package servlet;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;
public class Demo2 {
/*
查询所有student对象
*/
public static void main(String[] args){
List list = new Demo2().findAll();
System.out.println(list);
}
public List findAll(){
Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
List list = null;
try {
//注册驱动
Class.forName("com.mysql.jdbc.Driver");
//获取连接
conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/kaorou","root", "root");
//定义sql
String sql = "select * from user ";
//获取执行sql的对象
stmt = conn.createStatement();
//执行sql
rs = stmt.executeQuery(sql);
//便利结果集,封装对象,装载集合
Student stu = null;
list = new ArrayList();
while(rs.next()){ //rs如果有下一个就循环,括号中的参数与数据库中的字段名一致
int id = rs.getInt("id");
String name = rs.getString("name");
int email = rs.getInt("email");
int age = rs.getInt("age");
//创建stu对象
stu = new Student();
stu.getId(id);
stu.getName(name);
stu.getEmail(email);
stu.getAge(age);
//装载集合
list.add(stu);
}
} catch (ClassNotFoundException | SQLException e) {
e.printStackTrace();
}finally { //先声明的后关
if (rs != null) {
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (stmt != null){
try {
stmt.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (conn != null){
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
return list;
}
}
package servlet;
/*
封装student表数据
*/
public class Student {
private int id;
private String name;
private int email;
private int age;
public int getId(int id) {
return this.id;
}
public void setId(int id) {
this.id = id;
}
public void getName(String name) {
}
public void setName(String name) {
this.name = name;
}
public int getEmail(int email) {
return this.email;
}
public void setEmail(int email) {
this.email = email;
}
public int getAge(int age) {
return this.age;
}
public void setAge(int age) {
this.age = age;
}
@Override
public String toString() {
return "Student{" +
"id=" + id +
", name='" + name + '\'' +
", sex='" + email + '\'' +
", age=" + age +
'}';
}
}
控制台报错:
[Student{id=0, name='null', sex='0', age=0}, Student{id=0, name='null', sex='0', age=0}, Student{id=0, name='null', sex='0', age=0}, Student{id=0, name='null', sex='0', age=0}, Student{id=0, name='null', sex='0', age=0}]