JDBC(oracle)

一.jdbc访问数据库的步骤:
1. 注册驱动
   Class.forName("oracle.jdbc.driver.OracleDriver");
2. 根据url/dbUser/dbPwd构造连接(Connection)
   Connection conn = DriverManager.getConnection(url, dbUser, dbPwd);
3. 根据Connection对象构造语句(Statement)对象
   由语句对象传递sql语句到数据库,并接收结果.
   Statement stmt = conn.createStatement();
  
   if 查询: 返回ResultSet
      ResultSet rs = stmt.executeQuery(sql);
   if DML(insert,update,delete): 返回影响的记录数
      int n = stmt.executeUpdate(sql);
4. 关闭资源   
   rs.close();
   stmt.close();
   conn.close();

需要用到的接口
java.sql.*
Connection
Statement 和PreparedStatement
ResultSet
DriverManager

例子：

 

package day1;
import java.sql.*;

public class JDBCDemo {
 //驱动
 private static final String DRIVER
  ="oracle.jdbc.driver.OracleDriver";
 //连接字符串
 private static String URL 
  = "jdbc:oracle:thin:@192.168.2.205:1521:hqr";
 //数据库的帐号和密码
 private static final String DBUSER = "openlab";
 private static final String DBPWD = "open123";

 /**
  * 使用JDBC API 连接数据库
  */
 public static void main(String[] args) {
  //findAllUers();
  System.out.println(login("1002","1234"));
 }
 
 private static void findAllUers() {
  try {
   //1.注册驱动
   Class.forName(DRIVER);
   //2.构造连接
   Connection conn 
   = DriverManager.getConnection(URL, DBUSER, DBPWD);
   //3.构造语句对象,执行sql语句,并接受结果
   String sql = "select * from users_hqr";
   Statement stmt = conn.createStatement();
   ResultSet rs = stmt.executeQuery(sql);
   //遍历结果集
   while(rs.next()){
    //操作一行数据
    System.out.println(rs.getString("name"));
   }
   
   //4.关闭资源
  } catch (Exception e) {
   e.printStackTrace();
  }
 }
}

封装成ConntceionUtils.java类
需要用到的ConnectionUtils.java类

package day1;
import java.io.*;
import java.sql.*;
import java.util.*;
/**
 * 工具类,负责读入属性文件中的参数
 * 注册驱动,获得连接,关闭资源
 */
public class ConnectionUtils {
 private static String driver;
 private static String url;
 private static String dbUser;
 private static String dbPwd;
 public static void getParam(String filename){
  Properties props = new Properties();
  try {
   //把file中的键值对数据装载入集合中
   props.load(new FileInputStream(new File(filename)));
   driver = props.getProperty("driver");
   url = props.getProperty("url");
   dbUser = props.getProperty("dbUser");
   dbPwd = props.getProperty("dbPwd");
  } catch (FileNotFoundException e) {
   e.printStackTrace();
  } catch (IOException e) {
   e.printStackTrace();
  }
 }
 /**
  * 根据四个全局变量参数构造连接对象并返回
  * @return Connection对象 
  */
 public static Connection getConnection(){
  Connection conn = null;
  try {
   getParam("src/db_oracle.properties");
   Class.forName(driver);
   conn = DriverManager.getConnection(url, dbUser, dbPwd);
  } catch (Exception e) {
   e.printStackTrace();
  }
  return conn;
  
 }
 public static void close(ResultSet rs){
  if(rs != null){
   try {
    rs.close();
   } catch (SQLException e) {
    e.printStackTrace();
   }
  }
 }
 public static void close(Statement stmt){
  if(stmt != null){
   try {
    stmt.close();
   } catch (SQLException e) {
    e.printStackTrace();
   }
  }
 }
 public static void close(Connection conn){
  if(conn != null){
   try {
    conn.close();
   } catch (SQLException e) {
    e.printStackTrace();
   }
  }
 }
 
}

二.JDBC 的 DML操作(增,改,删)

例子:

package day1;
import java.sql.*;
public class JDBCDemo_DML {
 public static void main(String[] args) {
  System.out.println(changePwd(1002,5678)?"update success":"update faild");
  System.out.println(deleteUser(1001)?"success":"faild");
  addUser(1015,"dsads",1234,"19212512457","24@2.com");
 }
 public static boolean changePwd(int id,int pwd){
  String sql = "update users_hqr set pwd = " + pwd +
     " where id = " + id;
  boolean flag  = false;
  Connection conn = ConnectionUtils.getConnection();
  Statement stmt = null;
  try {
   stmt = conn.createStatement();
   int n = stmt.executeUpdate(sql);
   if(n == 1){
    flag = true;
   }
  } catch (SQLException e) {
   e.printStackTrace();
  } finally{
   ConnectionUtils.close(stmt);
   ConnectionUtils.close(conn);
  }
  return flag;
 }
 
 /**
  * 删除考生
  * @param id 指定的id
  * @return if成功返回true,否则返回false;
  */
 public static boolean deleteUser(int id){
  String sql = "delete users_hqr where id = " + id;
  boolean flag = false;
  Connection conn = ConnectionUtils.getConnection();
  Statement stmt = null;
  try {
   stmt = conn.createStatement();
   int n = stmt.executeUpdate(sql);
   if (n == 1) {
    flag = true;
   }
  } catch (SQLException e) {
   e.printStackTrace();
  } finally {
   ConnectionUtils.close(stmt);
   ConnectionUtils.close(conn);
  }
  return flag;
 }
 /**
 *添加用户方法1
 */
 public static boolean addUser_1(int id,int pwd,String name,
   String phone,String email){
  String sql = "insert into users_hqr " +
    "values ("+id+",'"+name+"',"+pwd+",'"+phone+"','"+email+"')" ;
  boolean flag  = false;
  Connection conn = ConnectionUtils.getConnection();
  Statement stmt = null;
  try {
   stmt = conn.createStatement();
   int n = stmt.executeUpdate(sql);
   if(n == 1){
    flag = true;
   }
  } catch (SQLException e) {
   e.printStackTrace();
  } finally{
   ConnectionUtils.close(stmt);
   ConnectionUtils.close(conn);
  }
  return flag;
 }
 /**
 *添加用户方法2
 */
 public static boolean addUser(int id,String name,int pwd,
   String phone,String email){
  String sql = "insert into users_hqr values(?,?,?,?,?)";
  boolean flag  = false;
  Connection conn = ConnectionUtils.getConnection();
  PreparedStatement stmt = null;
  try {
   stmt = conn.prepareStatement(sql);
   //给sql语句中的占位符赋值
   stmt.setInt(1, id); 
   stmt.setString(2, name);
   stmt.setInt(3, pwd);
   stmt.setString(4, phone);
   stmt.setString(5, email);
   stmt.executeUpdate();
  } catch (Exception e) {
   e.printStackTrace();
  } finally{
   ConnectionUtils.close(stmt);
   ConnectionUtils.close(conn);
  }
  return flag;
 }
}

三.JDBC中的事务(需要导入ConnectionUtils类)
sqlplus: 显式终止事务(提交 或 回滚)
  set autocommit on|off :切换是否自动提交
 默认关闭自动提交(off)
JDBC:自动提交,autocommit on
  conn.setAutoCommit(false);
 dml1: -500;
 dml2:+500;
 if(没有问题) conn.commit();
 else conn.rollback

例子:
1.帐户表,帐户A,帐户B
2.程序TransactionDemo
conn.setAutoCommit(false);
int n1 = stmt.executeUpdate(sql1);
int n2 = stmt.executeUpdate(sql2);

TransactionDemo.java:

package day2;
import java.sql.*;

import day1.ConnectionUtils;
/**
 * 测试JDBC中的事务
 * @author soft01
 *
 */
public class TransactionDemo {
 public static void main(String[] args) {
  transferMoney(500);
 }
 /**
  * 转帐，从帐户A转到帐户B
  */
 public static void transferMoney(double money){
  String sql1 = "update account_hqr set money = money - " + money
   + " where id = 'A' ";
  String sql2 = "update account_hqr set money = money + " + money
   + " where id = 'B' ";
  Connection conn = ConnectionUtils.getConnection();
  Statement stmt = null;
  try{
   conn.setAutoCommit(false);//关闭自动提交
   stmt = conn.createStatement();
   int n1 = stmt.executeUpdate(sql1);
   int n2 = stmt.executeUpdate(sql2);
   if(n1==1 && n2==1){
    conn.commit();
   }else{
    conn.rollback();
   }
  }catch (Exception e){
   try {
    conn.rollback();
   } catch (SQLException e1) {
    // TODO Auto-generated catch block
    e1.printStackTrace();
   }
   e.printStackTrace();
  } finally{
   ConnectionUtils.close(stmt);
   ConnectionUtils.close(conn);
  }
  
 }

}

四.JDBC中的批处理
批处理:批量处理SQL语句
 缓存:用来存放批量的SQL语句.

比如:JDBC中批量执行insert语句
1.create table mytemp_hqr(id number primary key);

2.BatchDemo.java
conn.setAutoCommit(false);
for(int i = 0; i < 10000; i +=){
 String sql =" insert into mytemp values(?)";
 stmt.addBatch(sql);
 if(i % 1000 ==0){
  stmt.executeBatch(); 
  stmt.clearBatch();
 }
}
stmt.executeBatch();
conn.commit();
批处理时必须关掉JDBC的自动提交功能

源代码:

package day2;
import java.sql.*;

import day1.ConnectionUtils;
/**
 * 测试JDBC批量处理操作
 * @author soft01
 *
 */
public class BatchDemo {
 public static void main(String[] args) {
  addTemp();
 }
 /**
  * 批量增加数据到mytemp_hqr表中
  */
 public static void addTemp() {
  String sql = "insert into mytemp_hqr values(?)";
  Connection conn = ConnectionUtils.getConnection();
  PreparedStatement stmt = null;
  try { 
   //关闭自动提交
   conn.setAutoCommit(false);
   //获得于编译语句对象
   stmt = conn.prepareStatement(sql);
   //循环100次,把sql加入到Batch中
   for(int i=1;i<=100;i++){
     
    stmt.setInt(1, i);
    stmt.addBatch();
    if(i % 10 ==0){
     stmt.executeBatch();
     stmt.clearBatch();
    }
   }
   stmt.executeBatch();
   conn.commit();
  } catch (SQLException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
 }
}