getConnection 区别

 1. 这是一个接口

package javax.sql;

DataSource.class

/**
   * <p>Attempts to establish a connection with the data source that
   * this <code>DataSource</code> object represents.
   *
   * @return  a connection to the data source
   * @exception SQLException if a database access error occurs
   */
  Connection getConnection() throws SQLException;

 2.这是一个dbcp实现类，返回由连接池管理的连接。

package org.apache.commons.dbcp2;

BasicDataSource.class

/**
     * Create (if necessary) and return a connection to the database.
     *
     * @throws SQLException if a database access error occurs
     * @return a database connection
     */
    @Override
    public Connection getConnection() throws SQLException {
        if (Utils.IS_SECURITY_ENABLED) {
            PrivilegedExceptionAction<Connection> action = new PaGetConnection();
            try {
                return AccessController.doPrivileged(action);
            } catch (PrivilegedActionException e) {
                Throwable cause = e.getCause();
                if (cause instanceof SQLException) {
                    throw (SQLException) cause;
                }
                throw new SQLException(e);
            }
        }
        return createDataSource().getConnection();
    }

 3. 创建连接并返回

package java.sql;

DriverManager.class

/**
     * Attempts to establish a connection to the given database URL.
     * The <code>DriverManager</code> attempts to select an appropriate driver from
     * the set of registered JDBC drivers.
     *
     * @param url a database url of the form
     * <code>jdbc:<em>subprotocol</em>:<em>subname</em></code>
     * @param user the database user on whose behalf the connection is being
     *   made
     * @param password the user's password
     * @return a connection to the URL
     * @exception SQLException if a database access error occurs
     */
    public static Connection getConnection(String url,
        String user, String password) throws SQLException {
        java.util.Properties info = new java.util.Properties();

        // Gets the classloader of the code that called this method, may
        // be null.
        ClassLoader callerCL = DriverManager.getCallerClassLoader();

        if (user != null) {
            info.put("user", user);
        }
        if (password != null) {
            info.put("password", password);
        }

        return (getConnection(url, info, callerCL));
    }