{"record":{"id":"338362f11e875c40","repo":"didi/DoKit","slug":"transformer-must-not-be-null","errorCode":null,"errorMessage":"Transformer must not be null.","messagePattern":"Transformer 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":779,"sourceCode":"      if (listener == null) {\n        throw new IllegalArgumentException(\"Listener must not be null.\");\n      }\n      if (this.listener != null) {\n        throw new IllegalStateException(\"Listener already set.\");\n      }\n      this.listener = listener;\n      return this;\n    }\n\n    /**\n     * Specify a transformer for all incoming requests.\n     * <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.\");","sourceCodeStart":761,"sourceCodeEnd":797,"githubUrl":"https://github.com/didi/DoKit/blob/626827cddb2feb2f3aee87a52a064b4e5ca2bed4/Android/dokit/src/main/java/com/didichuxing/doraemonkit/picasso/DokitPicasso.java#L761-L797","documentation":"DokitPicasso.Builder.requestTransformer() throws IllegalArgumentException when passed a null RequestTransformer. The transformer rewrites incoming requests before execution and must be a real object. Fail-fast null guard on configuration.","triggerScenarios":"Calling builder.requestTransformer(null), usually from an optional transformer variable that was never assigned.","commonSituations":"Feature-flagged transformers (e.g. CDN URL rewriting enabled only in some flavors) whose reference is null when the flag is off.","solutions":["Pass a non-null RequestTransformer","Skip the call when no transformation is needed","Initialize the transformer reference in all code paths before passing it"],"exampleFix":"// before\nbuilder.requestTransformer(flag ? new CdnTransformer() : null); // IllegalArgumentException when flag off\n\n// after\nif (flag) {\n  builder.requestTransformer(new CdnTransformer());\n}","handlingStrategy":"validation","validationCode":"if (transformer != null) { builder.requestTransformer(transformer); }","typeGuard":null,"tryCatchPattern":null,"preventionTips":["Only register transformers when the feature flag that creates them is on"],"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"}