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本文主要研究一下spring cloud gateway的GatewayFilter

GatewayFilter

spring-cloud-gateway-core-2.0.0.RC2-sources.jar!/org/springframework/cloud/gateway/filter/GatewayFilter.java

/** * Contract for interception-style, chained processing of Web requests that may * be used to implement cross-cutting, application-agnostic requirements such * as security, timeouts, and others. Specific to a Gateway * * Copied from WebFilter * * @author Rossen Stoyanchev * @since 5.0 */public interface GatewayFilter extends ShortcutConfigurable {	String NAME_KEY = "name";	String VALUE_KEY = "value";	/**	 * Process the Web request and (optionally) delegate to the next	 * {@code WebFilter} through the given {@link GatewayFilterChain}.	 * @param exchange the current server exchange	 * @param chain provides a way to delegate to the next filter	 * @return {@code Mono
    
     } to indicate when request processing is complete	 */	Mono
     
       filter(ServerWebExchange exchange, GatewayFilterChain chain);}
     
    

如注释所说，主要用于类似切面的非功能性需求，比如安全、超时控制等。其直接的实现类为OrderedGatewayFilter、ModifyResponseGatewayFilter、GatewayFilterAdapter

OrderedGatewayFilter

spring-cloud-gateway-core-2.0.0.RC2-sources.jar!/org/springframework/cloud/gateway/filter/OrderedGatewayFilter.java

public class OrderedGatewayFilter implements GatewayFilter, Ordered {	private final GatewayFilter delegate;	private final int order;	public OrderedGatewayFilter(GatewayFilter delegate, int order) {		this.delegate = delegate;		this.order = order;	}	public GatewayFilter getDelegate() {		return delegate;	}	@Override	public Mono
    
      filter(ServerWebExchange exchange, GatewayFilterChain chain) {		return this.delegate.filter(exchange, chain);	}	@Override	public int getOrder() {		return this.order;	}	@Override	public String toString() {		final StringBuilder sb = new StringBuilder("OrderedGatewayFilter{");		sb.append("delegate=").append(delegate);		sb.append(", order=").append(order);		sb.append('}');		return sb.toString();	}}
    

实现了Order接口

ModifyResponseGatewayFilter

spring-cloud-gateway-core-2.0.0.RC2-sources.jar!/org/springframework/cloud/gateway/filter/factory/rewrite/ModifyResponseBodyGatewayFilterFactory.java

public class ModifyResponseGatewayFilter implements GatewayFilter, Ordered {		private final Config config;		public ModifyResponseGatewayFilter(Config config) {			this.config = config;		}		@Override		@SuppressWarnings("unchecked")		public Mono
    
      filter(ServerWebExchange exchange, GatewayFilterChain chain) {			ServerHttpResponseDecorator responseDecorator = new ServerHttpResponseDecorator(exchange.getResponse()) {				@Override				public Mono
     
       writeWith(Publisher
       body) {					ResolvableType inElementType = ResolvableType.forClass(config.getInClass());					ResolvableType outElementType = ResolvableType.forClass(config.getOutClass());					MediaType contentType = exchange.getResponse().getHeaders().getContentType();					Optional
      
       > reader = getHttpMessageReader(codecConfigurer, inElementType, contentType);					Optional
       
        > writer = getHttpMessageWriter(codecConfigurer, outElementType, null);					if (reader.isPresent() && writer.isPresent()) {						ResponseAdapter responseAdapter = new ResponseAdapter(body, getDelegate().getHeaders());						Flux
         modified = reader.get().read(inElementType, responseAdapter, config.getInHints())								.cast(inElementType.resolve())								.flatMap(originalBody -> Flux.just(config.rewriteFunction.apply(exchange, originalBody)))								.cast(outElementType.resolve());						return getDelegate().writeWith(								writer.get().write((Publisher)modified, outElementType, null, getDelegate(),										config.getOutHints())						);					}					// TODO: error? log?					return getDelegate().writeWith(body);				}				@Override				public Mono
        
          writeAndFlushWith(Publisher
         > body) {					return writeWith(Flux.from(body)							.flatMapSequential(p -> p));				}			};			return chain.filter(exchange.mutate().response(responseDecorator).build());		}		@Override		public int getOrder() {			return NettyWriteResponseFilter.WRITE_RESPONSE_FILTER_ORDER - 1;		}	}
        
       
      
     
    

主要用于修改response

GatewayFilterAdapter

spring-cloud-gateway-core-2.0.0.RC2-sources.jar!/org/springframework/cloud/gateway/handler/FilteringWebHandler.java

private static class GatewayFilterAdapter implements GatewayFilter {		private final GlobalFilter delegate;		public GatewayFilterAdapter(GlobalFilter delegate) {			this.delegate = delegate;		}		@Override		public Mono
    
      filter(ServerWebExchange exchange, GatewayFilterChain chain) {			return this.delegate.filter(exchange, chain);		}		@Override		public String toString() {			final StringBuilder sb = new StringBuilder("GatewayFilterAdapter{");			sb.append("delegate=").append(delegate);			sb.append('}');			return sb.toString();		}	}
    

将GlobalFilter转为GatewayFilter的适配器

GatewayFilterFactory

spring-cloud-gateway-core-2.0.0.RC2-sources.jar!/org/springframework/cloud/gateway/filter/factory/GatewayFilterFactory.java

@FunctionalInterfacepublic interface GatewayFilterFactory
    
      extends ShortcutConfigurable, Configurable
     
       {	String NAME_KEY = "name";	String VALUE_KEY = "value";	// useful for javadsl	default GatewayFilter apply(Consumer
      
        consumer) {		C config = newConfig();		consumer.accept(config);		return apply(config);	}	default Class
       
         getConfigClass() {		throw new UnsupportedOperationException("getConfigClass() not implemented");	}	@Override	default C newConfig() {		throw new UnsupportedOperationException("newConfig() not implemented");	}	GatewayFilter apply(C config);	default String name() {		//TODO: deal with proxys		return NameUtils.normalizeFilterFactoryName(getClass());	}	@Deprecated	default ServerHttpRequest.Builder mutate(ServerHttpRequest request) {		return request.mutate();	}}
       
      
     
    

spring cloud gateway采用工厂模式来生成GatewayFilter，可以看到这里定义了apply方法，根据config来生成GatewayFilter。GatewayFilterFactory有几个抽象类，分别是AbstractGatewayFilterFactory、AbstractNameValueGatewayFilterFactory(继承了AbstractGatewayFilterFactory)、AbstractChangeRequestUriGatewayFilterFactory。

AbstractGatewayFilterFactory

spring-cloud-gateway-core-2.0.0.RC2-sources.jar!/org/springframework/cloud/gateway/filter/factory/AbstractGatewayFilterFactory.java

public abstract class AbstractGatewayFilterFactory
    
     		extends AbstractConfigurable
     
       implements GatewayFilterFactory
      
        {	@SuppressWarnings("unchecked")	public AbstractGatewayFilterFactory() {		super((Class
       
        ) Object.class);	}	public AbstractGatewayFilterFactory(Class
        
          configClass) {		super(configClass);	}	public static class NameConfig {		private String name;		public String getName() {			return name;		}		public void setName(String name) {			this.name = name;		}	}}
        
       
      
     
    

它的直接实现类如下：

• HystrixGatewayFilterFactory
• ModifyRequestBodyGatewayFilterFactory
• ModifyResponseBodyGatewayFilterFactory
• PrefixPathGatewayFilterFactory
• PreserveHostHeaderGatewayFilterFactory
• RedirectToGatewayFilterFactory
• RemoveRequestHeaderGatewayFilterFactory
• RemoveResponseHeaderGatewayFilterFactory
• RequestRateLimiterGatewayFilterFactory
• RetryGatewayFilterFactory
• RewritePathGatewayFilterFactory
• SaveSessionGatewayFilterFactory
• SecureHeadersGatewayFilterFactory
• SetPathGatewayFilterFactory
• SetStatusGatewayFilterFactory
• StripPrefixGatewayFilterFactory

AbstractNameValueGatewayFilterFactory

spring-cloud-gateway-core-2.0.0.RC2-sources.jar!/org/springframework/cloud/gateway/filter/factory/AbstractNameValueGatewayFilterFactory.java

public abstract class AbstractNameValueGatewayFilterFactory extends AbstractGatewayFilterFactory
    
      {	public AbstractNameValueGatewayFilterFactory() {		super(NameValueConfig.class);	}	public List
     
       shortcutFieldOrder() {        return Arrays.asList(GatewayFilter.NAME_KEY, GatewayFilter.VALUE_KEY);    }	@Validated	public static class NameValueConfig {		@NotEmpty		protected String name;		@NotEmpty		protected String value;		public String getName() {			return name;		}		public NameValueConfig setName(String name) {			this.name = name;			return this;		}		public String getValue() {			return value;		}		public NameValueConfig setValue(String value) {			this.value = value;			return this;		}		@Override		public String toString() {			return new ToStringCreator(this)					.append("name", name)					.append("value", value)					.toString();		}	}}
     
    

将泛型限定为AbstractNameValueGatewayFilterFactory.NameValueConfig，其实现类如下：

• AddRequestHeaderGatewayFilterFactory
• AddRequestParameterGatewayFilterFactory
• AddResponseHeaderGatewayFilterFactory
• SetRequestHeaderGatewayFilterFactory
• SetResponseHeaderGatewayFilterFactory

AbstractChangeRequestUriGatewayFilterFactory

spring-cloud-gateway-core-2.0.0.RC2-sources.jar!/org/springframework/cloud/gateway/filter/factory/AbstractChangeRequestUriGatewayFilterFactory.java

/** * This filter changes the request uri by * {@link #determineRequestUri(ServerWebExchange, T)} logic. * * @author Toshiaki Maki */public abstract class AbstractChangeRequestUriGatewayFilterFactory
    
     		extends AbstractGatewayFilterFactory
     
       {	private final int order;	public AbstractChangeRequestUriGatewayFilterFactory(Class
      
        clazz, int order) {		super(clazz);		this.order = order;	}	public AbstractChangeRequestUriGatewayFilterFactory(Class
       
         clazz) {		this(clazz, RouteToRequestUrlFilter.ROUTE_TO_URL_FILTER_ORDER + 1);	}	protected abstract Optional
        
          determineRequestUri(ServerWebExchange exchange,			T config);	public GatewayFilter apply(T config) {		return new OrderedGatewayFilter((exchange, chain) -> {			Optional
         
           uri = this.determineRequestUri(exchange, config); uri.ifPresent(u -> { Map
          
            attributes = exchange.getAttributes(); attributes.put(GATEWAY_REQUEST_URL_ATTR, u); }); return chain.filter(exchange); }, this.order); }}
          
         
        
       
      
     
    

通过GATEWAY_REQUEST_URL_ATTR设置新的uri，其直接实现类为

• RequestHeaderToRequestUriGatewayFilterFactory(通过header的值来设定uri)

GatewayFilterFactory.apply

spring-cloud-gateway-core-2.0.0.RC2-sources.jar!/org/springframework/cloud/gateway/route/RouteDefinitionRouteLocator.java

private List
    
      loadGatewayFilters(String id, List
     
       filterDefinitions) {		List
      
        filters = filterDefinitions.stream()				.map(definition -> {					GatewayFilterFactory factory = this.gatewayFilterFactories.get(definition.getName());					if (factory == null) {                        throw new IllegalArgumentException("Unable to find GatewayFilterFactory with name " + definition.getName());					}					Map
       
         args = definition.getArgs();					if (logger.isDebugEnabled()) {						logger.debug("RouteDefinition " + id + " applying filter " + args + " to " + definition.getName());					}                    Map
        
          properties = factory.shortcutType().normalize(args, factory, this.parser, this.beanFactory);                    Object configuration = factory.newConfig();                    ConfigurationUtils.bind(configuration, properties,                            factory.shortcutFieldPrefix(), definition.getName(), validator);                    GatewayFilter gatewayFilter = factory.apply(configuration);                    if (this.publisher != null) {                        this.publisher.publishEvent(new FilterArgsEvent(this, id, properties));                    }                    return gatewayFilter;				})				.collect(Collectors.toList());		ArrayList
         
           ordered = new ArrayList<>(filters.size()); for (int i = 0; i < filters.size(); i++) { GatewayFilter gatewayFilter = filters.get(i); if (gatewayFilter instanceof Ordered) { ordered.add(gatewayFilter); } else { ordered.add(new OrderedGatewayFilter(gatewayFilter, i + 1)); } } return ordered; }
         
        
       
      
     
    

这里通过factory去实例化每个route的GatewayFilter

小结

spring cloud gateway的GatewayFilter主要是通过GatewayFilterFactory来生产的。而GatewayFilterFactory主要有三个抽象类：

• AbstractGatewayFilterFactory
  • HystrixGatewayFilterFactory
  • ModifyRequestBodyGatewayFilterFactory
  • ModifyResponseBodyGatewayFilterFactory
  • PrefixPathGatewayFilterFactory
  • PreserveHostHeaderGatewayFilterFactory
  • RedirectToGatewayFilterFactory
  • RemoveRequestHeaderGatewayFilterFactory
  • RemoveResponseHeaderGatewayFilterFactory
  • RequestRateLimiterGatewayFilterFactory
  • RetryGatewayFilterFactory
  • RewritePathGatewayFilterFactory
  • SaveSessionGatewayFilterFactory
  • SecureHeadersGatewayFilterFactory
  • SetPathGatewayFilterFactory
  • SetStatusGatewayFilterFactory
  • StripPrefixGatewayFilterFactory
• AbstractNameValueGatewayFilterFactory(继承了AbstractGatewayFilterFactory)
  • AddRequestHeaderGatewayFilterFactory
  • AddRequestParameterGatewayFilterFactory
  • AddResponseHeaderGatewayFilterFactory
  • SetRequestHeaderGatewayFilterFactory
  • SetResponseHeaderGatewayFilterFactory
• AbstractChangeRequestUriGatewayFilterFactory
  • RequestHeaderToRequestUriGatewayFilterFactory

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