java连接oracle异常

Exception in thread "main" java.sql.SQLException: Io 异常: The Network Adapter could not establish the connection
at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:111)
at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:145)
at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:254)
at oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:386)
at oracle.jdbc.driver.PhysicalConnection.<init>(PhysicalConnection.java:413)
at oracle.jdbc.driver.T4CConnection.<init>(T4CConnection.java:164)
at oracle.jdbc.driver.T4CDriverExtension.getConnection(T4CDriverExtension.java:34)
at oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:752)
at java.sql.DriverManager.getConnection(Unknown Source)
at java.sql.DriverManager.getConnection(Unknown Source)
at abc.Test.main(Test.java:20)
源代码：public static void main(String[] args) throws SQLException {
try {
Class.forName("oracle.jdbc.driver.OracleDriver");
} catch (ClassNotFoundException e) {
throw new ExceptionInInitializerError(e);
}
String user = "jiandong";
String password = "jd";
String url = "jdbc:oracle:thin:@localhost:1521:jiandong_data";
Connection conn = (Connection)DriverManager.getConnection(url, user, password);
Statement st = (Statement)conn.createStatement();
ResultSet rs = (ResultSet)st.executeQuery("select * from jd_user");
while(rs.next()){
System.out.println(rs.getObject(1) + "\t" + rs.getObject(2) + "\t"
+ rs.getObject(3) + "\t" + rs.getObject(4));
}

rs.close();
st.close();
conn.close();

}oracle数据库自己使用正常，所有服务都已经开启，用户名密码都正确，使用的jar包为classes12.jar