Integrating Tess4J OCR into a Spring Boot Backend Service

Overview – This article explains how to integrate Tess4J , a Java wrapper for the Tesseract OCR engine, into a Spring Boot project to recognize text from both local and remote images.

Background – With the growing need for automated text extraction from images, using Tess4J provides a powerful and easy‑to‑use interface for OCR within Java applications.

Part 1: Environment Setup

Ensure the following tools are installed before starting:

JDK 1.8 or higher

Maven

The latest version of Spring Boot

Tess4J version 4.x or newer

Part 2: Add Dependencies

Add the Tess4J dependency to your pom.xml :

<dependencies>
    <dependency>
        <groupId>net.sourceforge.tess4j</groupId>
        <artifactId>tess4j</artifactId>
        <version>4.5.4</version>
    </dependency>
    <!-- other dependencies -->
</dependencies>

Download the appropriate language data (e.g., chi_sim.traineddata ) from the official Tessdata repository or the provided Baidu Cloud link.

Part 3: Create OCR Service Class

Implement a Spring service that wraps Tess4J calls:

@Service
public class OcrService {
    public String recognizeText(File imageFile) throws TesseractException {
        Tesseract tesseract = new Tesseract();
        // Set the path to the tessdata folder (optional for English)
        tesseract.setDatapath("
");
        tesseract.setLanguage("chi_sim");
        return tesseract.doOCR(imageFile);
    }

    public String recognizeTextFromUrl(String imageUrl) throws Exception {
        URL url = new URL(imageUrl);
        InputStream in = url.openStream();
        Files.copy(in, Paths.get("downloaded.jpg"), StandardCopyOption.REPLACE_EXISTING);
        File imageFile = new File("downloaded.jpg");
        return recognizeText(imageFile);
    }
}

The recognizeText method processes a local file, while recognizeTextFromUrl downloads a remote image before performing OCR.

Part 4: Build REST Controller

Create endpoints for uploading an image or providing a URL:

@RestController
@RequestMapping("/api/ocr")
public class OcrController {
    private final OcrService ocrService;

    public OcrController(OcrService ocrService) {
        this.ocrService = ocrService;
    }

    @PostMapping("/upload")
    public ResponseEntity
uploadImage(@RequestParam("file") MultipartFile file) {
        try {
            File convFile = new File(System.getProperty("java.io.tmpdir") + "/" + file.getOriginalFilename());
            file.transferTo(convFile);
            String result = ocrService.recognizeText(convFile);
            return ResponseEntity.ok(result);
        } catch (Exception e) {
            e.printStackTrace();
            return ResponseEntity.badRequest().body("Recognition error: " + e.getMessage());
        }
    }

    @GetMapping("/recognize-url")
    public ResponseEntity
recognizeFromUrl(@RequestParam("imageUrl") String imageUrl) {
        try {
            String result = ocrService.recognizeTextFromUrl(imageUrl);
            return ResponseEntity.ok(result);
        } catch (Exception e) {
            e.printStackTrace();
            return ResponseEntity.badRequest().body("URL recognition error: " + e.getMessage());
        }
    }
}

Part 5: Testing

Test the service locally by uploading an image file via the /api/ocr/upload endpoint, and test remote image processing using /api/ocr/recognize-url with a publicly accessible image URL.

Conclusion

Following these steps gives you a functional Spring Boot service capable of OCR on both local and remote images. Adjust the tessdata path and language settings as needed for multilingual scenarios.