Java uses escaped characters to filter tags in HTML

In web development, HTML text data is often processed and HTML tags need to be filtered out to ensure the security and purity of page display. Java provides escape characters to filter HTML tags. This article will introduce how to use escape characters in Java to filter tags in HTML.

HTML tags and escape characters

HTML tags are text contained in angle brackets that define the structure and style of a web page. For example<p>Indicates paragraphs,<a>Indicates links, etc. In order to filter HTML tags, we can use escape characters to convert special characters in the tag into their corresponding entity characters to achieve the purpose of filtering.

Java implements the method of filtering HTML tags

Here is a simple Java method for filtering tags in HTML text:

public class HtmlFilter {
    public static String filterHtmlTags(String html) {
        if (html == null || ()) {
            return "";
        }
        return ("&lt;[^&gt;]*&gt;", "");
    }
    public static void main(String[] args) {
        String htmlText = "&lt;p&gt;Hello, &lt;b&gt;World&lt;/b&gt;!&lt;/p&gt;";
        String filteredText = filterHtmlTags(htmlText);
        ("Filter the text after HTML tags:" + filteredText);
    }
}

Running results

Run the above code and the output result is as follows:

plaintextCopy code
Text filtered after HTML tags: Hello, World!

Web content display

In actual web development, it is often necessary to obtain content with HTML tags from a database or other data source, and then display it to the user on the page. In order to prevent users from entering malicious HTML tags or scripts, we need to filter these contents and display only plain text content.

Sample code:

Here is a simple example that demonstrates how to get content containing HTML tags from a database, filter out HTML tags in it using Java, and then display plain text content on a web page.

public class HtmlFilterExample {
    public static String filterHtmlTags(String html) {
        if (html == null || ()) {
            return "";
        }
        return ("&lt;[^&gt;]*&gt;", "");
    }
    public static void main(String[] args) {
        // Simulate content with HTML tags read from the database        String htmlContent = "&lt;h1&gt;Welcome to our website！&lt;/h1&gt;&lt;p&gt;Please check the latest &lt;a href='#'>Product Information</a>.  </p>";        // Filter the content after HTML tags        String filteredContent = filterHtmlTags(htmlContent);
        // Output filtered plain text content        ("Filter the content after HTML tags:" + filteredContent);
    }
}

In this example, we simulate getting content with HTML tags from the databasehtmlContent, and then passfilterHtmlTags()Methods filter the content HTML tags and finally output the filtered plain text content.

Detailed introduction: Escape characters

In computer programming, escape characters are special characters that represent some special characters or characters with special meanings. Typically, these characters cannot be represented directly or entered, so they need to be represented by escaped characters. In Java and other programming languages, common escape characters include, but are not limited to:

\n: Line break
\t: Tab characters
\\: Backslash
\": Double quotes
\': Single quotes The format of escaped characters is usually started with a backslash (\) followed by a character representing a special character. When the compiler or interpreter encounters an escaped character, the character that follows is interpreted as a character with a special meaning, rather than a character literally. The role of escaped characters includes but is not limited to:
Represents special characters: for example, line breaks, tab characters, etc. Entering these characters directly may be interpreted as ordinary characters, and their special meaning can be clearly expressed by escaping characters.
Prevent ambiguity: Some characters themselves have special meanings. If you need to represent these characters in the literal form, you need to use escape characters to avoid ambiguity with the grammar of the language. When processing text data, escape characters are often used to escape special characters. For example, when processing HTML text in Java, escape characters can be used to filter or convert HTML tags to ensure the security and correctness of page content.

Summarize

Through the Java method introduced in this article, we can easily use escape characters to filter tags in HTML text to ensure plain text display of the output content. This helps prevent malicious script injection and protects the security of web page content. Hope this article will be helpful for your understanding of the use of escape characters to filter HTML tags in Java. The above is this skill

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