配置管理库 typesafe.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。

特性：

• 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true JSON 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)

目前config只支持配置文件，如果想从数据库获取配置文件，需要自己定义。 config库很擅长合并配置。

Example

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

application.conf：

conf.foo="This value comes from simple-app's application.conf"
conf.whatever = "This value comes from simple-app's application.conf"

application.properties:

properties.foo="This value comes from simple-app's application.properties"
properties.whatever = "This value comes from simple-app's application.properties"

application.json:

{
    "id":1,
    "label":"person",
    "outE":{
 "uses":[
 {
 "id":16,
 "inV":11,
 "properties":{
 "skill":5
}
},
 {
 "id":15,
 "inV":10,
 "properties":{
 "skill":4
}
}
 ],
 "develops":[
 {
 "id":13,
 "inV":10,
 "properties":{
 "since":2009
}
},
 {
 "id":14,
 "inV":11,
 "properties":{
 "since":2010
}
}
 ]
},
    "properties":{
 "name":[
 {
 "id":0,
 "value":"marko"
}
 ],
 "location":[
 {
 "id":6,
 "value":"san diego",
 "properties":{
 "startTime":1997,
 "endTime":2001
}
},
 {
 "id":7,
 "value":"santa cruz",
 "properties":{
 "startTime":2001,
 "endTime":2004
}
},
 {
 "id":8,
 "value":"brussels",
 "properties":{
 "startTime":2004,
 "endTime":2005
}
},
 {
 "id":9,
 "value":"santa fe",
 "properties":{
 "startTime":2005
}
}
 ]
}
}

public class SimpleTypesafeConfig {
private Config config;

public SimpleTypesafeConfig(Config config) {
this.config = config;
        config.checkValid(ConfigFactory.defaultReference(), "conf");
    }
public SimpleTypesafeConfig() {
this(ConfigFactory.load());
    }
public void printSetting(String path) {
        System.out.println("The setting '" + path + "' is: " + config.getString(path));
    }
public static void main(String[] args) {
        SimpleTypesafeConfig s = new SimpleTypesafeConfig();
        s.printSetting("properties.whatever");//application.properties

//output: The setting 'properties.whatever' is: "This value comes from simple-app's application.properties"
        s.printSetting("conf.whatever");//application.conf

//output:The setting 'conf.whatever' is: This value comes from simple-app's application.conf
        s.printSetting("label");//application.conf

//output: person
    }
}

其中核心加载代码：

config.checkValid(ConfigFactory.defaultReference(), "conf");

底层调用：

    private static ClassLoader checkedContextClassLoader(String methodName) {
        ClassLoader loader = Thread.currentThread().getContextClassLoader();
if(loader == null) {
throw new BugOrBroken("Context class loader is not set for the current thread; if Thread.currentThread().getContextClassLoader() returns null, you must pass a ClassLoader explicitly to ConfigFactory." + methodName);
        } else {
return loader;
        }
    }