一、背景

顾名思义，插件化开发就是将某个功能代码封装为一个插件模块，通过插件中心的配置来下载、激活、禁用、或者卸载，主程序无需再次重启即可获取新的功能，从而实现快速集成。当然，实现这样的效果，必须遵守一些插件接口的标准，不能与已有的功能冲突。目前能支持插件化开发的成熟框架很多，但本文仅从思路的实现角度，从0到1实现简单的插件化开发框架。

二、实现思路

思路：定义插件接口 -> 实现插件接口 -> 通过反射机制加载插件 -> 调用插件方法。

开发语言：支持反射机制的所有高级语言均可实现插件式开发，或有 FFI 调用 Native 函数的编程语言。

三、Java 通过反射机制实现插件化开发

1、创建插件接口

定义插件接口：一个执行方法

package service;/*** 通用插件接口** @author yushanma* @since 2023/3/5 16:36*/
public interface IPluginService {/*** 执行插件*/public void run();
}

2、实现插件接口

package impl;
import service.IPluginService;/*** 打印插件** @author yushanma* @since 2023/3/5 16:37*/
public class MyPrinterPlugin implements IPluginService {@Overridepublic void run() {System.out.println("执行插件方法...");}
}

3、插件中心

管理与加载插件。

Step 1、插件实体类封装

package entity;import lombok.Data;/*** 插件实体类** @author yushanma* @since 2023/3/5 16:44*/
@Data
public class PluginEntity {/*** 插件名*/private String pluginName;/*** 插件路径*/private String jarPath;/*** 字节码名字*/private String className;
}

需要获取插件名、插件实现的Jar包路径、字节码路径

Step 2、通过反射机制实现插件实例化

package loader;import entity.PluginEntity;
import exception.PluginException;
import lombok.Data;
import lombok.NoArgsConstructor;
import service.IPluginService;import java.io.File;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.HashMap;
import java.util.List;
import java.util.Map;/*** 插件管理器** @author yushanma* @since 2023/3/5 16:44*/
@Data
@NoArgsConstructor
public class PluginManager {private Map<String, Class<?>> clazzMap = new HashMap<>();public PluginManager(List<PluginEntity> plugins) throws PluginException {initPlugins(plugins);}public void initPlugin(PluginEntity plugin) throws PluginException {try {//URL url = new URL("file:" + plugin.getJarPath());URL url = new File(plugin.getJarPath()).toURI().toURL();URLClassLoader classLoader = new URLClassLoader(new URL[]{url});Class<?> clazz = classLoader.loadClass(plugin.getClassName());clazzMap.put(plugin.getClassName(), clazz);} catch (Exception e) {throw new PluginException("plugin " + plugin.getPluginName() + " init error: >>> " + e.getMessage());}}public void initPlugins(List<PluginEntity> plugins) throws PluginException {for (PluginEntity plugin : plugins) {initPlugin(plugin);}}public IPluginService getInstance(String className) throws PluginException {Class<?> clazz = clazzMap.get(className);Object instance = null;try {instance = clazz.newInstance();} catch (Exception e) {throw new PluginException("plugin " + className + " instantiate error," + e.getMessage());}return (IPluginService) instance;}
}

Step 3、通过 XML 文件来配置管理插件

        <dependency><groupId>org.dom4j</groupId><artifactId>dom4j</artifactId><version>2.1.1</version></dependency>

package conf;import entity.PluginEntity;
import exception.PluginException;
import org.dom4j.Document;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;import java.io.File;
import java.util.ArrayList;
import java.util.List;/*** 解析 XML 插件配置** @author yushanma* @since 2023/3/5 16:44*/
public class PluginXmlParser {public static List<PluginEntity> getPluginList() throws PluginException {List<PluginEntity> list = new ArrayList<>();SAXReader saxReader = new SAXReader();Document document = null;try {document = saxReader.read(new File("src/main/resources/plugin.xml"));} catch (Exception e) {throw new PluginException("read plugin.xml error," + e.getMessage());}Element root = document.getRootElement();List<?> plugins = root.elements("plugin");for (Object pluginObj : plugins) {Element pluginEle = (Element) pluginObj;PluginEntity plugin = new PluginEntity();plugin.setPluginName(pluginEle.elementText("name"));plugin.setJarPath(pluginEle.elementText("jar"));plugin.setClassName(pluginEle.elementText("class"));list.add(plugin);}return list;}}

<!-- plugin.xml -->
<?xml version="1.0" encoding="UTF-8"?>
<plugins><plugin><name>测试插件</name><jar>plugins/PrinterPlugin-1.0-SNAPSHOT.jar</jar><class>impl.MyPrinterPlugin</class></plugin><plugin><name>测试插件</name><jar>plugins/PrinterPlugin-1.0-SNAPSHOT.jar</jar><class>impl.MyPrinterPlugin</class></plugin>
</plugins>

Step 4、解析 XML 文件并加载插件

package loader;import conf.PluginXmlParser;
import entity.PluginEntity;
import exception.PluginException;
import service.IPluginService;import java.util.List;/*** 插件加载器** @author yushanma* @since 2023/3/5 16:44*/
public class PluginLoader {public void run() throws PluginException {// 从配置文件加载插件List<PluginEntity> pluginList = PluginXmlParser.getPluginList();PluginManager pluginManager = new PluginManager(pluginList);for (PluginEntity plugin : pluginList) {IPluginService pluginService = pluginManager.getInstance(plugin.getClassName());System.out.println("开始执行[" + plugin.getPluginName() + "]插件...");// 调用插件pluginService.run();System.out.println("[" + plugin.getPluginName() + "]插件执行完成");}// 动态加载插件
//        PluginEntity plugin = new PluginEntity();
//        plugin.setPluginName("");
//        plugin.setJarPath("");
//        plugin.setClassName("");
//        pluginManager.initPlugin(plugin);
//        IPluginService pluginService = pluginManager.getInstance("");
//        pluginService.run();}
}

4、测试效果

import exception.PluginException;
import loader.PluginLoader;/*** desc** @author yushanma* @since 2023/3/5 16:44*/
public class DemoMain {public static void main(String[] args) throws PluginException {PluginLoader loader = new PluginLoader();loader.run();}
}

四、Rust 通过 libloader 库实现插件化开发

通过 libloader 库可以调用动态链接库函数，需要 FFI 支持。

Step 1、创建 lib

cargo new --lib mydll

// 有参数没有返回值
#[no_mangle]
pub fn println(str: &str) {println!("{}", str);
}// 有参数有返回值
#[no_mangle]
pub fn add(a: usize, b: usize) -> usize {a + b
}// 没有参数没有返回值
#[no_mangle]
pub fn print_hello() {println!("Hello");
}// 字符串类型
#[no_mangle]
pub fn return_str(s1: &str) -> &str{s1
}

Step 2、toml 配置编译类型

[package]
name = "mydll"
version = "0.1.0"
edition = "2021"# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html[dependencies]# rlib：Rust库，这是cargo new默认的种类，只能被Rust调用；
# dylib：Rust规范的动态链接库，windows上编译成.dll，linux上编译成.so，也只能被Rust调用；
# cdylib：满足C语言规范的动态链接库，windows上编译成.dll，linux上编译成.so，可以被其他语言调用
# staticlib：静态库，windows上编译成.lib，linux上编译成.a，可以被其他语言调用[lib]
crate-type = ["cdylib"]

Step 3、编译为 dll

cargo build

可以看到，所有的函数都被正常导出，具体原理请参考：https://fasterthanli.me/articles/so-you-want-to-live-reload-rust

Step 4、动态加载 dll

use cstr::cstr;
use libloader::*;
use std::{ffi::CStr,os::raw::c_char};fn main() {get_libfn!("dll/mydll.dll", "println", println, (), s: &str);println("你好");get_libfn!("dll/mydll.dll", "add", add, usize, a: usize, b: usize);println!(" 1 + 2 = {}", add(1, 2));get_libfn!("dll/mydll.dll", "print_hello", print_hello, bool);print_hello();get_libfn!("dll/mydll.dll","return_str", return_str,*const c_char, s: *const c_char);let str = unsafe { CStr::from_ptr(return_str(cstr!("你好 ").as_ptr())) };print!("out {}", str.to_str().unwrap());
}

五、C# 通过反射机制实现插件化开发

Step 1、定义插件接口

namespace PluginInterface
{public interface IPlugin{// 获取插件名字public string GetName();// 获取插件所提供的功能列表public string[] GetFunction();// 执行插件某个功能public bool Execute(string fn);}}

Step 2、实现插件接口

using PluginInterface;
using System;
using System.Linq;namespace MyPlugin
{public class PrinterPlugin : IPlugin{private static readonly string PLUGIN_NAME = "PrinterPlugin";// 获取插件名字public string GetName(){return PLUGIN_NAME;}// 获取插件所提供的功能列表public string[] GetFunction(){return PrinterFunc.FuncDics.Keys.ToArray();}// 执行插件某个功能public bool Execute(string fn){return PrinterFunc.Run(fn);}// 传参功能public static object PrintLabel(string sn){Console.WriteLine($"打印标签{sn}...DONE");return true;}}
}

using System;
using System.Collections.Generic;namespace MyPlugin
{// 封装打印机支持的功能internal class PrinterFunc{// 功能字典public static Dictionary<string, Func<bool>> FuncDics = new Dictionary<string, Func<bool>>{{"PrintPhoto",PrintPhoto },{"PrintDoc",PrintDoc }};// 执行某个功能public static bool Run(string name){if (!FuncDics.ContainsKey(name)){return false;}return (bool)FuncDics[name].Invoke();}// 打印照片public static bool PrintPhoto(){Console.WriteLine("打印照片...DONE");return true;}// 打印文档public static bool PrintDoc(){Console.WriteLine("打印文档...DONE");return true;}}}

Step 3、通过反射实例化插件

using PluginInterface;
using System;
using System.Collections.Generic;
using System.IO;
using System.Reflection;namespace CLI.Loader
{public class PluginLoader{// 初始化时加载插件public PluginLoader(){LoadPlugin();}public Dictionary<string, IPlugin> ListName = new Dictionary<string, IPlugin>();// 加载所有插件public void LoadPlugin(){try{// 清除所有插件缓存ListName.Clear();// 插件文件夹string fileName = "D:\\AwsomeWorkSpace\\CLI\\Plugins\\net5.0\\";// 获取所有插件文件DirectoryInfo info = new DirectoryInfo(fileName);FileInfo[] files = info.GetFiles();foreach (FileInfo file in files){if (!file.FullName.EndsWith(".dll")){continue;}// 通过反射机制创建插件实例Assembly assembly = Assembly.LoadFile(file.FullName);Type[] types = assembly.GetTypes();foreach (Type type in types){// 如果某些类实现了预定义的插件接口，则认为该类适配与主程序(是主程序的插件)if (type.GetInterface("IPlugin") != null){// 创建该类实例IPlugin plugin = assembly.CreateInstance(type.FullName) as IPlugin;if (plugin == null){throw new Exception("插件错误");}ListName.Add(plugin.GetName(), plugin);// 调用插件的某个传参方法MethodInfo printLabel = type.GetMethod("PrintLabel");object res = printLabel.Invoke(plugin, parameters: new object[] { "HQ31122222222222" });Console.WriteLine(res?.ToString());// 调用插件内部的 Execute 方法MethodInfo execute = type.GetMethod("Execute");res = execute.Invoke(plugin, parameters: new object[] { "PrintPhoto" });Console.WriteLine(res?.ToString());res = execute.Invoke(plugin, parameters: new object[] { "PrintDoc" });Console.WriteLine(res?.ToString());}}}}catch (Exception e){Console.WriteLine(e.Message);}}// 插件启动public void Start(){Console.WriteLine("==== 插件中心 ====");Console.WriteLine("1--加载插件列表");Console.WriteLine("2--重新刷新插件");int switchVal = int.Parse(Console.ReadLine());switch (switchVal){case 1:GetPluginList();break;case 2:LoadPlugin();break; ;}}// 加载插件列表public void GetPluginList(){Console.WriteLine("--------插件列表--------");foreach (var VARIABLE in ListName.Keys){Console.WriteLine($"----{VARIABLE}");}Console.WriteLine("--------请输入插件名--------");GetPluginFunc(Console.ReadLine());}// 加载插件功能public void GetPluginFunc(string pluginName){if (!ListName.ContainsKey(pluginName)){return;}IPlugin plugin = ListName[pluginName];string[] funcList = plugin.GetFunction();for (int i = 0; i < funcList.Length; i++){Console.WriteLine(funcList[i]);plugin.Execute(funcList[i]);}}}
}

ok，可以看到，插件化开发的实现并不复杂，但是其中用到的反射机制会消耗部分性能，并且 dll 也会存在一些逆向工程或者反向注入等信安问题，需要谨慎使用。当然，框架的完善更是任重道远的过程。

六、.NET 6/7 导出非托管函数能力

环境：Visual Studio 2022 / .NET7

参考：https://github.com/dotnet/runtime/tree/main/src/coreclr/nativeaot/docs

Step 1、创建类库项目

dotnet new classlib -o mydll -f net6.0

Step 2、配置 AOT Native

<Project Sdk="Microsoft.NET.Sdk"><PropertyGroup><TargetFramework>net7.0</TargetFramework><ImplicitUsings>enable</ImplicitUsings><Nullable>enable</Nullable><PublishAot>true</PublishAot></PropertyGroup></Project>

Step 3、导出非托管函数

using System.Runtime.InteropServices;
using Seagull.BarTender.Print;namespace ClassLibrary1
{public class Class1{// 无参数有返回值[UnmanagedCallersOnly(EntryPoint = "IsOk")]public static bool IsOk(){return true;}// 有参数无返回值[UnmanagedCallersOnly(EntryPoint = "MyPrinter")]public static void MyPrinter(IntPtr pString){try{if (pString != IntPtr.Zero){string str = new(Marshal.PtrToStringAnsi(pString));Console.WriteLine(str);}}catch (Exception e){Console.WriteLine(">>> Exception " + e.Message);}}// 有参数有返回值[UnmanagedCallersOnly(EntryPoint = "MyConcat")]public static IntPtr MyConcat(IntPtr pString1, IntPtr pString2){string concat = "";try{if (pString1 != IntPtr.Zero && pString2 != IntPtr.Zero){string str1 = new(Marshal.PtrToStringAnsi(pString1));string str2 = new(Marshal.PtrToStringAnsi(pString2));concat = string.Concat(str1, str2);}}catch (Exception e){concat = e.Message;}return Marshal.StringToHGlobalAnsi(concat);}// 无参数无返回值[UnmanagedCallersOnly(EntryPoint = "PrintHello")]public static void PrintHello(){Console.WriteLine(">>> Hello");}}
}

Step 4、查看导出结果

dotnet publish /p:NativeLib=Shared /p:SelfContained=true -r win-x64 -c release

可以看到 native 、publish 文件夹，里面的 dll 文件

函数正常导出，最后一个是默认导出的函数。