使用Java编写一个好用的解析配置工具类

public class PropertiesAPIs {

    public static void main(String[] args) {

        Properties properties = new Properties();

        //增加
//        properties.put(null, "abc");    报错NullPointerException
//        properties.put("a", null);      报错NullPointerException

        properties.put("john", 100);
        properties.put("wakoo", 100);
        properties.put("john", 11);     //相同的 key 会覆盖

        System.out.println("properties =" + properties);

        System.out.println(properties.get("john"));     //11
        System.out.println(properties.get("wakoo"));    //100
    }
}

ip=localhost
user=root
password=123456
datasource=druid

public class PropertiesLoadUtils {

    public static void main(String[] args) throws IOException {

        Properties properties = new Properties();

        //load()可传入 Reader 或者 InputStream
        properties.load(PropertiesLoadUtils.class.getResourceAsStream("/mysql.properties"));
//        properties.load(new FileReader("src/main/resources/mysql.properties"));

        //将所有 k-v 显示
        properties.list(System.out);
        System.out.println("----");
        System.out.println(properties.get("user"));     //root
        System.out.println(properties.get("password")); //123456
        System.out.println(properties.get("ip"));       //localhost
        System.out.println(properties.get("datasource"));   //druid

        //设置属性
        properties.setProperty("user", "Wakoo");
        System.out.println(properties.get("user")); //Wakoo

        //设置中文并且写入到 .properties 文件
        properties.setProperty("user", "加瓦编程");
    
        //中文默认会以 Unicode 编码写入
        properties.store(new FileOutputStream("src/main/resources/mysql.properties"),"写入中文");

        
        //重新读取，查看是否正确编码中文
        properties.load(new FileReader("src/main/resources/mysql.properties"));
        System.out.println(properties.getProperty("user"));
    }
}

<dependency>
  <groupId>cn.hutool</groupId>
  <artifactId>hutool-all</artifactId>
  <version>${yours.version}</version>
</dependency>

Props props = new Props("test.properties");
String user = props.getProperty("user");
String driver = props.getStr("driver");

public class HutoolProps {
    public static void main(String[] args) throws IOException {

        //加载方式一: 基于 InputStream
//        InputStream in = HutoolProps.class.getResourceAsStream("/mysql.properties");
//        Props props = new Props();

        //加载方式二: 基于绝对路径字符串, 支持定义编码
        Props props = new Props("mysql.properties", StandardCharsets.UTF_8);

        //加载方式三: 传入 Properties 对象
//        Properties properties = new Properties();
//        properties.load(new FileReader("src/main/resources/mysql.properties"));
//        Props props = new Props(properties);

        //还有其他方式....

        //获取单个配置项
        
        System.out.println("user属性值:" + props.getStr("user"));  //root
        System.out.println("user属性值:" + props.getStr("adim", "ROOT"));  //ROOT
        
        //所有属性键值
        Enumeration<?> enumeration = props.propertyNames();
        System.out.println("属性有如下:");
        while (enumeration.hasMoreElements()) {
            System.out.println(enumeration.nextElement());
        }

        Set<Map.Entry<Object, Object>> entries = props.entrySet();
        System.out.println("---- 遍历所有配置项 ----");
        for (Map.Entry<Object, Object> entry : entries) {
            System.out.println("key:" + entry.getKey() + " -> value:" + entry.getValue());
        }
        System.out.println("--------");

        //设置值，无给定键创建之。设置后未持久化
        props.setProperty("ip", "127.0.0.1");

        //若为 true, 配置文件更变时自动修改
        /*
         启动一个 SimpleWatcher 线程监控
            this.watchMonitor = WatchUtil.createModify(this.resource.getUrl(), new SimpleWatcher() {
                public void onModify(WatchEvent<?> event, Path currentPath) {
                    Props.this.load();
                }
            });
            this.watchMonitor.start();
         */
        props.autoLoad(true);
    }
}

<dependency>
    <groupId>org.yaml</groupId>
    <artifactId>snakeyaml</artifactId>
    <version>${yours.version}</version>            
</dependency>

user: root
password: 123456
datasource: druid
ip: 127.0.0.1

public class YamlUtils {

    public static void main(String[] args) {

        //基于 SankeYaml 工具类完成转换
        Yaml yaml = new Yaml();

        //基于 InputStream
        InputStream inputStream = YamlUtils.class
        .getClassLoader().getResourceAsStream("application.yml");

        //可直接封装成 Map
        /*
         * Parse the only YAML document in a stream and produce the corresponding Java object.
         *
         * @param io data to load from (BOM is respected to detect encoding and removed from the data)
         * @param <T> the class of the instance to be created
         * @return parsed object

        @SuppressWarnings("unchecked")
        public <T> T load(InputStream io) {
            return (T) loadFromReader(new StreamReader(new UnicodeReader(io)), Object.class);
        }
         */
        Map<String, Object> map = yaml.load(inputStream);

        for (String s : map.keySet()) {
            System.out.println("key:" + s + " -> value:" + map.get(s));
        }
    }
}

import lombok.Data;

/**
 * @description:
 * user: root
 * password: 123456
 * datasource: druid
 * ip: 127.0.0.1
 */
@Data
public class DbConfig {

    private String user;
    private String password;
    private String datasource;
    private String ip;
}

import org.junit.Test;
import org.yaml.snakeyaml.LoaderOptions;
import org.yaml.snakeyaml.Yaml;
import org.yaml.snakeyaml.constructor.Constructor;

@Test
public void testNestObj() {

    //Constructor 为 snakeyaml 依赖包内 class
    Yaml yaml = new Yaml(new Constructor(DbConfig.class, new LoaderOptions()));

    DbConfig dbConfig = null;

    //基于 FileReader
    try (FileReader reader = new FileReader("src/main/resources/application.yml")) {
        //加载 yaml 配置, 自动转换为 DbConfig
        dbConfig = yaml.load(reader);
        System.out.println(dbConfig);

        //查询 DbConfig 对象属性
        System.out.println(dbConfig.getUser());
        System.out.println(dbConfig.getPassword());
        System.out.println(dbConfig.getIp());
        System.out.println(dbConfig.getDatasource());
    } catch (IOException e) {
        System.out.println(e.getMessage());
        throw new RuntimeException(e);
    }
}