Java中保持扩展性的实现方法

阿里妹导读

在日常的开发中，作者总结了平常用到的一些低成本、保持扩展性的套路，分享出来，欢迎大家讨论。

前言

SOLID(单一、开闭、里式替换、接口隔离、依赖倒置)五大原则和23种设计模式(常见的单例、构建者、装饰、适配、代理、组合、模板等等)，小伙伴们对这些肯定都很熟悉。这些原则和设计模式能够辅助我们，让我们在设计的时候有所抉择，从而达到高内聚、低耦合的目的。

那说到设计，肯定会提到架构两个字，常见的架构名词：分层架构、六边形架构、SOA架构、CQRS架构、EDA架构等等。我个人对架构的理解是边界的确认以及边界内部元素的组合，其实只要是程序员，他就一定是架构师，只不过是好的架构师还是不那么好的架构师；人人都是架构师，我认为这句话是没有问题的，区别在于他的认知决定了他所能确认的边界、如何更高效的组合内部元素；技术的架构师肯定侧重于技术，业务的架构师肯定侧重于业务，商品的架构师所能看到的边界大概率还是局限在商品域，ICBU架构组的架构师更多考虑是横向的业务支撑。以上是我个人对架构两个字的理解，今天我们不讨论具体架构，我们讨论一些套路，在日常的开发中，我总结了些我平常用到的一些低成本、保持扩展性的套路，分享出来，欢迎大家讨论。

基于管道(pipeline)的套路

关键点

管道(Pipeline)----用于串联阀门的管道通路

阀门(PipelineValue)----用于每一个节点处理实际业务诉求

管道上下文(PipelineContext)----用于管道上下文中数据的扭转

适用场景

当你的数据流需要经过很多同等逻辑处理时，可以考虑使用此套路，便于后续扩展

实现代码

Pipeline/StandardPipeline

package com.example.ownertest.dm.pipelline;


/**
 * @Author: linear.zw
 * @Date: 2023/10/25 19:46
 */
public interface Pipeline {


    /**
     * 执行
     *
     * @return
     */
    boolean invoke(PipelineContext pipelineContext);


    /**
     * 添加值
     *
     * @param pipelineValue
     * @return
     */
    boolean addValue(PipelineValue pipelineValue);


    /**
     * 移除值
     *
     * @param pipelineValue
     * @return
     */
    boolean removeValue(PipelineValue pipelineValue);
}








package com.example.ownertest.dm.pipelline;


import java.util.List;


import com.google.common.collect.Lists;
import lombok.Data;
import lombok.extern.slf4j.Slf4j;


/**
 * @Author: linear.zw
 * @Date: 2023/10/25 19:46
 */
@Data
@Slf4j
public class StandardPipeline implements Pipeline {


    private List pipelineValueList = Lists.newArrayList();


    @Override
    public boolean invoke(PipelineContext pipelineContext) {
        boolean isResult = true;
        for (PipelineValue pipelineValue :
            pipelineValueList) {
            try {
                isResult = pipelineValue.execute(pipelineContext);
                if (!isResult) {
                    log.error("{},exec is wrong", pipelineValue.getClass().getSimpleName());
                }


            } catch (Exception e) {
                log.error(e.getMessage(), e);
            }
        }


        return isResult;
    }


    @Override
    public boolean addValue(PipelineValue pipelineValue) {
        if (pipelineValueList.contains(pipelineValue)) {
            return true;
        }


        return pipelineValueList.add(pipelineValue);
    }


    @Override
    public boolean removeValue(PipelineValue pipelineValue) {
        return pipelineValueList.remove(pipelineValue);
    }
}

PipelineContext/StandardPipelineContext

package com.example.ownertest.dm.pipelline;


/**
 * @Author: linear.zw
 * @Date: 2023/10/25 19:47
 */
public interface PipelineContext {


    String FOR_TEST = "forTest";


    /**
     * 设置
     *
     * @param contextKey
     * @param contextValue
     */
    void set(String contextKey, Object contextValue);


    /**
     * 获取值
     *
     * @param contextKey
     * @return
     */
    Object get(String contextKey);
}








package com.example.ownertest.dm.pipelline;


import java.util.Map;


import com.google.common.collect.Maps;


/**
 * @Author: linear.zw
 * @Date: 2023/10/25 19:47
 */
public class StandardPipelineContext implements PipelineContext {


    private Map contentMap = Maps.newConcurrentMap();


    @Override
    public void set(String contextKey, Object contextValue) {
        contentMap.put(contextKey, contextValue);
    }


    @Override
    public Object get(String contextKey) {
        return contentMap.get(contextKey);
    }
}

PipelineValue/AbstractPipelineValue/GraySwitchValue/ForTestValue

package com.example.ownertest.dm.pipelline;


/**
 * @Author: linear.zw
 * @Date: 2023/10/25 19:47
 */
public interface PipelineValue {


    /**
     * 节点执行
     *
     * @param pipelineContext
     * @return
     */
    boolean execute(PipelineContext pipelineContext);


}






package com.example.ownertest.dm.pipelline;


/**
 * @Author: linear.zw
 * @Date: 2023/10/25 19:48
 */
public abstract class AbstractPipelineValue implements PipelineValue {


    @Override
    public boolean execute(PipelineContext pipelineContext) {


        System.out.println(this.getClass().getSimpleName() + " start ");


        boolean result = doExec(pipelineContext);


        System.out.println(this.getClass().getSimpleName() + " end ");


        return result;
    }


    protected abstract boolean doExec(PipelineContext pipelineContext);
}




package com.example.ownertest.dm.pipelline;


/**
 * @Author: linear.zw
 * @Date: 2023/10/25 19:48
 */
public class GraySwitchValue extends AbstractPipelineValue {
    @Override
    public boolean doExec(PipelineContext pipelineContext) {


        pipelineContext.set(PipelineContext.FOR_TEST, true);


        return true;
    }
}






package com.example.ownertest.dm.pipelline;


/**
 * @Author: linear.zw
 * @Date: 2023/10/25 19:48
 */
public class ForTestValue extends AbstractPipelineValue {
    @Override
    public boolean doExec(PipelineContext pipelineContext) {


        return true;
    }
}

PipelineClient

package com.example.ownertest.dm.pipelline;


/**
 * 入口类
 *
 * @Author: linear.zw
 * @Date: 2023/10/25 19:48
 */
public class PipelineClient {


    public static void main(String[] args) {


        // 管道初始化
        Pipeline pipeline = new StandardPipeline();


        // value扩展
        PipelineValue pipelineValue = new GraySwitchValue();
        PipelineValue pipelineValue2 = new ForTestValue();


        // 上下文
        PipelineContext pipelineContext = new StandardPipelineContext();


        pipeline.addValue(pipelineValue);
        pipeline.addValue(pipelineValue2);


        // 调用管道
        pipeline.invoke(pipelineContext);


    }
}

常见框架中的应用

网络层的扛把子netty框架中，例如ChannelPipeline、ChannelHandler、ChannelHandlerContext，分别用于处理tcp拆包、加解码等等之类。

基于责任链(filterchain)的套路

关键点

来源--https://www.oracle.com/java/technologies/intercepting-filter.html

过滤器(Filter)----实际处理业务的节点

过滤链(FilterChain)----串联过滤器的链条

适用场景

例如常见的web请求场景

实现代码

Filter/ForTest1Filter/ForTest2Filter

package com.example.ownertest.dm.filter;


/**
 * @Author: linear.zw
 * @Date: 2023/10/26 19:22
 */
public interface Filter {


    void doFilter(HttpRequest httpRequest,FilterChain filterChain);
}






package com.example.ownertest.dm.filter;


/**
 * @Author: linear.zw
 * @Date: 2023/10/26 19:22
 */
public class ForTest1Filter implements Filter {
    @Override
    public void doFilter(HttpRequest httpRequest, FilterChain filterChain) {
        // do


        System.out.println(this.getClass().getSimpleName() + " before " + System.currentTimeMillis());


        filterChain.doFilter(httpRequest);


        // after


        System.out.println(this.getClass().getSimpleName() + " end " + System.currentTimeMillis());


    }
}










package com.example.ownertest.dm.filter;


/**
 * @Author: linear.zw
 * @Date: 2023/10/26 19:22
 */
public class ForTest2Filter implements Filter {
    @Override
    public void doFilter(HttpRequest httpRequest, FilterChain filterChain) {
        // do


        System.out.println(this.getClass().getSimpleName() + " before " + System.currentTimeMillis());


        filterChain.doFilter(httpRequest);


        // after


        System.out.println(this.getClass().getSimpleName() + " end " + System.currentTimeMillis());
    }
}

FilterChain/StandardFilterChain

package com.example.ownertest.dm.filter;


/**
 * @Author: linear.zw
 * @Date: 2023/10/26 19:23
 */
public interface FilterChain {


    void doFilter(HttpRequest httpRequest);


    void addFilter(Filter filter);
}








package com.example.ownertest.dm.filter;


import java.util.List;


import com.google.common.collect.Lists;


/**
 * @Author: linear.zw
 * @Date: 2023/10/26 19:24
 */
public class StandardFilterChain implements FilterChain {


    private List filterList = Lists.newArrayList();


    private int currentIndex = 0;


    @Override
    public void doFilter(HttpRequest httpRequest) {
        if (currentIndex == filterList.size()) { return; }


        Filter filter = filterList.get(currentIndex);


        currentIndex = currentIndex + 1;


        filter.doFilter(httpRequest, this);
    }


    @Override
    public void addFilter(Filter filter) {
        if (filterList.contains(filter)) {
            return;
        }


        filterList.add(filter);
    }


}

HttpRequest/StandardHttpRequest

package com.example.ownertest.dm.filter;


/**
 * @Author: linear.zw
 * @Date: 2023/10/26 19:24
 */
public interface HttpRequest {
}








package com.example.ownertest.dm.filter;


/**
 * @Author: linear.zw
 * @Date: 2023/10/26 19:24
 */
public class StandardHttpRequest implements HttpRequest {
}

FilterClient----入口测试

package com.example.ownertest.dm.filter;


/**
 * @Author: linear.zw
 * @Date: 2023/10/26 19:25
 */
public class FilterClient {


    public static void main(String[] args) {
        FilterChain filterChain = new StandardFilterChain();


        filterChain.addFilter(new ForTest1Filter());
        filterChain.addFilter(new ForTest2Filter());


        filterChain.doFilter(new StandardHttpRequest());
    }
}

常见框架中的应用

hsf的filter机制，服务端扩展的ServerFilter和客户端扩展的ClientFilter；

开发过java web的小伙伴都知道的servlet，servlet的入口即是FilterChain、Filter；

基于组合/模板的套路

关键点

处理器注册器----用于存储处理器的集合

处理器工厂----用于创建处理器

处理器----实际的处理器以及扩展的实现

处理器上下文----处理器上下文，用于参数的传递

适用场景

适合于有共性、后续持续扩展的场景

实现代码

PiiHandlerRegistry----处理器注册器

package com.example.ownertest.dm.comp;


import java.lang.reflect.Field;
import java.util.List;
import java.util.Map;


import com.google.common.collect.Maps;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.collections4.CollectionUtils;
import org.apache.commons.lang3.StringUtils;


/**
 * @Author: linear.zw
 * @Date: 2023/10/31 20:45
 */
@Slf4j
public class PiiHandlerRegistry {


    private static Map piiDomainFieldHandlerMap = Maps.newHashMap();


    public static void putHandler(String piiDomainFieldName, PiiDomainFieldHandler piiDomainFieldHandler) {
        if (StringUtils.isEmpty(piiDomainFieldName)) {
            log.warn(" piiDomainFieldName is null,continue");
            return;
        }


        if (piiDomainFieldHandler == null) {
            log.warn(piiDomainFieldName + " piiDomainFieldHandler is null,continue");
            return;
        }


        if (!piiDomainFieldHandlerMap.containsKey(piiDomainFieldName)) {
            piiDomainFieldHandlerMap.put(piiDomainFieldName, piiDomainFieldHandler);
        }
    }


    public static  int handlerRead(T domain, Field domainField, PiiContent piiContent) {
        int num = 0;
        for (Map.Entry piiDomainFieldHandlerEntry :
            piiDomainFieldHandlerMap.entrySet()) {
            if (piiDomainFieldHandlerEntry.getValue().isSupport(domain, domainField)) {
                piiDomainFieldHandlerEntry.getValue().handlerRead(domain, domainField, piiContent);
            }
        }
        return num;
    }


    public static  int handlerWrite(T domain, Field domainField, PiiContent piiContent) {
        int num = 0;
        for (Map.Entry piiDomainFieldHandlerEntry :
            piiDomainFieldHandlerMap.entrySet()) {
            if (piiDomainFieldHandlerEntry.getValue().isSupport(domain, domainField)) {
                piiDomainFieldHandlerEntry.getValue().handlerWrite(domain, domainField, piiContent);
            }
        }
        return num;
    }


    public static Map getPiiDomainFieldHandlerMap() {
        return piiDomainFieldHandlerMap;
    }


    public static void init() {
        List piiDomainFieldHandlerList = PiiDomainFieldHandlerFactory
            .createPiiDomainFieldHandler();
        if (CollectionUtils.isNotEmpty(piiDomainFieldHandlerList)) {


            for (PiiDomainFieldHandler piiDomainFieldHandler :
                piiDomainFieldHandlerList) {
                putHandler(piiDomainFieldHandler.getPiiDomainMeta(), piiDomainFieldHandler);
            }
        }
    }
}

PiiDomainFieldHandlerFactory----处理器工厂

package com.example.ownertest.dm.comp;


import java.util.List;


import com.google.common.collect.Lists;


/**
 * @Author: linear.zw
 * @Date: 2023/10/31 20:46
 */
public class PiiDomainFieldHandlerFactory {


    /**
     * 创建领域处理器
     *
     * @return
     */
    public static List createPiiDomainFieldHandler() {
        List piiDomainFieldHandlerList = Lists.newArrayList();


        //
        piiDomainFieldHandlerList.add(new ForTestSupportFieldHandler());
        piiDomainFieldHandlerList.add(new ForTestNotSupportFieldHandler());


        return piiDomainFieldHandlerList;
    }
}

PiiDomainFieldHandler/PiiDomainFieldHandlerBase/ForTestNotSupportFieldHandler/ForTestSupportFieldHandler----处理器

package com.example.ownertest.dm.comp;


import java.lang.reflect.Field;


/**
 * @Author: linear.zw
 * @Date: 2023/10/31 20:46
 */
public interface PiiDomainFieldHandler {


    /**
     * 处理实际操作
     * 读----从PiiContent获取数据回填domain
     *
     * @param domain
     * @param domainField
     * @param piiContent
     * @param 
     * @return
     */
     boolean handlerRead(T domain, Field domainField, PiiContent piiContent);


    /**
     * 处理实际操作
     * 写----将domain中需要写入pii的字段数据写入PiiContent
     *
     * @param domain
     * @param domainField
     * @param piiContent
     * @param 
     * @return
     */
     boolean handlerWrite(T domain, Field domainField, PiiContent piiContent);


    /**
     * 当前处理器是否支持该领域对象
     *
     * @param domain
     * @param domainField
     * @param 
     * @return
     */
     boolean isSupport(T domain, Field domainField);


    /**
     * 获取处理器对应的元信息
     *
     * @return
     */
    String getPiiDomainMeta();
}








package com.example.ownertest.dm.comp;


import java.lang.reflect.Field;


import lombok.extern.slf4j.Slf4j;


/**
 * @Author: linear.zw
 * @Date: 2023/10/31 20:47
 */
@Slf4j
public abstract class PiiDomainFieldHandlerBase implements PiiDomainFieldHandler {


    @Override
    public  boolean handlerRead(T domain, Field domainField, PiiContent piiContent) {
        // to do business read


        return true;
    }


    @Override
    public  boolean handlerWrite(T domain, Field domainField, PiiContent piiContent) {


        // to do business write


        return true;
    }
}








package com.example.ownertest.dm.comp;


import java.lang.reflect.Field;


/**
 * @Author: linear.zw
 * @Date: 2023/10/31 20:47
 */
public class ForTestSupportFieldHandler extends PiiDomainFieldHandlerBase {
    @Override
    public  boolean isSupport(T domain, Field domainField) {


        if (this.getClass().getSimpleName().equalsIgnoreCase(domain.getClass().getSimpleName())) {


            // to do business


            System.out.println(this.getClass().getSimpleName() + " is support, to do some business");


            return true;
        }


        return false;
    }


    @Override
    public String getPiiDomainMeta() {
        return this.getClass().getSimpleName();
    }
}






package com.example.ownertest.dm.comp;


import java.lang.reflect.Field;


/**
 * @Author: linear.zw
 * @Date: 2023/10/31 20:48
 */
public class ForTestNotSupportFieldHandler extends PiiDomainFieldHandlerBase {
    @Override
    public  boolean isSupport(T domain, Field domainField) {


        if (this.getClass().getSimpleName().equalsIgnoreCase(domain.getClass().getSimpleName())) {


            // to do business


            System.out.println(this.getClass().getSimpleName() + " is support, to do some business");


            return true;
        }


        return false;
    }


    @Override
    public String getPiiDomainMeta() {
        return this.getClass().getSimpleName();
    }
}

PiiContent----上下文

package com.example.ownertest.dm.comp;


import java.util.Map;


import com.google.common.collect.Maps;
import lombok.Data;


/**
 * @Author: linear.zw
 * @Date: 2023/10/31 20:48
 */
@Data
public class PiiContent {


    public static String FORTEST="fortest";


    private Map piiDataMap = Maps.newHashMap();


    private Map piiContextMap = Maps.newHashMap();


    public void putPiiData(String domainFieldName, Object domainFieldValue) {
        piiDataMap.put(domainFieldName, domainFieldValue);
    }


    public Object getPiiData(String domainFieldName) {
        return piiDataMap.get(domainFieldName);
    }


    public void putPiiContext(String contextName, Object contextNameValue) {
        piiContextMap.put(contextName, contextNameValue);
    }


    public Object getPiiContext(String contextName) {
        return piiContextMap.get(contextName);
    }
}

PiiClient----入口的测试类

package com.example.ownertest.dm.comp;


import java.util.Map;


/**
 * @Author: linear.zw
 * @Date: 2023/10/31 20:48
 */
public class PiiClient {


    public static void main(String[] args) {
        PiiHandlerRegistry.init();


        // 遍历处理器
        for (Map.Entry entryHandler :
            PiiHandlerRegistry.getPiiDomainFieldHandlerMap().entrySet()) {
            System.out.println(entryHandler.getKey() + "	" + entryHandler.getValue().getPiiDomainMeta());
        }


        //
        PiiContent piiContent = new PiiContent();
        piiContent.putPiiContext(PiiContent.FORTEST, PiiContent.FORTEST);


        // 请求处理
        System.out.println("ForTestSupportFieldHandler start");
        PiiHandlerRegistry.handlerRead(new ForTestSupportFieldHandler(), null, piiContent);
        System.out.println("ForTestSupportFieldHandler end");


        // 请求处理
        System.out.println("ForTestNotSupportFieldHandler start");
        PiiHandlerRegistry.handlerRead(new ForTestNotSupportFieldHandler(), null, piiContent);
        System.out.println("ForTestNotSupportFieldHandler end");


    }
}

常见框架中的应用

这个就太多了，例如spring最核心的BeanPostProcessor机制，通过org.springframework.beans.factory.support.AbstractBeanFactory#beanPostProcessors管理一些列的beanPostProcessors，在spring上下文org.springframework.context.support.AbstractApplicationContext#refresh的时候，进行bean的init(InitDestroyAnnotationBeanPostProcessor)、解析注解(ScheduledAnnotationBeanPostProcessor、AutowiredAnnotationBeanPostProcessor)、解析aop（AnnotationAwareAspectJAutoProxyCreator）等等。

基于注解的套路

关键点

注解元定义----用来定义通用的元信息；

注解解析器----解析类上是否有指定的注解，进而进行对应的扩展操作；

spring的BeanPostProcessor----这里是借用spring的BeanPostProcessor机制，在spring容器初始化的时候，进行回调，完成预期的扩展行为；

适用场景

简化内部使用

实现代码

ForTestAnnotation----注解元定义

package com.example.ownertest.dm.annotation;


import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;


import org.springframework.stereotype.Component;


/**
 * 用于测试的标识注解
 *
 * @Author: linear.zw
 * @Date: 2023/11/1 10:21
 */
@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Component
public @interface ForTestAnnotation {
}

ForTestAnnotationProcessor----注解解析器

package com.example.ownertest.dm.annotation;


import org.springframework.aop.support.AopUtils;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.core.annotation.AnnotationUtils;
import org.springframework.stereotype.Component;


/**
 * 注解解析器
 * @Author: linear.zw
 * @Date: 2023/11/1 10:25
 */
@Component
public class ForTestAnnotationProcessor implements BeanPostProcessor {
    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {


        // 获取目标类是否有ForTestAnnotation注解
        ForTestAnnotation annotation = AnnotationUtils.findAnnotation(AopUtils.getTargetClass(bean),
            ForTestAnnotation.class);


        if (annotation == null) {
            return bean;
        }


        // 处理想要的扩展
        System.out.println(beanName + " has ForTestAnnotation");


        return bean;
    }


    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        return bean;
    }
}

ForTestBean----测试bean

package com.example.ownertest.dm.annotation;


/**
 * @Author: linear.zw
 * @Date: 2023/11/1 10:26
 */
@ForTestAnnotation
public class ForTestBean {


    public ForTestBean() {
        System.out.println(ForTestBean.class.getSimpleName() + " init");
    }
}

ForTestClient---测试入口

package com.example.ownertest.dm.annotation;


import org.springframework.context.annotation.AnnotationConfigApplicationContext;


/**
 * @Author: linear.zw
 * @Date: 2023/11/1 10:26
 */
public class ForTestClient {


    public static void main(String[] args) {
        AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(
            "com.example.ownertest.dm.annotation");


        System.out.println(ForTestClient.class.getSimpleName());
    }
}

常见框架中的应用

例如集团内部的spring-boot-alibaba-diamond-autoconfigure

基于事件分发的套路

关键点

事件源--事件触发者

事件--标识产生的来源

事件监听器--事件的关注者，即处理者

事件分发器--用于将事件源的事件转发给事件监听器

实现代码

EventSource/EventSourceForTest/EventSourceForTest2

package com.example.ownertest.dm.event;


/**
 * 发出事件
 * @Author: linear.zw
 * @Date: 2023/11/1 14:12
 */
public interface EventSource {


    /**
     * 发出事件
     *
     * @return
     */
    Event fireEvent();
}










package com.example.ownertest.dm.event;


/**
 * @Author: linear.zw
 * @Date: 2023/11/1 14:14
 */
public class EventSourceForTest implements EventSource {
    @Override
    public Event fireEvent() {


        Event event = new EventForTest();
        System.out.println(getClass().getSimpleName() + " 	 fireEvent " + event.getName());


        return event;
    }
}










package com.example.ownertest.dm.event;


/**
 * @Author: linear.zw
 * @Date: 2023/11/1 14:15
 */
public class EventSourceForTest2 implements EventSource {
    @Override
    public Event fireEvent() {


        Event event = new EventForTest2();
        System.out.println(getClass().getSimpleName() + " 	 fireEvent " + event.getName());


        return event;
    }
}

Event/EventForTest/EventForTest2

package com.example.ownertest.dm.event;


/**
 * @Author: linear.zw
 * @Date: 2023/11/1 14:15
 */
public interface Event {


    /**
     * 事件名称
     *
     * @return
     */
    String getName();
}








package com.example.ownertest.dm.event;


/**
 * @Author: linear.zw
 * @Date: 2023/11/1 14:17
 */
public class EventForTest implements Event {
    @Override
    public String getName() {
        return getClass().getSimpleName();
    }
}








package com.example.ownertest.dm.event;


/**
 * @Author: linear.zw
 * @Date: 2023/11/1 14:17
 */
public class EventForTest2 implements Event {
    @Override
    public String getName() {
        return getClass().getSimpleName();
    }
}

EventListener/EventListenerForTest

package com.example.ownertest.dm.event;


/**
 * @Author: linear.zw
 * @Date: 2023/11/1 14:17
 */
public interface EventListener {


    /**
     * 是否支持此事件
     *
     * @param event
     * @return
     */
    boolean supportEvent(Event event);


    /**
     * 处理事件
     *
     * @return
     */
    boolean handlerEvent(Event event);
}










package com.example.ownertest.dm.event;


/**
 * @Author: linear.zw
 * @Date: 2023/11/1 14:18
 */
public class EventListenerForTest implements EventListener {
    @Override
    public boolean supportEvent(Event event) {


        return event.getName().contains("Test");
    }


    @Override
    public boolean handlerEvent(Event event) {


        System.out.println(this.getClass().getSimpleName() + "	 handler " + event.getName());


        return true;
    }
}

EventDispatcher/EventListenerManager

package com.example.ownertest.dm.event;


import org.apache.commons.collections4.CollectionUtils;


/**
 * @Author: linear.zw
 * @Date: 2023/11/1 14:18
 */
public class EventDispatcher {


    /**
     * 单例模式
     */
    private static EventDispatcher eventDispatcher = new EventDispatcher();


    private EventDispatcher() {


    }


    /**
     * 分发事件
     *
     * @param event
     * @return
     */
    public static boolean dispatchEvent(Event event) {
        if (CollectionUtils.isNotEmpty(EventListenerManager.getEventListenerList())) {
            for (EventListener eventListener :
                EventListenerManager.getEventListenerList()) {
                if (eventListener.supportEvent(event)) {
                    eventListener.handlerEvent(event);
                }
            }
        }
        return true;
    }
}






package com.example.ownertest.dm.event;


import java.util.List;


import com.google.common.collect.Lists;


/**
 * @Author: linear.zw
 * @Date: 2023/11/1 14:18
 */
public class EventListenerManager {


    private static List eventListenerList = Lists.newArrayList();


    /**
     * 添加事件监听器
     *
     * @param eventListener
     * @return
     */
    public static boolean addEventListener(EventListener eventListener) {
        if (!eventListenerList.contains(eventListener)) {
            return eventListenerList.add(eventListener);
        }


        return true;
    }


    /**
     * 移除事件监听器
     *
     * @param eventListener
     * @return
     */
    public static boolean removeEventListener(EventListener eventListener) {
        if (eventListenerList.contains(eventListener)) {
            return eventListenerList.remove(eventListener);
        }


        return true;
    }


    public static List getEventListenerList() {
        return eventListenerList;
    }
}

EventClient

package com.example.ownertest.dm.event;


/**
 * @Author: linear.zw
 * @Date: 2023/11/1 14:19
 */
public class EventClient {


    public static void main(String[] args) {


        // 创建事件源
        EventSource eventSourceForTest = new EventSourceForTest();
        EventSource eventSourceForTest2 = new EventSourceForTest2();


        // 创建事件监听器
        EventListener eventListener = new EventListenerForTest();
        EventListenerManager.addEventListener(eventListener);


        // 发布事件
        EventDispatcher.dispatchEvent(eventSourceForTest.fireEvent());
        EventDispatcher.dispatchEvent(eventSourceForTest2.fireEvent());


    }
}

基于SPI机制的套路

关键点

服务调用方

服务实现方----以接口名称为文件名称，放在META-INF/services，值为该接口的实现

标准服务接口

适用场景

实现代码

SpiServiceLoaderHelper

package com.example.ownertest.dm.spi;


import java.util.Iterator;
import java.util.Objects;
import java.util.ServiceLoader;


/**
 * @Author: linear.zw
 * @Date: 2023/11/1 15:32
 */
public class SpiServiceLoaderHelper {


    public static ProductPackageRemoteServiceInterface getProductPackageRemoteServiceInterface() {
        // 先从缓存中加载
        Object serviceCache = DependServiceRegistryHelper.getDependObject(ProductPackageRemoteServiceInterface.class);
        if (serviceCache != null) {
            return (ProductPackageRemoteServiceInterface) serviceCache;
        }
        // spi 方式加载
        ProductPackageRemoteServiceInterface serviceInterface = loadSpiImpl(ProductPackageRemoteServiceInterface.class);
        // 防止注入的bean为空 提前进行判断 以免业务执行出现问题
        boolean isExist = true;
        if (Objects.isNull(serviceInterface)) {
            isExist = false;
        } else if (Objects.isNull(serviceInterface.getProductPackageRemoteService())) {
            isExist = false;
        }
        if (!isExist) {
            throw new RuntimeException("getProductPackageRemoteService load impl failed,please check spi service");
        }
        // 添加进统一的依赖管理
        DependServiceRegistryHelper.registry(ProductPackageRemoteServiceInterface.class, serviceInterface);
        return serviceInterface;
    }


    /**
     * 以spi的方式加载实现类
     *
     * @param cls
     * @param 

     * @return
     */
    private static 
 P loadSpiImpl(Class
 cls) {
        ServiceLoader
 spiLoader = ServiceLoader.load(cls);
        Iterator
 iaIterator = spiLoader.iterator();
        if (iaIterator.hasNext()) {
            return iaIterator.next();
        }
        return null;
    }
}

DependServiceRegistryHelper

package com.example.ownertest.dm.spi;


import java.util.Map;


import com.google.common.collect.Maps;


/**
 * @Author: linear.zw
 * @Date: 2023/11/1 15:35
 */
public class DependServiceRegistryHelper {


    /**
     * 存储策略依赖的服务,统一管理
     */
    private static Map dependManagerMap = Maps.newHashMap();


    public static boolean registryMap(Map dependManagerMap) {
        for (Map.Entry dependEntry :
            dependManagerMap.entrySet()) {
            registry(dependEntry.getKey(), dependEntry.getValue());
        }
        return true;
    }


    public static boolean registry(Class cls, Object dependObject) {
        dependManagerMap.put(cls.getCanonicalName(), dependObject);
        return true;
    }


    public static Object getDependObject(Class cls) {


        return dependManagerMap.get(cls.getCanonicalName());
    }
}

SpiServiceLoaderClientTest

package com.example.ownertest.dm.spi;


/**
 * @Author: linear.zw
 * @Date: 2023/11/1 15:37
 */
public class SpiServiceLoaderClientTest {


    public static void main(String[] args) {
        ProductPackageRemoteServiceInterface productPackageRemoteServiceInterface
            = SpiServiceLoaderHelper.getProductPackageRemoteServiceInterface();


    }
}

常见框架中的应用

目前大多数中台的策略包，都是基于spi方式的，动态加载业务的实现，进而达到扩展的目的；

例如google开源的auto-service，通过注解的方式，自动生成spi的实现目录；

最后

程序员大多数都是实干派，所以，你的套路有哪些，评论区有你的位置，Show me the code。

审核编辑：汤梓红