pxb1988/dex2jar · error · DexException

error on reading Annotation of class

Error message

error on reading Annotation of class 

What it means

DexFileReader wraps any exception from read_annotation_set_item while reading a class's annotations in a DexException('error on reading Annotation of class ', e), preserving the cause. It means the class_annotation_set_off pointed at data that failed to decode (bad offsets, malformed annotation items, or internal reader errors). The original stack trace is in the cause chain.

Solutions

1. Inspect the wrapped cause (e.getCause()) to find the real decode failure and fix that
2. Re-obtain/re-extract the dex — corruption from bad archive extraction is common
3. Rebuild the dex from source if you control it; or skip annotations via config flag SKIP_ANNOTATION when constructing DexFileReader
4. Verify the APK is not packed/protected (packers often corrupt annotation offsets) — unpack first or use a different sample

Example fix

// before
DexFileReader r = new DexFileReader(file, 0); // all features
// after: skip annotations to avoid the fragile path
int config = DexFileReader.SKIP_CODE | DexFileReader.SKIP_ANNOTATION;
DexFileReader r = new DexFileReader(file, config);

try {
    new DexFileReader(file, config).accept(visitor);
} catch (DexException e) {
    if (e.getMessage() != null && e.getMessage().startsWith("error on reading Annotation of class")) {
        Throwable root = e; while (root.getCause() != null) root = root.getCause();
        log.warn("Annotations unreadable for " + file + ": " + root);
        return parseSkippingAnnotations(file); // retry with SKIP_ANNOTATION
    }
    throw e;
}

When it happens

Trigger: Opening a dex whose class_def has a nonzero annotations_off pointing to malformed/corrupt annotation_set_item data; offset tables misparsed earlier in the same read; reading dex produced by a broken tool.

Common situations: Obfuscated/packed APKs with deliberately mangled annotation offsets; corrupted dex from incomplete zip extraction; dex2jar failing on an app and reporting this wrapper instead of the root cause.

Understand the failure class

Background: "failed to read file", EACCES, ENOENT and "could not read <path>" errors: when a program can't read a file from disk — this error's family across 49 libraries.

Related errors

• while accept annotation in field
• while accept annotation in method
• Odex unsupported.
• Magic unsupported.
• Endian_tag unsupported

AI-assisted analysis of pxb1988/dex2jar@b5bda4fb49 (2026-09-08). Data as JSON: /api/errors/c44e433b523c68a1. Report an issue: GitHub.

Appendix: source

Thrown at dex-reader/src/main/java/com/googlecode/d2j/reader/DexFileReader.java:813

                    int field_annotations_offset = annotationsDirectoryItemIn.getInt();
                    fieldAnnotationPositions.put(field_idx, field_annotations_offset);
                }
                for (int i = 0; i < method_annotation_size; i++) {
                    int method_idx = annotationsDirectoryItemIn.getInt();
                    int method_annotation_offset = annotationsDirectoryItemIn.getInt();
                    methodAnnotationPositions.put(method_idx, method_annotation_offset);
                }
                for (int i = 0; i < parameter_annotation_size; i++) {
                    int method_idx = annotationsDirectoryItemIn.getInt();
                    int parameter_annotation_offset = annotationsDirectoryItemIn.getInt();
                    paramAnnotationPositions.put(method_idx, parameter_annotation_offset);
                }

                if (class_annotations_off != 0) {
                    try {
                        read_annotation_set_item(class_annotations_off, dcv);
                    } catch (Exception e) {
                        throw new DexException("error on reading Annotation of class ", e);
                    }
                }
            }
        } else {
            fieldAnnotationPositions = null;
            methodAnnotationPositions = null;
            paramAnnotationPositions = null;
        }

        if (class_data_off != 0) {
            ByteBuffer in = classDataIn;
            in.position(class_data_off);

            int static_fields = readULeb128i(in);
            int instance_fields = readULeb128i(in);
            int direct_methods = readULeb128i(in);
            int virtual_methods = readULeb128i(in);
            {

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