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Data Extraction in Java
Data extraction, also known as web data extraction or web harvesting, collects information and resources from websites or HTML documents. With Aspose.HTML for Java, an application can load HTML, inspect the DOM, select elements with XPath or CSS selectors, save web pages, and download linked files.
Use
HTMLDocument to load an HTML source, then navigate DOM nodes or select the required elements with
evaluate() for XPath or
querySelectorAll() for CSS selectors. Choose the focused guides below when you need to save a web page, download a known file, or extract image and SVG resources.
Aspose.HTML is an HTML document-processing API rather than a complete web-crawling platform. The application remains responsible for choosing source URLs, defining selectors, controlling traversal, and storing the extracted results.
Data Extraction Topics
- HTML Navigation – navigate DOM nodes, inspect elements, and select content with XPath or CSS selectors.
- Save a Website or Web Page – save an individual web page or website content as HTML with related resources.
- Save File from URL – download a file when its URL is already known.
- Extract Images from Website – locate regular images and icons on a web page and save them locally.
- Extract SVG from Website – extract inline SVG markup and download external SVG resources.
- Extract Text from HTML – read all body text or extract selected headings, paragraphs, and list items.
- Extract HTML Tables – select table rows and cells from local files or webpage URLs and export the values to CSV or TXT.
- Extract Links from HTML – read anchor text and
hrefvalues or collect unique absolute links from a webpage.
Choose a Java Data Extraction Method
| Task | Start with |
|---|---|
| Inspect an HTML document, traverse nodes, or select elements | XPath, CSS selectors, and DOM traversal in HTML Navigation |
| Apply focused CSS selector queries | Use CSS Selectors in Java |
| Apply structural or positional XPath expressions | Use XPath in HTML with Java |
| Read all body text or text from selected elements | Extract Text from HTML |
| Extract table rows and cells to CSV or TXT | Extract HTML Tables |
Read anchor text and href values or resolve absolute links | Extract Links from HTML |
| Save a page together with related resources | Save a Website or Web Page |
| Download a resource from a known URL | Save File from URL |
| Find and save raster images, icons, or SVG content | Extract Images from Website or Extract SVG from Website |
Common Data Extraction Issues
| Issue | Likely cause | What to check |
|---|---|---|
| XPath or CSS selector returns no elements | The selector does not match the DOM loaded from the source. | Inspect the actual document structure and test the selector against the available elements and attributes. |
| A relative image, SVG, or file URL cannot be downloaded | The resource reference was used without the document base URL. | Resolve relative references against the page URL or base URI before requesting the resource. |
| A saved page is missing a linked resource | Resource handling settings, traversal depth, or URL restrictions excluded it. | Review the save options and confirm that the resource URL is accessible. |
| A downloaded file is empty or has unexpected content | The request returned an error page, redirect, or another media type. | Check the response status and content type before saving the response body. |
FAQ
Is Aspose.HTML for Java a web scraper?
Aspose.HTML for Java provides HTML loading, DOM navigation, selectors, and resource-handling APIs that can be used in a data extraction workflow. It does not replace the application logic required to crawl URLs, schedule requests, or store collected data.
Should I use XPath or CSS selectors?
Use CSS selectors for familiar matching by tag, class, ID, or attribute. XPath is useful when selection depends on document hierarchy, node relationships, or path expressions. Both approaches operate on the DOM loaded by the application.
Can I extract text and attributes from HTML?
Yes. After locating an element through DOM navigation, XPath, or a CSS selector, Java code can read its text content and attributes. Start with the HTML Navigation guide for the available selection approaches.
Other Platforms
- Data Extraction in C# – extract data from HTML documents with Aspose.HTML for .NET.
- Data Extraction in Python – extract data from HTML documents with Aspose.HTML for Python via .NET.
Try AI Keyword Extractor
Aspose.HTML offers AI Keyword Extractor, an online tool for extracting keywords from a web page, plain text, or a file. Paste the content or URL, choose the settings, and run the extraction without writing Java code.
