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本文介绍了Java中保持扩展性的几种套路和实现。希望能对遇到类似问题的同学有所帮助。
本文来自于微信公众号阿里云开发者，由火龙果软件Linda编辑、推荐。 |
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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<PipelineValue> 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);
}
}
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PipelineContext/StandardPipelineContext
package com.example.ownertest.dm.pipelline;
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<String, Object> 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);
}
}
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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;
}
}
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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);
}
}
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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
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
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());
}
}
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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<Filter> 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);
}
}
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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 {
}
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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());
}
}
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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.Abstract
ApplicationContext#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 {
}
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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;
}
}
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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");
}
}
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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());
}
}
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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()
+ " \t 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()
+ " \t fireEvent " + event.getName());
return event;
}
}
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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()
+ "\t handler " + event.getName());
return true;
}
}
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EventDispatcher/EventListenerManager
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.get
DependObject(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.get
ProductPackageRemoteService()))
{
isExist = false;
}
if (!isExist) {
throw new RuntimeException("getProduct
PackageRemoteService
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 <P>
* @return
*/
private static <P> P loadSpiImpl(Class<P>
cls) {
ServiceLoader<P> spiLoader = ServiceLoader.load(cls);
Iterator<P> iaIterator = spiLoader.iterator();
if (iaIterator.hasNext()) {
return iaIterator.next();
}
return null;
}
}
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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());
}
}
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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 <P>
* @return
*/
private static <P> P loadSpiImpl(Class<P>
cls) {
ServiceLoader<P> spiLoader = ServiceLoader.load(cls);
Iterator<P> iaIterator = spiLoader.iterator();
if (iaIterator.hasNext()) {
return iaIterator.next();
}
return null;
}
}
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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<String, Object> dependManagerMap
= Maps.newHashMap();
public static boolean registryMap(Map<Class,
Object> dependManagerMap) {
for (Map.Entry<Class, Object> 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());
}
}
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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();
}
}
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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。
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