用idea+maven實現JDBC

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pom.xml的配置：

<!-- https://mvnrepository.com/artifact/junit/junit -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>

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

public class QueryAll {
    public static void main(String[] args){
        Connection conn= null;
        Statement stmt = null;
        ResultSet rs = null;
        try {
            //Class.forName("com.mysql.jdbc.Driver");
            String url ="jdbc:mysql://localhost/sunnie?useUnicode=true&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC&useSSL=true";
            String username="root";
            String password="password";
            conn = DriverManager.getConnection(url,username,password);
            stmt = conn.createStatement();
            String sql = "select * from user";
            rs = stmt.executeQuery(sql);
            while(rs.next()) {
                System.out.println("用戶名：" + rs.getString(2)+" 密碼："+ rs.getString("password"));
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (rs!=null)
                try {
                    rs.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            if (stmt!=null)
                try {
                    stmt.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            if (conn!=null)
                try {
                    conn.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
        }
    }
}

注意的問題：

（1）新版本的mysql裏面要指明serverTimezone和是否進行SSL連接。

serverTimezone=UTC&useSSL=true

否則就會出現警告或者報錯。

java.sql.SQLException: The server timezone value 'UTC' is unrecognized or represents more than one timezone. You must configure either the server or JDBC driver (via the serverTimezone configuration property) to use a more specifc timezone value if you want to utilize timezone support.

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.

（2）新版本mysql已經不再需要手動加載驅動，即不用寫下面這行

Class.forName("com.mysql.jdbc.Driver");

寫了反而會出警告

Loading class `com.mysql.jdbc.Driver'. This is deprecated. The new driver class is `com.mysql.cj.jdbc.Driver'. The driver is automatically registered via the SPI and manual loading of the driver class is generally unnecessary.