java连接数据库查询

对整个表进行查询并输出

package text;
import java.sql.*;
import java.util.Collection;
import java.util.Scanner;
public class Demo2 {
	public static void main(String args[]) {
		String URL="jdbc:mysql://localhost:3306/db";    
   	 String USER="root";
   	 String PASSWORD="root";   
   	 Statement sta=null;
   	 Connection con=null;
   	 ResultSet rs =null;
   	try {
		Class.forName("com.mysql.jdbc.Driver");
		con=DriverManager.getConnection(URL,USER,PASSWORD);
		sta =con.createStatement();
		String sql="select * from s ";
		rs =sta.executeQuery(sql);
		while(rs.next()) {
			int id=rs.getInt("id");
			String name=rs.getString("name");
			int age =rs.getInt("age");
			System.out.println(id+"-->"+name+"-->"+age);
		}
	} catch (ClassNotFoundException e) {
		// TODO Auto-generated catch block
		e.printStackTrace();
	} catch (SQLException e) {
		// TODO Auto-generated catch block
		e.printStackTrace();
	}
   	finally {
   		if(rs!=null)
   		try {
			rs.close();
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
   		if(sta!=null)
			try {
				sta.close();
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
   		if(con!=null)
			try {
				con.close();
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
   	}
	}
}

对输入的用户名密码进行查询与表中原有的进行比对

package text;
import java.sql.*;
import java.util.Collection;
import java.util.Scanner;
public class Demo4 {
	 String URL="jdbc:mysql://localhost:3306/db";    
	 String USER="root";
     String PASSWORD="root";   
	public void login(){
		 Statement sta=null;
	   	 Connection con=null;
	   	 ResultSet rs =null;
			try {
				Class.forName("com.mysql.jdbc.Driver");
				con=DriverManager.getConnection(URL, USER, PASSWORD);
				sta =con.createStatement();
				Scanner sc=new Scanner(System.in);
				System.out.println("请输入用户名:");
				String u=sc.nextLine();
				System.out.println("请输入密码:");
				String paw=sc.nextLine();
				String sql="select count(*) from text where username='"+u+"' and password='"+paw+"'";
				rs=sta.executeQuery(sql);
				int count =-1;
				while(rs.next()) {
					count=rs.getInt(1);
				}
				 if(count>0)
	         	System.out.println("login succe！");
	             else
	         	 System.out.println("login error!");
			} catch (ClassNotFoundException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
            catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
	}
	public static void main(String args[]) {
		Demo4 d =new Demo4();
		d.login();
	}
}