java定制网站连接数据库
步骤
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1.定制网站加载数据库
Class.forName("com.mysql.jdbc.Driver");
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2.定制网站链接数据库
public static final String url="jdbc:mysql://localhost:3306/Product?userUnicode=true&characterEncoding=utf8&useSSL=false"; public static final String user ="root"; public static final String password="root";Connection conn = DriverManager.getConnection(url, user, password);
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3.定制网站数据库操纵对象
String sql="SQL语句"; PreparedStatement pst=conn.prepareStatement(sql);//定制网站表示预编译的SQL定制网站语句的对象。 //SQL定制网站语句已预编译并存储在PreparedStatement对象中。 定制网站然后可以使用该对象多定制网站次有效地执行此语句
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4.执行SQL语句
pst.execute();
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5.定制网站关闭数据库
conn.close();pst.close();
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基础的增删改查
思路: 先将基本的框架写出来 ,增删改查都在方法里面写
创建商品类
商品类 大概就是创建属性,get set 方法,构造有参无参方法,toString方法等几个
package com.po;//重写equals和HashCode两个方法public class Product { private int id; private String name; private double price; public Product(int id, String name, double price) { super(); this.id = id; this.name = name; this.price = price; } public Product(String name, double price) { super(); this.name = name; this.price = price; } private String info; private String param; 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 double getPrice() { return price; } public void setPrice(double price) { this.price = price; } public String getInfo() { return info; } public void setInfo(String info) { this.info = info; } public String getParam() { return param; } public void setParam(String param) { this.param = param; } public Product() { super(); // TODO Auto-generated constructor stub } public Product(int id, String name, double price, String info, String param) { super(); this.id = id; this.name = name; this.price = price; this.info = info; this.param = param; } public Product(String name, double price, String info, String param) { super(); this.name = name; this.price = price; this.info = info; this.param = param; } @Override public String toString() { return "Product [id=" + id + ", name=" + name + ", price=" + price + ", info=" + info + ", param=" + param + "]"; } @Override public boolean equals(Object obj) { boolean flag=false; if(this==obj) { flag=false; }else if(obj instanceof Product){ Product p=(Product)obj; if(this.id==p.id&&this.name.equals(p.name)) { flag=true; } } return flag; } @Override public int hashCode() { // TODO Auto-generated method stub return id+name.hashCode(); } }
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创建接口方法类
定义出增删改查的方法类;
public interface IPoroductDAO { //增加的方法 int add(Product p); //删除的方法 int delete(int id); //修改的方法 int update(Product p); //根据id查询的方法 Product query(int id); //全部查询的方法 List<Product> query();}
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因为连接数据库有冗余所以将连接数据库的公共各部分提出到新的类里面
即连接数据库的第1 ,2,5步提出来
package com.util;import java.sql.Connection;import java.sql.DriverManager;import java.sql.PreparedStatement;import java.sql.SQLException;public class DBConnection { public static final String url="jdbc:mysql://localhost:3306/Product?useUnicode=true&charaEncoding=utf8"; public static final String user ="root"; public static final String password="123456"; //类第一次加载的时候执行一次 static { try { //1.加载驱动 Class.forName("com.mysql.jdbc.Driver"); } catch (ClassNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); }//有可能报错 } //2.数据库链接 public static Connection getConn() { Connection conn =null; try { conn= DriverManager.getConnection(url, user, password); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); }return conn; } public static void close(Connection conn,PreparedStatement pst) { try { //5.关闭数据库 conn.close(); pst.close(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } } }
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创建方法实现的类
public class ProductDAOmp1 implements IPoroductDAO { //将声明放在公共部分以便调取 //与特定数据库的连接(会话)。 执行SQL语句并在连接的上下文中返回结果。 Connection对象的数据库能够提供描述其表,其支持的SQL语法,其存储过程,此连接的功能等的信息。 该信息是用getMetaData方法获得的。 Connection conn =null; PreparedStatement pst =null;}
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增删改查的方法都在ProductDAOmp1类中
一下是为了更直观的浏览
增加商品方法
public int add(Product p) { try { //获取到含有连接数据库信息的类 conn=DBConnection.getConn(); //3.数据库操纵对象 String sql="Insert into goods (name,price,info,param) values(?,?,?,?)" pst=conn.prepareStatement(sql);//SQL语句已预编译并存储在PreparedStatement对象中。 //setString(int parameterIndex, String x) 将指定的参数设置为给定的Java String值 pst.setString(1,p.getName()); //即将p.getName()所获得值赋给第1个问号的地方 pst.setDouble(2.p.getPrice());//同理将getPrice()所获得的值赋给第2个问号地方 pst.setString(3, p.getInfo()); pst.setString(4,p.getParam()); //执行sql语句 pst.executeUpdate(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); }finally { //5.关闭数据库 DBConnection.close(conn, pst); } }}
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删除商品的方法
public int delete(int id) { int flag = 0; try { //调用写好的数据库驱动类 conn=DBConnection.getConn(); //3.数据库操纵对象 String sql="delete from goods where id=?"; pst= conn.prepareStatement(sql); //给参数赋值 pst.setInt(1, id);//parameterIndex 代表第几个❓ //4.执行SQL flag = pst.executeUpdate(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); }finally { //5.关闭数据库 DBConnection.close(conn, pst); } return flag; }
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根据id进行查询的方法
public Product query(int id) {//与之前不同的是需要用到集合 将从ResultSet取到的值赋给Arraylist以便输出 //连接数据库 conn=DBConnection.getConn();//创建集合 List<Product> list=new ArrayList<Product>(); //3.数据库操纵对象 String sql="select * from goods where id=?"; pst=conn.prepareStatement(sql); pst.set(1,p.getId()); //因为executeQery会有ResultSet的返回值 ResultSet rs=pst.executeQuery(); //将rs中的值取出给到集合里面 while(rs.next()){ Product p=new Product(); p.setId(rs.getInt("id"));//将rs中获取到的id赋值给p p.setName(rs.getString("name")); p.setPrice(rs.getDouble("price")); p.setInfo(rs.getString("info")); p.setParam(rs.getString("param")); //添加到容器 list.add(p); } //遍历输出 for(int i=0;i<list.size();i++) { System.out.println(list.get(i)); } } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); }finally { //关闭 DBConnection.close(conn, pst); } return null; }
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将所有元素都查询出来
public List<Product> query() { //连接数据库 ArrayList list=new ArrayList<Product>(); conn=DBConnection.getconn(); //数据库操纵对象 String sql="select * from goods" pst=conn.prepareStatement(sql); ResultSet rs= pst.executeQuery(); while(rs.next()){ Product p new Product(); p.setInt(rs.getInt("id")); p.setString(rs.getString("name")); p.setDouble (rs.getDouble("price")); p.setInfo(rs.getString("info")); p.setParam(rs.getString("param")); list.add(p); } for(int i=0;i<;list.size();i++){ System.out.println(list.get(i)); } } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); }finally { //5.关闭数据库 DBConnection.close(conn, pst); } } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); }finally { //5.关闭数据库 DBConnection.close(conn, pst); } }
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根据id对数据进行修改
public int update(Product p) {//连接数据库conn=DBConnection.getconn();//数据库操纵对象 String sql="update goods set name=?,price=? where id =?" pst=conn.prepareStatement(sql); pst.setString(1,p.setName()); pst.setDouble(2,p.setPrice()); pst.setInt(3,p.getId()); pst.executeUpdate(); } } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } return 0; }}
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这样几种方法就构造完成
编写test类进行测试
package com.view;import java.util.List;import java.util.Scanner;import com.dao.IPoroductDAO;import com.dao.ProductDAOmp1;import com.po.Product;public class Test { public static void main(String[] args) { // 循环写一个菜单的切换 // 输入1--添加 2--删除 3--查询 Scanner sc = new Scanner(System.in); IPoroductDAO pro = new ProductDAOmp1(); while (true) { System.out.println("请输入你的操作:1--添加 2--删除 3--查询单个 4--查询所有 5--进行商品修改 6-退出系统"); int k = sc.nextInt(); if (k == 1) { System.out.println("输入name:"); String name = sc.next(); System.out.println("输入price:"); double price = sc.nextDouble(); System.out.println("输入info:"); String info = sc.next(); System.out.println("输入param:"); String param = sc.next(); Product p = new Product( name, price, info, param); pro.add(p); } else if (k == 2) { System.out.println("输入要删除的id:"); int id = sc.nextInt(); // 调用delete方法 int flag = pro.delete(id); if (flag == 1) { System.out.println("成功删除id为"+id+"的商品"); } else if(flag == 0){ System.out.println("没找到此商品"); } } else if (k == 3) { System.out.println("输入要查询的id:"); int id = sc.nextInt(); pro.query(id); }else if(k==5){ System.out.println("请输入要修改商品的id号码"); int a=sc.nextInt(); System.out.println("请输入要修改的名称"); String b=sc.next(); System.out.println("请输入要修改的价格"); Double c=sc.nextDouble(); Product p = new Product(a,b,c); pro.update(p); }else if(k==6) { System.exit(0);; } } }}
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