JDBC BaseDao工具类

package com.msb.blog;

import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.Field;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;
import java.util.Properties;

public class BaseDao {

    private static final String URL;
    private static final String DRIVER;
    private static final String USERNAME;
    private static final String PASSWORD;

    // 读取properties
    static {
        Properties properties = new Properties();
        InputStream is = BaseDao.class.getResourceAsStream("/db.properties");
        try {
            properties.load(is);
        } catch (IOException e) {
            e.printStackTrace();
        }
        // 赋值
        URL = properties.getProperty("URL");
        DRIVER = properties.getProperty("DRIVER");
        USERNAME = properties.getProperty("USERNAME");
        PASSWORD = properties.getProperty("PASSWORD");
        try {
            // 释放InputStream
            is.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }


    /**
     * 获取Sql连接
     *
     * @return
     */
    private Connection getConnection() {
        Connection conn = null;
        try {
            Class.forName(DRIVER);
            conn = DriverManager.getConnection(URL, USERNAME, PASSWORD);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return conn;
    }

    /**
     * 修改
     *
     * @param sql
     * @param param
     * @return
     */
    public int executeUpdate(String sql, Object... param) {
        Connection connection = getConnection();
        PreparedStatement preparedStatement = null;
        int result = 0;
        try {
            connection.setAutoCommit(false);
            preparedStatement = connection.prepareStatement(sql);
            for (int i = 0; i < param.length; i++) {
                preparedStatement.setObject(i + 1, param[i]);
            }
            result = preparedStatement.executeUpdate();
            connection.commit();

        } catch (SQLException e) {
            e.printStackTrace();
            try {
                connection.rollback();
            } catch (SQLException e1) {
                e1.printStackTrace();
            }
        } finally {
            closeAll(connection, preparedStatement);
        }

        return result;
    }

    /**
     * 查询
     *
     * @param sql
     * @param param
     * @return
     */
    public List executeQuery(Class clazz, String sql, Object... param) {
        ArrayList<Object> result = new ArrayList<>();
        Connection connection = getConnection();
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;
        try {
            preparedStatement = connection.prepareStatement(sql);
            for (int i = 0; i < param.length; i++) {
                preparedStatement.setObject(i + 1, param[i]);
            }
            resultSet = preparedStatement.executeQuery();
            ResultSetMetaData metaData = resultSet.getMetaData();
            int columnCount = metaData.getColumnCount();
            while (resultSet.next()) {
                Object obj = clazz.newInstance();
                for (int i = 1; i <= columnCount; i++) {
                    String columnName = metaData.getColumnName(i);
                    Field field = clazz.getDeclaredField(columnName.toLowerCase());
                    field.setAccessible(true);
                    field.set(obj,resultSet.getObject(columnName));
                }
                result.add(obj);
            }

        } catch (SQLException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        }finally {
            closeAll(connection,preparedStatement,resultSet);
        }
        return result;
    }

    /**
     * 释放
     *
     * @param conn
     * @param pstmt
     * @param rs
     */
    public void closeAll(Connection conn, PreparedStatement pstmt, ResultSet rs) {
        try {
            if (rs != null) {
                rs.close();
            }
            if (pstmt != null) {
                pstmt.close();
            }
            if (conn != null) {
                conn.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    /**
     * 释放
     *
     * @param conn
     * @param pstmt
     */
    public void closeAll(Connection conn, PreparedStatement pstmt) {
        try {
            if (pstmt != null) {
                pstmt.close();
            }
            if (conn != null) {
                conn.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

}

　　

ps：两个比较容易忘记的参数

url:jdbc:mysql://localhost:3306/test

driver:com.mysql.jdbc.Driver