<connectionStrings>
    <!--SQLServer数据库连接-->
    <add name="conn_sqlserver" connectionString="server=127.0.0.1;uid=testuser;pwd=testPwd;database=db_test;pooling=true;min pool size=10;max pool size=1024;connection lifetime=300;packet size=1000" providerName="System.Data.SqlClient"/>
    <!--MySQL数据库连接-->
    <add name="conn_mysql" connectionString="Data Source=127.0.0.1; Database=db_test; User Id=testuser;Password=testPwd; pooling=false; CharSet=utf8; Port=3306" providerName="MySql.Data.MySqlClient"/>
    <!--SQLite数据库连接-->
    <add name="conn_sqlite" connectionString="Data Source=|DataDirectory|\db_test.db3; Pooling=true; FailIfMissing=false" providerName="System.Data.SQLite" />
  </connectionStrings>
  <!-- 解决DbProviderFactories.GetFactory(ProviderName)出现的异常：“找不到请求的 .Net Framework Data Provider。可能没有安装。” -->
  <system.data>
    <DbProviderFactories>
      <remove invariant="System.Data.SQLite"/>
      <add name="SQLite Data Provider" invariant="System.Data.SQLite" description=".Net Framework Data Provider for SQLite" type="System.Data.SQLite.SQLiteFactory, System.Data.SQLite, Version=1.0.105.2, Culture=neutral, PublicKeyToken=db937bc2d44ff139" />
      <remove invariant="MySQL Data Provider"/>
      <add name="MySQL Data Provider" invariant="MySql.Data.MySqlClient" description=".Net Framework Data Provider for MySQL" type="MySql.Data.MySqlClient.MySqlClientFactory, MySql.Data, Version=6.9.9.0, Culture=neutral, PublicKeyToken=c5687fc88969c44d" />
    </DbProviderFactories>
  </system.data>

// mysql
driver="com.mysql.jdbc.Driver";
url = "jdbc:mysql://localhost:3306/db_test?useUnicode=true&characterEncoding=UTF8";
conn = getConnection(driver,url, "user", "password");
System.out.println("与mysql数据库连接" + (null == conn ? "失败" : "成功"));
// sqlite        
driver="SQLite.JDBCDriver";
url = "jdbc:sqlite:/C:/db_test.db3";
conn = getConnection(driver,url);
System.out.println("与sqlite数据库连接" + (null == conn ? "失败" : "成功"));
// sqlserver        
driver="com.mysql.jdbc.Driver";
url = "jdbc:sqlserver://localhost:1433;DatabaseName=db_test";
conn = getConnection(driver,url, "user", "password");
System.out.println("与sql server数据库连接" + (null == conn ? "失败" : "成功"));
// oracle
driver="oracle.jdbc.driver.OracleDriver";
url = "jdbc:oracle:thin:@localhost:1521:orcl";
conn = getConnection(driver,url, "user", "password");
System.out.println("与oracle数据库连接" + (null == conn ? "失败" : "成功"));

public static Connection getConnection(String driver, String url, String user, String password) {
    Connection conn = null;
    try {
        //初始化驱动包     
        Class.forName(driver);
        conn = DriverManager.getConnection(url, user, password);

    } catch (Exception e) {
        e.printStackTrace();
    }
    return conn;
}

// PDO连接MySQL的DSN字符串 (需要打开php配置文件中的"extension=php_pdo_mysql.dll"选项)
mysql:dbname=db_test;host=127.0.0.1;port=3306;charset=utf8
// PDO连接SQLite的DSN字符串 (需要打开php配置文件中的"extension=php_pdo_sqlite.dll"选项)
sqlite:test_db.db3
// PDO通过ODBC连接SQL Server的DSN字符串 (需要打开php配置文件中的"extension=php_pdo_odbc.dll"选项)
odbc:Driver={SQL Server};Server=127.0.0.1,1433;Database=db_test;
// PDO连接SQL Server的DSN字符串（配置非常麻烦，建议使用ODBC方式。PHP5.3.6以上的版本中php_mssql.dll，php_pdo_mssql.dll都已经不见了,只有一个php_pdo_odbc.dll,所以最新最好的php连接mssql方法应该是使用ODBC的驱动模式。）
sqlsrv:Database=db_test;Server=127.0.0.1,1433
// PDO连接PostgreSQL的DSN字符串 (需要打开php配置文件中的"extension=php_pdo_pgsql.dll"选项)
pgsql:dbname=db_test;host=127.0.0.1;port=5432
// PDO连接Oracle的DSN字符串 (需要打开php配置文件中的"extension=php_pdo_oci.dll"选项)
oci:dbname=//127.0.0.1:5432/db_test