JDBC是实现java程序对各种数据库的访问，是一组类和接口，位于java.sql与javax.sql包
//1、加载驱动
Class.forName("com.mysql.jdbc.Driver");
//2、建立连接
String url="jdbc:mysql://localhost:3306/myschool";
String user ="root" ;
String password = "aaaaa123";
con= DriverManager.getConnection(url, user, password);
//创建sql语句
String sql ="SELECT studentno,studentName FROM student";
//创建对象
pstm =con.prepareStatement(sql);
//执行sql语句
rs=pstm.executeQuery();
//处理结果
System.out.println("编号：\t姓名：");
while(rs.next()) {
System.out.println(rs.getInt("studentno")+"\t"+rs.getString("studentName"));
}
//关闭资源
rs.close();
pstm.close();
con.close();Class.forName() 后加载 反射，事先不知道加载哪个类，运行时进行加载（桥接） 而Student stu =new Student() 先加载类
//增加数据
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Timestamp;
public class Test3 {
public static void main(String[] args) {
ResultSet rs =null;
PreparedStatement pstm=null;
Connection con =null;
//1、加载驱动
try {
Class.forName("com.mysql.jdbc.Driver");
//2、建立连接
String url="jdbc:mysql://localhost:3306/kgcnews";
String user ="root" ;
String password = "aaaaa123";
con= DriverManager.getConnection(url, user, password);
//创建sql语句
String sql ="INSERT INTO news_category (NAME,createDate) VALUES (?,?)";
//创建对象
pstm =con.prepareStatement(sql);
//给占位符赋值
pstm.setString(1, "哈哈");
pstm.setTimestamp(2, new Timestamp(10));
//执行sql语句
int i=pstm.executeUpdate();
//处理结果
if(i>=1) {
System.out.println("增加成功");
}else {
System.out.println("未增加");
}
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}finally {
if(null !=pstm) {
try {
pstm.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if(null !=con) {
try {
con.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
}增删改操作类似，只是替换sql语句即可
-
表示层
实际开发中的网页或者我们这里的test包，相当于现实中单客户
-
逻辑业务层
处理逻辑业务，我们这里的service包，相当于现实中的经理
-
数据处理层
底层处理数据层，这里的dao以及entity包，相当于员工
为什么要进行JDBC封装？ 主要是因为业务代码和数据访问代码的耦合。这就导致了可读性差、不利于后期修改和维护、不利于代码复用。 所以我们采用面向接口编程，可以降低代码之间的耦合性。
- 先建entity包，这个包中放实体类，这里我们放pet类,，将数据库表中的字段作为pet的属性，并为其添加set和get方法，以及相应的有参和无参构造方法
package entity;
public class Pet {
private int id;
private String name;
private int health;
private int love;
private String strain;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getHealth() {
return health;
}
public void setHealth(int health) {
this.health = health;
}
public int getLove() {
return love;
}
public void setLove(int love) {
this.love = love;
}
public String getStrain() {
return strain;
}
public void setStrain(String strain) {
this.strain = strain;
}
public Pet() {
super();
}
public Pet(int id, String name, int health, int love, String strain) {
super();
this.id = id;
this.name = name;
this.health = health;
this.love = love;
this.strain = strain;
}
}-
建dao包，写BaseDao基类
package dao; /** * 基类 * 1.创建连接对象 * 2.关闭资源 * 3.增加，删除，修改操作 * 4.查询方法 * @author Administrator * */ import java.io.IOException; import java.io.InputStream; import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.util.Properties; public class BaseDao { //静态变量可以保证类被加载的时候已经为连接参数赋值，并且只会执行一次 private static String driver =null; private static String url =null; private static String user =null; private static String password =null; /* * 静态代码块 */ static { Properties proper = new Properties(); InputStream is = BaseDao.class.getClassLoader().getResourceAsStream("database.properties"); try { proper.load(is); } catch (IOException e) { e.printStackTrace(); }finally { try { if(null!=is) { is.close(); } } catch (IOException e) { e.printStackTrace(); } } //为静态代码块赋值 driver=proper.getProperty("driver"); url=proper.getProperty("url"); user=proper.getProperty("user"); password=proper.getProperty("password"); } protected Connection conn =null; protected PreparedStatement pstmt =null; protected ResultSet rs =null; /** * 获取连接对象 * @return */ public Connection getConnection() { try { //1、加载驱动类 Class.forName(driver); //2、创建连接对象 conn=DriverManager.getConnection(url,user,password); } catch (Exception e) { e.printStackTrace(); } return conn; } /** * 关闭资源 * @param conn * @param pstmt * @param rs */ public void closeAll(Connection conn,PreparedStatement pstmt,ResultSet rs) { try { if(null!=conn) { conn.close(); } } catch (Exception e) { e.printStackTrace(); } try { if(null!=pstmt) { pstmt.close(); } } catch (Exception e) { e.printStackTrace(); } try { if(null!=rs) { rs.close(); } } catch (Exception e) { e.printStackTrace(); } } /** * 增删改操作 * @param sql * @param params * @return */ public int exxcutUpdate(String sql,Object[] params) { this.getConnection(); int result=-1; try { //3、创建prepareStatement对象 pstmt=conn.prepareStatement(sql); //4、为占位符赋值 if(null!=params) { for (int i = 0; i < params.length; i++) { pstmt.setObject(i+1, params[i]); } } //5.调用方法：执行sql语句 result=pstmt.executeUpdate(); } catch (SQLException e) { e.printStackTrace(); }finally { this.closeAll(conn, pstmt, rs); } return result; } /** * 查询方法 * @param sql * @param params * @return */ public ResultSet executQuery(String sql,Object... params) { this.getConnection(); try { //3、创建prepareStatement对象 pstmt=conn.prepareStatement(sql); //4、为占位符赋值 if(null!=params) { for (int i = 0; i < params.length; i++) { pstmt.setObject(i+1, params[i]); } } //5.调用方法：执行sql语句 rs=pstmt.executeQuery(); } catch (SQLException e) { e.printStackTrace(); } return rs; } }
-
写数据处理层的接口
package dao; import java.util.List; import entity.Pet; /** * 接口 * @author Administrator * */ public interface PetDao { /** * 查询所有宠物列表 * @return */ public List<Pet> findaLLPet(); /** * 根据编号查询宠物列表 * @param id * @return */ public Pet findAllPetById(int id); /** * 新增宠物 * @param pet * @return */ public int addPet(Pet pet); }
-
写数据处理层实现类PetDaoImpl，在dao包下面建子包impl
注意建子包要父包名点子包名，然后设置包的显示顺序
package dao.impl; import java.sql.SQLException; import java.util.ArrayList; import java.util.List; import dao.BaseDao; import dao.PetDao; import entity.Pet; /** * 实现类 * @author Administrator * */ public class PetDaoImpl extends BaseDao implements PetDao{ /** * 查询所有宠物 */ @Override public List<Pet> findaLLPet() { List<Pet> list =null; try { String sql = "SELECT id,NAME,health,love,strain FROM pet"; Object[] params=null; //调用方法 rs=this.executQuery(sql, params); if(null!=rs) { list = new ArrayList<>(); while(rs.next()) { Pet pet =new Pet(); pet.setId(rs.getInt("id")); pet.setName(rs.getString("name")); pet.setHealth(rs.getInt("health")); pet.setLove(rs.getInt("love")); pet.setStrain(rs.getString("strain")); list.add(pet); } } } catch (Exception e) { e.printStackTrace(); }finally { this.closeAll(conn, pstmt, rs); } return list; } /** * 根据id查宠物信息 */ @Override public Pet findAllPetById(int id) { Pet pet=null; try { String sql = "SELECT id,NAME,health,love,strain FROM pet WHERE id=?"; Object[] params= {id}; //调用方法 rs=this.executQuery(sql, params); if(null!=rs) { while(rs.next()) { pet =new Pet(); pet.setId(rs.getInt("id")); pet.setName(rs.getString("name")); pet.setHealth(rs.getInt("health")); pet.setLove(rs.getInt("love")); pet.setStrain(rs.getString("strain")); } } } catch (Exception e) { e.printStackTrace(); }finally { this.closeAll(conn, pstmt, rs); } return pet; } @Override public int addPet(Pet pet) { String sql ="INSERT INTO pet (id,NAME,health,love,strain) VALUES (DEFAULT,?,?,?,?)"; Object[] params= {pet.getName(),pet.getHealth(),pet.getLove(),pet.getStrain()}; int result =-1; try { result=this.exxcutUpdate(sql, params); } catch (Exception e) { e.printStackTrace(); } return result; } }
-
建service包，写业务处理层的接口PetService
package service; import java.util.List; import entity.Pet; /** * 业务逻辑类 * @author Administrator * */ public interface PetService { //查询所有宠物信息 public List<Pet> getAllPet(); //查询指定id宠物信息 public Pet getPetById(int id); //注册 public boolean register(Pet pet); }
-
写业务处理层的实现类PetServiceImpl，在service包下再建一个包叫impl
package service.impl; import java.util.List; import dao.PetDao; import dao.impl.PetDaoImpl; import entity.Pet; import service.PetService; /** * 业务逻辑类 实现类 * @author Administrator * */ public class PetServiceImpl implements PetService{ PetDao petDao = new PetDaoImpl(); //查询所有宠物信息 @Override public List<Pet> getAllPet() { return petDao.findaLLPet(); } //查询指定id宠物信息 @Override public Pet getPetById(int id) { return petDao.findAllPetById(id); } //注册（增加宠物） @Override public boolean register(Pet pet) { int result = petDao.addPet(pet); if(result==-1) { return false; }else { return true; } } }
-
建表示层测试包test
package test; import java.util.Scanner; import entity.Pet; import service.PetService; import service.impl.PetServiceImpl; /** * 表示层 * 测试类 * @author Administrator * */ public class Test { public static void main(String[] args) { Scanner input = new Scanner(System.in); PetService petService= new PetServiceImpl(); Pet pet =null; /*//测试查询所有宠物信息 List<Pet> list =petService.getAllPet(); System.out.println("编号 \t姓名\t健康值\t亲密度\t品种"); for (int i = 0; i < list.size(); i++) { pet=list.get(i); System.out.println(pet.getId()+"\t"+pet.getName()+"\t"+pet.getHealth()+"\t"+pet.getLove()+"\t"+pet.getStrain()); } */ /*//测试查询指定id宠物信息 System.out.print("请输入您要查找的宠物的id："); int id =input.nextInt(); pet=petService.getPetById(id); System.out.println("编号 \t姓名\t健康值\t亲密度\t品种"); System.out.println(pet.getId()+"\t"+pet.getName()+"\t"+pet.getHealth()+"\t"+pet.getLove()+"\t"+pet.getStrain());*/ //注册测试 pet = new Pet(); System.out.print("请输入姓名："); pet.setName(input.next()); System.out.print("请输入健康值："); pet.setHealth(input.nextInt()); System.out.print("请输入亲密度："); pet.setLove(input.nextInt()); System.out.print("请输入亲品种："); pet.setStrain(input.next()); boolean isSuccess=petService.register(pet); if(isSuccess) { System.out.println("注册成功1"); }else { System.out.println("注册失败1"); } } }
public class BaseDao {
//静态变量可以保证类被加载的时候已经为连接参数赋值，并且只会执行一次
private static String driver =null;
private static String url =null;
private static String user =null;
private static String password =null;
/*
* 静态代码块
*/
static {
Properties proper = new Properties();
InputStream is = BaseDao.class.getClassLoader().getResourceAsStream("database.properties");
try {
proper.load(is);
} catch (IOException e) {
e.printStackTrace();
}finally {
try {
if(null!=is) {
is.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
//为静态代码块赋值
driver=proper.getProperty("driver");
url=proper.getProperty("url");
user=proper.getProperty("user");
password=proper.getProperty("password");
}
}
项目右键new一个resouces folder，然后new一个file，名字以.properties作为后缀名，配置文件是键值对形式存在，名字自己宿便取
driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/epet?useUnicade=true&characterEncoding=UTF-8
user=root
password=aaaaa123/*
SQLyog Ultimate v11.24 (32 bit)
MySQL - 5.1.47-community : Database - epet
------
*/
/*!40101 SET NAMES utf8 */;
/*!40101 SET SQL_MODE=''*/;
/*!40014 SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0 */;
/*!40014 SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0 */;
/*!40101 SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='NO_AUTO_VALUE_ON_ZERO' */;
/*!40111 SET @OLD_SQL_NOTES=@@SQL_NOTES, SQL_NOTES=0 */;
CREATE DATABASE /*!32312 IF NOT EXISTS*/`epet` /*!40100 DEFAULT CHARACTER SET utf8 */;
USE `epet`;
/*Table structure for table `master` */
DROP TABLE IF EXISTS `master`;
CREATE TABLE `master` (
`id` int(11) NOT NULL AUTO_INCREMENT COMMENT '序号',
`name` varchar(12) DEFAULT NULL COMMENT '姓名',
`password` varchar(20) DEFAULT NULL COMMENT '密码',
`money` int(11) DEFAULT NULL COMMENT '元宝数',
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8;
/*Data for the table `master` */
insert into `master`(`id`,`name`,`password`,`money`) values (1,'jack','1234',2000),(2,'rose','1234',3000),(3,'smith','1234',4000);
/*Table structure for table `pet` */
DROP TABLE IF EXISTS `pet`;
CREATE TABLE `pet` (
`id` int(11) NOT NULL AUTO_INCREMENT COMMENT '序号',
`name` varchar(12) DEFAULT NULL COMMENT '昵称',
`health` int(11) DEFAULT NULL COMMENT '健康值',
`love` int(11) DEFAULT NULL COMMENT '亲密度',
`strain` varchar(20) DEFAULT NULL COMMENT '品种',
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=11 DEFAULT CHARSET=utf8;
/*Data for the table `pet` */
insert into `pet`(`id`,`name`,`health`,`love`,`strain`) values (1,'欧欧',80,15,'雪瑞纳'),(5,'亚亚',100,0,'拉布拉多'),(9,'美美',90,66,'雪瑞纳'),(10,'菲菲',90,50,'拉布拉多');
/*!40101 SET SQL_MODE=@OLD_SQL_MODE */;
/*!40014 SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS */;
/*!40014 SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS */;
/*!40111 SET SQL_NOTES=@OLD_SQL_NOTES */;