL : "+gmail);
System.out.println("YAHOO : "+yahoo);
System.out.println();
rs.first();
System.out.println("Displaying records for first row");
id = rs.getInt("id");
gmail = rs.getString("gmail");
yahoo = rs.getString("yahoo");
//Displaying records in last row
System.out.println("ID : "+id);
System.out.println("GMAIL : "+gmail);
System.out.println("YAHOO : "+yahoo);
System.out.println();
rs.next();
System.out.println("Displaying records for next row");
id = rs.getInt("id");
gmail = rs.getString("gmail");
yahoo = rs.getString("yahoo");
//Displaying records in last row
System.out.println("ID : "+id);
System.out.println("GMAIL : "+gmail);
System.out.println("YAHOO : "+yahoo);
}catch(SQLException e){
e.printStackTrace();
}catch(ClassNotFoundException e){
System.out.println("Plese check the driver class path "+e.getMessage());
}finally{
if(stmt != null){
stmt.close();
}
if(dbConnection != null){
dbConnection.close();
}
}
}
}
輸出
個顯示記錄最後一行 ID:5 GMAIL:NAVEEN YAHOO:naveenrockz
顯示記錄第一行 ID:1 GMAIL:vinothvino YAHOO:vinothasd爲下一行
顯示記錄ID:2 GMAIL:ajithvirje YAHOO:ajith234
請讓我明白。爲什麼我的代碼不能在CODE SAMPLE 1程序中獲取任何記錄?
下面的圖像表示emp4表
如何向我們展示堆棧跟蹤或第一個代碼的輸出不正確運行? –
是的,它不工作。它只是顯示了一個像這樣的異常「java.sql.SQLException:結果集開始之前」,但如果我評論第41行,那麼它沒有任何問題......但我想提取這些數據,並希望在去之前顯示它以執行操作(最後,第一,下一個) –