表结构：

create table test(
    id varchar2(32) primary key,
    name varchar2(32)
);

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
 
public class Test {
 
    /**
     * 使用Statement.RETURN_GENERATED_KEYS 指定返回生成主键
     */
    public static void main(String[] args) {
 
        PreparedStatement pst = null;
        ResultSet rs = null;
        Connection conn = ConnectionManager.getConnection();
        String sql = "insert into test(id,name) values(?,?)";
        try {
            //String generatedColumns[] = { "ID" };  //获得指定ID
            pst = conn.prepareStatement(sql, Statement.RETURN_GENERATED_KEYS); // 指定返回生成的主键
            pst.setString(1, "123x");
            pst.setString(2, "test");
            int ii = pst.executeUpdate();
 
            // 检索对象生成的键
            rs = pst.getGeneratedKeys();
            if (rs.next()) {
                System.out.println("数据主键：" + rs.getString(1));
            }
            ConnectionManager.closeAll(rs, pst, conn); // 关闭资源
 
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
 
public class ConnectionManager {
    public static final String DRIVER = "oracle.jdbc.driver.OracleDriver";
    public static final String URL = "jdbc:oracle:thin:@localhost:1521/orcl";
    public static final String USERNAME = "root";
    public static final String PASSWORD = "root";
    /**
     * 通过静态代码块 注册数据库驱动
     */
    static{
        try {
            Class.forName(DRIVER);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
 
    /**
     * 获得Connection
     *
     * @return
     */
    public static Connection getConnection() {
        Connection conn = null;
        try {
            conn = DriverManager.getConnection(URL,USERNAME,PASSWORD);
        }catch (SQLException e) {
            e.printStackTrace();
        }
        return conn;
    }
 
    /**
     * 关闭ResultSet
     * @param rs
     */
    public static void closeResultSet(ResultSet rs) {
        if (rs != null) {
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
 
    /**
     * 关闭Statement
     * @param st
     */
    public static void closeStatement(Statement st) {
        if (st != null) {
            try {
                st.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
 
    /**
     * 关闭Connection
     * @param conn
     */
    public static void closeConnection(Connection conn) {
        if (conn != null) {
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
    /**
     * 关闭全部
     * @param rs
     * @param sta
     * @param conn
     */
    public static void closeAll(ResultSet rs,Statement sta,Connection conn){
        closeConnection(conn);
        closeStatement(sta);
        closeResultSet(rs);
    }
 
}

数据主键：AAAT2zAANAAACalAAB

数据主键：oracle.sql.ROWID@452bb7e0

其实是test表的ROWID字段值

如果要获得指定的ID字段值 可以用如下方法：

String generatedColumns[] = { "ID" };
pst = conn.prepareStatement(sql, generatedColumns);

出处：http://blog.csdn.net/itmyhome1990/article/details/41600309

JDBC Insert语句插入Oracle数据库返回数据主键