druid数据库连接池工具类

依赖的jar包 druid-1.1.9.jar

package com.zhanghan.utils;import com.alibaba.druid.pool.DruidDataSource;
import com.alibaba.druid.pool.DruidDataSourceFactory;
import sun.applet.Main;import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.Properties;/*** @author zhanghan* @create 2022-02-01 10:53*/
public class JDBCUtils {public static void main(String[] args) {}
//    声明数据库连接池private static DruidDataSource dataSource;//    静态代码块初始化static {Properties prop = new Properties();
//    读取JDBC.properties配置文件try {InputStream is = JDBCUtils.class.getClassLoader().getResourceAsStream("jdbc.properties");prop.load(is);
//        创建数据库连接池dataSource = (DruidDataSource) DruidDataSourceFactory.createDataSource(prop);System.out.println(dataSource.getConnection());} catch (Exception e) {e.printStackTrace();}
}/*** 获取数据库连接池中的链接* 如果返回null，说明获取链接失败，优质就是成功*/
public static Connection getConnection(){Connection connection = null;try {connection = dataSource.getConnection();}catch (SQLException e){e.printStackTrace();}return  connection;
}/*** 关闭连接，放回数据库连接池* @param connection*/public static  void close(Connection connection){if(connection!=null){try {connection.close();} catch (SQLException e) {e.printStackTrace();}}}
}

3.BaseDao

再javaWeb开发的过程中，可以创建一个抽象类baseDao来简便Dao层的开发，代码如下使用QueryRunner

依赖的jar包

package com.zhanghan.dao.impl;import com.zhanghan.utils.JDBCUtils;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import org.apache.commons.dbutils.handlers.ScalarHandler;import java.sql.Connection;
import java.sql.SQLException;
import java.util.List;/*** @author zhanghan* @create 2022-02-01 11:24*/
public abstract  class  BaseDao {//使用dautils操作数据库private QueryRunner queryRunner = new QueryRunner();/*** update()方法用来执行 insert/update/deleta语句* @return 如果返回-1说明执行失败，其他表示正常，影响的行数*/public int update(String sql,Object ... args){Connection connection = JDBCUtils.getConnection();try {int update = queryRunner.update(connection, sql, args);return  update;} catch (SQLException e) {e.printStackTrace();}finally{JDBCUtils.close(connection);}return  -1;}/*** 查询返回一个javaBean的* @param sql 执行的sql 语句* @param type 返回的对象类型* @param args sql对应的参数* @param <T> 返回的类型的泛型* @return*/public <T> T queryForOne(String sql,Class<T> type,Object ... args){Connection connection = JDBCUtils.getConnection();try {return  queryRunner.query(connection,sql,new BeanHandler<T>(type),args);} catch (SQLException e) {e.printStackTrace();}finally{JDBCUtils.close(connection);}return null;}/*** 查询返回多个javaBean的* @param sql 执行的sql 语句* @param type 返回的对象类型* @param args sql对应的参数* @param <T> 返回的类型的泛型* @return*/public <T> List<T> queryForList(String sql,Class<T> type,Object ... args){Connection connection = JDBCUtils.getConnection();try {return  queryRunner.query(connection,sql,new BeanListHandler<T>(type),args);} catch (SQLException e) {e.printStackTrace();}finally{JDBCUtils.close(connection);}return null;}/*** 查询返回一行一列的情况* @param sql* @param args* @return*/public Object queryForSingleValue(String sql,Object ... args){Connection connection = JDBCUtils.getConnection();try {return  queryRunner.query(connection,sql,new ScalarHandler(),args);} catch (Exception e) {e.printStackTrace();}finally{JDBCUtils.close(connection);}return  null;}
}