Credit: Data Science Central
Web scraping or crawling is the process of extracting data from any website. The data does not necessarily have to be in the form of text, it could be images, tables, audio or video. It requires downloading and parsing the HTML code in order to scrape the data that you require.
Since data is growing at a fast clip on the web, it is not possible to manually copy and paste it. At times, it is not possible for technical reasons. In any case, web scraping and crawling enables this process of fetching the data in an easy and automated fashion. As it is automated, there’s no upper limit to how much data you can extract. In other words, you can extract large quantities of data from disparate sources.
Data has always been important but of late, businesses have begun to use data in order to make business decisions. As businesses rely heavily on data for decision making, web scraping has, in turn, grown in significance. However, as data needs to be collated from different sources, it is even more important to leverage web scraping as it can make this entire exercise quite easy and hassle-free.
As information is scattered all over the digital space in the form of news, social media posts, images on Instagram, articles, e-commerce sites etc., web scraping is the most efficient way to keep an eye on the big picture and derive business insights that can propel your enterprise. In this context, java web scraping/crawling libraries can come in quite handy. Here’s a list of best java web scraping/crawling libraries which can help you to crawl and scrape the data you want from the Internet.
1. Apache Nutch
Apache Nutch is one of the most efficient and popular open source web crawler software projects. It’s great to use because it offers varied extensible interfaces such as Parse, Index and Scoring Filter’s custom implementations such as Apache Tika for parsing. Moreover, it is also possible to use pluggable indexing for Apache Solr, Elastic Search etc.
- Highly scalable and relatively feature rich crawler.
- Features like politeness, which obeys robots.txt rules.
- Robust and scalable – Nutch can run on a cluster of up to 100 machines.
StormCrawler stands out as it serves a library and collection of resources that developers can use for building their own crawlers. StormCrawler is also preferred by many for use cases in which the URL to fetch and parse come as streams. However, you can also use it for large scale recursive crawls particularly where low latency is needed.
- low latency
- easy to extend
- polite yet efficient
jsoup is great as a Java library which helps you navigate the real-world HTML. Developers love it because offers quite a convenient API for extracting and manipulating data, making use of the best of DOM, CSS and jquery-like methods.
- Fully supports CSS selectors
- Sanitize HTML
- Built-in proxy support
- Provides a slick API to traverse the HTML DOM tree to get the elements of interest.
- The library provides a fast, ultra-light headless browser
- Web pagination discovery
- Customizable caching & content handlers
5. Norconex HTTP Collector
If you are looking for open source web crawlers related to enterprise needs, Norconex is what you need.
Norconex is a great tool because it enables you to crawl any kind of web content that you need. You can use it as you wish- as a full-featured collector or embed it in your own application. Moreover, it works well on any operating system. It can crawl millions of pages on a single server of median capacity.
- Highly scalable – Can crawl millions on a single server of average capacity
- OCR support on images and PDFs
- Configurable crawling speed
- Language detection
WebSPHINX (Website-Specific Processors for HTML INformation eXtraction) is an excellent tool as a Java class library and interactive development environment for web crawlers. WebSPHINX comprises two main parts: the Crawler Workbench and the WebSPHINX class library.
- Provide a graphical user interface that lets you configure and control a customizable web crawler
HtmlUnit is a headless web browser written in Java.
It’s a great tool because it allows high-level manipulation of websites from other Java code, including filling and submitting forms and clicking hyperlinks.
- Provides high-level API, taking away lower-level details away from the user.
- It can be configured to simulate a specific Browser.
Gecco is also a hassle-free lightweight web crawler developed with Java language. Gecco framework is preferred for its remarkable scalability. The framework is based on the principle of open and close design, the provision to modify the closure and the expansion of open.
- Support for asynchronous Ajax requests in the page
- Support the download proxy server randomly selected
- Using Redis to realize distributed crawling
As the applications of web scraping grow, the use of Java web scraping libraries is also set to accelerate. Since there are various libraries, and each one has its own unique features, it will require some study on the part of the end user. However, it will also depend on the respective needs of different end users which will determine which tool would suit better. Once the needs are clear, it would be possible to leverage these tools and power your web scraping endeavours in order to gain a competitive advantage!