Java之JDBC查询结果集封装到对象

User类：

package com.xiao.pojo;

/**
* @author 笑笑
* @Date   2018年3月15日上午9:20:28
*
*/
public class User {

private int uid = 0;
private String username = null;
private String password = null;
private int age = 0;
private String gender = null;
private String email = null;

//空参构造器
public User() {
}
//有参构造器
public User(int uid, String username, String password, int age, String gender, String email) {
this.uid = uid;
this.username = username;
this.password = password;
this.age = age;
this.gender = gender;
this.email = email;
}
public int getUid() {
return uid;
}
public void setUid(int uid) {
this.uid = uid;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getGender() {
return gender;
}
public void setGender(String gender) {
this.gender = gender;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
//重写toString
@Override
public String toString() {
return "User [uid=" + uid + ", username=" + username + ", password=" + password + ", age=" + age + ", gender="
+ gender + ", email=" + email + "]";
}

}

封装测试类-JDBC_02.java：

package com.xiao.jdbc;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;
import org.junit.Test;

import com.xiao.pojo.User;
import com.xiao.utils.JDBCUtils_01;

/**
* @author 笑笑
* @Date   2018年3月15日下午1:15:20
*
*/
public class JDBC_02 {

//把结果集封装到对象
@Test
public void test() throws Exception{
//使用工具类注册并获取连接
Connection cn = JDBCUtils_01.getConnection();
//书写SQL语句
String sql = "select * from user_tb";
//获取SQL语句预编译对象
PreparedStatement ps = cn.prepareStatement(sql);
//执行SQL语句
ResultSet rs = ps.executeQuery();
//创建对象集合
List<User> list = new ArrayList<>();
//处理结果集
while(rs.next()){
/*方式一:获取到的每列数据，使用setXXX()方法手动封装到User对象中
User u = new User();
u.setUid(rs.getInt("uid"));
u.setUsername(rs.getString("username"));
u.setPassword(rs.getString("password"));
u.setAge(rs.getInt("age"));
u.setGender(rs.getString("gender"));
u.setEmail(rs.getString("email"));*/
//方式二：用有参构造器封装
User u = new User(
rs.getInt("uid"),rs.getString("username"),
rs.getString("password"),rs.getInt("age"),
rs.getString("gender"),rs.getString("email")
);
//将封装的对象放入到集合中
list.add(u);
}
//增强for遍历对象集合
for (User user : list) {
System.out.println(user);
}
//释放资源
JDBCUtils_01.relase(cn, ps, rs);
}

}

工具类-JDBCUtils_01.java：

package com.xiao.utils;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
/**
* @author 笑笑
* @Date   2018年3月15日上午10:55:16
*
*/
public class JDBCUtils_01 {
//注册并获取数据库连接
public static Connection getConnection() throws Exception{
//1.注册驱动
Class.forName("com.mysql.jdbc.Driver");
//2.声明数据库连接信息，获取数据库连接
String url = "jdbc:mysql://localhost:3306/all_db";
String username = "root";
String password = "root";
Connection cn =  DriverManager.getConnection(url, username, password);
return cn;
}
//释放资源
public static void relase(Connection cn,Statement st,ResultSet rs) throws Exception{
if(rs!=null){
rs.close();
}
if(st!=null){
st.close();
}
if(cn!=null){
cn.close();
}
}

}