喜歡用新不用久，所以我裝軟體基本都是遵循去下載安裝最新版本的軟體，畢竟新的軟體功能多，雖然小坑和小問題也多，但是大部分坑你搜一搜網上都有前人給你填平了，這裡記錄一下自己學習JAVA JDBC連線資料庫時的一個小問題

就是連線資料庫驅動的時（使用了mysql-connector-java-8.0.11.jar驅動包），如下

 //驅動類com.mysql.jdbc.Driver
			Class.forName("com.mysql.jdbc.Driver");
			System.out.println("資料庫載入成功!"); 
// 建立與資料庫的Connection連線
 Connection c = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/how2java?characterEncoding=UTF-8","root","admin");    
 

會出現警告①

Establishing SSL connection without server's identityverification is not recommended. According to MySQL 5.5.45+, 5.6.26+ and 5.7.6+requirements SSL connection must be established by default if explicit optionisn't set. For compliance with existing applications not using SSL theverifyServerCertificate property is set to 'false'. You need either toexplicitly disable SSL by setting useSSL=false, or set useSSL=true and providetruststore for server certificate verification.
 

原因

驅動程式的描述字串com.mysql.jdbc.Driver是mysql5.0及以前的老寫法

而mysql6.0以後 包括我用的8.0需要這樣寫com.mysql.cj.jdbc.Driver

警告②

Establishing SSL connection without server's identity verification is not recommended. According to MySQL 5.5.45+, 5.6.26+ and 5.7.6+ requirements SSL connection must be established by default if explicit option isn't set. For compliance with existing applications not using SSL the verifyServerCertificate property is set to 'false'. You need either to explicitly disable SSL by setting useSSL=false, or set useSSL=true and provide truststore for server certificate verification.
java.sql.SQLException: The server time zone value '???ú±ê×??±??' is unrecognized or represents more than one time zone. You must configure either the server or JDBC driver (via the serverTimezone configuration property) to use a more specifc time zone value if you want to utilize time zone support.
 

原因

MySQL在高版本需要指明是否進行SSL連線。解決方案： 在mysql連線字串url中加入ssl=true或者false即可，如下所示

"jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf8&useSSL=false&serverTimezone=Hongkong"

完整的程式碼如下

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

public class TestJDBC {
	public static void main(String[] args) {
		//初始化驅動
		try {
            //老版驅動類com.mysql.jdbc.Driver
            //如果忘記了第一個步驟的導包，就會丟擲ClassNotFoundException
			Class.forName("com.mysql.cj.jdbc.Driver");
			System.out.println("資料庫載入成功!");
			
			Connection c = DriverManager.getConnection("jdbc:mysql://localhost:3306/test?"
					                                 + "useUnicode=true&characterEncoding=utf8&"
					                                 + "useSSL=false&serverTimezone=Hongkong","root","admin");
			System.out.println("連線成功，獲取連線物件： " + c);
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		} catch (SQLException e) {
			e.printStackTrace();
		}
	}
	
}

其中test是本機資料庫名，root和admin是mysql安裝時建立的賬戶和密碼。

serverTimezone=HongKong 是設定時區，可以填UTC、Asia/Shanghai等等，UTC要比中國時區早8個小時。

待更新。。