13、使用DBUtils操作数据库

1、DBUtils对jdbc的操作,进行了封装.简化了jdbc的操作

2、在实现的MyDBUtils中使用了C3P0数据库,C3P0的配置文件如下

<?xml version="1.0" encoding="UTF-8"?>


<c3p0-config>
	<default-config name="mysql">
		<property name="driverClass">com.mysql.jdbc.Driver</property>
		<property name="jdbcUrl">
			jdbc:mysql://localhost:3306/testdatabase
		</property>
		<property name="user">root</property>
		<property name="password">1234</property>

		<property name="acquireIncrement">5</property>
		<property name="initialPoolSize">10</property>
		<property name="minPoolSize">5</property>
		<property name="maxPoolSize">20</property>


	</default-config>



</c3p0-config>

3、实体类User的代码

       

package com.jdbc.entity;

public class User {
	private int id;
	private String uname;
	private int age;

	public User() {
	}

	public int getId() {
		return id;
	}

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

	public String getUname() {
		return uname;
	}

	public void setUname(String uname) {
		this.uname = uname;
	}

	public int getAge() {
		return age;
	}

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

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

}

4、简化的MyDBUtils的代码如下

     

package com.jdbc.dbutils;

import java.sql.Connection;
import java.sql.SQLException;
import javax.sql.DataSource;
import com.mchange.v2.c3p0.ComboPooledDataSource;

public class MyDBUtils {
	/**
	 * 使用C3P0数据库连接池,用于获取数据库的连接,提高效率
	 */
	private static ComboPooledDataSource dataSource = null;

	/**
	 * 在第一次加载GenericityJDBCUtils类的时候,利用C3P0,初始化dataSource
	 * 然后利用dataSource,可以方便的去获取数据库的连接
	 */
	static {
		try {
			dataSource = new ComboPooledDataSource("mysql");
		} catch (Exception e) {
			throw new RuntimeException(e);
		}
	}

	/**
	 * 返回关联数据库连接池的dataSource
	 */
	public static DataSource getDataSource() {
		return dataSource;
	}

	/**
	 * 获取一个数据库的连接
	 * 
	 * @return
	 */
	public static Connection getConnection() {
		try {
			return dataSource.getConnection();
		} catch (SQLException e) {
			throw new RuntimeException(e);
		}
	}

}

 5、利用UserDao去操作数据库的代码,实现如下 

    

package com.jdbc.dbutils.userdao;

import java.util.ArrayList;
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 com.jdbc.dbutils.MyDBUtils;
import com.jdbc.entity.User;

/**
 * 用于操作user表
 * 
 */
public class UserDao {
	/**
	 * 根据用户id来查询用户
	 * 
	 * @param id
	 * @return
	 */
	public User findById(int id) {
		QueryRunner qr = null;
		User user = null;
		try {
			qr = new QueryRunner(MyDBUtils.getDataSource());
			String sql = "select * from user where id = ?";
			user = (User) qr.query(sql, id, new BeanHandler(User.class));
			return user;
		} catch (Exception e) {
			throw new RuntimeException(e);
		}
	}

	/**
	 * 查询所有的用户
	 * 
	 * @return
	 */
	public List<User> findAll() {
		QueryRunner qr = null;
		List<User> users = new ArrayList<User>();
		try {
			qr = new QueryRunner(MyDBUtils.getDataSource());
			String sql = "select * from user ";
			users = (List<User>) qr.query(sql, new BeanListHandler(User.class));
			return users;
		} catch (Exception e) {
			throw new RuntimeException(e);
		}
	}

	/**
	 * 根据分页条件来查询用户
	 * 
	 * @param start
	 * @param size
	 * @return
	 */
	public List<User> findFenYe(int start, int size) {
		QueryRunner qr = null;
		List<User> users = new ArrayList<User>();
		try {
			qr = new QueryRunner(MyDBUtils.getDataSource());
			String sql = "select * from user limit ? , ? ";
			users = (List<User>) qr.query(sql, new Object[] { start, size },
					new BeanListHandler(User.class));
			return users;
		} catch (Exception e) {
			throw new RuntimeException(e);
		}
	}

	/**
	 * 增加一个用户到数据库
	 * 
	 * @param user
	 */
	public void add(User user) {
		QueryRunner qr = null;
		try {
			qr = new QueryRunner(MyDBUtils.getDataSource());
			String sql = "insert into user( uname , age ) values( ? , ? ) ";
			qr.update(sql, new Object[] { user.getUname(), user.getAge() });
		} catch (Exception e) {
			throw new RuntimeException(e);
		}
	}

	/**
	 * 根据sql和paras 更新数据库
	 * 
	 * @param sql
	 * @param paras
	 */
	public void update(String sql, Object[] paras) {
		QueryRunner qr = null;
		try {
			qr = new QueryRunner(MyDBUtils.getDataSource());
			qr.update(sql, paras);
		} catch (Exception e) {
			throw new RuntimeException(e);
		}
	}

}

6、测试代码如下

       

package com.jdbc.dbutils.userdao;

import java.util.List;

import org.junit.Test;

import com.jdbc.entity.User;

public class UserDaoTest {

	@Test
	public void testFindById() {
		UserDao userDao = new UserDao();
		User user = userDao.findById(1);
		System.out.println(user);
	}

	@Test
	public void testFindAll() {
		UserDao userDao = new UserDao();
		List<User> users = userDao.findAll();
		for (User user : users)
			System.out.println(user);
	}

	@Test
	public void testFindFenYe() {
		UserDao userDao = new UserDao();
		List<User> users = userDao.findFenYe(0, 2);
		for (User user : users)
			System.out.println(user);
	}

	@Test
	public void testAdd() {
		UserDao userDao = new UserDao();
		User user = new User();
		user.setAge(18);
		user.setUname("哈哈");
		userDao.add(user);
	}

	@Test
	public void testDelete() {
		UserDao userDao = new UserDao();
		String sql = "delete from user where id = ? ";
		Object[] paras = { 4 };
		userDao.update(sql, paras);
	}

	@Test
	public void testUpdate() {
		UserDao userDao = new UserDao();
		String sql = "update user set uname = ? where id = ? ";
		Object[] paras = { "haha", 5 };
		userDao.update(sql, paras);
	}
}