jdbcUtil02.java

?

//单例模式
public final class jdbcUtil02 {
?static String url = "jdbc:mysql://localhost:3306/jdbc";
?static String username = "root";
?static String password = "root";
?
?//private static jdbcUtil02 instance = new jdbcUtil02();
?private static jdbcUtil02 instance= null;
?//构造私有化
?private jdbcUtil02(){
??
?}
?
?//提供一个公共的static方法
?public static jdbcUtil02 getInstance(){
??if (instance==null) {
???//延迟加载? 使用的时候new
???//处理并发问题? 可以加锁
???synchronized (jdbcUtil02.class) {
????instance = new jdbcUtil02();
???}
??}
??return instance;
?}
?
?public static Connection getConnection() throws SQLException {
??return DriverManager.getConnection(url, username, password);
?}
?
?public static void free(Statement st, Connection conn, ResultSet rs) {
??try {
???if (rs != null) {
????rs.close();
???}
??} catch (SQLException e) {
???e.printStackTrace();
??} finally {
???try {
????if (conn != null) {
?????conn.close();
????}
???} catch (SQLException e2) {
????e2.printStackTrace();
???} finally {
????try {
?????if (st != null) {
??????st.close();
?????}
????} catch (SQLException e2) {
?????e2.printStackTrace();
????}
???}
??}
?}
}

?

?

package com.sg.test;

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

import org.junit.Test;

public class JdbcCRUDTest {
?// 查询
?@Test
?public void select() throws Exception {
??Connection conn = jdbcUtil02.getInstance().getConnection();
??Statement st = conn.createStatement();
??ResultSet rs = st.executeQuery("select * from user");

??while (rs.next()) {
???System.out.println("id:" + rs.getInt("id") + "\n name:"
?????+ rs.getString("name") + "\n age:" + rs.getInt("age")
?????+ "\n sex" + rs.getString("sex") + "\n brithday:"
?????+ rs.getDate("brithday"));
??}
??// 关闭资源
??jdbcUtil02.free(st, conn, rs);
?}
?//添加
?@Test
?public void insert() throws Exception {
??Connection conn = jdbcUtil02.getInstance().getConnection();
??Statement st = conn.createStatement();
??String sql = "insert into user values(4,'name1',20,'nan','1992-12-28')";
??int i = st.executeUpdate(sql);
??System.out.println("i = "+i);
??
?}
?//修改
?@Test
?public void update() throws Exception {
??Connection conn = jdbcUtil02.getInstance().getConnection();
??Statement st = conn.createStatement();
??String sql = "update user set age = 30 where id = 1";
??int i = st.executeUpdate(sql);
??
?}
?//删除
?@Test
?public void delete() throws Exception {
??Connection conn = jdbcUtil02.getInstance().getConnection();
??Statement st = conn.createStatement();
??String sql = "delete from user where id > 2";
??int i = st.executeUpdate(sql);
??
?}
?
}