????? 数据库技术

　　实例293 加载JDBC驱动程序

import java.sql.DriverManager;
import java.util.Enumeration;

public class UseMySQLDriver {
	public static void main(String[] args) {
		try {
			// 初始化并加载MySQL驱动程序
			Class.forName("com.mysql.jdbc.Driver");
			Enumeration em = DriverManager.getDrivers();
			// 显示驱动程序信息
			while (em.hasMoreElements()) {
				System.out.println(em.nextElement());
			}
			// 处理加载数据库中可能出现的异常
		} catch (Exception e) {
			System.out.println("加载数据库驱动程序出现异常");
		}
	}
}

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　　实例294 通过JDBC对数据库进行查询

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;

public class JDBCSearch {
	static ResultSet rs = null;
	public static void main(String[] args) throws SQLException {
		try {
			Class.forName("com.mysql.jdbc.Driver");// 加载驱动程序
			Connection con = DriverManager.getConnection(
					"jdbc:mysql://localhost:3306/myuser", "root", "root");// 建立链接
			Statement usest = con.createStatement();// 创建Statement对象
			usest.setMaxRows(100);// 设置选项
			ResultSet users = usest.executeQuery("select * from gods");// 执行查询
			System.out.println("ResultSet MaxRows:" + usest.getMaxRows());
			System.out.println("Query Time Out:" + usest.getMaxRows() + "\n");
			String sqlstr = "select * from gods where price>?";// 执行参数查询
			PreparedStatement ps = con.prepareStatement(sqlstr);// 创建PreparedStatement对象
			ps.setString(1, "15");
			rs = ps.executeQuery();
			ResultSetMetaData rsmd = rs.getMetaData();// 获取结果集中的列名及其类型
			int cc = rsmd.getColumnCount();
			System.out.println("ColumnName\t\tColumnType");
			for (int i = 1; i <= cc; i++) {
				System.out.println(rsmd.getColumnClassName(i) + "\t"
						+ rsmd.getColumnTypeName(i));
			}
			con.close();// 关闭对象
		} catch (ClassNotFoundException e) {
			System.out.println(e.getMessage());
			e.printStackTrace();
		}
	}
}

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　　实例295 数据库更新

import java.io.UnsupportedEncodingException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class JDBCUpdate {
	public static void main(String[] args) throws SQLException,
			UnsupportedEncodingException {
		String name, type, size, strn;
		String depict, price, offers;
		try {
			Class.forName("com.mysql.jdbc.Driver");// 加载驱动程序
			Connection con = DriverManager.getConnection(
					"jdbc:mysql://localhost:3306/myuser", "root", "root");// 建立链接
			Statement st = con.createStatement();// 创建Statement对象
			strn = "alter table gods add column size varchar(12)";// 向表中添加列
			st.executeUpdate(strn);
			strn = "INSERT INTO gods(name, type, depict,price, offers,sizes) VALUES ('Shiseido', 'Cosmetics','meibaibs','280','SOFINA','250ml');";
			st.executeUpdate(strn);
			strn = "INSERT INTO gods(name, type, depict,price, offers) VALUES ('Lamp','luminaire','Cartoon images','28','no');";
			st.executeUpdate(strn);
			ResultSet rs = st.executeQuery("select * from gods");// 执行查询
			System.out.println("商品名称\t商品类别\t商品描述\t商品价格\t优惠商品尺码");
			while (rs.next()) {
				name = new String(rs.getString("name").getBytes("iso8859-1"),
						"gb2312");
				price = new String(rs.getString("price").getBytes("iso8859-1"),
						"gb2312");
				depict = new String(rs.getString("depict")
						.getBytes("iso8859-1"), "gb2312");
				type = new String(rs.getString("type").getBytes("iso8859-1"),
						"gb2312");
				size = rs.getString("size");
				offers = new String(rs.getString("offers")
						.getBytes("iso8859-1"), "gb2312");
				System.out.println(name + " " + type + " " + depict + " "
						+ price + " " + offers + " " + size);
			}
			con.close();// 关闭连接
		} catch (ClassNotFoundException e) {
			System.out.println(e.getMessage());
			e.printStackTrace();
		}
	}
}

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