将Java连接到MySQL数据库

Question

如何用Java连接MySQL数据库？

当我尝试时，我得到了

java.sql.SQLException: No suitable driver found for jdbc:mysql://database/table
    at java.sql.DriverManager.getConnection(DriverManager.java:689)
    at java.sql.DriverManager.getConnection(DriverManager.java:247)

或

java.lang.ClassNotFoundException: com.mysql.jdbc.Driver

或者

java.lang.ClassNotFoundException: com.mysql.cj.jdbc.Driver

Answer 1

Answer 2

DriverManager是一种相当古老的做事方式。更好的方法是获取DataSource，或者通过查看已经为您配置的应用服务器容器来获取：{/ p>

Context context = new InitialContext();
DataSource dataSource = (DataSource) context.lookup("java:comp/env/jdbc/myDB");

或直接从数据库驱动程序中实例化和配置一个：

MysqlDataSource dataSource = new MysqlDataSource();
dataSource.setUser("scott");
dataSource.setPassword("tiger");
dataSource.setServerName("myDBHost.example.org");

然后从中获取连接，与上面相同：

Connection conn = dataSource.getConnection();
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery("SELECT ID FROM USERS");
...
rs.close();
stmt.close();
conn.close();

Answer 3

初始化数据库常量

创建常量属性数据库用户名，密码，URL和驱动程序，轮询限制等。

// init database constants
private static final String DATABASE_DRIVER = "com.mysql.jdbc.Driver";
private static final String DATABASE_URL = "jdbc:mysql://localhost:3306/database_name";
private static final String USERNAME = "root";
private static final String PASSWORD = "";
private static final String MAX_POOL = "250"; // set your own limit

初始化连接和属性

建立连接后，最好存储以便重复使用。

// init connection object
private Connection connection;
// init properties object
private Properties properties;

创建属性

属性对象保存连接信息，检查它是否已设置。

// create properties
private Properties getProperties() {
    if (properties == null) {
        properties = new Properties();
        properties.setProperty("user", USERNAME);
        properties.setProperty("password", PASSWORD);
        properties.setProperty("MaxPooledStatements", MAX_POOL);
    }
    return properties;
}

连接数据库

现在使用初始化的常量和属性连接到数据库。

// connect database
public Connection connect() {
    if (connection == null) {
        try {
            Class.forName(DATABASE_DRIVER);
            connection = DriverManager.getConnection(DATABASE_URL, getProperties());
        } catch (ClassNotFoundException | SQLException e) {
            // Java 7+
            e.printStackTrace();
        }
    }
    return connection;
}

断开数据库

完成数据库操作后，只需关闭连接即可。

// disconnect database
public void disconnect() {
    if (connection != null) {
        try {
            connection.close();
            connection = null;
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

一起

在更改database_name，用户名和密码等后直接使用此类MysqlConnect。

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

public class MysqlConnect {
    // init database constants
    private static final String DATABASE_DRIVER = "com.mysql.jdbc.Driver";
    private static final String DATABASE_URL = "jdbc:mysql://localhost:3306/database_name";
    private static final String USERNAME = "root";
    private static final String PASSWORD = "";
    private static final String MAX_POOL = "250";

    // init connection object
    private Connection connection;
    // init properties object
    private Properties properties;

    // create properties
    private Properties getProperties() {
        if (properties == null) {
            properties = new Properties();
            properties.setProperty("user", USERNAME);
            properties.setProperty("password", PASSWORD);
            properties.setProperty("MaxPooledStatements", MAX_POOL);
        }
        return properties;
    }

    // connect database
    public Connection connect() {
        if (connection == null) {
            try {
                Class.forName(DATABASE_DRIVER);
                connection = DriverManager.getConnection(DATABASE_URL, getProperties());
            } catch (ClassNotFoundException | SQLException e) {
                e.printStackTrace();
            }
        }
        return connection;
    }

    // disconnect database
    public void disconnect() {
        if (connection != null) {
            try {
                connection.close();
                connection = null;
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

如何使用？

初始化数据库类。

// !_ note _! this is just init
// it will not create a connection
MysqlConnect mysqlConnect = new MysqlConnect();

代码中的其他地方......

String sql = "SELECT * FROM `stackoverflow`";
try {
    PreparedStatement statement = mysqlConnect.connect().prepareStatement(sql);
    ... go on ...
    ... go on ...
    ... DONE ....
} catch (SQLException e) {
    e.printStackTrace();
} finally {
    mysqlConnect.disconnect();
}

这都是：）如果有什么要改进的话就编辑吧！希望这有用。

Answer 4

String url = "jdbc:mysql://127.0.0.1:3306/yourdatabase";
String user = "username";
String password = "password";

// Load the Connector/J driver
Class.forName("com.mysql.jdbc.Driver").newInstance();
// Establish connection to MySQL
Connection conn = DriverManager.getConnection(url, user, password);

Answer 5

这是从MySQL数据库中获取数据所需的最低限度：

Class.forName("com.mysql.jdbc.Driver").newInstance();
Connection conn = DriverManager.getConnection
   ("jdbc:mysql://localhost:3306/foo", "root", "password");

Statement stmt = conn.createStatement();
stmt.execute("SELECT * FROM `FOO.BAR`");
stmt.close();
conn.close();

添加异常处理，配置等。

Answer 6

使用useSSL的MySQL JDBC连接。

private String db_server = BaseMethods.getSystemData("db_server");
private String db_user = BaseMethods.getSystemData("db_user");
private String db_password = BaseMethods.getSystemData("db_password");

private String connectToDb() throws Exception {
   String jdbcDriver = "com.mysql.jdbc.Driver";
   String dbUrl = "jdbc:mysql://" + db_server  +
        "?verifyServerCertificate=false" +
        "&useSSL=true" +
        "&requireSSL=true";
    System.setProperty(jdbcDriver, "");
    Class.forName(jdbcDriver).newInstance();

    Connection conn = DriverManager.getConnection(dbUrl, db_user, db_password);
    Statement statement = conn.createStatement();
    String query = "SELECT EXTERNAL_ID FROM offer_letter where ID =" + "\"" + letterID + "\"";
    ResultSet resultSet = statement.executeQuery(query);
    resultSet.next();
    return resultSet.getString(1);
}

Answer 7

您可以看到从Java应用程序here连接MySQL数据库的所有步骤。对于其他数据库，您只需要在第一步中更改驱动程序。请确保您提供正确的数据库路径并更正用户名和密码。

访问http://apekshit.com/t/51/Steps-to-connect-Database-using-JAVA

Answer 8

您需要在类路径中使用mysql连接器jar。

Java中的

JDBC API使数据库具有一切功能。使用JDBC我们可以编写Java应用程序 1.发送查询或将SQL更新到DB（任何关系数据库） 2.检索并处理来自DB的结果

通过以下三个步骤，我们可以从任何数据库中检索数据

Connection con = DriverManager.getConnection(
                     "jdbc:myDriver:DatabaseName",
                     dBuserName,
                     dBuserPassword);

Statement stmt = con.createStatement();
ResultSet rs = stmt.executeQuery("SELECT a, b, c FROM Table");

while (rs.next()) {
    int x = rs.getInt("a");
    String s = rs.getString("b");
    float f = rs.getFloat("c");
}

Answer 9

短而甜的代码。

try
    {       
        Class.forName("com.mysql.jdbc.Driver");
        System.out.println("Driver Loaded");
        conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/testDB","root","");
        //Database Name - testDB, Username - "root", Password - ""
        System.out.println("Connected...");         
    }
    catch(Exception e)
    {
        e.printStackTrace();
    }

对于SQL Server 2012

try
    {
        String url = "jdbc:sqlserver://KHILAN:1433;databaseName=testDB;user=Khilan;password=Tuxedo123"; 
       //KHILAN is Host and 1433 is port number     
        Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
        System.out.println("Driver Loaded");
        conn = DriverManager.getConnection(url);
        System.out.println("Connected...");
    }
    catch(Exception e)
    {
        e.printStackTrace();
    }

Answer 10

Connection我前段时间使用它，它看起来是最简单的方法，但也有建议if声明 - 确切

Connection con = DriverManager.getConnection(
                     "jdbc:myDriver:DatabaseName",
                     dBuserName,
                     dBuserPassword);
if (con != null){
 //..handle your code there 
}

或者像这样的事情：）

可能有一些情况，而getConnection可以返回null：）

Answer 11

MySql JDBC Connection：

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

Connection con=DriverManager.getConnection("jdbc:mysql://localhost:3306/DatabaseName","Username","Password");         
Statement stmt=con.createStatement();            
stmt = con.createStatement();
ResultSet rs=stmt.executeQuery("Select * from Table");  

Answer 12

怎么样

• 设置驱动程序以运行快速示例

1. Go to https://dev.mysql.com/downloads/connector/j/, get the latest version of Connector/J

2. Remember to set the classpath to include the path of the connector jar file.
If we don't set it correctly, below errors can occur:

No suitable driver found for jdbc:mysql://127.0.0.1:3306/msystem_development

java.lang.ClassNotFoundException: com.mysql.jdbc:Driver

• 要设置CLASSPATH

方法1：设置CLASSPATH变量。

export CLASSPATH=".:mysql-connector-java-VERSION.jar"
java MyClassFile

在上面的命令中，我将CLASSPATH设置为当前文件夹和mysql-connector-java-VERSION.jar文件。因此，当执行java MyClassFile命令时，java应用程序启动器将尝试在CLASSPATH中加载所有Java类。 它发现Drive类=> BOOM错误消失了。

方法2：

java -cp .:mysql-connector-java-VERSION.jar MyClassFile

注意：Class.forName（“ com.mysql.jdbc.Driver”）;此时间自2019年4月开始弃用。

希望这可以帮助某人！

Answer 13

短代码

public class DB {

    public static Connection c;

    public static Connection getConnection() throws Exception {
        if (c == null) {
            Class.forName("com.mysql.jdbc.Driver");
            c =DriverManager.getConnection("jdbc:mysql://localhost:3306/DATABASE", "USERNAME", "Password");
        }
        return c;
    }

    // Send data TO Database
    public static void setData(String sql) throws Exception {
        DB.getConnection().createStatement().executeUpdate(sql);
    }

    // Get Data From Database
    public static ResultSet getData(String sql) throws Exception {
        ResultSet rs = DB.getConnection().createStatement().executeQuery(sql);
        return rs;
    }
}

Answer 14

下载JDBC驱动程序

下载链接（独立于特定平台）：https://dev.mysql.com/downloads/connector/j/

将JDBC驱动程序移动到C驱动器

解压缩文件并移动到C：\驱动器。您的驱动程序路径应类似于C:\mysql-connector-java-8.0.19\mysql-connector-java-8.0.19

运行Java

java -cp "C:\mysql-connector-java-8.0.19\mysql-connector-java-8.0.19\mysql-connector-java-8.0.19.jar" testMySQL.java

testMySQL.java

import java.sql.*;
import java.io.*;

public class testMySQL {
    public static void main(String[] args) {
    // TODO Auto-generated method stub
        try
        {  
            Class.forName("com.mysql.cj.jdbc.Driver");  
            Connection con=DriverManager.getConnection(  
                "jdbc:mysql://localhost:3306/db?useSSL=false&useUnicode=true&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC","root","");  
            Statement stmt=con.createStatement();  
            ResultSet rs=stmt.executeQuery("show databases;");  
            System.out.println("Connected");  
        }
        catch(Exception e)
        {
            System.out.println(e);
        }

    }  

}