关于增删改查的例子

通过前面的练习发现自己对于增删改查的知识仍然不够熟练，今天进行一个基于课程管理的增删改查功能的实现。

Dbutil:

package com.zh.util;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
import java.sql.SQLException;

public class DButil {
    public static Connection getConnection(){
        Connection conn = null;
        try {
        Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
        String url="jdbc:mysql://localhost:3306/teacher_class?serverTimezone=UTC";
        conn=DriverManager.getConnection(url, "root", "hao19990507.");
        }catch (Exception e){
            e.printStackTrace();
        }
        return conn;
    }
    
    public static void close(Statement sta,Connection con){
        if (sta != null) {
            try {
                sta.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        
        if (con != null) {
            try {
                con.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
    public static void close(ResultSet rs,Statement sta,Connection con){
        if (rs != null) {
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        
        if (sta != null) {
            try {
                sta.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        
        if (con != null) {
            try {
                con.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

bean:

package com.zh.entity;



    public class bean {
    private String place;
    private String teacher_name;
    private String class_name;
    public String get_place() {
        return place;
    }
    public void set_place(String place) {
        this.place=place;
    }
    public String get_teacher_name() {
        return teacher_name;
    }
    public void set_teacher_name(String teacher_name) {
        this.teacher_name=teacher_name;
    }
    public String get_class_name() {
        return class_name;
    }
    public void set_class_name(String class_name) {
        this.class_name=class_name;
    }
    public bean() {};
    
    public bean(String place,String teacher_name,String class_name) {
        this.place=place;
        this.teacher_name=teacher_name;
        this.class_name=class_name;
        }
}

data_dao:

package com.zh.dao;
import java.util.*;
import java.sql.*;
import com.zh.entity.*;
import com.zh.util.*;
import java.sql.*;
public class data_dao {
    /*增加
     * 
     */
public void add(bean Bean) {
    String sql="insert into class_message values('"+Bean.get_place()+"','"+Bean.get_teacher_name()+"','"+Bean.get_class_name()+"')";
    Connection conn = DButil.getConnection();
    Statement state = null;
    try {
        state = conn.createStatement();
        state.executeUpdate(sql);
    } catch (Exception e) {
        e.printStackTrace();
    } 
}
/*删除
 * 
 */
public void deleteByteacher_name(String teacher_name) {
    boolean f=false;
    String sql="delete from class_message where teacher_name='"+teacher_name+"'";
    Connection conn=DButil.getConnection();
    Statement state = null;
    
    try {
        
        state = conn.createStatement();
        state.executeUpdate(sql);
    } catch (SQLException e) {
        e.printStackTrace();
    } 
    
    }
         /* 修改
         * 
         */

public void updata(bean b) {
    String sql="updata class_message set place='"+b.get_place()+"', teacher_name='"+b.get_teacher_name()+"',class_name='"+b.get_class_name()+"' where teacher_name='"+b.get_teacher_name()+"'";
    
    Connection conn=DButil.getConnection();
    Statement state = null;
    try {
        state = conn.createStatement();
        state.executeUpdate(sql);
    } catch (SQLException e) {
        e.printStackTrace();
    } 
    

}
/**
 * 验证课程名称是否唯一
 */
public List<bean> isOnly_class_name(String class_name) {
    List list=new ArrayList<bean>();
    String sql="select name from class_message where class_name='"+class_name+"'";
    Connection conn=DButil.getConnection();
    Statement state=null;
    ResultSet rs = null;
    try {
        state = conn.createStatement();
        rs = state.executeQuery(sql);
        while(rs.next()) {
            String class_name1=rs.getString("class_name");
            String teacher_name=rs.getString("teacher_name");
            String place=rs.getString("place");
            bean b=new bean(place,teacher_name,class_name1);
            list.add(b);
        }
    } catch (SQLException e) {
    e.printStackTrace();
}
    return list;
}

                                                                                                                                                                                                                                                                       
/**
 * 通过teacher_name获得一个bean对象
 */
public bean findByteacher_name(String teacher_name) {
        Connection conn=null;
    Statement state=null;
    
    try {
        conn=DButil.getConnection();
        String sql="select*from class_message where teacher_name='"+teacher_name+"'";
        
        state=conn.createStatement();
        ResultSet rs=state.executeQuery(sql);
        bean u=new bean();;
        while(rs.next()) {
            String t_name=rs.getString("teacher_name");
            String c_name=rs.getString("class_name");
            String place=rs.getString("place");
            u.set_class_name(c_name);
            u.set_place(place);
            u.set_teacher_name(t_name);
            return u;
        }
    }catch (Exception e) {
        e.printStackTrace();
        }

return null;
}
/*
 * 显示全部
 */
public List<bean> findAll(){
    Connection conn=DButil.getConnection();
    List<bean> list=new ArrayList<bean>();
    bean b=null;
    try {
    Statement sta=conn.createStatement();
    String sql="select * from class_message";
    ResultSet rs=sta.executeQuery(sql);
        while(rs.next()) {
            b=new bean();
            String t_name,c_name,place;
            t_name=rs.getString("teacher_name");
            c_name=rs.getString("c_name");
            place=rs.getString("place");
            b.set_class_name(c_name);
            b.set_place(place);
            b.set_teacher_name(t_name);
            list.add(b);
        }
    }catch (Exception e) {
        e.printStackTrace();
    }
    for(int i=0;i<list.size();i++) {
        bean br=(bean)list.get(i);
        System.out.println(br.get_teacher_name());
    }
    return list;
}
}

Userservice:

package com.zh.service;
import java.util.*;
import com.zh.dao.*;
import com.zh.entity.*;
public class Userservice {
public boolean insertUser(String place,String teacher_name,String class_name) {
    data_dao dao=new data_dao();
    bean b=new bean();
    b.set_class_name(class_name);
    b.set_place(place);
    b.set_teacher_name(teacher_name);
    try {
    dao.add(b);
    return true;
    }catch (Exception e) {
        e.printStackTrace();
        return false;
    }
}
public boolean deleteUser(String teacher_name) {
    data_dao dao=new data_dao();
    bean b=dao.findByteacher_name(teacher_name);
    if(b!=null) {
        dao.deleteByteacher_name(teacher_name);
        return true;
    }else 
        return false;
}
public boolean updataByteacher_name(String place,String class_name,String teacher_name) {
    data_dao dao=new data_dao();
    bean b=new bean(place,class_name,teacher_name);
    try {
        dao.updata(b);
        return true;
    }catch (Exception e) {
        e.printStackTrace();
        return false;
    }
    }
public boolean isOnly_classname(String class_name) {
    data_dao dao=new data_dao();
    try {
        List list=dao.isOnly_class_name(class_name);
        if(list.size()>1)
            return true;
        else
            return false;
    }catch (Exception e) {
        e.printStackTrace();
        return false;
    }
}

public List<bean> findAll_user(){
    data_dao dao=new data_dao();
    List list=dao.findAll();
    return list;
}
}