java登录以及连接数据库的温习

学完一部分android相关知识点后,为了下周的java测试，我还是反回来重新的学习了上学期的知识点java,在今天打开eclipse之后，对于自己之前自己所写过的东西还有连接数据库的内容，已经有所忘记，今天我就根据一个案例重新写了一下增删改查的代码，这里只对比较重要的代码进行展示：

DB.java:

package com.db;

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



public class DB {
    private static String mysqlname = "database";//数据库名
    private static Connection con;
    private static Statement stm;
    private static ResultSet rs;
    private static String coursename = "com.mysql.jdbc.Driver";
    private static String url = "jdbc:mysql://127.0.0.1:3306/"+mysqlname+"?useUnicode=true&characterEncoding=GB18030&useSSL=false&serverTimezone=GMT&allowPublicKeyRetrieval=true";
    
    public static Connection getCon() {
        try {
            Class.forName(coursename);
            System.out.println("注册驱动成功");
        }catch(ClassNotFoundException e) {
            e.printStackTrace();
        }
        try {
            con = DriverManager.getConnection(url,"root","20000604");
            System.out.println("建立连接成功");
        }catch(Exception e){
            e.printStackTrace();
            con = null;
        }
        return con;
    }
    
    public static void close(Statement stm,Connection connection) {
        if(stm!=null) {
            try {
                stm.close();
            }catch(SQLException e) {
                e.printStackTrace();
            }
        }
        if(connection!=null) {
            try {
                connection.close();
            }catch(SQLException e) {
                e.printStackTrace();
            }
        }
    }
        
    //关闭
    public static void close(ResultSet rs,Statement stm,Connection connection) {
        if(rs!=null) {
            try {
                rs.close();
            }catch(SQLException e) {
            e.printStackTrace();
            }
        }
        if(stm!=null) {
            try {
                stm.close();
            }catch(SQLException e) {
                e.printStackTrace();
            }
        }
        if(connection!=null) {
            try {
                connection.close();
            }catch(SQLException e) {
                e.printStackTrace();
            }
        }
    }
    public static void main(String[] args)
    {
        getCon();
    }
}

Dao.java:

package com.dao;

import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;

import com.bean.staff;
import com.db.DB;
import com.mysql.jdbc.Connection;
import com.mysql.jdbc.PreparedStatement;

public class Dao {
    //根据名称进行查询
        @SuppressWarnings("static-access")
        public static staff selectName_staff(String staff_name) {
            String tablename = "staff";
            System.out.println("select staff where name = "+staff_name);
            staff sta=null;
            DB db=new DB();
            Connection con = (Connection) db.getCon();
            try {
                Statement stm = con.createStatement();
                ResultSet rs = stm.executeQuery("select * from "+tablename+" where name='" + staff_name + "'");
                if(rs.next())
                {
                    sta = new staff();
                    System.out.println("select the stu from mysql");
                    sta.setJobid(rs.getString("jobid"));
                    sta.setName(rs.getString("name"));
                    sta.setSex(rs.getString("sex"));
                    sta.setBirthday(rs.getString("birthday"));
                    sta.setDepartment(rs.getString("department"));
                    sta.setRole(rs.getString("role"));
                    sta.setPassword(rs.getString("password"));
                    //bean.setValue2(Integer.parseInt(rs.getString("teacher")));
                    //bean.setValue3(Boolean.parseBoolean(rs.getString("address")));
                    System.out.println("name of the stu is "+rs.getString("staff_name"));
                }
                db.close(rs,stm, con);
            }catch(Exception e) {
                e.printStackTrace();
            }
            return sta;
        }
        //添加普通员工信息
        @SuppressWarnings("static-access")
        public boolean add_staff(staff staff) {
            String tablename = "staff";//表名
            DB db=new DB();
            Connection con = (Connection) db.getCon();
            
            try {
                String sql="insert into "+tablename+"(jobid,name,sex,birthday,department,role,password) values ('"+staff.getJobid()+"','"+staff.getName()+"','"+staff.getSex()+"','"+staff.getBirthday()+"','"+staff.getDepartment()+"','"+staff.getRole()+"','"+staff.getPassword()+"')";
                Statement stm = con.createStatement();
                System.out.println(sql);
                stm.execute(sql);
                db.close(stm, con);
            }catch(Exception e) {
                e.printStackTrace();
                System.out.println("add false");
                return false;
            }
            System.out.println("add true");
            return true;
        }
        //根据员工名字进行删除
        @SuppressWarnings("static-access")
        public static boolean delete_staff(String name)
        {
            //String tablename ="test";
            DB db=new DB();
            Connection con = (Connection) db.getCon();
            //Connection con=null;
            PreparedStatement stm=null;
            try {
                con=(Connection) DB.getCon();
                String sql="delete from staff where name='"+name+"'";
                //String sql="delete from test where name='"+bean.getName()+"'";
                System.out.println(sql);
                stm=(PreparedStatement) con.prepareStatement(sql);
                stm.executeUpdate();
                return true;
            }
            catch(SQLException e)
            {
                e.printStackTrace();
            }
            finally {
                db.close(stm, con);
            }
            return false;
        }
        
        //根据员工名字进行修改
        @SuppressWarnings("static-access")
        public boolean update_staff(staff stu) {
            Connection con=null;
            PreparedStatement stm=null;
            String tablename="staff";
            DB db=new DB();
            try {
                con=(Connection) DB.getCon();
                //String sql="update "+tablename+" set teacher=?,classroom=? where name=?";
                String sql="update "+tablename+" set jobid=?,sex=?,birthday=?,department=?,role=?,password=? where name=?";
                //String sql="update "+tablename+"set teacher=?,classroom=? where name=?";
                stm=(PreparedStatement) con.prepareStatement(sql);
                
                //stm.setString(3,bean.getName());
                //stm.setString(1, bean.getTeacher());
                //stm.setString(2,bean.getClassroom());
                stm.setString(1,stu.getJobid());
                stm.setString(2,stu.getSex());
                stm.setString(3,stu.getBirthday());
                stm.setString(4,stu.getDepartment());
                stm.setString(5,stu.getRole());
                stm.setString(6,stu.getPassword());
                stm.setString(6,stu.getName());

                stm.executeUpdate();
            }
            catch(SQLException e)
            {
                e.printStackTrace();
                return false;
            }
            finally {
                db.close(stm, con);
                return true;
            }
        }
        //浏览员工全部信息
        @SuppressWarnings("static-access")
         public ArrayList<staff> selectList_staff(){
           Connection con=null;
            PreparedStatement stm=null;
            ResultSet rs=null;
            ArrayList<staff> listbean=new ArrayList<staff>();
            String tablename="staff";
            DB db=new DB();
            try {
                con=(Connection) db.getCon();
                String sql="select * from "+tablename;
                stm=(PreparedStatement) con.prepareStatement(sql);
                rs=stm.executeQuery();
                while(rs.next()){
                    String jobid=rs.getString("jobid");
                    String name=rs.getString("name");
                    String sex=rs.getString("sex");
                    String birthday=rs.getString("birthday");
                    String department=rs.getString("department");
                    String role=rs.getString("role");
                    String password=rs.getString("password");
                    staff stu=new staff(0,jobid,name,sex,birthday,department,role,password);
                    listbean.add(stu);
                    
                }
            } 
            catch(SQLException e)
            {
                e.printStackTrace();
            }
            finally
            {
                db.close(stm, con);
            }
            return listbean;
       }
}

在这里遇到最多的问题是dao.java中对sql语句的书写，这也是出现问题最多的地方，希望自己更加的熟练，不断坚持，加油。