数据库小框架之——C3P0Utils
今天老师讲了一下如何简化后台编程，给我们挑了一个数据库后台的框架——C3P0Utils。一直是自己写的数据库操作代码，除了一些比较难的会用到框架，像数据库这种基
本上就自己写了。现在回过头来看，以前虽然是把基本功打扎实了，但是重复造了N多个轮子，而且有代码时候老是出一些小毛病（要么就是这里忘记初始化，要么就是那里忘记
捕捉异常，或者就是这个包没导进来。。。。。），浪费了自己N多时间在找Bug上面，很多时候本来热情澎湃的自己都被这些低级的毛病给折磨的要死。
虽然很多人会说上面那些错误是你粗心大意了。好吧，我承认我是有点粗心，但是谁没有个大意的时候，谁能保证在任何情况下都不会出错，谁能保证在代码量巨大的情况
下，所有东西都自己写？懂得了原理后，用人家的框架就会节省很多时间。就像牛顿说的：”站在巨人的肩膀上“，这样才能飞的更高。根本不用重复造轮子，时间不是多的没地
方用的，应该用到更有价值的地方去。
出于比较的想法，我把平常自己写的跟用框架之后的做一个对比：
一、平常自己写的：
package com.david_kuper_ma.utils;
import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;
public final class JdbcUtils {
//连接数据库的参数
private static String url = null;
private static String user = null;
private static String driver = null;
private static String password = null;
private JdbcUtils () {
}
private static JdbcUtils instance = null;
public static JdbcUtils getInstance() {
if (instance == null) {
synchronized (JdbcUtils.class) {
if (instance == null) {
instance = new JdbcUtils();
}
}
}
return instance;
}
//配置文件
private static Properties prop = new Properties();
//注册驱动
static {
try {
//利用类加载器读取配置文件
InputStream is = JdbcUtils.class.getClassLoader().getResourceAsStream("dbInfo.properties");
prop.load(is);
url = prop.getProperty("url");
user = prop.getProperty("user");
driver = prop.getProperty("driver");
password = prop.getProperty("password");
Class.forName(driver);
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
//该方法获得连接
public Connection getConnection() throws SQLException {
return DriverManager.getConnection(url, user, password);
}
//释放资源
public void free(Connection conn, Statement st, ResultSet rs) {
if (rs != null) {
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
} finally {
}
}
if (st != null) {
try {
st.close();
} catch (SQLException e) {
e.printStackTrace();
} finally {
}
}
if (conn != null) {
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
package com.david_kuper_ma.impl;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.List;
import com.david_kuper_ma.dao.DAO;
import com.david_kuper_ma.entity.User;
import com.david_kuper_ma.utils.JdbcUtils;
import com.mysql.jdbc.PreparedStatement;
public class DaoImplByJdbcUtils implements DAO {
private String sql = null;
PreparedStatement pstmt = null;
ResultSet rSet = null;
@Override
public void addUser(User user) {
// TODO Auto-generated method stub
sql = "insert into user (username,password,email) values(?,?,?)";
Connection connection = null;
try {
connection = JdbcUtils.getInstance().getConnection();
System.out.println("连接成功");
pstmt = (PreparedStatement) connection.prepareStatement(sql);
pstmt.setString(1, user.getUsername());
pstmt.setString(2, user.getPassword());
pstmt.setString(3, user.getEmail());
int count = pstmt.executeUpdate();
if (count > 0) {
System.out.println("插入成功！");
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally {
JdbcUtils.getInstance().free(connection,pstmt,null);
}
}
@Override
public void updateUser(User user) {
// TODO Auto-generated method stub
}
@Override
public void deleteUser(int id) {
// TODO Auto-generated method stub
}
@Override
public User queryByNameAndPwd(String username, String password) {
// TODO Auto-generated method stub
return null;
}
@Override
public List<User> queryAll() {
// TODO Auto-generated method stub
return null;
}
}
属性文件（dbInfo.properties）：
driver=com.mysql.jdbc.Driver url=jdbc:mysql://127.0.0.1:3306/db_training user=root password=root
二、用了C3P0Utils框架后：
<pre name="code" class="java">package com.david_kuper_ma.utils;
import javax.sql.DataSource;
import com.mchange.v2.c3p0.ComboPooledDataSource;
public class C3P0Utils {
private static DataSource dataSource = new ComboPooledDataSource();
public static DataSource getDatasource(){
return dataSource;
}
}
package com.david_kuper_ma.impl;
import java.sql.SQLException;
import java.util.List;
import org.apache.commons.dbutils.QueryRunner;
import com.david_kuper_ma.dao.DAO;
import com.david_kuper_ma.entity.User;
import com.david_kuper_ma.utils.C3P0Utils;
public class DaoImplByDBUtils implements DAO {
QueryRunner qr = new QueryRunner(C3P0Utils.getDatasource());
/**
* 就一行代码就完成了插入的操作
*/
@Override
public void addUser(User user) {
// TODO Auto-generated method stub
String sql = "insert into user(username,password,email) values(?,?,?)";
Object[] params = new Object[]{user.getUsername(),user.getPassword(),user.getEmail()};
try {
qr.update(sql,params);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
@Override
public void updateUser(User user) {
// TODO Auto-generated method stub
String sql = "update user set username = ? where id = ?";
Object[] params = new Object[]{user.getUsername(),user.getId()};
try {
qr.update(sql, params);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
@Override
public void deleteUser(int id) {
// TODO Auto-generated method stub
}
@Override
public User queryByNameAndPwd(String username, String password) {
// TODO Auto-generated method stub
return null;
}
@Override
public List<User> queryAll() {
// TODO Auto-generated method stub
return null;
}
}
配置文件（c3p0-config.xml）：
<?xml version="1.0" encoding="UTF-8"?>
<c3p0-config>
<default-config>
<!-- 数据库连接属性 -->
<property name="driverClass">com.mysql.jdbc.Driver</property>
<property name="jdbcUrl">jdbc:mysql://127.0.0.1:3306/db_training</property>
<property name="user">root</property>
<property name="password">root</property>
<!-- 连接池相应的属性 -->
<property name="initialPoolSize">10</property>
<property name="maxIdleTime">30</property>
<property name="maxPoolSize">100</property>
<property name="minPoolSize">10</property>
<property name="maxStatements">200</property>
</default-config>
</c3p0-config>