【JAVA高级】——封装JDBC中的DaoUtils工具类（Object类型方法）

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🥭本文内容：封装JDBC中的DaoUtils工具类（Object类型方法）

文章目录

- 一、commonsUpdae方法
- 二、commonsSelect方法
- 三、RowMapper类封装resultSet结果集
- 四、综合案例
- - 1、com.cxyzxc.www.utils包
  - - 【1】DaoUtils工具类完整代码
    - 【2】DBUtils工具类完整代码
    - 【3】DateUtils工具类完整代码
  - 2、com.cxyzxc.www.entity包
  - 3、com.cxyzxc.www.advanced包
  - 4、com.cxyzxc.www.advanced.impl包
  - 5、com.cxyzxc.www.dao包
  - 6、com.cxyzxc.www.dao.impl包
  - 7、com.cxyzxc.www.service包
  - 8、com.cxyzxc.www.service.impl包
  - 9、com.cxy.zxc.view包
  - - 【1】测试插入数据
    - 【2】测试删除数据
    - 【3】测试修改数据
    - 【4】测试查询一条数据
    - 【5】测试查询所有数据

在Dao层的DaoImpl类中，对数据表进行的增、删、改、查操作方法中存在很多相同的代码，可以将这些相同的代码抽取出来封装到一个类中，形成DaoUtils工具类，实现复用。以查询teacher表为例。

一、commonsUpdae方法

该方法是对数据表进行增、删、改的公共方法。

// 增、删、改三个方法封装成一个方法
public int commonsUpdate(String sql, Object... args) {
	Connection connection = null;
	PreparedStatement preparedStatement = null;
	// 获取数据库连接对象
	connection = DBUtils.getConnection();

	try {
		// 获取SQL语句发送对象
		preparedStatement = connection.prepareStatement(sql);
		if (args != null) {
			// 绑定参数
			for (int i = 0; i < args.length; i++) {
				preparedStatement.setObject(i + 1, args[i]);
			}
		}
		// 执行SQL语句
		int result = preparedStatement.executeUpdate();
		return result;
	} catch (SQLException e) {
		e.printStackTrace();
	} finally {
		DBUtils.closeAll(null, preparedStatement, null);
	}
	return 0;
}

二、commonsSelect方法

该方法是对数据表进行查询的公共方法，可以查询一条数据，也可以查询多条数据。不管是查询一条数据还是查询多条数据，都将查询到的数据封装到Object类型的集合中。

public List<Object> commonsSelect(String sql,RowMapper rowMapper, Object... args) {
		Connection connection = null;
	PreparedStatement preparedStatement = null;
	ResultSet resultSet = null;
	List<Object> objectList = new ArrayList<Object>();
	// 获取数据库连接对象
	connection = DBUtils.getConnection();

	try {
		// 获取SQL语句发送对象
		preparedStatement = connection.prepareStatement(sql);
		if (args != null) {
			// 绑定参数
			for (int i = 0; i < args.length; i++) {
				preparedStatement.setObject(i + 1, args[i]);
			}
		}
		// 执行SQL语句
		resultSet = preparedStatement.executeQuery();

		while (resultSet.next()) {
			Object object = rowMapper.getRow(resultSet);
			objectList.add(object);
		}
		return objectList;

	} catch (SQLException e) {
		e.printStackTrace();
	}finally {
		DBUtils.closeAll(null, preparedStatement, resultSet);
	}

	return null;
}

三、RowMapper类封装resultSet结果集

使用查询方法从表中查询出来的结果存储在ResultSet结果集中，需要从ResultSet结果集中遍历出数据封装成对应对象，然后将封装出来的对象返回给DaoImpl类使用。这个封装的过程由RowMapper类完成。

package com.cxyzxc.www.examples01;

/**
 * 数据封装类，专门用来处理查询返回的resultSet结果集
 * 
 * 针对每一个实体类，封装一个RowMapper类
 */
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Date;

public class RowMapper {
	
	public static Object getRow(ResultSet resultSet){
		
		Teacher teacher = null;
		
		try {
			//返回的结果集中有哪些字段，RowMapper类是知道的，因为他是实体类的封装类
			int tid = resultSet.getInt("tid");
			String name = resultSet.getString("name");
			int age = resultSet.getInt("age");
			Date bornDate = resultSet.getDate("bornDate");
			String email = resultSet.getString("email");
			String address = resultSet.getString("address");
			
			teacher = new Teacher(tid, name, age, bornDate, email, address);
			return teacher;
		} catch (SQLException e) {
			e.printStackTrace();
		}
		
		return null;
		
	}

}

四、综合案例

综合案例完全按照三层架构实现，创建不同的包存放不同的接口、实现类、工具类、测试类等代码。使用数据库中的teacher表来完成综合案例。

1、com.cxyzxc.www.utils包

该包用来存放项目开发所需要的数据库连接工具类DBUtils类、日期时间转换工具类DateUtils类，数据库操作工具类DaoUtils类

【1】DaoUtils工具类完整代码

package com.cxyzxc.www.utils;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

import com.cxyzxc.www.advanced.RowMapper;

public class DaoUtils {

	// 增、删、改三个方法封装成一个方法
	public int commonsUpdate(String sql, Object... args) {
		Connection connection = null;
		PreparedStatement preparedStatement = null;
		// 获取数据库连接对象
		connection = DBUtils.getConnection();

		try {
			// 获取SQL语句发送对象
			preparedStatement = connection.prepareStatement(sql);
			if (args != null) {
				// 绑定参数
				for (int i = 0; i < args.length; i++) {
					preparedStatement.setObject(i + 1, args[i]);
				}
			}
			// 执行SQL语句
			int result = preparedStatement.executeUpdate();
			return result;
		} catch (SQLException e) {
			e.printStackTrace();
		} finally {
			DBUtils.closeAll(null, preparedStatement, null);
		}
		return 0;
	}

	public List<Object> commonsSelect(String sql,RowMapper rowMapper, Object... args) {
		Connection connection = null;
		PreparedStatement preparedStatement = null;
		ResultSet resultSet = null;
		List<Object> objectList = new ArrayList<Object>();
		// 获取数据库连接对象
		connection = DBUtils.getConnection();

		try {
			// 获取SQL语句发送对象
			preparedStatement = connection.prepareStatement(sql);
			if (args != null) {
				// 绑定参数
				for (int i = 0; i < args.length; i++) {
					preparedStatement.setObject(i + 1, args[i]);
				}
			}
			// 执行SQL语句
			resultSet = preparedStatement.executeQuery();

			while (resultSet.next()) {
				Object object = rowMapper.getRow(resultSet);
				objectList.add(object);
			}
			return objectList;

		} catch (SQLException e) {
			e.printStackTrace();
		}finally {
			DBUtils.closeAll(null, preparedStatement, resultSet);
		}

		return null;
	}

}

【2】DBUtils工具类完整代码

package com.cxyzxc.www.utils;

import java.io.IOException;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;

/**
 * 跨平台方案 注册驱动 获取连接 释放资源
 */
public class DBUtils {
	// 读取配置文件的Map
	private static final Properties PROPERTIES = new Properties();
	// 声明一个ThreadLocal<Connection>对象用来存储数据库连接对象
	private static ThreadLocal<Connection> threadLocal = new ThreadLocal<Connection>();

	static {
		// 通过复用本类自带流，读取配置文件中的数据
		InputStream is = DBUtils.class.getResourceAsStream("/db.properties");

		try {
			// 通过prop对象将流中的配置信息分隔成键值对,将配置文件内容加载到properties集合
			PROPERTIES.load(is);
			// 注册驱动，通过driverName的键获取对应的值（com.mysql.jdbc.Driver）
			Class.forName(PROPERTIES.getProperty("driver"));
		} catch (IOException e) {
			e.printStackTrace();
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		}
	}

	// 获取连接对象
	public static Connection getConnection() {
		// 将当前线程中绑定的Connection对象赋值给connection变量
		Connection connection = threadLocal.get();
		try {
			// 如果连接对象为null，则创建一个连接对象
			if (connection == null) {
				connection = DriverManager.getConnection(
						PROPERTIES.getProperty("url"),
						PROPERTIES.getProperty("username"),
						PROPERTIES.getProperty("password"));
				// 将创建的连接对象存储到当前线程中共享
				threadLocal.set(connection);
			}

		} catch (SQLException e) {
			e.printStackTrace();
		}
		return connection;
	}

	// 释放所有资源
	public static void closeAll(Connection connection, Statement statement,
			ResultSet resultSet) {
		try {
			if (resultSet != null) {
				resultSet.close();
			}
			if (statement != null) {
				statement.close();
			}
			if (connection != null) {
				connection.close();
				// 将connection从threadLocal中移除
				threadLocal.remove();
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}
	}

	// 3、开启事务
	public static void startTransaction() {
		Connection connection = null;
		try {
			connection = getConnection();
			connection.setAutoCommit(false);
		} catch (SQLException e) {
			e.printStackTrace();
		}
	}

	// 4、提交事务
	public static void commitTransaction() {
		Connection connection = getConnection();
		try {
			connection.commit();
		} catch (SQLException e) {
			e.printStackTrace();
		} finally {
			DBUtils.closeAll(connection, null, null);
		}
	}

	// 5、回滚事务
	public static void rollbackTransaction() {
		Connection connection = getConnection();
		try {
			connection.rollback();
		} catch (SQLException e) {
			e.printStackTrace();
		} finally {
			DBUtils.closeAll(connection, null, null);
		}
	}
}

【3】DateUtils工具类完整代码

package com.cxyzxc.www.utils;

import java.text.ParseException;
import java.text.SimpleDateFormat;

/**
 * 日期时间工具类DateUtils
 */
public class DateUtils {

	private static final SimpleDateFormat SIMPLEDATEFORMAT = new SimpleDateFormat("yyyy-MM-dd");

	// 字符串转换为java.util.Date类型日期时间
	public static java.util.Date strDateToUtilDate(String strDate) {
		try {
			return SIMPLEDATEFORMAT.parse(strDate);
		} catch (ParseException e) {
			e.printStackTrace();
		}
		return null;
	}

	// java.util.Date类型日期时间转换为java.sql.Date类型日期时间
	public static java.sql.Date utilDateToSqlDate(java.util.Date date) {
		// long date.getTime():返回自 1970 年 1 月 1 日 00:00:00 GMT以来此 Date对象表示的毫秒数
		return new java.sql.Date(date.getTime());
	}

	// java.util.Date类转换为字符串类型
	public static String utilDateToString(java.util.Date date) {
		return SIMPLEDATEFORMAT.format(date);
	}

}

2、com.cxyzxc.www.entity包

该包用来存储实体类，根据teacher表创建实体类Teacher类

package com.cxyzxc.www.entity;

import java.util.Date;

public class Teacher {
	/** 教师编号 */
	private int tid;
	/** 姓名 */
	private String name;
	/** 年龄 */
	private int age;
	/** 出生日期 */
	private Date bornDate;
	/** 邮箱 */
	private String email;
	/** 住址 */
	private String address;

	// 无参构造方法
	public Teacher() {
		super();
	}

	// 有参构造方法
	public Teacher(String name, int age, Date bornDate, String email,
			String address) {
		super();
		this.name = name;
		this.age = age;
		this.bornDate = bornDate;
		this.email = email;
		this.address = address;
	}

	public Teacher(int tid, String name, int age, Date bornDate, String email,
			String address) {
		super();
		this.tid = tid;
		this.name = name;
		this.age = age;
		this.bornDate = bornDate;
		this.email = email;
		this.address = address;
	}

	// getXxx()/setXxx()方法
	public int getTid() {
		return tid;
	}

	public void setTid(int tid) {
		this.tid = tid;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		this.age = age;
	}

	public Date getBornDate() {
		return bornDate;
	}

	public void setBornDate(Date bornDate) {
		this.bornDate = bornDate;
	}

	public String getEmail() {
		return email;
	}

	public void setEmail(String email) {
		this.email = email;
	}

	public String getAddress() {
		return address;
	}

	public void setAddress(String address) {
		this.address = address;
	}

	// 重写Object类中的toString()方法
	@Override
	public String toString() {
		return "tid=" + tid + ", name=" + name + ", age=" + age + ", bornDate="
				+ bornDate + ", email=" + email + ", address=" + address;
	}

}

3、com.cxyzxc.www.advanced包

该包中存放RowMapper接口，用来约束封装对象的ORM

package com.cxyzxc.www.advanced;

import java.sql.ResultSet;

/**
 * 该接口用来约束封装对象的ORM
 */
public interface RowMapper {
	
	Object getRow(ResultSet resultSet);

}

4、com.cxyzxc.www.advanced.impl包

package com.cxyzxc.www.advanced.impl;

/**
 * 数据封装类，专门用来处理查询返回的resultSet结果集
 * 
 * 针对每一个实体类，封装一个RowMapper类
 */
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Date;

import com.cxyzxc.www.advanced.RowMapper;
import com.cxyzxc.www.entity.Teacher;

public class TeacherRowMapper implements RowMapper {

	@Override
	public Object getRow(ResultSet resultSet) {
		Teacher teacher = null;
		try {
			// 返回的结果集中有哪些字段，RowMapper类是知道的，因为他是实体类的封装类
			int tid = resultSet.getInt("tid");
			String name = resultSet.getString("name");
			int age = resultSet.getInt("age");
			Date bornDate = resultSet.getDate("bornDate");
			String email = resultSet.getString("email");
			String address = resultSet.getString("address");

			teacher = new Teacher(tid, name, age, bornDate, email, address);
			return teacher;
		} catch (SQLException e) {
			e.printStackTrace();
		}

		return null;
	}

}

5、com.cxyzxc.www.dao包

该包用来存放操作数据库的接口

package com.cxyzxc.www.dao;

import java.util.List;

import com.cxyzxc.www.entity.Teacher;

public interface TeacherDao {
	//增
	int insert(Teacher teacher);
	
	//删
	int delete(int tid);
	
	//改
	int update(Teacher teacher);
	
	//查单个
	Teacher selectOne(int tid);
	
	//查所有
	List<Teacher> selectAll();
	

}

6、com.cxyzxc.www.dao.impl包

该包用来存放数据库操作接口的实现类

package com.cxyzxc.www.dao.impl;

import java.util.ArrayList;
import java.util.List;

import com.cxyzxc.www.advanced.RowMapper;
import com.cxyzxc.www.advanced.impl.TeacherRowMapper;
import com.cxyzxc.www.dao.TeacherDao;
import com.cxyzxc.www.entity.Teacher;
import com.cxyzxc.www.utils.DaoUtils;

public class TeacherDaoImpl implements TeacherDao {
	/*
	 * （1）该类中提供对teacher表进行增、删、改、查单个、查所有5个方法。
	 * 
	 * （2）该类中的代码只做数据库访问操作，不做任何业务逻辑操作。
	 * 
	 * （3）该类只对数据库一张表进行操作，从而实现复用
	 */

	DaoUtils daoUtils = new DaoUtils();
	RowMapper rowMapper = new TeacherRowMapper();

	// 新增：向teacher表中插入一条数据（一条数据对应一个Teacher对象）,插入成功，返回一个受影响行数值（int类型）
	@Override
	public int insert(Teacher teacher) {

		String sql = "insert into `teacher`(name,age,bornDate,email,address) values(?,?,?,?,?);";

		// 赋值
		Object[] args = { teacher.getName(), teacher.getAge(),
				teacher.getBornDate(), teacher.getEmail(), teacher.getAddress() };

		return daoUtils.commonsUpdate(sql, args);
	}

	// 删除：根据教师tid删除一条数据,删除成功，返回一个受影响行数值（int类型）
	@Override
	public int delete(int tid) {

		String sql = "delete from teacher where tid = ?;";
		return daoUtils.commonsUpdate(sql, tid);

	}

	// 修改：修改teacher表中的数据，可能对任意的一个字段进行修改，所以方法中直接传递一个对象进行修改,修改成功，返回一个受影响行数值（int类型）
	@Override
	public int update(Teacher teacher) {

		String sql = "update teacher set name = ?,age = ?,bornDate = ?,email = ?,address = ? where tid = ?;";

		Object[] args = { teacher.getName(), teacher.getAge(),
				teacher.getBornDate(), teacher.getEmail(),
				teacher.getAddress(), teacher.getTid() };
		return daoUtils.commonsUpdate(sql, args);
	}

	// 查询单个：根据教师tid查询一条数据，查询成功返回一个结果集（ResultSet类型）,从结果集中取出元素，封装成一个Teacher对象，将该对象返回
	@Override
	public Teacher selectOne(int tid) {

		String sql = "select * from teacher where tid = ?;";
		List<Object> objectList = daoUtils.commonsSelect(sql, rowMapper, tid);

		if (objectList.size() == 1) {
			Teacher teacher = (Teacher) objectList.get(0);
			return teacher;
		} else {
			return null;
		}
	}

	// 查询所有：将teacher表中的所有数据全部查询出来，查询成功返回一个结果集（ResultSet类型）,从结果集中取出元素，封装成多个Teacher对象，将多个对象存储在集合中，返回这个集合
	@Override
	public List<Teacher> selectAll() {

		List<Teacher> teacherList = new ArrayList<Teacher>();
		String sql = "select * from teacher;";
		DaoUtils daoUtils = new DaoUtils();
		Object[] args = null;
		List<Object> objectList = daoUtils.commonsSelect(sql, rowMapper, args);
		for (int i = 0; i < objectList.size(); i++) {
			teacherList.add((Teacher) objectList.get(i));
		}
		return teacherList;
	}

}

7、com.cxyzxc.www.service包

该包用来存储业务层接口代码

package com.cxyzxc.www.service;

import java.util.List;

import com.cxyzxc.www.entity.Teacher;

public interface TeacherService {
	
	//添加老师
	int addTeacher(Teacher teacher);
	
	//删除老师
	int deleteTeacher(int tid);
	
	//修改老师
	int updateTeacher(Teacher teacher);
	
	//查询一个老师
	Teacher selectOne(int tid);
	
	//查询所有老师
	List<Teacher> selectAll();

}

8、com.cxyzxc.www.service.impl包

该包用来存储service层实现类代码

package com.cxyzxc.www.service.impl;

import java.util.List;

import com.cxyzxc.www.dao.impl.TeacherDaoImpl;
import com.cxyzxc.www.entity.Teacher;
import com.cxyzxc.www.service.TeacherService;

public class TeacherServiceImpl implements TeacherService {

	@Override
	public int addTeacher(Teacher teacher) {

		TeacherDaoImpl teacherDaoImpl = new TeacherDaoImpl();

		Teacher teacher2 = teacherDaoImpl.selectOne(teacher.getTid());

		if (teacher2 == null) {
			return teacherDaoImpl.insert(teacher);
		} else {
			System.out.println("老师已存在");
		}

		return 0;

	}

	@Override
	public int deleteTeacher(int tid) {
		TeacherDaoImpl teacherDaoImpl = new TeacherDaoImpl();
		Teacher teacher2 = teacherDaoImpl.selectOne(tid);

		if (teacher2 == null) {
			System.out.println("你要删除的老师不存在，无法删除");
		} else {
			return teacherDaoImpl.delete(tid);
		}
		return 0;

	}

	@Override
	public int updateTeacher(Teacher teacher) {
		TeacherDaoImpl teacherDaoImpl = new TeacherDaoImpl();
		Teacher teacher2 = teacherDaoImpl.selectOne(teacher.getTid());
		if (teacher2 == null) {
			System.out.println("你要修改的老师不存在，无法修改");
		} else {
			return teacherDaoImpl.update(teacher);
		}
		return 0;
	}
	
	@Override
	public Teacher selectOne(int tid){
		TeacherDaoImpl teacherDaoImpl = new TeacherDaoImpl();
		Teacher teacher =teacherDaoImpl.selectOne(tid);
		return teacher;
	}
	
	@Override
	public List<Teacher> selectAll(){
		TeacherDaoImpl teacherDaoImpl = new TeacherDaoImpl();
		return teacherDaoImpl.selectAll();
	}

}

9、com.cxy.zxc.view包

该包用来存储测试类

【1】测试插入数据

package com.cxyzxc.www.view;

import com.cxyzxc.www.entity.Teacher;
import com.cxyzxc.www.service.TeacherService;
import com.cxyzxc.www.service.impl.TeacherServiceImpl;
import com.cxyzxc.www.utils.DateUtils;

public class TestTeacherServiceImpl01Insert {

	public static void main(String[] args) {

		
		TeacherService teacherService = new TeacherServiceImpl();
		
		Teacher teacher = new Teacher(1004, "王五", 30, DateUtils.strDateToUtilDate("1992-10-07"), "13645678912@qq.com", "安徽合肥庐阳区");
		
		int result =teacherService.addTeacher(teacher);
		
		if(result!=0){
			System.out.println("老师添加成功");
		}

	}

}

【2】测试删除数据

package com.cxyzxc.www.view;

import com.cxyzxc.www.service.TeacherService;
import com.cxyzxc.www.service.impl.TeacherServiceImpl;

public class TestTeacherServiceImpl02Delete {

	public static void main(String[] args) {
		
		TeacherService teacherService = new TeacherServiceImpl();
				
		int result =teacherService.deleteTeacher(1004);
		
		if(result!=0){
			System.out.println("删除成功");
		}

	}

}

【3】测试修改数据

package com.cxyzxc.www.view;

import com.cxyzxc.www.entity.Teacher;
import com.cxyzxc.www.service.TeacherService;
import com.cxyzxc.www.service.impl.TeacherServiceImpl;
import com.cxyzxc.www.utils.DateUtils;

public class TestTeacherServiceImpl03Update {

	public static void main(String[] args) {

		TeacherService teacherService = new TeacherServiceImpl();

		Teacher teacher = new Teacher(1003, "王五", 30,
				DateUtils.strDateToUtilDate("1992-08-07"),
				"13677881122@qq.com", "安徽合肥政务区");

		int result = teacherService.updateTeacher(teacher);
		
		if(result!=0){
			System.out.println("修改成功");
		}
	}

}

【4】测试查询一条数据

package com.cxyzxc.www.view;

import com.cxyzxc.www.entity.Teacher;
import com.cxyzxc.www.service.TeacherService;
import com.cxyzxc.www.service.impl.TeacherServiceImpl;

public class TestTeacherServiceImpl04SelectOne {

	public static void main(String[] args) {

		TeacherService teacherService = new TeacherServiceImpl();

		Teacher teacher = teacherService.selectOne(1002);

		if (teacher != null) {
			System.out.println(teacher);
		} else {
			System.out.println("你查询的老师不存在");
		}

	}

}

【5】测试查询所有数据

package com.cxyzxc.www.view;

import java.util.List;

import com.cxyzxc.www.entity.Teacher;
import com.cxyzxc.www.service.TeacherService;
import com.cxyzxc.www.service.impl.TeacherServiceImpl;

public class TestTeacherServiceImpl05SelectAll {

	public static void main(String[] args) {
		
		TeacherService teacherService = new TeacherServiceImpl();

		List<Teacher> listTeacher = teacherService.selectAll();

		for (int i = 0; i < listTeacher.size(); i++) {
			System.out.println(listTeacher.get(i));
		}
	}

}