Handle loading of external resources documents Leave feedback

Member	Description
`getUri()`	The URI of the external resource.
`setUri(String)`	Changes the URI of the external resource.
`isSkipped()`, `setSkipped(boolean)`	Gets or sets the value that indicates whether the resource is skipped.
`getData()`, `setData(byte[])`	Gets or sets the content of the resource.

Create the handler class

ExternalResourceHandler is a Java class, not an interface. The java module can implement only Java interfaces in JavaScript (java.newProxy), so the subclass must be written in Java. The following small class forwards onLoading calls to java.util.function.Consumer, which can be implemented in JavaScript:

package com.example;

import com.groupdocs.parser.options.ExternalResourceHandler;
import com.groupdocs.parser.options.ExternalResourceLoadingArgs;
import java.util.function.Consumer;

// Forwards onLoading calls to a callback that can be implemented in JavaScript
public class CallbackResourceHandler extends ExternalResourceHandler {
    private final Consumer<ExternalResourceLoadingArgs> callback;

    public CallbackResourceHandler(Consumer<ExternalResourceLoadingArgs> callback) {
        this.callback = callback;
    }

    @Override
    public void onLoading(ExternalResourceLoadingArgs args) {
        callback.accept(args);
        super.onLoading(args);
    }
}

Save it as com/example/CallbackResourceHandler.java and compile it into a JAR with the JDK against the JAR of the package:

javac --release 8 -cp node_modules/@groupdocs/groupdocs.parser/lib/groupdocs-parser-nodejs-26.9.jar -d out com/example/CallbackResourceHandler.java
jar cf handlers.jar -C out .

Use the handler

Here are the steps to handle loading of external resources:

Add the JAR with the handler class to java.classpath before the first call to the package;
Implement the callback with java.newProxy('java.util.function.Consumer', ...);
Create an instance of the ParserSettings class with the handler;
Create an instance of the Parser class with the settings and call the getImages method.

The following code sample shows how to load only the installation.png image of the HTML document and skip other images:

const path = require('path');
const java = require('java');
// Add the JAR with the handler class before the JVM starts
java.classpath.push(path.join(__dirname, 'handlers.jar'));
const groupdocs = require('@groupdocs/groupdocs.parser');

const CallbackResourceHandler = java.import('com.example.CallbackResourceHandler');

// Called before any external resource loads. It allows to skip unnecessary file loading.
const onLoading = java.newProxy('java.util.function.Consumer', {
  accept: (args) => {
    // Check if the file name ends with installation.png
    if (!args.getUri().endsWith('installation.png')) {
      // Otherwise skip this file
      args.setSkipped(true);
    }
  },
});

// Create an instance of ParserSettings to pass External Resource Handler
const settings = new groupdocs.ParserSettings(new CallbackResourceHandler(onLoading));
// Create an instance of Parser class with the settings
const parser = new groupdocs.Parser('installation.html', settings);
try {
  // Extract images from HTML document
  const images = parser.getImages();
  // Iterate over extracted images
  const it = images.iterator();
  while (it.hasNext()) {
    // Print the type of image
    console.log(String(it.next().getFileType()));
  }
} finally {
  parser.close();
}
process.exit(0);

installation.html references installation.png, installation_1.png and installation_2.png. Without the handler three images are extracted; with the handler only one:

Portable Network Graphic (.png)

Note
java.classpath.push has effect only before the JVM is created. Call it before the first call to @groupdocs/groupdocs.parser (for example, before setting the license).

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Handle loading of external resources documents Leave feedback

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Create the handler class

Use the handler

More resources

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