JDBC实现数据库的增删查改二

摘要：preparedstatement实现增删查改的操作： Statement 和 PreparedStatement之间的关系和区别. 关系：PreparedStatement继承自Statement,都是接口 区别：PreparedStatement可以使用占位符，是预编译的，批处理比Statement效率高

详解：

1、PreparedStatement：表示预编译的 sql 语句的对象。 接口：public interface PreparedStatement extends Statement之间的继承关系 sql 语句被预编译并存储在 PreparedStatement 对象中。然后可以使用此对象多次高效地执行该语句。 注：用于设置 IN 参数值的设置方法（setShort、setString 等等）必须指定与输入参数的已定义 sql 类型兼容的类型。例如，如果 IN 参数具有 sql 类型 INTEGER，那么应该使用 setInt 方法，问号的位置也是应该注意的，因为第一个问好的位置为1，第二个问号的位置为2.以此类推。

2、我觉的最好的就是不用在进行数据的拼接。

增加数据库的信息的操作：

 

package com.hm.test03;

import java.sql.Connection;
import java.sql.PreparedStatement;

import com.hm.connect.Demo01;
import com.hm.model.User;

public class Demo04 {

    private static  void add(User user) throws Exception {
        // Todo Auto-generated method stub
        Demo01 db = new Demo01();
        
        Connection con = db.getcon();
        
        String sql = "insert into t_user value(?,?,?)";
            
        PreparedStatement pstmt = con.prepareStatement(sql);
        
        pstmt.setString(1, user.getId());
        
        pstmt.setString(2, user.getName());
        
        pstmt.setString(3, user.getpassword());
        
        int result = pstmt.executeUpdate();
        
        pstmt.close();
        
        db.closeCon(con);
        
        System.out.println(result);
        
        
    }
    
    public static void main(String[] args) throws Exception {
        User user = new User("48","dwubudw","ehubfeb");
        
        add(user);
    }
}

 

 

 

修改数据库的信息：

package com.hm.test03;

import java.sql.Connection;
import java.sql.PreparedStatement;

import com.hm.connect.Demo01;
import com.hm.model.User;

public class Demo1 {
    private static Demo01 db = new Demo01();  
    
    public static int updatebook (User user) throws Exception {
        Connection con =  db.getcon();
        
        
        String sql = "update t_user set username = ?,password = ? where id = ?";
        
        PreparedStatement pstmt = con.prepareStatement(sql);
        
        pstmt.setString(1,user.getName() );
        pstmt.setString(2,user.getpassword());
        pstmt.setString(3, user.getId());
        
        int result = pstmt.executeUpdate();
        
        pstmt.close();
        db.getcon();
        return result;
        
        
    }
    public static void main(String[] args) throws Exception {
        User user = new User("2","nijao","ebfekbw");
        
        int result =  updatebook(user);
        
        System.out.println(result);
                
                
    }
}

删除数据信息的操作：

package com.hm.test03;

import java.sql.Connection;
import java.sql.PreparedStatement;

import com.hm.connect.Demo01;
import com.hm.model.User;

public class Demo2 {
 
    private  static Demo01 db = new Demo01 ();
    
    private static int  delete(User user ) throws Exception {
        // Todo Auto-generated method stub
        Connection  con = db.getcon();
        String sql = "delete from t_user where id = ?";
        
        PreparedStatement pstmt = con.prepareStatement(sql);
        pstmt.setString(1, user.getId());
        int result = pstmt.executeUpdate();
        pstmt.close();
        db.closeCon(con);
        return result;
    }
    
    public static void main(String[] args) throws Exception {
        User user  = new User("5","hdeu","heufuwbfu");
        
        int result = delete(user);
        
        System.out.println(result);
    }
}

查看数据库信息的操作：（三种方式不同的查看方式）

package com.hm.test03;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;

import com.hm.connect.Demo01;
import com.hm.model.User;


public class Demo03 {

    private static Demo01 db = new Demo01();
    
    
    private static void list() throws Exception {
        Connection con  = db.getcon();
        
        String sql = "select *from t_user";
        
        PreparedStatement pstmt = con.prepareStatement(sql);//預處理進行占位使用
        
        ResultSet  rs = pstmt.executeQuery();
        
        while (rs.next()) {
            String id  = rs.getString(1);
            String name = rs.getString(2);
            String password = rs.getString(3);
            
            System.out.println("id = " + id +",name = " + name + ",password = " + password);
        }
        
        
    }
    private static void list1() throws Exception {
        Connection con  = db.getcon();
        
        String sql = "select *from t_user";
        
        PreparedStatement pstmt = con.prepareStatement(sql);//預處理進行占位使用
        
        ResultSet  rs = pstmt.executeQuery();
        
        while (rs.next()) {
            String id  = rs.getString("id");
            String name = rs.getString("userName");
            String password = rs.getString("password");
            
            System.out.println("id = " + id +",name = " + name + ",password = " + password);
        }
        
        
    }
    private static List<User> list3() throws Exception{
        List <User> userlist  = new ArrayList<User>();
        
        Connection con = db.getcon();
        
        String sql = "select *from t_user";
        
        PreparedStatement pstmt  = con.prepareStatement(sql);
        
        ResultSet rs = pstmt.executeQuery();
        
        while(rs.next()) {
            String id = rs.getString("id");
            
            String name  = rs.getString("userName");
            
            String password  = rs.getString("password");
            
            User user = new User(id, name, password);
            
            userlist.add(user);
        }
        
        
        return userlist;
    }
    
    public static void main(String[] args) throws Exception {
        list();
        System.out.println("===============================");
        list1();
        System.out.println("===============================");
        List <User> userlist = list3();
        
        for (User user : userlist) {
            System.out.println(user);
        }
        
        
    }
}