Question

java怎么把数据库的东西导入LIST中

本人小白 还请大神详细说明

Answer 1

本例使用 mysql 数据库，演示将数据库 test 的 tb_users 表中的用户信息存储到 List 中

代码如下：

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;

// 用户类，存储单个用户信息
class User {
	
	private int id;
	
	private String name;

	public User(int id, String name) {
		this.id = id;
		this.name = name;
	}

	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;
	}

	@Override
	public String toString() {
		return "User [id=" + id + ", name=" + name + "]";
	}
}

public class Demo1 {

	public static void main(String[] args) throws ClassNotFoundException, SQLException {
		
		// 本例使用 mysql 数据库，演示将数据库 test 的 tb_users 表中的用户信息
		// 放到 List 中
		
		// 加载数据驱动
		Class.forName("com.mysql.jdbc.Driver");
		
		// 数据库连接字符串, 此例数据库为 test
		String url = "jdbc:mysql://localhost:3306/test";
		String user = "root";	// 数据库用户名
		String password = "";	// 数据库密码
		
		// 打开一个数据连接
		Connection conn = DriverManager.getConnection(url, user, password);
		
		Statement stmt = conn.createStatement();
		
		// 获取表 tb_users 所有用户信息到结果集中
		ResultSet rs = stmt.executeQuery("SELECT id, name FROM tb_users");
		
		// 定义一个存放用户信息的 List
		List<User> users = new ArrayList<>();
		
		// 提取用户信息，并将用户信息放入 List
		while (rs.next()) {
			
			// 获取用户ID
			int id = rs.getInt(1);
			
			// 获取用户名
			String name = rs.getString(2);
			
			users.add(new User(id, name));
		}

		rs.close();
		stmt.close();
		conn.close();
		
		// 显示用户信息
		
		for (User u : users) {
			System.out.println(u);
		}
	}
}

Answer 2

创建数据库连接，写查询语句进行查询，返回数据

Answer 3

private String url="jdbc:mysql://localhost:3306/sexy?useUnicode=true&charset=utf-8";
private String user="root";
private String password="root";
private String driver="com.mysql.jdbc.Driver";
Connection conn=null;
PreparedStatement ps=null;
ResultSet rs=null;
//连接数据库
Class.forName(driver);
conn= DriverManager.getConnection(url, user, password);
PreparedStatement ps = getConnnection().prepareStatement(sql);
ResultSet rs = ps.executeQuery();
List<Emp> list=new ArrayList()<Emp>;
//把连接数据库的result返回给emp类，加入到list集合中
while (rs.next()) {
Emp emp = new Emp();
emp.setId(rs.getInt(1));
emp.setName(rs.getString(2));
emp.setBirthday(rs.getDate(3));
emp.setSex(rs.getString(4));
list.add(emp);
}
} catch (SQLException e) {
e.printStackTrace();
}
//得到的list就是从数据库查到的数据集合
//Emp entity实体类
package entity;
import java.sql.Date;
public class Emp {
private int id;
private String name;
private String sex;
private Date birthday;
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 String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}

public String toString() {
return "Emp [id=" + id + ", name=" + name + ", sex=" + sex
+ ", birthday=" + birthday + "]";
}
public Emp(int id, String name, String sex, Date birthday) {
super();
this.id = id;
this.name = name;
this.sex = sex;
this.birthday = birthday;
}
public Emp() {
super();
}

}
Emp数据库表sql表
/*
Navicat MySQL Data Transfer
Source Server : Sexy_Girl
Source Server Version : 50087
Source Host : localhost:3306
Source Database : sexy
Target Server Type : MYSQL
Target Server Version : 50087
File Encoding : 65001
Date: 2018-03-26 15:08:01
*/
SET FOREIGN_KEY_CHECKS=0;
-- ----------------------------
-- Table structure for `emp`
-- ----------------------------
DROP TABLE IF EXISTS `emp`;
CREATE TABLE `emp` (
`id` int(19) NOT NULL auto_increment,
`name` char(19) default NULL,
`birthday` date default NULL,
`sex` char(5) default NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=18 DEFAULT CHARSET=gbk;
-- ----------------------------
-- Records of emp
-- ----------------------------
INSERT INTO `emp` VALUES ('1', 'QWE', '2017-01-01', '男');
INSERT INTO `emp` VALUES ('2', 'EWQ', '2017-01-02', '男');
INSERT INTO `emp` VALUES ('3', 'QQ', '1993-01-01', '女');
INSERT INTO `emp` VALUES ('4', 'ne', '1970-01-02', '女');
INSERT INTO `emp` VALUES ('5', 'ne', '1970-01-02', '女');
INSERT INTO `emp` VALUES ('6', 'ne', '1970-01-02', '女');
INSERT INTO `emp` VALUES ('7', 'ne', '1970-01-02', '女');
INSERT INTO `emp` VALUES ('8', 'ne', '1970-01-02', '女');
INSERT INTO `emp` VALUES ('9', 'ne', '1970-01-02', '女');
INSERT INTO `emp` VALUES ('10', 'ne', '1970-01-02', '女');
INSERT INTO `emp` VALUES ('11', 'ne', '2016-01-01', '女');
INSERT INTO `emp` VALUES ('12', 'ne', '2016-01-01', '女');
INSERT INTO `emp` VALUES ('13', 'ne', '2016-01-01', '女');
INSERT INTO `emp` VALUES ('14', 'ne', '2016-01-01', '女');
INSERT INTO `emp` VALUES ('15', 'ne', '2016-01-01', '女');
INSERT INTO `emp` VALUES ('16', 'ne', '2016-01-01', '女');
INSERT INTO `emp` VALUES ('17', 'ne', '2016-01-01', '女');

Answer 4

public List<Account> find(String ownerName) {

return namedParameterJdbcTemplate

.query("select id,owner_name,balance,access_time,locked from account where owner_name = :ownerName",

Collections.singletonMap("ownerName", ownerName),

new RowMapper<Account>() {

public Account mapRow(ResultSet rs, int rowNum)

throws SQLException {

Account account = new Account();

account.setId(rs.getLong("id"));

account.setOwnerName(rs.getString("owner_name"));

account.setBalance(rs.getDouble("balance"));

account.setAccessTime(rs

.getTimestamp("access_time"));

account.setLocked(rs.getBoolean("locked"));

return account;

}

});

}

参考：网页链接

Chapter 4：使用Spring进行JDBC数据访问