[1]JDBC简单介绍和示例

JDBC简单介绍和示例

 

Jdbc单例类:JdbcUtilsSing.java

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

public final class JdbcUtilsSing {
	private String url = "jdbc:mysql://localhost:3306/jdbc";
	private String user = "root";
	private String password = "";

	// private static JdbcUtilsSing instance = new JdbcUtilsSing();
	private static JdbcUtilsSing instance = null;

	private JdbcUtilsSing() {
	}

	public static JdbcUtilsSing getInstance() {
		if (instance == null) {
			synchronized (JdbcUtilsSing.class) {
				if (instance == null) {
					instance = new JdbcUtilsSing();
				}
			}
		}
		return instance;
	}

	static {
		try {
			Class.forName("com.mysql.jdbc.Driver");
		} catch (ClassNotFoundException e) {
			throw new ExceptionInInitializerError(e);
		}
	}

	public Connection getConnection() throws SQLException {
		return DriverManager.getConnection(url, user, password);
	}

	public void free(ResultSet rs, Statement st, Connection conn) {
		try {
			if (rs != null)
				rs.close();
		} catch (SQLException e) {
			e.printStackTrace();
		} finally {
			try {
				if (st != null)
					st.close();
			} catch (SQLException e) {
				e.printStackTrace();
			} finally {
				if (conn != null)
					try {
						conn.close();
					} catch (SQLException e) {
						e.printStackTrace();
					}
			}
		}
	}
}

 

Jdbc工具类：JdbcUtils.java

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

public final class JdbcUtils {
	private static String url = "jdbc:mysql://localhost:3306/jdbc";
	private static String user = "root";
	private static String password = "";

	private JdbcUtils() {
	}

	static {
		try {
			Class.forName("com.mysql.jdbc.Driver");
		} catch (ClassNotFoundException e) {
			throw new ExceptionInInitializerError(e);
		}
	}

	public static Connection getConnection() throws SQLException {
		return DriverManager.getConnection(url, user, password);
	}

	public static void free(ResultSet rs, Statement st, Connection conn) {
		try {
			if (rs != null)
				rs.close();
		} catch (SQLException e) {
			e.printStackTrace();
		} finally {
			try {
				if (st != null)
					st.close();
			} catch (SQLException e) {
				e.printStackTrace();
			} finally {
				if (conn != null)
					try {
						conn.close();
					} catch (SQLException e) {
						e.printStackTrace();
					}
			}
		}
	}
}

 

 

 

链接和测试实例:

Test.java

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


public class Test {

	/**
	 * @param args
	 * @throws Exception
	 */
	public static void main(String[] args) throws Exception {
		template(); 

	}

	static void template() throws Exception {
		Connection conn = null;
		Statement st = null;
		ResultSet rs = null;
		try {
			// 2.建立连接
			conn = JdbcUtils.getConnection();
			// conn = JdbcUtilsSing.getInstance().getConnection();
			// 3.创建语句
			st = conn.createStatement();

			// 4.执行语句
			rs = st.executeQuery("select * from user");

			// 5.处理结果
			while (rs.next()) {
				// 参数中的1,2,3,4是指sql中的列索引
				System.out.println(rs.getObject(1) + "\t" + rs.getObject(2)
						+ "\t" + rs.getObject(3) + "\t" + rs.getObject(4));
			}
		} finally {
			JdbcUtils.free(rs, st, conn);
		}

	}

	static void test() throws SQLException, ClassNotFoundException {
		// 1.注册驱动
		DriverManager.registerDriver(new com.mysql.jdbc.Driver());
		System.setProperty("jdbc.drivers", "com.mysql.jdbc.Driver");
		Class.forName("com.mysql.jdbc.Driver");// 推荐方式

		// 2.建立连接
		String url = "jdbc:mysql://localhost:3306/jdbc";
		String user = "root";
		String password = "";
		Connection conn = DriverManager.getConnection(url, user, password);

		// 3.创建语句
		Statement st = conn.createStatement();

		// 4.执行语句
		ResultSet rs = st.executeQuery("select * from user");

		// 5.处理结果
		while (rs.next()) {
			System.out.println(rs.getObject(1) + "\t" + rs.getObject(2) + "\t"
					+ rs.getObject(3) + "\t" + rs.getObject(4));
		}

		// 6.释放资源
		rs.close();
		st.close();
		conn.close();
	}
}