Use constant utility classes instead of constant interfaces (#2081)

spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/hystrix/HystrixConstants.java

@@ -19,8 +19,12 @@ package org.springframework.cloud.netflix.hystrix;
 /**
  * @author Spencer Gibb
  */
-public interface HystrixConstants {
+public class HystrixConstants {
 
-	String HYSTRIX_STREAM_DESTINATION = "springCloudHystrixStream";
+	public static final String HYSTRIX_STREAM_DESTINATION = "springCloudHystrixStream";
+
+	private HystrixConstants() {
+		throw new AssertionError("Must not instantiate constant utility class");
+	}
 
 }

spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/zuul/filters/support/FilterConstants.java

@@ -26,190 +26,195 @@ import com.netflix.zuul.ZuulFilter;
 /**
  * @author Spencer Gibb
  */
-public interface FilterConstants {
+public class FilterConstants {
 
 	// KEY constants -----------------------------------
 
 	/**
 	 * Zuul {@link com.netflix.zuul.context.RequestContext} key for use in {@link org.springframework.cloud.netflix.zuul.filters.pre.ServletDetectionFilter}
 	 */
-	String IS_DISPATCHER_SERVLET_REQUEST_KEY = "isDispatcherServletRequest";
+	public static final String IS_DISPATCHER_SERVLET_REQUEST_KEY = "isDispatcherServletRequest";
 
 	/**
 	 * Zuul {@link com.netflix.zuul.context.RequestContext} key for use in {@link org.springframework.cloud.netflix.zuul.filters.route.SendForwardFilter}
 	 */
-	String FORWARD_TO_KEY = "forward.to";
+	public static final String FORWARD_TO_KEY = "forward.to";
 
 	/**
 	 * Zuul {@link com.netflix.zuul.context.RequestContext} key for use in TODO: determine use
 	 */
-	String PROXY_KEY = "proxy";
+	public static final String PROXY_KEY = "proxy";
 
 	/**
 	 * Zuul {@link com.netflix.zuul.context.RequestContext} key for use in {@link org.springframework.cloud.netflix.zuul.filters.route.RibbonRoutingFilter}
 	 */
-	String REQUEST_ENTITY_KEY = "requestEntity";
+	public static final String REQUEST_ENTITY_KEY = "requestEntity";
 
 	/**
 	 * Zuul {@link com.netflix.zuul.context.RequestContext} key for use in to override the path of the request.
 	 */
-	String REQUEST_URI_KEY = "requestURI";
+	public static final String REQUEST_URI_KEY = "requestURI";
 
 	/**
 	 * Zuul {@link com.netflix.zuul.context.RequestContext} key for use in {@link org.springframework.cloud.netflix.zuul.filters.route.RibbonRoutingFilter}
 	 */
-	String RETRYABLE_KEY = "retryable";
+	public static final String RETRYABLE_KEY = "retryable";
 
 	/**
 	 * Zuul {@link com.netflix.zuul.context.RequestContext} key for use in {@link org.springframework.cloud.netflix.zuul.filters.post.SendResponseFilter}
 	 */
-	String ROUTING_DEBUG_KEY = "routingDebug";
+	public static final String ROUTING_DEBUG_KEY = "routingDebug";
 
 	/**
 	 * Zuul {@link com.netflix.zuul.context.RequestContext} key for use in {@link org.springframework.cloud.netflix.zuul.filters.route.RibbonRoutingFilter}
 	 */
-	String SERVICE_ID_KEY = "serviceId";
+	public static final String SERVICE_ID_KEY = "serviceId";
 
 	// ORDER constants -----------------------------------
 
 	/**
 	 * Filter Order for {@link DebugFilter#filterOrder()}
 	 */
-	int DEBUG_FILTER_ORDER = 1;
+	public static final int DEBUG_FILTER_ORDER = 1;
 
 	/**
 	 * Filter Order for {@link org.springframework.cloud.netflix.zuul.filters.pre.FormBodyWrapperFilter#filterOrder()}
 	 */
-	int FORM_BODY_WRAPPER_FILTER_ORDER = -1;
+	public static final int FORM_BODY_WRAPPER_FILTER_ORDER = -1;
 
 	/**
 	 * Filter Order for {@link org.springframework.cloud.netflix.zuul.filters.pre.PreDecorationFilter}
 	 */
-	int PRE_DECORATION_FILTER_ORDER = 5;
+	public static final int PRE_DECORATION_FILTER_ORDER = 5;
 
 	/**
 	 * Filter Order for {@link org.springframework.cloud.netflix.zuul.filters.route.RibbonRoutingFilter#filterOrder()}
 	 */
-	int RIBBON_ROUTING_FILTER_ORDER = 10;
+	public static final int RIBBON_ROUTING_FILTER_ORDER = 10;
 
 	/**
 	 * Filter Order for {@link org.springframework.cloud.netflix.zuul.filters.post.SendErrorFilter#filterOrder()}
 	 */
-	int SEND_ERROR_FILTER_ORDER = 0;
+	public static final int SEND_ERROR_FILTER_ORDER = 0;
 
 	/**
 	 * Filter Order for {@link SendForwardFilter#filterOrder()}
 	 */
-	int SEND_FORWARD_FILTER_ORDER = 500;
+	public static final int SEND_FORWARD_FILTER_ORDER = 500;
 
 	/**
 	 * Filter Order for {@link org.springframework.cloud.netflix.zuul.filters.post.SendResponseFilter#filterOrder()}
 	 */
-	int SEND_RESPONSE_FILTER_ORDER = 1000;
+	public static final int SEND_RESPONSE_FILTER_ORDER = 1000;
 
 	/**
 	 * Filter Order for {@link org.springframework.cloud.netflix.zuul.filters.route.SimpleHostRoutingFilter#filterOrder()}
 	 */
-	int SIMPLE_HOST_ROUTING_FILTER_ORDER = 100;
+	public static final int SIMPLE_HOST_ROUTING_FILTER_ORDER = 100;
 
 	/**
 	 * filter order for {@link Servlet30WrapperFilter#filterOrder()}
 	 */
-	int SERVLET_30_WRAPPER_FILTER_ORDER = -2;
+	public static final int SERVLET_30_WRAPPER_FILTER_ORDER = -2;
 
 	/**
 	 * filter order for {@link org.springframework.cloud.netflix.zuul.filters.pre.ServletDetectionFilter#filterOrder()}
 	 */
-	int SERVLET_DETECTION_FILTER_ORDER = -3;
+	public static final int SERVLET_DETECTION_FILTER_ORDER = -3;
 
 	// Zuul Filter TYPE constants -----------------------------------
 
 	/**
 	 * {@link ZuulFilter#filterType()} error type.
 	 */
-	String ERROR_TYPE = "error";
+	public static final String ERROR_TYPE = "error";
 
 	/**
 	 * {@link ZuulFilter#filterType()} post type.
 	 */
-	String POST_TYPE = "post";
+	public static final String POST_TYPE = "post";
 
 	/**
 	 * {@link ZuulFilter#filterType()} pre type.
 	 */
-	String PRE_TYPE = "pre";
+	public static final String PRE_TYPE = "pre";
 
 	/**
 	 * {@link ZuulFilter#filterType()} route type.
 	 */
-	String ROUTE_TYPE = "route";
+	public static final String ROUTE_TYPE = "route";
 
 	// OTHER constants -----------------------------------
 
 	/**
 	 * Zuul {@link com.netflix.zuul.context.RequestContext} key for use in {@link org.springframework.cloud.netflix.zuul.filters.route.SendForwardFilter}
 	 */
-	String FORWARD_LOCATION_PREFIX = "forward:";
+	public static final String FORWARD_LOCATION_PREFIX = "forward:";
 
 	/**
 	 * default http port
 	 */
-	int HTTP_PORT = 80;
+	public static final int HTTP_PORT = 80;
 
 	/**
 	 * default https port
 	 */
-	int HTTPS_PORT = 443;
+	public static final int HTTPS_PORT = 443;
 
 	/**
 	 * http url scheme
 	 */
-	String HTTP_SCHEME = "http";
+	public static final String HTTP_SCHEME = "http";
 
 	/**
 	 * https url scheme
 	 */
-	String HTTPS_SCHEME = "https";
+	public static final String HTTPS_SCHEME = "https";
 
 	// HEADER constants -----------------------------------
 
 	/**
 	 * X-* Header for the matching url. Used when routes use a url rather than serviceId
 	 */
-	String SERVICE_HEADER = "X-Zuul-Service";
+	public static final String SERVICE_HEADER = "X-Zuul-Service";
 
 	/**
 	 * X-* Header for the matching serviceId
 	 */
-	String SERVICE_ID_HEADER = "X-Zuul-ServiceId";
+	public static final String SERVICE_ID_HEADER = "X-Zuul-ServiceId";
 
 	/**
 	 * X-Forwarded-For Header
 	 */
-	String X_FORWARDED_FOR_HEADER = "X-Forwarded-For";
+	public static final String X_FORWARDED_FOR_HEADER = "X-Forwarded-For";
 
 	/**
 	 * X-Forwarded-Host Header
 	 */
-	String X_FORWARDED_HOST_HEADER = "X-Forwarded-Host";
+	public static final String X_FORWARDED_HOST_HEADER = "X-Forwarded-Host";
 
 	/**
 	 * X-Forwarded-Prefix Header
 	 */
-	String X_FORWARDED_PREFIX_HEADER = "X-Forwarded-Prefix";
+	public static final String X_FORWARDED_PREFIX_HEADER = "X-Forwarded-Prefix";
 
 	/**
 	 * X-Forwarded-Port Header
 	 */
-	String X_FORWARDED_PORT_HEADER = "X-Forwarded-Port";
+	public static final String X_FORWARDED_PORT_HEADER = "X-Forwarded-Port";
 
 	/**
 	 * X-Forwarded-Proto Header
 	 */
-	String X_FORWARDED_PROTO_HEADER = "X-Forwarded-Proto";
+	public static final String X_FORWARDED_PROTO_HEADER = "X-Forwarded-Proto";
 
 	/**
 	 * X-Zuul-Debug Header
 	 */
-	String X_ZUUL_DEBUG_HEADER = "X-Zuul-Debug-Header";
+	public static final String X_ZUUL_DEBUG_HEADER = "X-Zuul-Debug-Header";
+
+	private FilterConstants() {
+		throw new AssertionError("Must not instantiate constant utility class");
+	}
+
 }

spring-cloud-netflix-eureka-client/src/main/java/org/springframework/cloud/netflix/eureka/EurekaClientConfigBean.java

@@ -38,14 +38,14 @@ import lombok.Data;
  */
 @Data
 @ConfigurationProperties(EurekaClientConfigBean.PREFIX)
-public class EurekaClientConfigBean implements EurekaClientConfig, EurekaConstants {
+public class EurekaClientConfigBean implements EurekaClientConfig {
 
 	public static final String PREFIX = "eureka.client";
 
 	@Autowired(required = false)
 	PropertyResolver propertyResolver;
 
-	public static final String DEFAULT_URL = "http://localhost:8761" + DEFAULT_PREFIX
+	public static final String DEFAULT_URL = "http://localhost:8761" + EurekaConstants.DEFAULT_PREFIX
 			+ "/";
 
 	public static final String DEFAULT_ZONE = "defaultZone";

spring-cloud-netflix-eureka-client/src/main/java/org/springframework/cloud/netflix/eureka/EurekaConstants.java

@@ -19,8 +19,12 @@ package org.springframework.cloud.netflix.eureka;
 /**
  * @author Spencer Gibb
  */
-public interface EurekaConstants {
+public class EurekaConstants {
 
-	String DEFAULT_PREFIX = "/eureka";
+	public static final String DEFAULT_PREFIX = "/eureka";
+
+	private EurekaConstants() {
+		throw new AssertionError("Must not instantiate constant utility class");
+	}
 
 }

spring-cloud-netflix-eureka-server/src/main/java/org/springframework/cloud/netflix/eureka/server/EurekaServerConfigBean.java

@@ -23,7 +23,6 @@ import java.util.Set;
 
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.context.properties.ConfigurationProperties;
-import org.springframework.cloud.netflix.eureka.EurekaConstants;
 import org.springframework.core.env.PropertyResolver;
 
 import com.netflix.eureka.EurekaServerConfig;
@@ -36,7 +35,7 @@ import lombok.Data;
  */
 @Data
 @ConfigurationProperties(EurekaServerConfigBean.PREFIX)
-public class EurekaServerConfigBean implements EurekaServerConfig, EurekaConstants {
+public class EurekaServerConfigBean implements EurekaServerConfig {
 
 	public static final String PREFIX = "eureka.server";