scala 中配置文件之 config

Typesafe的Config库，纯Java写成、零外部依赖、代码精简、功能灵活、API友好。支持Java properties、JSON、JSON超集格式HOCON以及环境变量。它也是Akka的配置管理库.

Overview

纯java实现，无任何依赖充分的测试支持: Java properties, JSON, and a human-friendly JSON superset可以合并各种格式的配置文件可以通过文件、urls、classpath加载配置支持多层嵌套的配置方式识别Java system properties, 如java -Dmyapp.foo.bar=10可以转换长短，大小等单位。如配置文件中timeout=10s,则可以转换成任意的毫秒或者类型转换，比如yes可以转换为boolean类型的trueJSON superset features:    comments    includes    substitutions ("foo" : ${bar}, "foo" : Hello ${who})    properties-like notation (a.b=c)    less noisy, more lenient syntax    substitute environment variables (logdir=${HOME}/logs)

example
默认加载classpath下的application.conf,application.json和application.properties文件。通过ConfigFactory.load()加载。

# these are our own config values defined by the appsimple-app {    answer=42}

# Here we override some values used by a librarysimple-lib.foo="This value comes from simple-app's application.conf"simple-lib.whatever = "This value comes from simple-app's application.conf"

public class SimpleLibContext {    private Config config;    //指定配置文件    public SimpleLibContext(Config config) {        this.config = config;        config.checkValid(ConfigFactory.defaultReference(), "simple-lib");    }    // 默认加载classpath下的application.*    public SimpleLibContext() {        this(ConfigFactory.load());    }    //打印    public void printSetting(String path) {        System.out.println("The setting '" + path + "' is: " + config.getString(path));    }    public static void main(String[] args) {        SimpleLibContext s = new SimpleLibContext();        s.printSetting("simple-app.answer");    }}

config 文件的操作
配置内容即可以是层级关系，也可以用”.”号分隔写成一行
如：

akka { host = "0.0.0.0" port = 9999} 

用“.” 写成一行,如：

akka.host = "0.0.0.0"akka.port = 9999 

当有多个配置文件时，可以使用include 引入，如

calculator { include "common" akka { remote.netty.port = 2552 }}

另外：
akka2使用Typesafe Config库，可以使用ConfigFactory.load()加载配置文件，默认加载classpath下的application.conf, application.json and application.properties文件。ActorSystem将会把这些配置和reference.conf合并（merge）起来。

如果要写akka应用，将配置写在classpath根目录下的application.conf文件中。
如果要写基于akka的lib包，将配置写在jar包内的根目录下的reference.conf文件中.

如果多个config 文件有冲突时，解决方案有
1. a.withFallback(b)? //a和b合并，如果有相同的key，以a为准
2. a.withOnlyPath(String path)? //只取a里的path下的配置
3. a.withoutPath(String path) //只取a里出path外的配置

大家可以参考一下，conifg 的api 描述

    /**     * Obtains the default reference configuration, which is currently created     * by merging all resources "reference.conf" found on the classpath and     * overriding the result with system properties. The returned reference     * configuration will already have substitutions resolved.     *      * <p>     * Libraries and frameworks should ship with a "reference.conf" in their     * jar.     *      * <p>     * The reference config must be looked up in the class loader that contains     * the libraries that you want to use with this config, so the     * "reference.conf" for each library can be found. Use     * {@link #defaultReference(ClassLoader)} if the context class loader is not     * suitable.     *      * <p>     * The {@link #load()} methods merge this configuration for you     * automatically.     *      * <p>     * Future versions may look for reference configuration in more places. It     * is not guaranteed that this method <em>only</em> looks at     * "reference.conf".     *      * @return the default reference config for context class loader     */    public static Config defaultReference() {        return defaultReference(checkedContextClassLoader("defaultReference"));    }