How to Choose the Best CSS Parser in Java?

CSS Parser Options in Java

Introduction

Developers seeking a CSS parser in Java often encounter the challenge of extracting styles from HTML elements. While the W3C SAC interface provides a foundation, finding comprehensive documentation can be difficult. Here's an exploration of potential solutions and a detailed code示例 to guide you.

Exploring CSS Parser Options

One notable option is CSSParser. Its error feedback capabilities are valuable, and here's a modified code sample for your reference:

<code class="java">package com.dlogic;

import com.steadystate.css.parser.CSSOMParser;
import org.w3c.css.sac.InputSource;
import org.w3c.dom.css.CSSStyleSheet;
import org.w3c.dom.css.CSSRuleList;
import org.w3c.dom.css.CSSRule;
import org.w3c.dom.css.CSSStyleRule;
import org.w3c.dom.css.CSSStyleDeclaration;
import java.io.*;

// Main class
public class CSSParserTest 
{

    public static void main(String[] args) {

        CSSParserTest oParser = new CSSParserTest();

        if (oParser.Parse("design.css")) {

            System.out.println("Parsing completed OK");

        } else {

            System.out.println("Unable to parse CSS");

        }   
    }


    public boolean Parse(String cssfile) 
    {

        FileOutputStream out = null; 
        PrintStream ps = null; 
        boolean rtn = false;

        try
        {
            // Access CSS file as a resource
            InputStream stream = oParser.getClass().getResourceAsStream(cssfile);

            // Create log file
            out = new FileOutputStream("log.txt");
            if (out != null)
            {
                ps = new PrintStream(out);
                System.setErr(ps); // Redirect stderr to log file
            } else {

                return rtn; 

            }


            // Parse CSS file
            InputSource source = new InputSource(new InputStreamReader(stream));
            CSSOMParser parser = new CSSOMParser();
            CSSStyleSheet stylesheet = parser.parseStyleSheet(source, null, null);

            // Inspect CSS DOM
            CSSRuleList ruleList = stylesheet.getCssRules();
            ps.println("Number of rules: " + ruleList.getLength());

            for (int i = 0; i < ruleList.getLength(); i++) 
            {
                CSSRule rule = ruleList.item(i);
                if (rule instanceof CSSStyleRule) 
                {
                    CSSStyleRule styleRule = (CSSStyleRule)rule;
                    ps.println("selector:" + i + ": " + styleRule.getSelectorText());
                    CSSStyleDeclaration styleDeclaration = styleRule.getStyle();

                    for (int j = 0; j < styleDeclaration.getLength(); j++) 
                    {
                        String property = styleDeclaration.item(j);
                        ps.println("property: " + property);
                        ps.println("value: " + styleDeclaration.getPropertyCSSValue(property).getCssText());
                        ps.println("priority: " + styleDeclaration.getPropertyPriority(property));   
                    }
                }
            }

            if (out != null) out.close();
            if (stream != null) stream.close();
            rtn = true;
        }
        catch (IOException ioe)
        {
            System.err.println ("IO Error: " + ioe);
        }
        catch (Exception e)
        {
            System.err.println ("Error: " + e);
        }
        finally
        {
            if (ps != null) ps.close(); 
        }

        return rtn;

    }
}</code>

Testing the CSS Parser

To test the parser, place a CSS file named "design.css" in your source directory and run the main method of CSSParserTest. The output will be logged to "log.txt" and include details about the CSS rules and styles.

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