Improve CommonFilter and WebServletConfig in Sentinel Web Servlet adapter

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

sentinel-adapter/sentinel-web-servlet/README.md

@@ -39,7 +39,7 @@ public class FilterConfig {
         registration.addUrlPatterns("/*");
         registration.setName("sentinelCommonFilter");
         registration.setOrder(1);
-        // Set whether to support the specified HTTP method for the filter.
+        // Set whether to support the specified HTTP method prefix for the filter.
         registration.addInitParameter(CommonFilter.HTTP_METHOD_SPECIFY, "false");
         return registration;
     }
@@ -47,6 +47,9 @@ public class FilterConfig {
 ```
 
 When a request is blocked, Sentinel servlet filter will display a default page indicating the request is rejected.
+The HTTP status code of the default block page is **429 (Too Many Requests)**. You can customize it
+via the `csp.sentinel.web.servlet.block.status` configuration item (since 1.7.0).
+
 If customized block page is set (via `WebServletConfig.setBlockPage(blockPage)` method),
 the filter will redirect the request to provided URL. You can also implement your own
 block handler (the `UrlBlockHandler` interface) and register to `WebCallbackManager`.
@@ -59,5 +62,5 @@ If you need to exclude some URLs (that should not be recorded as Sentinel resour
 leverage the `UrlCleaner` interface. You may unify the unwanted URLs to the empty string `""` or `null`,
 then the URLs will be excluded (since Sentinel 1.6.3).
 
-`RequestOriginParser` interface is useful for extracting request origin (e.g. IP or appName from HTTP Header)
+The `RequestOriginParser` interface is useful for extracting request origin (e.g. IP or appName from HTTP Header)
 from HTTP request. You can implement your own `RequestOriginParser` and register to `WebCallbackManager`.

sentinel-adapter/sentinel-web-servlet/src/main/java/com/alibaba/csp/sentinel/adapter/servlet/CommonFilter.java

@@ -39,21 +39,30 @@ import com.alibaba.csp.sentinel.context.ContextUtil;
 import com.alibaba.csp.sentinel.slots.block.BlockException;
 import com.alibaba.csp.sentinel.util.StringUtil;
 
-/***
+/**
  * Servlet filter that integrates with Sentinel.
  *
- * @author zhaoyuguang
  * @author youji.zj
  * @author Eric Zhao
+ * @author zhaoyuguang
  */
 public class CommonFilter implements Filter {
 
-    public final static String HTTP_METHOD_SPECIFY = "HTTP_METHOD_SPECIFY";
     /**
-     * Use the path of the url as the context, if necessary, but pay attention to the number of context EntranceNode
+     * Specify whether the URL resource name should contain the HTTP method prefix (e.g. {@code POST:}).
+     */
+    public static final String HTTP_METHOD_SPECIFY = "HTTP_METHOD_SPECIFY";
+    /**
+     * If enabled, use the URL path as the context name, or else use the default
+     * {@link WebServletConfig#WEB_SERVLET_CONTEXT_NAME}. Please pay attention to the number of context (EntranceNode),
+     * which may affect the memory footprint.
+     *
+     * @since 1.7.0
      */
-    public final static String WEB_CONTEXT_UNIFY = "WEB_CONTEXT_UNIFY";
+    public static final String WEB_CONTEXT_UNIFY = "WEB_CONTEXT_UNIFY";
+
     private final static String COLON = ":";
+
     private boolean httpMethodSpecify = false;
     private boolean webContextUnify = true;
 
@@ -87,7 +96,8 @@ public class CommonFilter implements Filter {
             if (!StringUtil.isEmpty(target)) {
                 // Parse the request origin using registered origin parser.
                 String origin = parseOrigin(sRequest);
-                ContextUtil.enter(webContextUnify ? WebServletConfig.WEB_SERVLET_CONTEXT_NAME : target, origin);
+                String contextName = webContextUnify ? WebServletConfig.WEB_SERVLET_CONTEXT_NAME : target;
+                ContextUtil.enter(contextName, origin);
                 urlEntry = SphU.entry(target, EntryType.IN);
                 // Add method specification if necessary
                 if (httpMethodSpecify) {

sentinel-adapter/sentinel-web-servlet/src/main/java/com/alibaba/csp/sentinel/adapter/servlet/config/WebServletConfig.java

@@ -18,19 +18,21 @@ package com.alibaba.csp.sentinel.adapter.servlet.config;
 import com.alibaba.csp.sentinel.adapter.servlet.CommonFilter;
 import com.alibaba.csp.sentinel.adapter.servlet.CommonTotalFilter;
 import com.alibaba.csp.sentinel.config.SentinelConfig;
+import com.alibaba.csp.sentinel.log.RecordLog;
 import com.alibaba.csp.sentinel.util.StringUtil;
 
 /**
- * @author zhaoyuguang
+ * The configuration center for Web Servlet adapter.
+ *
  * @author leyou
+ * @author zhaoyuguang
  */
-public class WebServletConfig {
+public final class WebServletConfig {
 
     public static final String WEB_SERVLET_CONTEXT_NAME = "sentinel_web_servlet_context";
 
-    public static final String BLOCK_PAGE = "csp.sentinel.web.servlet.block.page";
-
-    public static final String BLOCK_PAGE_HTTP_STATUS = "csp.sentinel.web.servlet.block.page.http.status";
+    public static final String BLOCK_PAGE_URL_CONF_KEY = "csp.sentinel.web.servlet.block.page";
+    public static final String BLOCK_PAGE_HTTP_STATUS_CONF_KEY = "csp.sentinel.web.servlet.block.status";
 
     private static final int HTTP_STATUS_TOO_MANY_REQUESTS = 429;
 
@@ -41,37 +43,52 @@ public class WebServletConfig {
      * @return the block page URL, maybe null if not configured.
      */
     public static String getBlockPage() {
-        return SentinelConfig.getConfig(BLOCK_PAGE);
+        return SentinelConfig.getConfig(BLOCK_PAGE_URL_CONF_KEY);
     }
 
     public static void setBlockPage(String blockPage) {
-        SentinelConfig.setConfig(BLOCK_PAGE, blockPage);
+        SentinelConfig.setConfig(BLOCK_PAGE_URL_CONF_KEY, blockPage);
     }
 
     /**
-     * Return status 429 in the default block page,
-     * you can use -Dcsp.sentinel.web.servlet.block.page.http.status=200 or other http status,
-     * to set http status which you want of the default block page.
-     * When csp.sentinel.web.servlet.block.page.http.status is empty or not number,
-     * the block page http status will be automatically set to 429(Too Many Requests).
+     * <p>Get the HTTP status when using the default block page.</p>
+     * <p>You can set the status code with the {@code -Dcsp.sentinel.web.servlet.block.status}
+     * property. When the property is empty or invalid, Sentinel will use 429 (Too Many Requests)
+     * as the default status code.</p>
      *
-     * @return block page http status
+     * @return the HTTP status of the default block page
+     * @since 1.7.0
      */
     public static int getBlockPageHttpStatus() {
-        String value = SentinelConfig.getConfig(BLOCK_PAGE_HTTP_STATUS);
+        String value = SentinelConfig.getConfig(BLOCK_PAGE_HTTP_STATUS_CONF_KEY);
         if (StringUtil.isEmpty(value)) {
-            setBlockPageHttpStatus(HTTP_STATUS_TOO_MANY_REQUESTS);
             return HTTP_STATUS_TOO_MANY_REQUESTS;
         }
         try {
-            return Integer.parseInt(SentinelConfig.getConfig(BLOCK_PAGE_HTTP_STATUS));
-        } catch (NumberFormatException e) {
+            int s = Integer.parseInt(value);
+            if (s <= 0) {
+                throw new IllegalArgumentException("Invalid status code: " + s);
+            }
+            return s;
+        } catch (Exception e) {
+            RecordLog.warn("[WebServletConfig] Invalid block HTTP status (" + value + "), using default 429");
             setBlockPageHttpStatus(HTTP_STATUS_TOO_MANY_REQUESTS);
         }
         return HTTP_STATUS_TOO_MANY_REQUESTS;
     }
 
+    /**
+     * Set the HTTP status of the default block page.
+     *
+     * @param httpStatus the HTTP status of the default block page
+     * @since 1.7.0
+     */
     public static void setBlockPageHttpStatus(int httpStatus) {
-        SentinelConfig.setConfig(BLOCK_PAGE_HTTP_STATUS, String.valueOf(httpStatus));
+        if (httpStatus <= 0) {
+            throw new IllegalArgumentException("Invalid HTTP status code: " + httpStatus);
+        }
+        SentinelConfig.setConfig(BLOCK_PAGE_HTTP_STATUS_CONF_KEY, String.valueOf(httpStatus));
     }
+
+    private WebServletConfig() {}
 }