JDBC一般流程及优化过程

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class Base {

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

}
static void template() 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 = "123456";
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();
}
}

public final class JdbcUtils {
private static String url = "jdbc:mysql://localhost:3306/jdbc";
private static String user = "root";
private static String password = "123456";

private JdbcUtils() {
}
//JVM加载类时就进行驱动注册
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();
}
}
}
}
}

public class Base {

/**
* @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);
}

}