jdbc ---- DBUTilDao 类

1， 列用工具包  阿里的

DbUtils: JDBC Utility Component Examples

再次封装成通用的 update, query

package com.ljs.dao;

import java.sql.Connection;
import java.util.ArrayList;
import java.util.List;

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 com.ljs.util.JDBCUtil;

public class DBUtilDao{

    QueryRunner qRunner = new QueryRunner();
    Connection connection = null;
    /*
     *  查询多条结果。
     */
    public<T> List<T> queryMutil(Class<T> clazz, String sql, Object...object){
        List<T> list = new ArrayList<>();
        try {
            connection = JDBCUtil.getConn();
            list = qRunner.query(connection, sql,new BeanListHandler<T>(clazz),object);
        }catch (Exception e) {

            e.printStackTrace();
        }finally {
            JDBCUtil.close(null, null, connection);
        }

        return list;
    }

    /*
     *  查询一条结果。
     */
    public<T> T queryOne(Class<T> clazz, String sql, Object...objects){

        try {
            connection = JDBCUtil.getConn();
            T t = clazz.newInstance();
            t = qRunner.query(connection, sql, new BeanHandler<T>(clazz), objects);

            return t;
        } catch (Exception e) {

            e.printStackTrace();
        }
        return null;
    }
    /*
     * 更新表
     */
    public<T> void update(String sql, Object...objects){

        try {
            connection = JDBCUtil.getConn();
            qRunner.update(connection, sql, objects);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    /*
     * 查询某个数scalar
     */
    public String scalar(String sql, Object...objects){

        try {
            connection = JDBCUtil.getConn();
            return qRunner.query(connection, sql,new ScalarHandler<>(), objects).toString();
        } catch (Exception e) {

            e.printStackTrace();
        }

        return null;
    }

}