Java ResultSet案例讲解

package com.lingaolu.Utils;

import java.io.FileReader;

import java.io.IOException;

import java.net.URL;

import java.sql.*;

import java.util.Properties;

/**

  * @author 林高禄

  * @create 2020-06-23-11:12

  */

public class JdbcUtils {

     private static String driver;

     private static String url;

     private static String userName;

     private static String pw;

     static {

         try {

             Properties p = new Properties();

             ClassLoader classLoader = JdbcUtils. class .getClassLoader();

             // 这个路径相对于src的路径来说

             URL resource = classLoader.getResource( "com/lingaolu/file/jdbc.properties" );

             String path = resource.getPath();

             p.load( new FileReader(path));

             driver = p.getProperty( "driver" );

             url = p.getProperty( "url" );

             userName = p.getProperty( "user" );

             pw = p.getProperty( "password" );

             Class.forName(driver);

         } catch (IOException e) {

             e.printStackTrace();

         } catch (ClassNotFoundException e) {

             e.printStackTrace();

         }

     }

     public static Connection createConnection() throws SQLException {

         return DriverManager.getConnection(url, userName, pw);

     }

     public static void close(Statement stmt,Connection con){

         if ( null != stmt){

             try {

                 stmt.close();

             } catch (SQLException e) {

                 e.printStackTrace();

             }

         }

         if ( null != con){

             try {

                 con.close();

             } catch (SQLException e) {

                 e.printStackTrace();

             }

         }

     }

     public static void close(ResultSet set,Statement s,Connection con){

         if ( null != set){

             try {

                 set.close();

             } catch (SQLException e) {

                 e.printStackTrace();

             }

         }

         close(s,con);

     }

}

package com.lingaolu.jdbcConnector;

/**

  * @author 林高禄

  * @create 2020-06-24-8:28

  */

public class Account {

     private int id;

     private String name;

     private double balance;

     private int myAge;

     public int getId() {

         return id;

     }

     public void setId( int id) {

         this .id = id;

     }

     public String getName() {

         return name;

     }

     public void setName(String name) {

         this .name = name;

     }

     public double getBalance() {

         return balance;

     }

     public void setBalance( double balance) {

         this .balance = balance;

     }

     public int getMyAge() {

         return myAge;

     }

     public void setMyAge( int myAge) {

         this .myAge = myAge;

     }

     @Override

     public String toString() {

         return "Account{" +

                 "id=" + id +

                 ", name='" + name + '\ '' +

                 ", balance=" + balance +

                 ", myAge=" + myAge +

                 '}' ;

     }

}

package com.lingaolu.jdbcConnector;

import com.lingaolu.Utils.JdbcUtils;

import java.sql.*;

import java.util.ArrayList;

import java.util.List;

/**

  * @author 林高禄

  * @create 2020-06-23-17:27

  */

public class Demo3 {

     public static void main(String[] args) {

         String sql = "select * from account" ;

         List<Account> accounts = fineAccount(sql);

         accounts.forEach(System.out::println);

         System.out.println( "----------------------------------" );

         sql = "select * from account where name='张三'" ;

         accounts = fineAccount(sql);

         accounts.forEach(System.out::println);

     }

     public static List<Account> fineAccount(String sql){

         Connection con = null ;

         Statement stmt = null ;

         ResultSet resultSet = null ;

         List<Account> rerurnList = new ArrayList<>();

         try {

             con = JdbcUtils.createConnection();

             stmt = con.createStatement();

             resultSet = stmt.executeQuery(sql);

             Account acc = null ;

             while (resultSet.next()){

                 // 引号里的字段要与表里的一样

                 int id = resultSet.getInt( "id" );

                 String name = resultSet.getString( "name" );

                 double balance = resultSet.getDouble( "balance" );

                 int age = resultSet.getInt( "age" );

                 acc = new Account();

                 acc.setId(id);

                 acc.setName(name);

                 acc.setBalance(balance);

                 acc.setMyAge(age);

                 rerurnList.add(acc);

             }

         } catch (SQLException e) {

             e.printStackTrace();

         } finally {

             JdbcUtils.close(resultSet,stmt,con);

         }

         return rerurnList;

     }

}