# 數據庫連接配置（#為注釋）
jdbc.driver=com.mysql.cj.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/test?useSSL=false
jdbc.username=root
jdbc.password=123456
# 連接池參數
jdbc.maxActive=20
jdbc.minIdle=5

import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;
import java.util.Set;

public class PropertiesReadDemo {
    public static void main(String[] args) {
        // 1. 創(chuàng)建Properties對象
        Properties props = new Properties();

        try (
            // 2. 獲取類路徑下的文件輸入流（自動關閉流）
            InputStream in = PropertiesReadDemo.class.getClassLoader().getResourceAsStream("db.properties")
        ) {
            if (in == null) {
                throw new RuntimeException("未找到db.properties文件");
            }

            // 3. 加載文件內容
            props.load(in);

            // 4. 讀取配置（方式1：指定key）
            String driver = props.getProperty("jdbc.driver");
            String url = props.getProperty("jdbc.url");
            System.out.println("數據庫驅動：" + driver);
            System.out.println("連接URL：" + url);

            // 4. 讀取配置（方式2：遍歷所有key）
            Set<String> keys = props.stringPropertyNames();
            System.out.println("\n所有配置：");
            for (String key : keys) {
                String value = props.getProperty(key);
                System.out.println(key + " = " + value);
            }

            // 4. 讀取配置（方式3：帶默認值）
            String port = props.getProperty("jdbc.port", "3306"); // 不存在則返回3306
            System.out.println("\n數據庫端口：" + port);

        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;

public class PropertiesAbsolutePathDemo {
    public static void main(String[] args) {
        Properties props = new Properties();
        // 絕對路徑
        String filePath = "D:/config/db.properties";

        try (InputStream in = new FileInputStream(filePath)) {
            props.load(in);
            System.out.println("用戶名：" + props.getProperty("jdbc.username"));
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Properties;

public class PropertiesWriteDemo {
    public static void main(String[] args) {
        // 1. 創(chuàng)建Properties對象并添加配置
        Properties props = new Properties();
        props.setProperty("app.name", "MyApplication");
        props.setProperty("app.version", "1.0.0");
        props.setProperty("app.author", "JavaDeveloper");

        // 2. 寫入文件
        String filePath = "src/main/resources/app.properties";
        try (OutputStream out = new FileOutputStream(filePath)) {
            // store(輸出流, 注釋)：注釋會被添加到文件開頭
            props.store(out, "Application Configuration");
            System.out.println("配置文件寫入成功：" + filePath);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

#Application Configuration
#Mon Jul 29 15:30:00 CST 2024
app.author=JavaDeveloper
app.name=MyApplication
app.version=1.0.0

public class ChineseEscapeDemo {
    public static void main(String[] args) {
        String chinese = "數據庫配置";
        // 轉為Unicode
        String unicode = new String(escapeChinese(chinese).getBytes());
        System.out.println(unicode); // 輸出：\u6570\u636E\u5E93\u914D\u7F6E
    }

    // 中文轉Unicode工具方法
    private static String escapeChinese(String str) {
        StringBuilder sb = new StringBuilder();
        for (char c : str.toCharArray()) {
            if (c > 127) {
                sb.append("\\u").append(Integer.toHexString(c));
            } else {
                sb.append(c);
            }
        }
        return sb.toString();
    }
}

import java.io.*;
import java.nio.charset.StandardCharsets;
import java.util.Properties;

public class PropertiesUtf8Demo {
    public static void main(String[] args) {
        // 1. 寫入UTF-8編碼的properties文件（含中文）
        Properties props = new Properties();
        props.setProperty("app.name", "我的應用");
        props.setProperty("app.desc", "這是一個測試應用");

        try (
            OutputStream out = new FileOutputStream("src/main/resources/app_utf8.properties");
            // 指定UTF-8編碼寫入
            Writer writer = new OutputStreamWriter(out, StandardCharsets.UTF_8)
        ) {
            props.store(writer, "UTF-8編碼的配置文件（含中文）");
        } catch (IOException e) {
            e.printStackTrace();
        }

        // 2. 讀取UTF-8編碼的properties文件
        try (
            InputStream in = new FileInputStream("src/main/resources/app_utf8.properties");
            // 指定UTF-8編碼讀取
            Reader reader = new InputStreamReader(in, StandardCharsets.UTF_8)
        ) {
            Properties readProps = new Properties();
            readProps.load(reader);
            System.out.println("應用名稱：" + readProps.getProperty("app.name")); // 輸出：我的應用
            System.out.println("應用描述：" + readProps.getProperty("app.desc")); // 輸出：這是一個測試應用
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

jdbc.driver=com.mysql.cj.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/test

<!-- 加載properties文件 -->
<context:property-placeholder location="classpath:db.properties"/>

<!-- 注入配置到Bean -->
<bean id="dataSource" class="com.zaxxer.hikari.HikariConfig">
    <property name="driverClassName" value="${jdbc.driver}"/>
    <property name="jdbcUrl" value="${jdbc.url}"/>
</bean>

db.username=root
db.password=123456

<configuration>
    <!-- 加載properties文件 -->
    <properties resource="mybatis.properties"/>

    <!-- 在數據源中引用 -->
    <environments default="development">
        <environment id="development">
            <dataSource type="POOLED">
                <property name="username" value="${db.username}"/>
                <property name="password" value="${db.password}"/>
            </dataSource>
        </environment>
    </environments>
</configuration>

props.setProperty("jdbc.url", "新URL");
// 必須調用store才能保存到文件
props.store(new FileOutputStream("db.properties"), "更新URL");