通过jdbc连接数据库，拢共分三步：
第一步：下载一个JDBC的驱动，然后把jar包扔到项目里并add to build path；
第二步：去本地oracle文件夹下找到“TNSNAMES.ORA”文件，打开找到对应数据库的连接字符串，作为jdbc的连接字符串；
第三步：写代码，通过jdbc连接数据库。
从网上找了段代码，做了下修改。以下为查询数据库表中所有字段及字段值类型，遍历数据库表中所有数据（其中xxx均为需要替换的信息）：
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData; public class ConnectDB {
public static void main(String[] args) {
connectDB();
} public static void connectDB() {
Connection con = null;
PreparedStatement pre = null;
ResultSet results = null;
ResultSetMetaData resultSetMetaData = null;
try {
Class.forName("oracle.jdbc.driver.OracleDriver");
System.out.println("开始尝试连接数据库！");
// 必须用oracle文件夹下"tnsnames.ora"配置文件中配置的连接字符串进行远程连接数据库
String url = "jdbc:oracle:" + "thin:@(DESCRIPTION =" + "(ADDRESS_LIST ="
+ "(ADDRESS = (PROTOCOL = TCP)(HOST = xxx)(PORT = xxx))" + ")" + "(CONNECT_DATA ="
+ "(SERVICE_NAME = xxx)" + ")" + ")";
String user = "xxx";
String password = "xxx";
con = DriverManager.getConnection(url, user, password);
System.out.println("连接成功！");
String sql = "select * from xxx";
pre = con.prepareStatement(sql);
System.out.println("开始执行SQL语句！");
results = pre.executeQuery();
resultSetMetaData = results.getMetaData();
int columnCount = resultSetMetaData.getColumnCount();
// 获取数据库表所有字段名及字段值类型
for (int i = 1; i <= columnCount; i++) {
System.out.println(resultSetMetaData.getColumnName(i) + ":" + resultSetMetaData.getColumnTypeName(i));
}
while (results.next()) {
for (int i = 1; i <= columnCount; i++) {
System.out.print(results.getString(i)+"\t\t");
}
System.out.println();
} } catch (Exception e) {
e.printStackTrace();
} finally {
try {
if (results != null)
results.close();
if (pre != null)
pre.close();
if (con != null)
con.close();
System.out.println("数据库连接已关闭！");
} catch (Exception e) {
e.printStackTrace();
}
}
}
}