网上商城_数据库jar包的使用

C3P0数据库Jar包的使用

0.导入数据库相关jar包

commons-dbutils-1.4.jar

c3p0-0.9.1.2.jar

1.配置C3P0-config.xml文件

<?xml version="1.0" encoding="UTF-8"?>
<c3p0-config>
    <!-- 数据库连接池 -->
    <default-config>
        <property name="user">root</property>
        <property name="password">admins</property>
        <property name="driverClass">com.mysql.jdbc.Driver</property>
        <property name="jdbcUrl">jdbc:mysql:///shop</property>
    </default-config>
</c3p0-config>   

2.然后写一个DataSourceUtils工具类

package com.shop.utils;

import com.mchange.v2.c3p0.ComboPooledDataSource;

import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

/**
 * 数据库连接工具
 */
public class DataSourceUtils {

    private static DataSource dataSource = new ComboPooledDataSource();

    private static ThreadLocal<Connection> tl = new ThreadLocal<Connection>();

    // 直接可以获取一个连接池
    public static DataSource getDataSource() {
        return dataSource;
    }

    // 获取连接对象
    public static Connection getConnection() throws SQLException {
        Connection con = tl.get();
        if (con == null) {
            con = dataSource.getConnection();
            tl.set(con);
        }
        return con;
    }

    // 开启事务
    public static void startTransaction() throws SQLException {
        Connection con = getConnection();
        if (con != null) {
            con.setAutoCommit(false);
        }
    }

    // 事务回滚
    public static void rollback() throws SQLException {
        Connection con = getConnection();
        if (con != null) {
            con.rollback();
        }
    }

    // 提交并且关闭资源及从ThreadLocal中释放
    public static void commitAndRelease() throws SQLException {
        Connection con = getConnection();
        if (con != null) {
            con.commit(); // 事务提交
            con.close();// 关闭资源
            tl.remove();// 从线程绑定中移除
        }
    }

    // 关闭资源方法
    public static void closeConnection() throws SQLException {
        Connection con = getConnection();
        if (con != null) {
            con.close();
        }
    }

    public static void closeStatement(Statement st) throws SQLException {
        if (st != null) {
            st.close();
        }
    }

    public static void closeResultSet(ResultSet rs) throws SQLException {
        if (rs != null) {
            rs.close();
        }
    }

}

3.最后在相关dao中就可以直接使用了

如：查询商品所有分类

//查询商品所有分类
public List<Category> findAllCategory() throws SQLException {
　　QueryRunner runner=new QueryRunner(DataSourceUtils.getDataSource());
　　String sql="select * from category";
　　return runner.query(sql,new BeanListHandler<Category>(Category.class));
}  

如：添加商品分类

//添加商品分类
public void saveProductCategory(Category category) throws SQLException{
    QueryRunner runner=new QueryRunner(DataSourceUtils.getDataSource());
    String sql="insert into category values(?,?)";
    runner.update(sql,category.getCid(),category.getCname());
}  

这里查询是用query方法，增删改用update方法；

查询需要映射到一个实体类，而增删改往往需要预编译参数