ResultSet
ResultSet是我们使用jdbc连接时，查询的一个返回结果集,ResultSet resultSet = stmt.executeQuery(sql),下面就使用例子介绍ResultSet的使用
例子是通过jdbc连接查account表中的数据，然后用实体类Account封装起来，返回这个类的集合。
jdbc工具类代码
package com.lingaolu.Utils;
import java.io.FileReader;
import java.io.IOException;
import java.net.URL;
import java.sql.*;
import java.util.Properties;
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);
}
}Account实体类代码
package com.lingaolu.jdbcConnector;
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 +
'}';
}
}测试Demo3的代码
package com.lingaolu.jdbcConnector;
import com.lingaolu.Utils.JdbcUtils;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;
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;
}
}表中的数据
运行输出：
Account{id=1, name='张三', balance=500.0, myAge=17}
Account{id=2, name='李四', balance=1000.0, myAge=16}
Account{id=7, name='张三', balance=600.0, myAge=19}
Account{id=11, name='林帅', balance=20000.0, myAge=18}
----------------------------------
Account{id=1, name='张三', balance=500.0, myAge=17}
Account{id=7, name='张三', balance=600.0, myAge=19}
结果与预期的一致
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