BasicDAO.java

package com.charlie.dao_.dao;

import com.charlie.jdbc.utils.JDBCUtilsByDruid;
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;

/**
 * 开发BasicDAO，是其它DAO的父类
 */
public class BasicDAO<T> {  // 泛型指定具体的类型

    private QueryRunner qr = new QueryRunner();

    // 开发通用的dml方法，针对任意的表，返回影响的行数
    public int update(String sql, Object... params) {
        Connection connection = null;
        try {
            connection = JDBCUtilsByDruid.getConnection();
            return qr.update(connection, sql, params);
        } catch (SQLException e) {
            // 将一个编译异常 -> 运行异常，抛出
            throw new RuntimeException(e);
        } finally {
            JDBCUtilsByDruid.close(null, null, connection);
        }
    }

    /***
     * 返回多个对象(即查询的结果是多行)，针对任意表
     * @param sql   sql语句，可以有？
     * @param clazz 传入一个类的 Class对象，比如 Actor.class
     * @param params    传入 ? 的具体值，可以是多个
     * @return  根据 Actor.class 返回对应的 ArrayList 集合
     */
    public List<T> queryMulti(String sql, Class<T> clazz, Object... params) {
        Connection connection = null;
        try {
            connection = JDBCUtilsByDruid.getConnection();
            return qr.query(connection, sql, new BeanListHandler<T>(clazz), params);
        } catch (SQLException e) {
            throw new RuntimeException(e);
        } finally {
            JDBCUtilsByDruid.close(null, null, connection);
        }
    }

    // 查询单行结果的通用方法
    public T querySingle(String sql, Class<T> clazz, Object... params) {
        Connection connection = null;
        try {
            connection = JDBCUtilsByDruid.getConnection();
            return qr.query(connection, sql, new BeanHandler<T>(clazz), params);
        } catch (SQLException e) {
            throw new RuntimeException(e);
        } finally {
            JDBCUtilsByDruid.close(null, null, connection);
        }
    }

    // 查询单行单列，即返回单值的方法
    public Object queryScalar(String sql, Object... params) {
        Connection connection = null;
        try {
            connection = JDBCUtilsByDruid.getConnection();
            return qr.query(connection, sql, new ScalarHandler(), params);
        } catch (SQLException e) {
            throw new RuntimeException(e);
        } finally {
            JDBCUtilsByDruid.close(null, null, connection);
        }
    }
}