.NET Core 3.0之深入源码理解Configuration(一)
configuration总体介绍
微软在.net core里设计出了全新的配置体系,并以非常灵活、可扩展的方式实现。从其源码来看,其运行机制大致是,根据其source,创建一个builder实例,并会向其添加provider,在我们使用配置信息的时候,会从内存中获取相应的provider实例。
.net core采用了统一的调用方式来加载不同类型的配置信息,并通过统一的抽象接口iconfigurationsource对配置源进行管理,这也是刚刚所说的灵活。而其扩展性就是我们可以自己自定义新的provider实例,而不会改变其原来的调用方式。接下来的文章将会基于consul,扩展一个新的provider实例。
在asp.net core 中,我们的应用配置是基于iconfigurationprovider的键值对。 我们先看一下思维导图:
基于上图,我们可以看到主要有键值对源有多种,分别是:
环境变量
命令行参数
各种形式的配置文件
内存对象
用户自定义扩展源
核心对象
在介绍.net core配置功能之前,先简要说明一下microsoft.extensions.configuration.abstractions,该组件抽象了.net core的配置功能,并对自定义扩展制定了新的标准。以下介绍的四个核心对象全部来自于该组件。
iconfiguration
该接口表示一组键/值应用程序配置属性,应用程序使用配置时的入口对象,.net core对其有多种扩展,其派生类包括位于统一类库的iconfigurationsection,以及microsoft.extensions.configuration类库中的configurationroot、configurationsection、iconfigurationroot。我们可以通过di获取iconfiguration实例。
它主要有以下三个方法:
- getchildren():获取直接子配置子节
- getreloadtoken():返回一个ichangetoken,可用于确定何时重新加载配置
- getsection(string):获取指定键的子节点
我们来看一下源码:
1: /// <summary>
2: /// represents a set of key/value application configuration properties.
3: /// </summary>
4: public interface iconfiguration
5: {
6: /// <summary>
7: /// gets or sets a configuration value.
8: /// </summary>
9: /// <param name="key">the configuration key.</param>
10: /// <returns>the configuration value.</returns>
11: string this[string key] { get; set; }
12:
13: /// <summary>
14: /// gets a configuration sub-section with the specified key.
15: /// </summary>
16: /// <param name="key">the key of the configuration section.</param>
17: /// <returns>the <see cref="iconfigurationsection"/>.</returns>
18: /// <remarks>
19: /// this method will never return <c>null</c>. if no matching sub-section is found with the specified key,
20: /// an empty <see cref="iconfigurationsection"/> will be returned.
21: /// </remarks>
22: iconfigurationsection getsection(string key);
23:
24: /// <summary>
25: /// gets the immediate descendant configuration sub-sections.
26: /// </summary>
27: /// <returns>the configuration sub-sections.</returns>
28: ienumerable<iconfigurationsection> getchildren();
29:
30: /// <summary>
31: /// returns a <see cref="ichangetoken"/> that can be used to observe when this configuration is reloaded.
32: /// </summary>
33: /// <returns>a <see cref="ichangetoken"/>.</returns>
34: ichangetoken getreloadtoken();
35: }
通常我们要求配置文件要有足够的灵活性,尤其是我们所扩展的配置信息存放在了其他服务器,当修改的时候我们很需要一套监控功能,以及时灵活的应对配置信息的修改。现在.net core为我们提供了这样一个功能,我们只需要自定义少量代码即可完成配置信息的同步。这个方法就是getreloadtoken(),其返回值是ichangetoken。此处对配置信息的同步只做一个引子,后面的文章会详细说明。
由于configurationroot、configurationsection聚集于iconfiguration接口,此处也对这两个类进行讨论,方便我们对.net core的配置功能有个更加形象的印象。这两个接口,本质上就是.net core关于配置信息的读取方式。
xml是使用比较广泛的一种数据结构,我们在配置xml时,一般会使用根节点、父节点、子节点之类的术语,此处也一样。
configurationroot是配置的根节点,也实现了iconfigurationroot,此接口只有一个方法,其主要功能就是实现对配置信息的重新加载,另外还包括一个iconfigurationprovider类型的集合属性。其源码如下
1: /// <summary>
2: /// represents the root of an <see cref="iconfiguration"/> hierarchy.
3: /// </summary>
4: public interface iconfigurationroot : iconfiguration
5: {
6: /// <summary>
7: /// force the configuration values to be reloaded from the underlying <see cref="iconfigurationprovider"/>s.
8: /// </summary>
9: void reload();
10:
11: /// <summary>
12: /// the <see cref="iconfigurationprovider"/>s for this configuration.
13: /// </summary>
14: ienumerable<iconfigurationprovider> providers { get; }
15: }
下面是configurationroot关于reload()方法的实现
1: /// <summary>
2: /// force the configuration values to be reloaded from the underlying sources.
3: /// </summary>
4: public void reload()
5: {
6: foreach (var provider in _providers)
7: {
8: provider.load();
9: }
10:
11: raisechanged();
12: }
通过源码我们知道,如果调用了reload()方法,所有类型的provider都会重新加载。
前面有configurationroot表示配置的根节点,那么configurationsection则表示非跟节点,毕竟父节点、子节点都是相对,所以此处使用非根节点。configurationsection继承于iconfigurationsection,该接口只有三个只读属性,分别表示配置信息的key、value以及路径信息,需要指出的是,此处的路径信息主要指从根节点到当前节点的路径,以表示当前节点的位置,类似于a:b:c可以表示节点c的位置,其中a、b、c都是configurationsection的key。以下是configurationsection的源码
1: /// <summary>
2: /// represents a section of application configuration values.
3: /// </summary>
4: public interface iconfigurationsection : iconfiguration
5: {
6: /// <summary>
7: /// gets the key this section occupies in its parent.
8: /// </summary>
9: string key { get; }
10:
11: /// <summary>
12: /// gets the full path to this section within the <see cref="iconfiguration"/>.
13: /// </summary>
14: string path { get; }
15:
16: /// <summary>
17: /// gets or sets the section value.
18: /// </summary>
19: string value { get; set; }
20: }
iconfigurationbuilder
该接口主要用于创建iconfigurationprovider,其派生类包括microsoft.extensions.configuration.configurationbuilder。其成员包括
两个只读属性:
- properties:获取可用于在iconfigurationbuilder之间共享数据的键/值集合
- sources:该属性用于缓存不同的配置源,以用于相对应的provider的创建
两个方法:
- add(iconfigurationsource source):新增iconfigurationsource,并添加到属性中sources中
- build():该方法遍历sources属性,并调用iconfigurationsource的build()方法,通过获取provider集合,最终创建iconfigurationroot对象
configurationbuilder源码如下
1: /// <summary>
2: /// used to build key/value based configuration settings for use in an application.
3: /// </summary>
4: public class configurationbuilder : iconfigurationbuilder
5: {
6: /// <summary>
7: /// returns the sources used to obtain configuration values.
8: /// </summary>
9: public ilist<iconfigurationsource> sources { get; } = new list<iconfigurationsource>();
10:
11: /// <summary>
12: /// gets a key/value collection that can be used to share data between the <see cref="iconfigurationbuilder"/>
13: /// and the registered <see cref="iconfigurationprovider"/>s.
14: /// </summary>
15: public idictionary<string, object> properties { get; } = new dictionary<string, object>();
16:
17: /// <summary>
18: /// adds a new configuration source.
19: /// </summary>
20: /// <param name="source">the configuration source to add.</param>
21: /// <returns>the same <see cref="iconfigurationbuilder"/>.</returns>
22: public iconfigurationbuilder add(iconfigurationsource source)
23: {
24: if (source == null)
25: {
26: throw new argumentnullexception(nameof(source));
27: }
28:
29: sources.add(source);
30: return this;
31: }
32:
33: /// <summary>
34: /// builds an <see cref="iconfiguration"/> with keys and values from the set of providers registered in
35: /// <see cref="sources"/>.
36: /// </summary>
37: /// <returns>an <see cref="iconfigurationroot"/> with keys and values from the registered providers.</returns>
38: public iconfigurationroot build()
39: {
40: var providers = new list<iconfigurationprovider>();
41: foreach (var source in sources)
42: {
43: var provider = source.build(this);
44: providers.add(provider);
45: }
46: return new configurationroot(providers);
47: }
48: }
此处令人感慨颇多,我们最终调用 configurationroot 的构造函数,究其原因是provider提供了统一的数据访问方式,不管是基于何种类型的provider,我们都可以调用其load()方法加载配置项。此外,iconfigurationbuilder本身有很多的扩展方法来注册数据源,比如addjsonfile()扩展方法。我们来看一下,我们常见的写法,
1: var builder = new configurationbuilder()
2:
3: .setbasepath(env.contentrootpath)
4:
5: .addjsonfile("appsettings1.json", false, true)
6:
7: .addjsonfile("appsettings2.json", false, true);
8:
9: configuration = builder.build();
iconfigurationsource
该接口表示应用程序配置的键值对。其派生类包括microsoft.extensions.configuration.chainedconfigurationsource、microsoft.extensions.configuration.memory.memoryconfigurationsource。另外该派生类还会在文件类配置场景下依赖microsoft.extensions.configuration.fileextensions组件。
它是所有配置源的抽象表示,包括json、xml、ini、环境变量等等。通过上文我们也知道了,iconfigurationbuilder会注册多个iconfigurationsource实例。它只有一个方法,就是build()方法,并返回iconfigurationprovider,由此可见,iconfigurationprovider的创建依赖于iconfigurationsource,这也是一一对应的关系。所有不同的源最终都会转化成统一的键值对表示。
以下为
1: /// <summary>
2: /// represents a source of configuration key/values for an application.
3: /// </summary>
4: public interface iconfigurationsource
5: {
6: /// <summary>
7: /// builds the <see cref="iconfigurationprovider"/> for this source.
8: /// </summary>
9: /// <param name="builder">the <see cref="iconfigurationbuilder"/>.</param>
10: /// <returns>an <see cref="iconfigurationprovider"/></returns>
11: iconfigurationprovider build(iconfigurationbuilder builder);
12: }
以下是memoryconfigurationsource的源码
1: /// <summary>
2: /// represents in-memory data as an <see cref="iconfigurationsource"/>.
3: /// </summary>
4: public class memoryconfigurationsource : iconfigurationsource
5: {
6: /// <summary>
7: /// the initial key value configuration pairs.
8: /// </summary>
9: public ienumerable<keyvaluepair<string, string>> initialdata { get; set; }
10:
11: /// <summary>
12: /// builds the <see cref="memoryconfigurationprovider"/> for this source.
13: /// </summary>
14: /// <param name="builder">the <see cref="iconfigurationbuilder"/>.</param>
15: /// <returns>a <see cref="memoryconfigurationprovider"/></returns>
16: public iconfigurationprovider build(iconfigurationbuilder builder)
17: {
18: return new memoryconfigurationprovider(this);
19: }
20: }
iconfigurationprovider
通过上文的介绍,我们可以知道iconfigurationprovider是统一的对外接口,对用户提供配置的查询、重新加载等功能。其派生类包括microsoft.extensions.configuration.configurationprovider、microsoft.extensions.configuration.chainedconfigurationprovider、microsoft.extensions.configuration.memory.memoryconfigurationprovider。另外该派生类还会在文件类配置场景下依赖microsoft.extensions.configuration.fileextensions组件。
以下是microsoft.extensions.configuration.configurationprovider的源码:
1: /// <summary>
2: /// base helper class for implementing an <see cref="iconfigurationprovider"/>
3: /// </summary>
4: public abstract class configurationprovider : iconfigurationprovider
5: {
6: private configurationreloadtoken _reloadtoken = new configurationreloadtoken();
7:
8: /// <summary>
9: /// initializes a new <see cref="iconfigurationprovider"/>
10: /// </summary>
11: protected configurationprovider()
12: {
13: data = new dictionary<string, string>(stringcomparer.ordinalignorecase);
14: }
15:
16: /// <summary>
17: /// the configuration key value pairs for this provider.
18: /// </summary>
19: protected idictionary<string, string> data { get; set; }
20:
21: /// <summary>
22: /// attempts to find a value with the given key, returns true if one is found, false otherwise.
23: /// </summary>
24: /// <param name="key">the key to lookup.</param>
25: /// <param name="value">the value found at key if one is found.</param>
26: /// <returns>true if key has a value, false otherwise.</returns>
27: public virtual bool tryget(string key, out string value)
28: => data.trygetvalue(key, out value);
29:
30: /// <summary>
31: /// sets a value for a given key.
32: /// </summary>
33: /// <param name="key">the configuration key to set.</param>
34: /// <param name="value">the value to set.</param>
35: public virtual void set(string key, string value)
36: => data[key] = value;
37:
38: /// <summary>
39: /// loads (or reloads) the data for this provider.
40: /// </summary>
41: public virtual void load()
42: { }
43:
44: /// <summary>
45: /// returns the list of keys that this provider has.
46: /// </summary>
47: /// <param name="earlierkeys">the earlier keys that other providers contain.</param>
48: /// <param name="parentpath">the path for the parent iconfiguration.</param>
49: /// <returns>the list of keys for this provider.</returns>
50: public virtual ienumerable<string> getchildkeys(
51: ienumerable<string> earlierkeys,
52: string parentpath)
53: {
54: var prefix = parentpath == null ? string.empty : parentpath + configurationpath.keydelimiter;
55:
56: return data
57: .where(kv => kv.key.startswith(prefix, stringcomparison.ordinalignorecase))
58: .select(kv => segment(kv.key, prefix.length))
59: .concat(earlierkeys)
60: .orderby(k => k, configurationkeycomparer.instance);
61: }
62:
63: private static string segment(string key, int prefixlength)
64: {
65: var indexof = key.indexof(configurationpath.keydelimiter, prefixlength, stringcomparison.ordinalignorecase);
66: return indexof < 0 ? key.substring(prefixlength) : key.substring(prefixlength, indexof - prefixlength);
67: }
68:
69: /// <summary>
70: /// returns a <see cref="ichangetoken"/> that can be used to listen when this provider is reloaded.
71: /// </summary>
72: /// <returns></returns>
73: public ichangetoken getreloadtoken()
74: {
75: return _reloadtoken;
76: }
77:
78: /// <summary>
79: /// triggers the reload change token and creates a new one.
80: /// </summary>
81: protected void onreload()
82: {
83: var previoustoken = interlocked.exchange(ref _reloadtoken, new configurationreloadtoken());
84: previoustoken.onreload();
85: }
86:
87: /// <summary>
88: /// generates a string representing this provider name and relevant details.
89: /// </summary>
90: /// <returns> the configuration name. </returns>
91: public override string tostring() => $"{gettype().name}";
92: }
通过源码,我们可以知道configurationprovider以字典类型缓存了多个provider对象,有需要的时候,从内存中获取即可,配置的加载通过load()方法实现,在configurationroot里我们介绍了其reload,并且说明其方法是在循环调用configurationprovider的load方法,但是此处只提供了一个虚方法,其目的是要交给其他具体的provider,比如环境变量、json、xml等,这些具体的provider可以从相应的配置源中获取配置信息。所有的子节点key通过getchildkeys方法实现,其重新加载方式通过configurationreloadtoken实例完成。
另外需要说明一下,在configurationprovider构造函数里,对字典进行了初始化,并同时设置了字典key不受大小写限制,这是一个需要注意的细节。
configuration组件结构
通过查看.net配置功能的源码,所有依赖均基于microsoft.extensions.configuration.abstractions,在其上有一层实现,即microsoft.extensions.configuration,其内部也多数是抽象实现,并提供了多个虚方法交给其派生组件,比如环境变量、命令行参数、各种文件型配置等,当然各种文件型配置还要依赖microsoft.extensions.configuration.fileextensions组件。
以下是.net core 3.0预览版里的configuration各个组件的结构图:
上一篇: php 读取文件乱码问题
下一篇: 科二教练的心都操碎了
推荐阅读
-
.NET Core 3.0之深入源码理解Configuration(二)
-
.NET Core 3.0之深入源码理解Configuration(三)
-
【.NET Core项目实战-统一认证平台】第十二章 授权篇-深入理解JWT生成及验证流程
-
.NET Core 3.0之深入源码理解Configuration(一)
-
.NET Core 3.0之创建基于Consul的Configuration扩展组件
-
【春华秋实】深入源码理解.NET Core中Startup的注册及运行
-
.NET Core 3.0之深入源码理解Configuration(三)
-
.NET Core 3.0之深入源码理解Configuration(二)
-
【.NET Core项目实战-统一认证平台】第十二章 授权篇-深入理解JWT生成及验证流程
-
【春华秋实】深入源码理解.NET Core中Startup的注册及运行