JDBC-基于C3p0配置连接

简易版的c3p0连接。

1.项目整体结构

这里的两个c3p0jar包必须有。

可以去http://mvnrepository.com/搜索jar包名下载，别浪费积分去csdn里面下载了...小编以前被坑过很多次。

2.新建c3p0-config.xml文件

   命名必须为c3p0-config.xml,

   必须放在src目录下，c3p0包会默认加载src目录下的c3p0-config.xml文件。

<?xml version="1.0" encoding="UTF-8"?>
<c3p0-config>
	<!-- 这是默认配置信息 -->
	<default-config>
		<!-- 连接四大参数配置 -->
		<property name="jdbcUrl">jdbc:mysql://localhost:3306/jdbctest</property>
		<property name="driverClass">com.mysql.jdbc.Driver</property>
		<property name="user">root</property>
		<property name="password">root</property>
		<!-- 池参数配置 -->
		<property name="acquireIncrement">3</property>
		<property name="initialPoolSize">10</property>
		<property name="minPoolSize">2</property>
		<property name="maxPoolSize">10</property>
	</default-config>
	
	<!-- 专门为oracle提供的配置信息 -->
	<named-config name="oracle-config">
	<property name="jdbcUrl">jdbc:mysql://localhost:3306/mydb1</property>
	<property name="driverClass">com.mysql.jdbc.Driver</property>
	<property name="user">root</property>
	<property name="password">123</property>
	<property name="acquireIncrement">3</property>
	<property name="initialPoolSize">10</property>
	<property name="minPoolSize">2</property>
	<property name="maxPoolSize">10</property>
	</named-config>
</c3p0-config>

3.新建JDBCUtil工具类

package com.test.uitls;

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

public class JDBCUtil {
	private static DataSource ds = new ComboPooledDataSource();

// 获取连接池
	public static DataSource getDataSource() {
		return ds;
	}

// 获取连接
	public static Connection getConnection() throws SQLException {
		return ds.getConnection();
	}

	/**
	 * 关闭连接
	 * @param resultSet
	 * @param pst
	 * @param connection
	 */
	public static void close(ResultSet resultSet, PreparedStatement pst, Connection connection) {
		if (resultSet != null) {
			try {
				resultSet.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
		if (pst != null) {
			try {
				pst.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
		if (connection != null) {
			try {
				connection.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
	}

}

4.数据库操作

package com.test.dao;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import com.test.uitls.JDBCUtil;

public class JDBCDao {
	/**
	 *  * 增加，删除，修改  
	 */
	public static void insertOrDeleteOrUpdate(String sql) {
		try {
			Connection connection = JDBCUtil.getConnection();
			PreparedStatement pst = connection.prepareStatement(sql);
			int execute = pst.executeUpdate();
			System.out.println("执行语句：" + sql + "," + execute + "行数据受影响");
			JDBCUtil.close(null, pst, connection);
		} catch (SQLException e) {
			System.out.println("异常提醒：" + e);
		}
	}

	/**
	 *  * 查询，返回结果集  
	 */
	public static List<Map<String, Object>> select(String sql) {
		List<Map<String, Object>> returnResultToList = null;
		try {
			Connection connection = JDBCUtil.getConnection();
			PreparedStatement pst = connection.prepareStatement(sql);
			ResultSet resultSet = pst.executeQuery();
//	returnResultToList = returnResultToList(resultSet);
			JDBCUtil.close(resultSet, pst, connection);
		} catch (SQLException e) {

			System.out.println("异常提醒：" + e);
		}
		return returnResultToList;
	}

	/**
	 *  * 数据返回集合  * @param resultSet  * @return  * @throws SQLException  
	 */
	public static List<Map<String, Object>> returnResultToList(ResultSet resultSet) {
		List<Map<String, Object>> values = null;
		try {
			// 键: 存放列的别名, 值: 存放列的值.
			values = new ArrayList<>();
			// 存放字段名
			List<String> columnName = new ArrayList<>();
			ResultSetMetaData rsmd = resultSet.getMetaData();
			for (int i = 0; i < rsmd.getColumnCount(); i++) {
				// 字段名
				columnName.add(rsmd.getColumnLabel(i + 1));
			}

			System.out.println("表字段为：");
			System.out.println(columnName);
			System.out.println("表数据为：");
			Map<String, Object> map = null;
			// 处理 ResultSet, 使用 while 循环
			while (resultSet.next()) {
				map = new HashMap<>();
				for (String column : columnName) {
					Object value = resultSet.getObject(column);
					map.put(column, value);
					System.out.print(value + "\t");
				}
				// 把一条记录的 Map 对象放入准备的 List 中
				values.add(map);
				System.out.println();
			}
		} catch (SQLException e) {
			System.out.println("异常提醒：" + e);
		}
		return values;
	}
}