JDBC操作mysql数据库(SqlHelper类封装)

 SqlHelper.java

package com.mqs.process;

import java.io.FileInputStream;
import java.sql.*;
import java.util.Properties;

public class SqlHelper {
    //定义需要的变量
    private static Connection ct=null;
    //在大多数情况下，使用PreparedStatement来替代Statement
    //这样可以防止sql注入
    private static PreparedStatement ps=null;
    private static ResultSet rs=null;
    private static CallableStatement cs=null;
    
    public static Connection getCt() {
        return ct;
    }

    public static PreparedStatement getPs() {
        return ps;
    }

    public static ResultSet getRs() {
        return rs;
    }
    
    //连接数据库参数
    private static String url="";
    private static String username="";
    private static String driver="";
    private static String password="";
    
    private static Properties pp=null;
    private static FileInputStream fis=null;
    
    //加载驱动，只需要一次
    static{
        try {
            //从dbinfo.propertis文件中读取配置信息
            pp = new Properties();
            fis=new FileInputStream("dbinfo.properties");
            pp.load(fis); 
            url=pp.getProperty("url");
            username=pp.getProperty("username");
            driver=pp.getProperty("driver");
            password=pp.getProperty("password");
            
            Class.forName("driver");
        } catch (Exception e) {
            // TODO: handle exception
        }finally{
            try {
                fis.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
            fis=null;
        }
    }
    
    //得到连接
    public static Connection getConnection(){
        try {
            ct = DriverManager.getConnection(url,username,password);
        } catch (Exception e) {
            // TODO: handle exception
        }
        return ct;
    }

    //统一的select
    public static ResultSet executeQuery(String sql,String parameters[]){
        try {
            ct=getConnection();
            ps=ct.prepareStatement(sql);
            if(parameters!=null&&!parameters.equals("")){
                for(int i=0;i<parameters.length;i++){
                    ps.setString(i+1,parameters[i]);
                }                    
            }
            rs=ps.executeQuery();
        } catch (Exception e) {
            e.printStackTrace();
            throw new RuntimeException(e.getMessage());
        }finally{
            //close(rs,ps,ct);
        }
        return rs;
    }
    
    //先写一个update/insert/delete
    public static void executeUpdate(String sql,String [] parameters){
        //1、创建一个ps
        try{
            ct=getConnection();
            ps=ct.prepareStatement(sql);
            //给？赋值
            if(parameters!=null){
                for(int i=0;i<parameters.length;i++){
                    ps.setString(i+1,parameters[i]);
                }
            }
            //执行
            ps.executeUpdate();
            
        }catch (Exception e){
            e.printStackTrace();//开发阶段
            //抛出异常，抛出运行异常，可以给调用该函数的函数一个选择
            //可以处理，也可以放弃处理
            throw new RuntimeException(e.getMessage());
        }finally{
            //关闭资源
            close(rs,ps,ct);
        }
    }
    

    
    
    //如果有多个update/delete/insert[需要考虑事务]
    public static void executeUpdate2(String sql[],String [][]parameters){
        try {
            //1、获得链接
            ct=getConnection();
            //因为这时，用户传入的可能是多个sql语句
            ct.setAutoCommit(false);
            for(int i=0;i<sql.length;i++){
                if(parameters[i]!=null){
                    ps=ct.prepareStatement(sql[i]);
                    for(int j=0;j<parameters[i].length;j++){
                        ps.setString(j+1, parameters[i][j]);
                    }
                    ps.executeUpdate();
                }
            }
            ct.commit();
            
        } catch (Exception e) {
            e.printStackTrace();//开发阶段
            
            //回滚
            try {
                ct.rollback();
            } catch (Exception e1) {
                e1.printStackTrace();
            }
            
            
            //抛出异常，抛出运行异常，可以给调用该函数的函数一个选择
            //可以处理，也可以放弃处理
            throw new RuntimeException(e.getMessage());
        }finally{
            close(rs,ps,ct);
        }
    }
    

    
    //分页问题
    public static ResultSet executeQuery2(){
        return null;
        
    }
    
    //调用存储过程
    //sql 像{call 过程(?,?,?)}
    public static void callPro1(String sql,String []parameters){
        try {
            ct=getConnection();
            cs=ct.prepareCall(sql);
            
            //?号赋值
            if(parameters!=null){
                for(int i=0;i<parameters.length;i++){
                    cs.setObject(i+1, parameters[i]);
                }
            }
            cs.execute();
            
        } catch (Exception e) {
            e.printStackTrace();
            throw new RuntimeException(e.getMessage());
        }finally{
            close(rs,cs,ct);
        }
    }
    
    //调用存储过程，有返回Result
    //未完成，见《韩顺平.2011最新j2ee视频教程.jdbc第4讲.超强SqlHelper工具类封装(2)》
    public static ResultSet callPro2(String sql,String []inparameters,String []outparameters){
        try {
            ct=getConnection();
            cs=ct.prepareCall(sql);
            if(inparameters!=null){
                for(int i=0;i<inparameters.length;i++){
                    cs.setObject(i+1,inparameters[i]);
                }
            }
        } catch (Exception e) {
            // TODO: handle exception
        }finally{
        }
        return null;
    }
    
    //关闭资源的函数
    public static void close(ResultSet rs,Statement ps,Connection ct){
        if(rs!=null){
            try {
                rs.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
            rs=null;
        }
        if(ps!=null){
            try {
                ps.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
            ps=null;
        }
        if(ct!=null){
            try {
                ct.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
            ct=null;
        }    
    }
}

 DbTest.java

package com.mqs.process;

import java.sql.*;
import java.util.ArrayList;

public class DbTest {
    public static void main(String[] args) {
        Connection ct =null;
        PreparedStatement ps=null;
        ResultSet rs=null;
        
        try {
            //1、获取数据库链接
            ct=SqlHelper.getConnection();
            //2、创建获取rs    
            String sql = "select * from news";
            
            String parameters[]={};
            rs=SqlHelper.executeQuery(sql,parameters);
            
            while(rs.next()){
                System.out.println(rs.getString(1)+"    "+rs.getString(2)+"        "+rs.getString(3));    
            }
            
        } catch (Exception e) {
            e.printStackTrace();
        }finally{
            if(rs!=null){
                try {
                    rs.close();
                } catch (Exception e) {
                    e.printStackTrace();
                }
                rs=null;
            }
            if(ps!=null){
                try {
                    ps.close();
                } catch (Exception e) {
                    e.printStackTrace();
                }
                ps=null;
            }
            if(ct!=null){
                try {
                    ct.close();
                } catch (Exception e) {
                    e.printStackTrace();
                }
                ct=null;
            }
            
        }

        
    }
}

dbinfo.properties

url=jdbc:mysql://127.0.0.1:3306/site?useUnicode=true&characterEncoding=UTF-8
username=root
driver=com.mysql.jdbc.Driver
password=654321

直接操作数据库的方法

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;

Connection conn = null;
        ResultSet rs = null;
        String sql = "select * from news";
        String url = "jdbc:mysql://127.0.0.1:3306/site?user=root&password=654321&useUnicode=true&characterEncoding=UTF-8";
        
        ArrayList<String[]> news = new ArrayList<String[]>();
        
        
        try{
            Class.forName("com.mysql.jdbc.Driver");
            conn = DriverManager.getConnection(url);
            java.sql.Statement stmt = conn.createStatement();
            rs = stmt.executeQuery(sql);
            while(rs.next()){
                String[] temp = {rs.getString(1),rs.getString(2),rs.getString(3)};
                news.add(temp);            
            }

        }catch (SQLException e) {
            System.out.println("MySQL操作错误");
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

自己写的封装

package com.yourcompany.util;

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

public class DbHelper {
    
    private static Connection conn=null;
    private static PreparedStatement ps=null;
    private static ResultSet rs = null;
    private static String url = "jdbc:mysql://127.0.0.1:3306/site?user=root&password=654321&useUnicode=true&characterEncoding=UTF-8";
    
    //private static String url = "jdbc:mysql://127.0.0.1:3306/site";
    
    //获取查询数据
    public static ResultSet getQuery(String sql,String parameters[]){
        try{
            Class.forName("com.mysql.jdbc.Driver");
            conn = DriverManager.getConnection(url);
            ps = conn.prepareStatement(sql);
            
            if(parameters!=null&&!parameters.equals("")){
                for(int i=0;i<parameters.length;i++){
                    ps.setString(i+1,parameters[i]);
                }                    
            }
            
            rs = ps.executeQuery();
        }catch (SQLException e) {
            System.out.println("MySQL操作错误");
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            
        }

        return rs;
    } 
    
    //关闭资源的函数
    public static void close(){
        if(rs!=null){
            try {
                rs.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
            rs=null;
        }
        if(ps!=null){
            try {
                ps.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
            ps=null;
        }
        if(conn!=null){
            try {
                conn.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
            conn=null;
        }
    }
}