Java_JDBC连接数据库_使用读取配置文件的方式

package com.homewoek3_4.dao;

import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Properties;

/**
 * 数据库连接通用类
 * @author Administrator
 */
public abstract class BaseDao {
    private static final String path = "database.properties";
    private static String DB_DRIVER;
    private static String DB_URL;
    private static String DB_USER;
    private static String DB_PWD;
    
    protected Connection conn = null;
    protected PreparedStatement ps = null;
    protected ResultSet rs = null;
    
    static {
        Properties pro = new Properties();
        InputStream io = BaseDao.class.getClassLoader().getResourceAsStream(path);
        try {
            //读取配置文件
            pro.load(io);
        } catch (IOException e) {
            e.printStackTrace();
        }
        DB_DRIVER = pro.getProperty("DB_DRIVER");
        DB_URL = pro.getProperty("DB_URL");
        DB_USER = pro.getProperty("DB_USER");
        DB_PWD = pro.getProperty("DB_PWD");
        try {
            //加载驱动类
            Class.forName(DB_DRIVER);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
    /**
     * 打开数据库连接
     */
    protected void openConn() {
        try {
            conn = DriverManager.getConnection(DB_URL, DB_USER, DB_PWD);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    /**
     * 关闭数据库连接
     */
    protected void closeConn() {
        try {
            if (rs != null) {
                rs.close();
            }
            if (ps != null) {
                ps.close();
            }
            if (conn != null) {
                conn.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    /**
     * 增删改
     * @param sql
     * @param obj
     * @return
     */
    protected int executeUpdate(String sql, Object...obj) {
        int result = -1;
        this.openConn();
        try {
            ps = conn.prepareStatement(sql);
            if (obj != null) {
                for (int i = 0; i < obj.length; i++) {
                    ps.setObject(i+1, obj[i]);
                }
            }
            result = ps.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return result;
    }
    /**
     * 查询
     * @param sql
     * @param obj
     * @return
     */
    protected void executeQuery(String sql, Object...obj) {
        this.openConn();
        try {
            ps = conn.prepareStatement(sql);
            if (obj != null) {
                for (int i = 0; i < obj.length; i++) {
                    ps.setObject(i+1, obj[i]);
                }
            }
            rs = ps.executeQuery();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

创建database.properties文件，注意：后缀名一定是properties。此格式的文件在MyEclipse中图标会变，这点很容易写错，要注意。

DB_DRIVER=com.mysql.jdbc.Driver
DB_URL=jdbc:mysql://localhost:3306/Pet?useUnicode=true&characterEncoding=utf8&useSSL=true
DB_USER=root
DB_PWD=111111