分2步。

1.从 HTML 中提取出纯文本（去掉标签）

import org.htmlparser.NodeFilter;
import org.htmlparser.Parser;
import org.htmlparser.beans.StringBean;
import org.htmlparser.filters.CssSelectorNodeFilter;
import org.htmlparser.util.NodeList;public class HtmlUtil {public static String getText(String html, String id) {try {Parser parser = new Parser(html);NodeFilter filter = new CssSelectorNodeFilter("#" + id);NodeList nList = parser.extractAllNodesThatMatch(filter);return nList == null || nList.size() == 0 ? null : nList.elementAt(0).toPlainTextString();} catch (Exception e) {e.printStackTrace();return null;}}public static String getTextByClass(String html, String css_class) {try {Parser parser = new Parser(html);NodeFilter filter = new CssSelectorNodeFilter("." + css_class);NodeList nList = parser.extractAllNodesThatMatch(filter);return nList == null || nList.size() == 0 ? null : nList.elementAt(0).toPlainTextString();} catch (Exception e) {e.printStackTrace();return null;}}/*** 获取网页中纯文本信息** @param html* @return* @throws Exception* @throws Exception*/public static String getText(String html) throws Exception {StringBean bean = new StringBean();bean.setLinks(false);bean.setReplaceNonBreakingSpaces(true);bean.setCollapse(true);// 返回解析后的网页纯文本信息Parser parser = Parser.createParser(html, "utf-8");parser.visitAllNodesWith(bean);parser.reset();String text = bean.getStrings();String reg = "[^\u4e00-\u9fa5]";text = text.replaceAll(reg, " ");return text;}
}

2.从纯文本中提取出中文关键字（TextRank关键词提取）

import com.hankcs.hanlp.HanLP;
import com.hankcs.hanlp.dictionary.stopword.CoreStopWordDictionary;
import com.hankcs.hanlp.seg.common.Term;import java.util.*;
import java.util.stream.Collectors;/*** TextRank关键词提取** @author hankcs*/
public class TextRankKeyword {public static final int MAX_KEY_WORDS = 7;/*** 阻尼系数（ＤａｍｐｉｎｇＦａｃｔｏｒ），一般取值为0.85*/static final float d = 0.618f;/*** 最大迭代次数*/static final int max_iter = 2000;static final float min_diff = 0.001f;public TextRankKeyword() {// jdk bug : Exception in thread "main" java.lang.IllegalArgumentException: Comparison method violates its general contract!System.setProperty("java.util.Arrays.useLegacyMergeSort", "true");}public String getKeyword(String title, String content) {List<Term> termList = HanLP.segment(title + content);List<String> wordList = new ArrayList<String>();for (Term t : termList) {if (shouldInclude(t)) {wordList.add(t.word);}}Map<String, Set<String>> words = new HashMap<String, Set<String>>();Queue<String> que = new LinkedList<String>();for (String w : wordList) {if (!words.containsKey(w)) {words.put(w, new HashSet<String>());}que.offer(w);if (que.size() > 5) {que.poll();}for (String w1 : que) {for (String w2 : que) {if (w1.equals(w2)) {continue;}words.get(w1).add(w2);words.get(w2).add(w1);}}}Map<String, Float> score = new HashMap<String, Float>();for (int i = 0; i < max_iter; ++i) {Map<String, Float> m = new HashMap<String, Float>();float max_diff = 0;for (Map.Entry<String, Set<String>> entry : words.entrySet()) {String key = entry.getKey();Set<String> value = entry.getValue();m.put(key, 1 - d);for (String other : value) {int size = words.get(other).size();if (key.equals(other) || size == 0) continue;m.put(key, m.get(key) + d / size * (score.get(other) == null ? 0 : score.get(other)));}max_diff = Math.max(max_diff, Math.abs(m.get(key) - (score.get(key) == null ? 0 : score.get(key))));}score = m;if (max_diff <= min_diff) break;}List<Map.Entry<String, Float>> entryList = new ArrayList<Map.Entry<String, Float>>(score.entrySet());Collections.sort(entryList, (o1, o2) -> (o1.getValue() - o2.getValue() > 0 ? -1 : 1));List<Map.Entry<String, Float>> list = entryList.stream().filter(w -> w.getKey().length() > 1).collect(Collectors.toList());String result = "";int nKeyword = MAX_KEY_WORDS > list.size() ? list.size() : MAX_KEY_WORDS;for (int i = 0; i < nKeyword; ++i) {result += list.get(i).getKey() + ';';}System.out.println(result);return result;}/*** 是否应当将这个term纳入计算，词性属于名词、动词、副词、形容词** @param term* @return 是否应当*/public boolean shouldInclude(Term term) {return CoreStopWordDictionary.shouldInclude(term);}
}

完整工程源代码：

https://github.com/KotlinSpringBoot/saber

附： 完整爬取各大著名技术站点的博客文章的源代码。