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Java Image Validation

How it works

  1. Upload image to the server.
  2. Validate image on the server side before storing it.

Jump to Complete Example

Image Upload

The Server Upload section explains the steps to upload an image to a server. You can validate images when you insert them in the editor, however that only checks the filename and not the mime type. It is advisable to make additional checks on the server side to make sure users only upload valid image formats.

Validate Extension

The editor's Java SDK can check the image extension before storing it on disk, and it also checks the mime type.

ImageOptions options = new ImageOptions();
options.setFieldname("myImage");
options.setValidation(new ImageValidation(new String[] { "gif", "jpeg", "jpg", "png", "svg", "blob" }, new String[] { "image/gif", "image/jpeg", "image/pjpeg", "image/x-png", "image/png", "image/svg+xml" }));

Map<Object, Object> responseData = Image.upload(request, fileRoute, options);

Custom Validation

You can also pass a custom method instead of validating the extension and mime type. This gives you full control on what types of images you want to store on disk. Below is an example of how to validate if an image is square.

ImageOptions options = new ImageOptions();
options.setFieldname("myImage");
options.setValidation(new ImageValidation(new CustomValidation() {

    @Override
    public boolean validate(String filePath, String mimeType) {

        BufferedImage image;
        try {
            image = ImageIO.read(new java.io.File(filePath));
        } catch (IOException e) {
            e.printStackTrace();
            return false;
        }

        if (image == null) {
            return false;
        }

        int width = image.getWidth();
        int height = image.getHeight();

        if (width != height) {
            return false;
        }

        return true;
    }
}));

Map<Object, Object> responseData = Image.upload(request, fileRoute, options);

Complete Example

<script>
  new FroalaEditor('.selector', {
    // Set the image upload URL.
    imageUploadURL: '/upload_image_validation'
  })
</script>
package com.froala.examples.servlets;

import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.annotation.MultipartConfig;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.froala.editor.CustomValidation;
import com.froala.editor.Image;
import com.froala.editor.image.ImageOptions;
import com.froala.editor.image.ImageValidation;
import com.google.gson.Gson;

/**
 * Servlet implementation class UploadImageValidation
 */
@WebServlet("/upload_image_validation")
@MultipartConfig
public class UploadImageValidation extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public UploadImageValidation() {
        super();
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
     *      response)
     */
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        String fileRoute = "/public/";

        ImageOptions options = new ImageOptions();
        options.setFieldname("myImage");
        options.setValidation(new ImageValidation(new CustomValidation() {

            @Override
            public boolean validate(String filePath, String mimeType) {

                BufferedImage image;
                try {
                    image = ImageIO.read(new java.io.File(filePath));
                } catch (IOException e) {
                    e.printStackTrace();
                    return false;
                }

                if (image == null) {
                    return false;
                }

                int width = image.getWidth();
                int height = image.getHeight();

                if (width != height) {
                    return false;
                }

                return true;
            }
        }));

        Map<Object, Object> responseData;
        try {
            responseData = Image.upload(request, fileRoute, options);
        } catch (Exception e) {
            e.printStackTrace();
            responseData = new HashMap<Object, Object>();
            responseData.put("error", e.toString());
        }
        String jsonResponseData = new Gson().toJson(responseData);
        response.setContentType("application/json");
        response.setCharacterEncoding("UTF-8");
        response.getWriter().write(jsonResponseData);
    }

}

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