java 讀取src下的db.properties

此也是將數據庫與java 的JDBC連接

//這是將db.properties數據流放入內存中
            InputStream ins =  Thread.currentThread().getContextClassLoader().getResourceAsStream("db.properties"); pro.load(ins); driver=pro.getProperty("driver"); url=pro.getProperty("url"); username=pro.getProperty("username"); password=pro.getProperty("password"); ins.close();

db.properties

#MySql
#driver=com.mysql.jdbc.Driver
#url=jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf-8
#username=root
#password=root

#oracle
driver=oracle.jdbc.driver.OracleDriver
url=jdbc:oracle:thin:@127.0.0.1:1521:orcl
username=scott
password=tiger

DBUtil.java

package com.edusk.util;

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;

public class DBUtil {
    private static String driver = "";
    private static String url = "";
    private static String username = "";
    private static String password = "";
    private Connection conn = null;
    
    /*
     * 靜態代碼塊
     */
    static{
        Properties pro = new Properties();
        try {
　　　　　　　//這是將db.properties數據流放入內存中
            InputStream ins =  Thread.currentThread().getContextClassLoader().getResourceAsStream("db.properties");
            pro.load(ins);
            driver=pro.getProperty("driver");
            url=pro.getProperty("url");
            username=pro.getProperty("username");
            password=pro.getProperty("password");
            ins.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    
    public Connection getConnection() {
        try {
            Class.forName(driver);
            conn = DriverManager.getConnection(url, username, password);
        } catch (ClassNotFoundException | SQLException e) {
            e.printStackTrace();
        }
        return conn;
    }
    
    /**
     * 關閉鏈接
     * @param con
     * @param ps
     * @param rs
     */
    public static void close(Connection conn,PreparedStatement ps,ResultSet rs){
        if(conn!=null){
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if(ps!=null){
            try {
                ps.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if(rs!=null){
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

 

測試文件

TestConnection.java

package com.edusk.test;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import com.edusk.util.DBUtil;

public class TestConnection {
    
    public static void main(String[] args) {
        Connection conn = new DBUtil().getConnection();
        try {
            PreparedStatement ps = conn.prepareStatement("select empno, ename from emp");
            ResultSet rs = ps.executeQuery();
            while(rs.next()) {
                System.out.println(rs.getInt(1)+" "+rs.getString(2));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}