连接数据库的工具类，以及相关用法

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前言：

首先申明，我不是什么技术大牛，我只是希望我在记笔记的同时，能帮助到需要帮助的人！

1.安装JDK
2.安装IDE(eclipse,MyEclipse) java 集成开发环境
3.安装JDBC，数据库驱动下载链接此版本为5.1.8
新建一个工具类 DBUtil 类

这里写图片描述

代码如下

package com.njcit.util;import java.sql.Connection;import java.sql.DriverManager;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;public class DBUtil {    private static String url = "jdbc:mysql://localhost:3306/office?useUnicode=true&characterEncoding=utf-8";//向数据库传输数据的时候会出现编码问题用这个解决:useUnicode=true&characterEncoding=utf-8    private static String user = "****";//连接数据库的用户名    private static String password = "****";//连接数据库的密码    private static String DBDRIVER = "com.mysql.jdbc.Driver";    public static Connection getConnection(){        Connection conn = null;        try {            try {                Class.forName(DBDRIVER) ;                 System.out.println("加载驱动成功") ;            } catch (ClassNotFoundException e) {                // TODO Auto-generated catch block                e.printStackTrace();            }            conn= DriverManager.getConnection(url, user, password);            System.out.println("连接成功") ;        } catch (SQLException e) {            e.printStackTrace();        }        return conn;    }    public static void close(Connection conn){        if(conn!=null){            try {                conn.close();            } catch (SQLException e) {                e.printStackTrace();            }        }    }    public static void close(Connection conn,PreparedStatement stmt){        if(conn!=null){            try {                conn.close();            } catch (SQLException e) {                e.printStackTrace();            }        }        if(stmt!=null){            try {                stmt.close();            } catch (SQLException e) {                e.printStackTrace();            }        }    } public static void close(Connection conn,PreparedStatement stmt,ResultSet rs){        if(conn!=null){            try {                conn.close();            } catch (SQLException e) {                e.printStackTrace();            }        }        if(stmt!=null){            try {                stmt.close();            } catch (SQLException e) {                e.printStackTrace();            }        }        if(rs!=null){            try {                rs.close();            } catch (SQLException e) {                e.printStackTrace();            }        }    }//测试连接是否成功//  public static void main(String[] args) {////      System.out.println(DBUtil.getConnection());//  }}

如何在其他类里面用到这个工具类呢

//这是一个实现类public class ApprovalImpDao{    public List<Approval> findAll() {        List<Approval> list =new ArrayList<Approval>();        Connection conn = null;        PreparedStatement stmt = null;        try {            conn = DBUtil.getConnection();//这边就是得到连接数据库            String sql = "select * from approval";            stmt = (PreparedStatement) conn.prepareCall(sql);            ResultSet rs = stmt.executeQuery();            while(rs.next()){                Approval  a = new Approval();                a.setApprove_type(rs.getString(1));                a.setApprove_reason(rs.getString(2));                a.setApprove_start(rs.getTimestamp(3));                a.setApprove_end(rs.getTimestamp(4));                a.setAppperson(rs.getString(6));                a.setId(rs.getInt(7));                a.setStatus(rs.getString(9));                a.setAppperson(rs.getString(15));                list.add(a);                }        } catch (SQLException e) {            e.printStackTrace();        }finally{            DBUtil.close(conn, stmt);        }        return list;    }    }

再来个测试类

public class Test {    public static void main(String[] args) {ApprovalDao dao = new ApprovalImpDao();        List<Approval> list = dao.findAll();        if (list.size()>0) {            for (int i = 0; i < list.size(); i++) {                Approval a = list.get(i);                HashMap<String, String> hsahMap = new HashMap<String, String>();                hsahMap.put("type", a.getApprove_type());                hsahMap.put("reason", a.getApprove_reason());                jsonArray.add(hsahMap);                }    System.out.println("打印出从数据库获取出来的值:"+jsonArray);        }        }    }}

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