java 持久化 jdbc的連接：
對(duì)于連接 準(zhǔn)備好對(duì)應(yīng)數(shù)據(jù)庫(kù)的jar：
java代碼中首先建立三個(gè)對(duì)象：

1. Class.forName(url) url為jar驅(qū)動(dòng)中路徑 比如oracle中：

   
   
   image.png
   
   

   來(lái)進(jìn)行加載驅(qū)動(dòng)

2. Connection 創(chuàng)建連接
3. Statement (PreparedStatement) 通過(guò)statement來(lái)發(fā)起對(duì)于數(shù)據(jù)庫(kù)的操作，PreparedStatement是預(yù)編譯的statement，對(duì)于使用他的好處是 （1）sql注入問(wèn)題
   (2) 提高效率 （對(duì)于他的占位符下標(biāo)是 1 開(kāi)始的）
   接下來(lái)就是對(duì)于數(shù)據(jù)庫(kù)操作拿到數(shù)據(jù) 對(duì)于數(shù)據(jù)的操作 ，最后記得關(guān)閉資源

具體java代碼 如下：

//用來(lái)連接數(shù)據(jù)庫(kù)的工具類
public class DBUtils {
    private static String driver="oracle.jdbc.driver.OracleDriver";
    private static String url = "jdbc:oracle:thin:@localhost:1521:xe";
    private static String user = "xz";
    private static String pwd = "xz";
    private static final ThreadLocal<Connection> 
                         threadLocal = new ThreadLocal<Connection>(); //多線程的多對(duì)象耗時(shí)操作
    //獲取connection連接對(duì)象
    public static Connection getConnection() throws ClassNotFoundException, SQLException{
        Connection conn = threadLocal.get();
        if(conn==null){
            Class.forName(driver);
            conn = DriverManager.getConnection(url,user,pwd);
            threadLocal.set(conn);
        }
        return conn;    
    }
    
    //關(guān)閉connection資源
    public static void conClose(){
        Connection con = threadLocal.get();
        if(con!=null){
            threadLocal.set(null);
            try {
                con.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        
        
    }
    
    //關(guān)閉資源
    public static void Close(ResultSet rs,Statement st){
        if(rs!=null){
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if(st!=null){
            try {
                st.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        
    }

}