MySQL_JDBC_DAO复习

最新推荐文章于 2023-04-04 11:47:58 发布

原创最新推荐文章于 2023-04-04 11:47:58 发布 · 143 阅读

0 ·

CC 4.0 BY-SA版权

本文介绍了一个典型的Java分层架构案例，包括View层、Service层、DAO层等，并详细展示了DAO层的设计与实现过程，特别是如何通过BasicDao类进行数据库操作。

view层

service层

dao层

bean实体类层

sql层

dao层属于处理sql语句的java类层次，通过处理sql语句实现ORM思想，数据库表字段到java实体类中的映射（此处小白自述，往不错误之处请大家见谅，还请大家能批评指正）

一、数据库层面

创建account数据表

二、java层面

Account实体类

package bean;

public class Account {

	private int id;
	private String username;
	private double balance;

	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}

	public String getUsername() {
		return username;
	}

	public void setUsername(String username) {
		this.username = username;
	}

	public double getBalance() {
		return balance;
	}

	public void setBalance(double balance) {
		this.balance = balance;
	}

	public Account(int id, String username, double balance) {
		super();
		this.id = id;
		this.username = username;
		this.balance = balance;
	}

	public Account() {
		super();
	}

	@Override
	public String toString() {
		return "Account [id=" + id + ", username=" + username + ", balance=" + balance + "]";
	}

}

BasicDao

package dao;

import java.sql.Connection;
import java.sql.SQLException;
import java.util.List;

import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import org.apache.commons.dbutils.handlers.ScalarHandler;

import utils.JDBCUtils;

/**
 * 封装一个通用的BasicDao
 * 
 * @author Administrator
 * 功能：
 * 1、增删改(所有的表都通用)
 * 2、获取单条记录(所有的表都通用)
 * 3、获取多条记录(所有的表都通用)
 * 4、获取单个值(所有的表都通用)
 */
public class BasicDao<T> {

	QueryRunner qr;
	{
		qr = new QueryRunner();
	}
	
	//增删改
	public int update(String sql,Object ... objects){
		Connection connection = null;
		try {
			connection = JDBCUtils.getConnection();
			return qr.update(connection, sql, objects);
		} catch (Exception e) {
			throw new RuntimeException();
		} finally{
			JDBCUtils.close(null, null, connection);
		}
	}
	
	//查询返回单条记录
	public T SearchOne(String sql,Class clazz,Object ... objects){
		Connection connection = null;
		try {
			connection = JDBCUtils.getConnection();
			return qr.query(connection, sql, new BeanHandler<T>(clazz), objects);
		} catch (Exception e) {
			throw new RuntimeException();
		} finally{
			JDBCUtils.close(null, null, connection);
		}
	}
	
	//查询返回多条记录
	public List<T> SearchMore(String sql,Class clazz,Object ... objects){
		Connection connection = null;
		try {
			connection = JDBCUtils.getConnection();
			return qr.query(connection, sql, new BeanListHandler<T>(clazz), objects);
		} catch (Exception e) {
			throw new RuntimeException();
		} finally{
			JDBCUtils.close(null, null, connection);
		}
	}
	
	//查询返回单值
	public Object Scalar(String sql,Class clazz,Object ... objects){
		Connection connection = null;
		try {
			connection = JDBCUtils.getConnection();
			return qr.query(connection, sql, new ScalarHandler(), objects);
		} catch (Exception e) {
			throw new RuntimeException();
		} finally{
			JDBCUtils.close(null, null, connection);
		}
	}
}

AccountDao

package dao;

import bean.Account;

public class AccountDao extends BasicDao<Account>{

}

TestAccountDao

package demo.connection4;

import java.util.List;

import org.junit.Test;

import bean.Account;
import dao.AccountDao;

public class TestAccountDao {
	
	@Test
	public void test1(){
		AccountDao dao = new AccountDao();
		List<Account> accounts = dao.SearchMore("select * from account", Account.class);
		for (Account account : accounts) {
			System.out.println(account);
		}
	}
}

TestAccountDao运行结果