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DDDplus Framework Dynamic Plugin Jar Support
There is a newer version: 2.1.1
/*
 * Copyright DDDplus Authors.
 *
 * Licensed under the Apache License version 2.0, available at http://www.apache.org/licenses/LICENSE-2.0
 */
package io.github.dddplus.runtime.registry;

import io.github.dddplus.annotation.Extension;
import io.github.dddplus.annotation.Partner;
import io.github.dddplus.plugin.IContainerContext;
import io.github.dddplus.plugin.IPlugin;
import io.github.dddplus.plugin.IPluginListener;
import lombok.Getter;
import lombok.extern.slf4j.Slf4j;
import org.springframework.context.ApplicationContext;

import java.io.File;
import java.lang.annotation.Annotation;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;

/**
 * A Plugin is a dynamic loadable Jar that has a dedicated class loader.
 * 
 * 
Plugin Jar，业务扩展包，是可以被动态加载的Jar = (Pattern + Extension) | (Partner + Extension)
 * 基于 ClassLoader 实现的业务模块隔离，每个Plugin Jar可以有独立的Spring上下文.
 */
@Slf4j
class Plugin implements IPlugin {

    @Getter
    private final String code;

    @Getter
    private final String version; // for rollback

    // the shared class loaders
    private final ClassLoader jdkClassLoader;
    private final ClassLoader containerClassLoader;

    // parent of pluginApplicationContext
    private final ApplicationContext containerApplicationContext;
    // Spring config locations
    private String[] configLocations;

    // each Plugin will have a specific plugin class loader
    private ClassLoader pluginClassLoader;

    private boolean useSpring;

    // each Plugin will have a specific Spring IoC with the same parent: the Container
    private PluginApplicationContext pluginApplicationContext;

    Plugin(String code, String version, ClassLoader jdkClassLoader, ClassLoader containerClassLoader, ApplicationContext containerApplicationContext) {
        this.code = code;
        this.version = version;
        this.jdkClassLoader = jdkClassLoader;
        this.containerClassLoader = containerClassLoader;
        this.containerApplicationContext = containerApplicationContext;

        // 由于pluginApplicationContext.parent is containerApplicationContext
        // 如都使用相同的plugin.xml，会造成Pattern Jar的plugin.xml冲了Partner Jar里的plugin.xml：假如Pattern Jar是静态加载的
        // 为此，让每个业务扩展包的配置文件不同，保证不冲突
        this.configLocations = new String[]{"/plugin-" + code + ".xml"};
    }

    void load(String jarPath, boolean useSpring, Class identityResolverAnnotation, IContainerContext ctx) throws Throwable {
        this.useSpring = useSpring;

        // each Plugin Jar has a specific PluginClassLoader
        pluginClassLoader = new PluginClassLoader(new URL[]{new File(jarPath).toURI().toURL()}, jdkClassLoader, containerClassLoader);

        // Spring load classes in jar
        Map, List> plugableMap = prepareClasses(jarPath, identityResolverAnnotation);
        log.info("Classes prepared, plugableMap {}", plugableMap);

        // IPluginListener 不通过Spring加载，而是手工加载、创建实例
        // 如果一个jar里有多个 IPluginListener 实现，只会返回第一个实例
        IPluginListener pluginListener = JarUtils.loadBeanWithType(pluginClassLoader, jarPath, IPluginListener.class);
        if (pluginListener != null) {
            pluginListener.onPrepared(ctx);
        }

        // 现在，新jar里的类已经被新的ClassLoader加载到内存了，也实例化了，但旧jar里的类仍然在工作
        preparePlugins(identityResolverAnnotation, plugableMap);
        log.info("Plugins index prepared for {}", identityResolverAnnotation.getSimpleName());

        // 内存里插件相关索引已准备好，现在切换
        commit(identityResolverAnnotation);
        log.info("Committed: {}", identityResolverAnnotation.getSimpleName());

        if (pluginListener != null) {
            pluginListener.onCommitted(ctx);
        }
    }

    void onDestroy() {
        // 把该Plugin下的所有类的所有引用处理干净，这样才能GC介入
        if (useSpring) {
            pluginApplicationContext.close();
        }
    }

    // Spring load all relevant classes in the jar using the new PluginClassLoader
    private Map, List> prepareClasses(String jarPath, Class identityResolverAnnotation) throws Throwable {
        if (useSpring) {
            log.debug("Spring loading Plugin with {}, {}, {} ...", jdkClassLoader, containerClassLoader, pluginClassLoader);
            long t0 = System.nanoTime();

            pluginApplicationContext = new PluginApplicationContext(configLocations, containerApplicationContext, pluginClassLoader);
            pluginApplicationContext.refresh();

            log.info("Spring {} loaded, cost {}ms", configLocations, (System.nanoTime() - t0) / 1000_000);
        }

        // 从Plugin Jar里把 IPlugable 挑出来，以便更新注册表
        List> annotations = new ArrayList<>(2);
        annotations.add(identityResolverAnnotation);
        annotations.add(Extension.class);
        return JarUtils.loadClassWithAnnotations(jarPath, annotations, null, pluginClassLoader);
    }

    private void preparePlugins(Class identityResolverAnnotation, Map, List> plugableMap) throws IllegalAccessException, InstantiationException {
        List identityResolverClasses = plugableMap.get(identityResolverAnnotation);
        if (identityResolverClasses != null && !identityResolverClasses.isEmpty()) {
            if (identityResolverAnnotation == Partner.class && identityResolverClasses.size() > 1) {
                throw new RuntimeException("One Partner jar can have at most 1 Partner instance!");
            }

            for (Class irc : identityResolverClasses) {
                log.info("Preparing index {} {}", identityResolverAnnotation.getSimpleName(), irc.getCanonicalName());

                if (useSpring) {
                    // 每次加载，由于 PluginClassLoader 是不同的，irc也不同
                    Object partnerOrPattern = pluginApplicationContext.getBean(irc);
                    RegistryFactory.preparePlugins(identityResolverAnnotation, partnerOrPattern);
                } else {
                    RegistryFactory.preparePlugins(identityResolverAnnotation, irc.newInstance()); // new instance here
                }
            }
        }

        List extensions = plugableMap.get(Extension.class);
        if (extensions != null && !extensions.isEmpty()) {
            for (Class extensionClazz : extensions) {
                log.info("Preparing index Extension {}", extensionClazz.getCanonicalName());

                // 这里extensionClazz是扩展点实现的类名 e,g. org.example.bp.oms.isv.extension.DecideStepsExt
                // 而不是 IDecideStepsExt。因此，不必担心getBean异常：一个extensionClazz有多个对象
                if (useSpring) {
                    Object extension = pluginApplicationContext.getBean(extensionClazz);
                    RegistryFactory.preparePlugins(Extension.class, extension);
                } else {
                    RegistryFactory.preparePlugins(Extension.class, extensionClazz.newInstance()); // new instance here
                }
            }
        }
    }

    private void commit(Class identityResolverAnnotation) {
        if (identityResolverAnnotation == Partner.class) {
            InternalIndexer.commitPartner();
        }
    }

    @Override
    public String toString() {
        return "Plugin:" + code + ":" + version;
    }
}