MySQL_(Java)提取工具类JDBCUtils

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　　MySQL_(Java)使用JDBC创建用户名和密码校验查询方法　　传送门

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　　使用工具类JDBCUtils意义：在做增、删除、修改、查询都需要获取Connection连接，使用完毕之后我们都需要关闭连接，这些工作是不断的重复在做的事情，所以我们可以把这些工作定义成一个工具类的方法，减少我们重复代码的编写

　　

　　MySQL数据库中的数据，数据库名garysql，表名garytb

　　

　　通过JDBC对MySQL中的数据进行查询

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

public class JDBC01 {

    public static void main(String[] args) throws SQLException  {
        selectAll();
    }

    public static void selectAll() throws SQLException {
        //注册驱动    使用驱动连接数据库
        Connection con = null;
        Statement stmt = null;
        ResultSet rs = null;
        try {
            con = JDBCUtils.getConnection();
            
            //数据库的增删改查
            stmt = con.createStatement();
            //返回一个结果集
            rs =stmt.executeQuery("select * from garytb");
            
            while(rs.next()) {
                //System.out.println(rs.getString(1)+","+rs.getString(2)+","+rs.getString(3));
                System.out.println(rs.getString("id")+","+rs.getString("username")+","+rs.getString("password"));
            }
        
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally {
            JDBCUtils.close(rs, stmt, con);
        }
    }

    public static boolean  selectByUernamePassword(String username,String password) throws SQLException {
        Connection con=null;
        Statement stmt = null;
        ResultSet rs = null;
        try {
            Class.forName("com.mysql.jdbc.Driver");
            
            String url ="jdbc:mysql://localhost:3306/garysql?useUnicode=true&characterEncoding=UTF8&useSSL=false";
            con = DriverManager.getConnection(url,"root","123456");
            stmt =con.createStatement();
            String sql = "select * from garytb where username = '"+username+"' and password = '"+password+"'";
            //System.out.println(sql);
            rs = stmt.executeQuery(sql);
            
            if(rs.next()) {
                return true;
            }else {
                return false;
            }
                
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally {
            if(rs!=null)
                rs.close();
            if(stmt!=null)
                stmt.close();
            if(con!=null)
                con.close();
        }
        
        return false;
    }

    public static boolean selectByUP2(String username,String password) throws SQLException{
        Connection con=null;
        Statement stmt = null;
        ResultSet rs = null;
        try {
            Class.forName("com.mysql.jdbc.Driver");
            
            String url ="jdbc:mysql://localhost:3306/garysql?useUnicode=true&characterEncoding=UTF8&useSSL=false";
            con = DriverManager.getConnection(url,"root","123456");
            
            String sql = "select * from garytb where username = ? and password = ?";
            PreparedStatement pstmt = con.prepareStatement(sql);
            //添加参数
            pstmt.setString(1, username);
            pstmt.setString(2, password);
            //进行查询
            rs = pstmt.executeQuery();
                
            if(rs.next()) {
                return true;
            }else {
                return false;
            }
                
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally {
            if(rs!=null)
                rs.close();
            if(stmt!=null)
                stmt.close();
            if(con!=null)
                con.close();
        }
        
        return false;
    }

    //pageNumber是页数，第几页，pageCount是每页显示多少个数据
    public static void selectUserByPage(int pageNumber,int pageCount) throws SQLException {
        //注册驱动    使用驱动连接数据库
                Connection con = null;
                PreparedStatement stmt = null;
                ResultSet rs = null;
                try {
                    Class.forName("com.mysql.jdbc.Driver");
                    
                    //String url ="jdbc:mysql://localhost:3306/garysql";
                    //指定编码查询数据库
                    String url ="jdbc:mysql://localhost:3306/garysql?useUnicode=true&characterEncoding=UTF8&useSSL=false";
                    String user = "root";
                    String password = "123456";
                    //建立和数据库的连接
                    con = DriverManager.getConnection(url,user,password);
                    
                    stmt = con.prepareStatement("select * from garytb limit ?,?");
                    stmt.setInt(1, (pageNumber-1)*pageCount );
                    stmt.setInt(2, pageCount);
                    
                    rs = stmt.executeQuery();
                    
                    while(rs.next()) {
                        //System.out.println(rs.getString(1)+","+rs.getString(2)+","+rs.getString(3));
                        System.out.println(rs.getString("id")+","+rs.getString("username")+","+rs.getString("password"));
                    }
                
                } catch (Exception e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }finally {
                    if(rs!=null)
                        rs.close();
                    if(stmt!=null)
                        stmt.close();
                    if(con!=null)
                        con.close();
                }
    }
}

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

public class JDBCUtils {
    
    private static final String connectionURL = "jdbc:mysql://localhost:3306/garysql?useUnicode=true&characterEncoding=UTF8&useSSL=false";
    private static final String username = "root";
    private static final String password = "123456";
    
    //创建数据库的连接
    public static Connection getConnection() {
        try {
            Class.forName("com.mysql.jdbc.Driver");
            return   DriverManager.getConnection(connectionURL,username,password);
        } catch (Exception e) {
            
            e.printStackTrace();
        }
        return null;
    }
    
    //关闭数据库的连接
    public static void close(ResultSet rs,Statement stmt,Connection con) throws SQLException {
        if(rs!=null)
            rs.close();
        if(stmt!=null)
            stmt.close();
        if(con!=null)
            con.close();
    }
}

 　　在JDBCUtils.java中实现构建对数据库的连接和关闭数据库操作

private static final String connectionURL = "jdbc:mysql://localhost:3306/garysql?useUnicode=true&characterEncoding=UTF8&useSSL=false";
    private static final String username = "root";
    private static final String password = "123456";
    
    //创建数据库的连接
    public static Connection getConnection() {
        try {
            Class.forName("com.mysql.jdbc.Driver");
            return   DriverManager.getConnection(connectionURL,username,password);
        } catch (Exception e) {
            
            e.printStackTrace();
        }
        return null;
    }
    
    //关闭数据库的连接
    public static void close(ResultSet rs,Statement stmt,Connection con) throws SQLException {
        if(rs!=null)
            rs.close();
        if(stmt!=null)
            stmt.close();
        if(con!=null)
            con.close();
    }

　　在JDBC01.java中需要对数据库中用户查询时直接调用JDBCUtils.java中方法即可

     //数据库的连接
    con = JDBCUtils.getConnection(); 

    //关闭数据库
    JDBCUtils.close(rs, stmt, con);               

　　例如查询MySQL中所有用户的信息

public static void selectAll() throws SQLException {
        //注册驱动    使用驱动连接数据库
        Connection con = null;
        Statement stmt = null;
        ResultSet rs = null;
        try {
            //数据库的连接
            con = JDBCUtils.getConnection();
            
            //数据库的增删改查
            stmt = con.createStatement();
            //返回一个结果集
            rs =stmt.executeQuery("select * from garytb");
            
            while(rs.next()) {
                //System.out.println(rs.getString(1)+","+rs.getString(2)+","+rs.getString(3));
                System.out.println(rs.getString("id")+","+rs.getString("username")+","+rs.getString("password"));
            }
        
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally {
            JDBCUtils.close(rs, stmt, con);
        }
    }