public class JdbcUtils {
//定义一个连接池
private static BasicDataSource bd = new BasicDataSource();
//工具类，私有他的无参构造
private JdbcUtils() {
super();
}
//使用静态代码块进行连接池的属性配置 
//静态代码块是随着类的加载而加载的且只加载一次（节省资源）
static {
/*
* 必须设置的项
*/
//设置mySQL的驱动
bd.setDriverClassName("com.mysql.jdbc.Driver");
//设置要连接数据库的URL
bd.setUrl("jdbc:mysql://localhost:3306/mydb");
//设置用户名
bd.setUsername("root");
//设置数据库密码
bd.setPassword("root");
/*
* 选择设置的项，不设置的话会有默认值跟着
*/
//初始化连接数
bd.setInitialSize(10);
//最大连接数
bd.setMaxActive(15);
//最大空闲连接数
bd.setMaxIdle(6);
//最小空闲连接数
bd.setMinIdle(3);
}
/**
* 获取连接池对象
* @return bd 连接池
*/
public static DataSource getDataSource() {
return bd;
}
}

public static void main(String[] args) throws Exception {
// 获得C3P0连接池对象
ComboPooledDataSource source = new ComboPooledDataSource();
// 设置驱动
source.setDriverClass("com.mysql.jdbc.Driver");
// 设置连接库的路径
source.setJdbcUrl("jdbc:mysql:///mydb");
// 设置用户名
source.setUser("root");
// 设置密码
source.setPassword("root");
// 通过连接池创建一个QueryRunner对象
QueryRunner runner = new QueryRunner(source);
// 测试
String sql = "SELECT * FROM users";
List<Object[]> list = runner.query(sql, new ArrayListHandler());
for (Object[] objects : list) {
for (Object object : objects) {
System.out.print(object + " ");
}
System.out.println();
}
}

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

public class C3p0Utils {
// 定义一个c3p0连接池
private static ComboPooledDataSource source;
// 定义一个连接对象
private static Connection connection;

private C3p0Utils() {
super();
}

static {
// 初始化连接池
source = new ComboPooledDataSource();
try {
// 获得一个连接
connection = source.getConnection();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

public static Connection getConnection() {
return connection;
}
}

/**
* 增加操作
* @throws SQLException
*/
private static void method01() throws SQLException {
// 通过工具类获得连接
Connection connection = JdbcUtilsConfig.getConnection();
// 获得QueryRunner对象
QueryRunner runner = new QueryRunner();
// 编写sql语句
String insert = "INSERT INTO sort(sname,sprice,sdesc) VALUES(?,?,?)";
// 执行update方法，也可以将数据存到Object数组里然后传入数组，返回值为影响的行数
int update = runner.update(connection, insert, "家具", 1000, "很好用");
System.out.println(update);
}

/**
* 更新操作
* 
* @throws SQLException
*/
private static void method02() throws SQLException {
// 通过工具类获得连接
Connection connection = JdbcUtilsConfig.getConnection();
// 获得QueryRunner对象
QueryRunner runner = new QueryRunner();
// 编写sql语句
String s = "UPDATE sort SET sname=?,sprice=?,sdesc=? WHERE sid=4";
// 执行update方法
runner.update(connection, s, "花卉", 100, "买给你爱的人");
//安静的关闭
DbUtils.closeQuietly(connection);
}

/**
* 删除操作
* 
* @throws SQLException
*/
private static void method03() throws SQLException {
// 通过工具类获得连接
Connection connection = JdbcUtilsConfig.getConnection();
// 创建一个QueryRunner对象，用来完成SQL语句的执行
QueryRunner qr = new QueryRunner();
// 执行SQL语句
String sql = "DELETE FROM zhangwu WHERE name = ?";
Object[] params = { "股票收入" };
int line = qr.update(connection, sql, params);
// 结果集的处理，影响的行数
System.out.println("line=" + line);
}

public static void main(String[] args) throws Exception {
// 通过工具类获得连接池对象
DataSource dataSource = C3p0Utils.getDataSource();
// 通过连接池创建一个QueryRunner对象
QueryRunner runner = new QueryRunner(dataSource);
// 编写sql语句
String sql = "SELECT * FROM users";
// 执行query方法传入ArrayListHandler返回集合
List<Object[]> list = runner.query(sql, new ArrayListHandler());
// 遍历集合
for (Object[] objects : list) {
for (Object object : objects) {
System.out.print(object + " ");
}
System.out.println();
}
}

/**
     * 商品详情查询
     * 
     * @param pid
     * @return product
     * @throws Exception
     */
    @Override
    public Product findByPid(String pid) throws Exception {
        //通过连接池创建QueryRunner对象
        QueryRunner queryRunner = new QueryRunner(C3p0Utils.getDataSourse());
        //根据传入的商品ID编写sql语句
        String sql = "SELECT * FROM product WHERE pid=?";
        //传入sql语句和BeanHandler结果集返回商品Bean
        Product product = queryRunner.query(sql, new BeanHandler<Product>(Product.class), pid);
        return product;
    }

    /**
     * 商品总数查询
     * @return totalCount
     * @throws Exception
     */
    @Override
    public Integer findAdmintotalCount() throws Exception {
        QueryRunner queryRunner = new QueryRunner(C3p0Utils.getDataSourse());
        //pflag字段为是否下架
        String sql = "SELECT COUNT(*) FROM product WHERE pflag=?";
        Long totalCount = (Long) queryRunner.query(sql, new ScalarHandler(),Product.UN_FLAG);
        //将Long转换成Integer类型返回
        return totalCount.intValue();
    }

/**
     * 根据类别查询商品
     * 
     * @param cid 商品ID
     * @param beginPage 起始页
     * @param pageSize 每页显示的条数
     * @return list
     * @throws Exception
     */
    @Override
    public List<Product> findPageByCid(String cid, Integer beginPage, Integer pageSize) throws Exception {
        QueryRunner queryRunner = new QueryRunner(C3p0Utils.getDataSourse());
        //分页查询
        String sql = "SELECT * FROM product WHERE cid=? AND pflag=? LIMIT ?,?";
        //BeanListHandler里泛型要写你查询实体Bean类型，传入参数为Bean.class
        List<Product> list = queryRunner.query(sql, new BeanListHandler<Product>(Product.class), cid, Product.UN_FLAG,
                beginPage, pageSize);
        //返回结合
        return list;
    }