如何使用JDBC从Java连接到Oracle数据库？

要连接Oracle数据库，首先需添加Oracle JDBC驱动并建立连接，1. 添加ojdbc驱动：使用Maven时可配置Oracle仓库或手动安装ojdbc8.jar到本地仓库，非Maven项目则直接下载JAR并加入classpath；2. 建立连接：JDBC 4.0以上无需显式加载驱动，使用DriverManager.getConnection()配合正确URL格式，如jdbc:oracle:thin:@localhost:1521:ORCL（SID）或jdbc:oracle:thin:@//localhost:1521/ORCLPDB1（服务名），并在代码中通过try-with-resources安全执行SQL；3. 注意SID与服务名的URL差异，必要时支持TNS或SSL连接；4. 常见问题包括驱动未找到（检查classpath）、ORA-12505错误（核对SID/服务名）、连接超时（确认监听和端口）以及Java版本兼容性（Java 8-17用ojdbc8）。正确配置后，标准JDBC操作即可正常运行，且应始终妥善处理SQLException。

Connecting to an Oracle database from Java using JDBC involves a few key steps: loading the driver, establishing a connection, and then working with SQL statements. Here's a straightforward guide to get you up and running.

1. Add the Oracle JDBC Driver (ojdbc)

Oracle’s JDBC driver is not in Maven Central by default due to licensing, but you can still include it in your project.

If using Maven:

You can manually install the ojdbc8.jar (for Java 8 ) into your local repository or use a repository that hosts it (like Oracle’s Maven repository after registration).

Alternatively, if you’ve downloaded the JAR:

<dependency>
    <groupId>com.oracle.database.jdbc</groupId>
    <artifactId>ojdbc8</artifactId>
    <version>21.7.0.0</version>
</dependency>

Note: You may need to configure Oracle’s Maven repository or install the JAR locally using mvn install.

Manual Setup:

If not using Maven, download the appropriate ojdbc JAR from Oracle’s website, and add it to your classpath.

2. Load the JDBC Driver and Connect

Starting from JDBC 4.0 (Java 6 ), loading the driver manually (Class.forName) is optional, but it's still sometimes used for clarity or older environments.

Connection URL Format:

jdbc:oracle:thin:@hostname:port:service_id
-- or
jdbc:oracle:thin:@//hostname:port/service_name

• Use : before SID (e.g., :ORCL)
• Use // before service name (e.g., /ORCLPDB1)

Example Code:

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

public class OracleJDBCExample {
    public static void main(String[] args) {
        // Database connection parameters
        String url = "jdbc:oracle:thin:@localhost:1521:ORCL";
        // or for service name: "jdbc:oracle:thin:@//localhost:1521/ORCLPDB1"
        String username = "your_username";
        String password = "your_password";

        try (Connection conn = DriverManager.getConnection(url, username, password);
             Statement stmt = conn.createStatement();
             ResultSet rs = stmt.executeQuery("SELECT 'Hello from Oracle' FROM DUAL")) {

            while (rs.next()) {
                System.out.println(rs.getString(1));
            }

        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

3. Common Connection Scenarios

• SID vs Service Name:

  • If connecting via SID: jdbc:oracle:thin:@host:port:SID
  • If connecting via Service Name: jdbc:oracle:thin:@//host:port/service_name

• Using TNS Names (Advanced):
  You can also use a TNS alias if configured:

  jdbc:oracle:thin:@(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=localhost)(PORT=1521))(CONNECT_DATA=(SERVICE_NAME=ORCLPDB1)))

• SSL or Wallet Connections:
  More complex setups (like Autonomous Database) may require additional parameters and Oracle Wallets.

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4. Troubleshooting Tips

• ClassNotFoundException: Make sure ojdbc8.jar (or similar) is in your classpath.
• ORA-12505: SID not found: Double-check SID vs service name syntax.
• ORA-12170: Connection timeout: Verify Oracle is running, listener is up, and port 1521 is open.
• Java Version Compatibility: Use ojdbc8.jar for Java 8–17, ojdbc11.jar for Java 11 , etc.

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Basically, once the driver is in place and the connection string is correct, standard JDBC operations (queries, updates, etc.) work as expected. Just remember to handle SQLException and use try-with-resources to manage connections safely.

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