simpleselect.java

电子工业出版社出版的《java2应用开发指南》配套光盘源代码

//【代码20-4-1】
import java.net.URL;
import java.sql.*;
class SimpleSelect 
{
	public static void main (String args[]) 
	{
			//JDBC-ODBC桥URL定义
		   String url   = "jdbc:odbc:my-dsn";
			//查询语句初始化
		   String query = "SELECT * FROM emp"; 
		   try
			{
		  		//加载JDBC-ODBC桥
			  Class.forName ("sun.jdbc.odbc.JdbcOdbcDriver");
			  DriverManager.setLogStream(System.out);
			  //建立连接
			Connection con = DriverManager.getConnection (url, "my-user", "my-passwd");
			//调用判断连接告警方法
			checkForWarning (con.getWarnings ());
	
			//获取DatabaseMetaData类型变量实例
			DatabaseMetaData dma = con.getMetaData ();
	
			System.out.println("\nConnected to " + dma.getURL());
			System.out.println("Driver       " + dma.getDriverName());
			System.out.println("Version      " + dma.getDriverVersion());
	
			//创建语句
			Statement stmt = con.createStatement ();
	
			//发送查询语句,创建返回结果的结果集
			ResultSet rs = stmt.executeQuery (query);
	
			//调用显示结果集内容的方法
			dispResultSet (rs);
	
			//关闭结果集
			rs.close();
	
			//关闭语句
			stmt.close();
	
			//关闭连接
			con.close();
		}
		catch (SQLException ex) 
		{
		   System.out.println ("\n*** SQLException caught ***\n");
			//显示异常信息
		   while (ex != null) 
			{
			  System.out.println ("SQLState: " +	ex.getSQLState ());
			  System.out.println ("Message:  " + ex.getMessage ());
			  System.out.println ("Vendor:   " +	ex.getErrorCode ());
			  ex = ex.getNextException ();
			  System.out.println ("");
			}
		}
		catch (java.lang.Exception ex) 
		{
			// Got some other type of exception.  Dump it.
			ex.printStackTrace ();
		}
	}
	//显示告警信息方法
	private static boolean checkForWarning (SQLWarning warn) throws SQLException  
	{
		boolean rc = false;
		//如果告警对象不为空,则显示告警内容
		if (warn != null) 
	{
			System.out.println ("\n *** Warning ***\n");
			rc = true;
			while (warn != null) 
	{
				System.out.println ("SQLState: " +warn.getSQLState ());
				System.out.println ("Message:  " +warn.getMessage ());
				System.out.println ("Vendor:   " +warn.getErrorCode ());
				System.out.println ("");
				warn = warn.getNextWarning ();
			}
		}
		return rc;
	}

	//显示结果集方法
	private static void dispResultSet (ResultSet rs)throws SQLException
	{
		int i;
	
		//获取ResultSetMetaData实例变量
		ResultSetMetaData rsmd = rs.getMetaData ();
	
		//驱动结果集的行数
		int numCols = rsmd.getColumnCount ();
	
		//显示每列的列名信息
		for (i=1; i<=numCols; i++) 
		{
			if (i > 1) System.out.print(",");
			System.out.print(rsmd.getColumnLabel(i));
		}
		System.out.println("");
		
		//依次读取结果集中的内容
		boolean more = rs.next ();
		while (more) 
		{
	
			//获取每列中的数据内容
			for (i=1; i<=numCols; i++) 
			{
				if (i > 1) System.out.print(",");
				System.out.print(rs.getString(i));
			}
			System.out.println("");
	
			//取得下一行的内容
			more = rs.next ();
		}
	}
}