JDBC连接的四个步骤

1.加载驱动程序
Class.forName("oracle.jdbc.driver.OracleDriver");

2. 建立连接
Connection conn = DriverMananger.getConnection("jdbc:oracle:thin:@127.0.0.1:1521:xe","用户名","密码");
3. 执行查询
4. 关闭数据库连接

==============实际的代码=================

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

public class JDBCExample {


public static void main(String[] args) {
  try {
   Class.forName("oracle.jdbc.driver.OracleDriver");
   String url="jdbc:oracle:thin:@127.0.0.1:1521:ora9";
   try {
    Connection conn=DriverManager.getConnection(url,"scott","tiger");
    Statement stmt=conn.createStatement();
    ResultSet rs=stmt.executeQuery("select * from dept");
    while(rs.next()){
     System.out.println("deptno"+rs.getInt(1));
     System.out.println("\tDname: "+rs.getString(2));
     System.out.println("\tLoc: "+rs.getString(3));
    }
    rs.close();
    stmt.close();
    conn.close();
   } catch (SQLException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
   }
  } catch (ClassNotFoundException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }

}

}

thin VS oci

先看看thin和oci的url写法上的区别： 
jdbc:oracle:thin:@server ip: service 
jdbc:oracle:oci:@service 
1）从使用上来说，oci必须在客户机上安装oracle客户端或才能连接，而thin就不需要，因此从使用上来讲thin还是更加方便，这也是thin比较常见的原因。 
2）原理上来看，thin是纯java实现tcp/ip的c/s通讯；而oci方式,客户端通过native java method调用c library访问服务端，而这个c library就是oci(oracle called interface)，因此这个oci总是需要随着oracle客户端安装（从oracle10.1.0开始，单独提供OCI Instant Client，不用再完整的安装client） 
3）它们分别是不同的驱动类别，oci是二类驱动， thin是四类驱动，但它们在功能上并无差异。 
4）虽然很多人说oci的速度快于thin，但找了半天没有找到相关的测试报告。

接下来再找找oci和thin的其他区别，发现有如下解释：

引用

Oracle provides four different types of JDBC drivers, for use in different deployment scenarios. The 10.1.0 drivers can access Oracle 8.1.7 and higher. While all Oracle JDBC drivers are similar, some features apply only to JDBC OCI drivers and some apply only to the JDBC Thin driver.

JDBC OCI client-side driver: This is a JDBC Type 2 driver that uses Java native methods to call entrypoints in an underlying C library. That C library, called OCI (Oracle Call Interface), interacts with an Oracle database. The JDBC OCI driver requires an Oracle client installation of the same version as the driver.

The use of native methods makes the JDBC OCI driver platform specific. Oracle supports Solaris, Windows, and many other platforms. This means that the Oracle JDBC OCI driver is not appropriate for Java applets, because it depends on a C library.

Starting from 10.1.0, the JDBC OCI driver is available for install with the OCI Instant Client feature, which does not require a complete Oracle client-installation. Please refer to Oracle Call Interface for more information.

JDBC Thin client-side driver: This is a JDBC Type 4 driver that uses Java to connect directly to Oracle. It implements Oracle's SQL*Net Net8 and TTC adapters using its own TCP/IP based Java socket implementation. The JDBC Thin driver does not require Oracle client software to be installed, but does require the server to be configured with a TCP/IP listener.

Because it is written entirely in Java, this driver is platform-independent. The JDBC Thin driver can be downloaded into any browser as part of a Java application. (Note that if running in a client browser, that browser must allow the applet to open a Java socket connection back to the server.)

JDBC Thin server-side driver: This is another JDBC Type 4 driver that uses Java to connect directly to Oracle. This driver is used internally within the Oracle database. This driver offers the same functionality as the client-side JDBC Thin driver (above), but runs inside an Oracle database and is used to access remote databases.

Because it is written entirely in Java, this driver is platform-independent. There is no difference in your code between using the Thin driver from a client application or from inside a server.

连接方式有以下几种：

Oralce provides four types of JDBC driver.

Thin Driver, a 100% Java driver for client-side use without an Oracle installation, particularly with applets. The Thin driver type is thin. To connect user scott with password tiger to a database with SID (system identifier) orcl through port 1521 of host myhost, using the Thin driver, you would write :
Connection conn = DriverManager.getConnection
("jdbc:oracle:thin:@myhost:1521:orcl", "scott", "tiger");

OCI Driver for client-side use with an Oracle client installation. The OCI driver type is oci. To connect user scott with password tiger to a database with SID (system identifier) orcl through port 1521 of host myhost, using the OCI driver, you would write :
Connection conn = DriverManager.getConnection
("jdbc:oracle:oci:@myhost:1521:orcl", "scott", "tiger");

Note that you can also specify the database by a TNSNAMES entry. You can find the available TNSNAMES entries listed in the file tnsnames.ora on the client computer from which you are connecting. For example, if you want to connect to the database on host myhost as user scott with password tiger that has a TNSNAMES entry of MyHostString, enter:
Connection conn = DriverManager.getConnection
("jdbc:oracle:oci8:@MyHostString","scott","tiger");

If your JDBC client and Oracle server are running on the same machine, the OCI driver can use IPC (InterProcess Communication) to connect to the database instead of a network connection. An IPC connection is much faster than a network connection.
Connection conn = DriverManager.getConnection
("jdbc:oracle:oci8:@","scott","tiger");

Server-Side Thin Driver, which is functionally the same as the client-side Thin driver, but is for code that runs inside an Oracle server and needs to access a remote server, including middle-tier scenarios. The Server-Side Thin driver type is thin and there is no difference in your code between using the Thin driver from a client application or from inside a server.
Server-Side Internal Driver for code that runs inside the target server, that is, inside the Oracle server that it must access. The Server-Side Internal driver type is kprb and it actually runs within a default session. You are already "connected". Therefore the connection should never be closed.
To access the default connection, write:
DriverManager.getConnection("jdbc:oracle:kprb:");
or:
DriverManager.getConnection("jdbc:default:connection:");

You can also use the Oracle-specific defaultConnection() method of the OracleDriver class which is generally recommended:
OracleDriver ora = new OracleDriver();
Connection conn = ora.defaultConnection();

Note: You are no longer required to register the OracleDriver class for connecting with the Server-Side Internal driver, although there is no harm in doing so. This is true whether you are using getConnection() or defaultConnection() to make the connection.
Any user name or password you include in the URL string is ignored in connecting to the server default connection. The DriverManager.getConnection() method returns a new Java Connection object every time you call it. Note that although the method is not creating a new physical connection (only a single implicit connection is used), it is returning a new object.
Again, when JDBC code is running inside the target server, the connection is an implicit data channel, not an explicit connection instance as from a client. It should never be closed.