Tip

Chapter 6: Crawling the Web with Java

Crawler technology is useful in many types of Web-related applications For example, you might use a crawler to look for broken links in a commercial Web site. You might also use a crawler to find changes to a Web site.

Although Web crawlers are conceptually easy, in that you just follow the links from one site to another, they are a bit challenging to create. One complication is that a list of links to be crawled must be maintained, and this list grows and shrinks as sites are searched. Another complication is the complexity of handling absolute versus relative links.

Fortunately, Java contains features that help make it easier to implement a Web crawler. First, Java's support for networking makes downloading Web pages simple. Second, Java's support for regular expression processing simplifies the finding of links. Third, Java's Collection Framework supplies the mechanisms needed to store a list of links.

The Web crawler developed in this chapter from the book The Art of Java, by Herbert Schildt and James Holmes, is called Search Crawler. It crawls the Web, looking for sites that contain strings matching those specified by the user. It displays the URLs of the sites in which matches are found. Although Search Crawler is a useful utility as is, its greatest benefit is found when it is used as a starting point for your own crawler-based applications.

Click here to download this free book chapter.

This was first published in September 2004

There are Comments. Add yours.

 
TIP: Want to include a code block in your comment? Use <pre> or <code> tags around the desired text. Ex: <code>insert code</code>

REGISTER or login:

Forgot Password?
By submitting you agree to receive email from TechTarget and its partners. If you reside outside of the United States, you consent to having your personal data transferred to and processed in the United States. Privacy
Sort by: OldestNewest

Forgot Password?

No problem! Submit your e-mail address below. We'll send you an email containing your password.

Your password has been sent to:

Disclaimer: Our Tips Exchange is a forum for you to share technical advice and expertise with your peers and to learn from other enterprise IT professionals. TechTarget provides the infrastructure to facilitate this sharing of information. However, we cannot guarantee the accuracy or validity of the material submitted. You agree that your use of the Ask The Expert services and your reliance on any questions, answers, information or other materials received through this Web site is at your own risk.