Java JDBC连接数据库常见操作总结

# db.properties
jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/demo?useUnicode=true&characterEncoding=UTF-8
jdbc.username=root
jdbc.password=123456
# paramter for BasicDataSource
initSize=2
maxActive=2

# db.properties
jdbc.driver=oracle.jdbc.OracleDriver
jdbc.url=jdbc:oracle:thin:localhost:1521:orcl
jdbc.username=root
jdbc.password=123456
# paramter for BasicDataSource
initSize=2
maxActive=2

package JDBC;
import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Properties;
/**
 * JDBC连接数据库管理工具类
 */
public class JDBC {
  static String driver;
  static String url;
  static String username;
  static String password;
  static {
    try {
      Properties cfg = new Properties();
      InputStream in = JDBC.class.getClassLoader().getResourceAsStream("db.properties");
      cfg.load(in);  //将文件内容加载到Properties对象中(以散列表形式存在)
      driver = cfg.getProperty("jdbc.driver");
      url = cfg.getProperty("jdbc.url");
      username = cfg.getProperty("jdbc.username");
      password = cfg.getProperty("jdbc.password");
      in.close();
    } catch (IOException e) {
      e.printStackTrace();
      throw new RuntimeException(e);
    }
  }
  /**
   * 创建数据库连接
   */
  public static Connection getConnection() {
    try {
      Class.forName(driver); //注册驱动
      Connection conn = DriverManager.getConnection(url, username, password);
      return conn;
    } catch (Exception e) {
      e.printStackTrace();
      throw new RuntimeException(e);
    }
  }
  /*
   * 关闭数据库的连接
   */
  public static void close(Connection conn) {
    if (conn != null) {
      try {
        conn.close();
      } catch (SQLException e) {
        e.printStackTrace();
      }
    }
  }
}

package JDBC;
import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.Properties;
import org.apache.commons.dbcp.BasicDataSource;
/**
 * 连接池版本的数据库连接管理工具类
 */
public class DBUtils {
  private static String driver;
  private static String url;
  private static String username;
  private static String password;
  private static int initSize;
  private static int maxActive;
  private static BasicDataSource dbs;
  static {
    dbs = new BasicDataSource();
    Properties cfg = new Properties();
    try {
      InputStream in = DBUtils.class.getClassLoader().getResourceAsStream("db.properties");
      cfg.load(in);
      // 初始化参数
      driver = cfg.getProperty("jdbc.driver");
      url = cfg.getProperty("jdbc.url");
      username = cfg.getProperty("jdbc.username");
      password = cfg.getProperty("jdbc.password");
      initSize = Integer.parseInt(cfg.getProperty("initSize"));
      maxActive = Integer.parseInt(cfg.getProperty("maxActive"));
      in.close();
      // 初始化连接池
      dbs.setDriverClassName(driver);
      dbs.setUrl(url);
      dbs.setUsername(username);
      dbs.setPassword(password);
      dbs.setInitialSize(initSize);
      dbs.setMaxActive(maxActive);
    } catch (IOException e) {
      e.printStackTrace();
      throw new RuntimeException(e);
    }
  }
  /**
   * 创建数据库连接,从连接池中获取连接,如果连接池满了,则等待.
   */
  public static Connection getConnection() {
    try {
      Connection conn = dbs.getConnection();
      return conn;
    } catch (SQLException e) {
      e.printStackTrace();
      throw new RuntimeException(e);
    }
  }
  /*
   * 关闭数据库的连接,归还到连接池
   */
  public static void close(Connection conn) {
    if (conn != null) {
      try {
        conn.close();
      } catch (SQLException e) {
        e.printStackTrace();
      }
    }
  }
  //回滚，仅在禁用自动提交时使用
  public static void rollback(Connection conn) {
    if (conn != null) {
      try {
        conn.rollback();
      } catch (SQLException e) {
        e.printStackTrace();
      }
    }
  }
}

Connection conn=null;
try{
  conn=DbUtils.getConnection();
  Statement st=conn.createStatement();
  String sql="select id, name from people";
  ResultSet rs=st.executeQuery(sql);
  while(rs.next()){
    int id=rs.getInt("id");
    String name=rs.getString("name");
    System.out.println(id+","+name);
  }
  //结果集元数据
  ResultSetMetaData meta = rs.getMetaData();
  int n = meta.getColumnCount(); //多少列
  for(int i=1; i<=n; i++){
    String name= meta.getColumnName(i); //获取列名
    System.out.println(name);
  }
  rs.close();//释放查询结果
  st.close();//释放语句对象
}catch(Exception e){
  e.printStackTrace();
}finally {
  DbUtils.close(conn);
}

try {
  conn = DBUtils.getConnection();
  conn.setAutoCommit(false);  //取消自动提交, 后续手动提交
  String sql="update people set name=? where id=? ";
  PreparedStatement ps= conn.prepareStatement(sql);
  //按照顺序发送参数
  ps.setString(1, "Lao Wang");
  ps.setInt(2, 100);
  //执行"执行计划"
  int n=ps.executeUpdate();
  conn.commit();  //手动提交
} catch (Exception e) {
  e.printStackTrace();
  DBUtils.rollback(conn); //异常回滚
}finally{
  DBUtils.close(conn);
}

Statement st=conn.createStatement();
st.addBatch(sql1); //sql1 添加到Statement的缓存中
st.addBatch(sql2);
st.addBatch(sql3);
int[] ary=st.executeBatch();  //执行一批SQL

PreparedStatement ps = conn.prepareStatement(sql);
ps.setInt(1, 1);
ps.setString(2, "wang");
ps.addBatch();   //将参数添加到ps缓存区
ps.setInt(1, 2);
ps.setString(2, "li");
ps.addBatch();   //将参数添加到ps缓存区
int[] ary = ps.executeBatch(); // 批量执行