{"record":{"id":"ea31de55f3daf221","repo":"didi/DoKit","slug":"requesthandler-must-not-be-null","errorCode":null,"errorMessage":"RequestHandler must not be null.","messagePattern":"RequestHandler must not be null\\.","errorType":"validation","errorClass":"IllegalArgumentException","httpStatus":null,"severity":"error","filePath":"Android/dokit/src/main/java/com/didichuxing/doraemonkit/picasso/DokitPicasso.java","lineNumber":791,"sourceCode":"     * <p>\n     * <b>NOTE:</b> This is a beta feature. The API is subject to change in a backwards incompatible\n     * way at any time.\n     */\n    public Builder requestTransformer(RequestTransformer transformer) {\n      if (transformer == null) {\n        throw new IllegalArgumentException(\"Transformer must not be null.\");\n      }\n      if (this.transformer != null) {\n        throw new IllegalStateException(\"Transformer already set.\");\n      }\n      this.transformer = transformer;\n      return this;\n    }\n\n    /** Register a {@link RequestHandler}. */\n    public Builder addRequestHandler(RequestHandler requestHandler) {\n      if (requestHandler == null) {\n        throw new IllegalArgumentException(\"RequestHandler must not be null.\");\n      }\n      if (requestHandlers == null) {\n        requestHandlers = new ArrayList<RequestHandler>();\n      }\n      if (requestHandlers.contains(requestHandler)) {\n        throw new IllegalStateException(\"RequestHandler already registered.\");\n      }\n      requestHandlers.add(requestHandler);\n      return this;\n    }\n\n    /**\n     * @deprecated Use {@link #indicatorsEnabled(boolean)} instead.\n     * Whether debugging is enabled or not.\n     */\n    @Deprecated public Builder debugging(boolean debugging) {\n      return indicatorsEnabled(debugging);\n    }","sourceCodeStart":773,"sourceCodeEnd":809,"githubUrl":"https://github.com/didi/DoKit/blob/626827cddb2feb2f3aee87a52a064b4e5ca2bed4/Android/dokit/src/main/java/com/didichuxing/doraemonkit/picasso/DokitPicasso.java#L773-L809","documentation":"DokitPicasso.Builder.addRequestHandler() throws IllegalArgumentException when passed a null RequestHandler. Request handlers resolve custom URI schemes (contacts, video thumbnails, etc.), so null is never valid. Fail-fast null guard.","triggerScenarios":"Calling builder.addRequestHandler(null), typically from a list of handlers that contains a null entry or an uninitialized handler field.","commonSituations":"Iterating a handler list built conditionally where one branch added null; handler instances created by reflection or DI that failed silently.","solutions":["Pass a non-null RequestHandler instance","Filter nulls out of the handler list before registering: handlers.removeAll(Collections.singleton(null))","Fix the factory/DI provider so it returns a real handler"],"exampleFix":"// before\nfor (RequestHandler h : handlers) {\n  builder.addRequestHandler(h); // IllegalArgumentException if h == null\n}\n\n// after\nfor (RequestHandler h : handlers) {\n  if (h != null) builder.addRequestHandler(h);\n}","handlingStrategy":"type-guard","validationCode":"for (RequestHandler h : handlers) { if (h != null) builder.addRequestHandler(h); }","typeGuard":"boolean isRegistrableHandler(RequestHandler h) { return h != null; }","tryCatchPattern":null,"preventionTips":["Filter nulls from handler collections before registration","Fail DI providers loudly instead of returning null handlers"],"tags":["android","picasso","builder","null-check"],"backgroundTag":null,"analyzedSha":"626827cddb2feb2f3aee87a52a064b4e5ca2bed4","analyzedAt":"2026-08-14T12:45:58.758Z","schemaVersion":2},"datasetVersion":"2026-08-15T22:17:37.221Z"}