Java碎碎事

转义URL中字符

• URLEncoder

  import org.junit.jupiter.api.Test;
  import org.springframework.boot.test.context.SpringBootTest;
  import java.io.UnsupportedEncodingException;
  import java.net.URLEncoder;
  
  @SpringBootTest
  class DemoApplicationTests {
  	@Test
  	void contextLoads() throws UnsupportedEncodingException {
  	    System.out.println("*****************Start...");
          String url = "http://localhost:8080/v1/leaders?name=";
          String queryString = "?name=" + URLEncoder.encode("App & Prouducts", "UTF-8").replaceAll("\\+", "%20");
          url += queryString
  	    System.out.println("*****************newStr: " + url);
          System.out.println("*****************End");
  	}
  }

Google Cahce

import java.util.concurrent.TimeUnit;
import com.google.common.cache.Cache;
import com.google.common.cache.CacheBuilder;

private static Cache<Integer, String> feedItemsCache = CacheBuilder.newBuilder().concurrencyLevel(1)
            .maximumSize(10).expireAfterWrite(6, TimeUnit.HOURS).build();

public String getUserNameById(int id) {
    String userName = feedItemsCache.getIfPresent(id);
    if(userName != null) {
        return userName;
    } else {
        return ....; //userName from db
    }
}

public static void flushAllCaches() {
    feedsCache.invalidateAll();
}

正则表达

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public static void main(String[] args) throws Exception {
    String blogs = "<img src=\"https://baidu.com/code/files/2020/05/face.jpg\" class=\"attachment-large size-large wp-post-image\" alt=\"\" /><p>Tutorials Point originated from the idea that there exists a class of readers who respond better to online content and prefer to learn new skills at their own pace from the comforts of their drawing rooms. </p><p>The journey commenced with <a rel=\"nofollow\" href=\"https://baidu.com/code/2020/05/28/people/\">topics ranging from {programming} languages</a> to web designing to academics <a rel=\"nofollow\" href=\"https://blogs.baidu.com/code\">and much more.</a>.</p>";
	Pattern p =Pattern.compile("<p>(?<description>.+?)</p>");
    Matcher matcher = p.matcher(blogs);
    if(matcher.find()) {
        System.out.println("********************description: " + matcher.group("description"));
    }

    Pattern p2 =Pattern.compile("<img\\s+src=\"(?<imgsrc>.+\\.\\w+)\"\\s+");
    Matcher matcher2 = p2.matcher(blogs);
    if(matcher2.find()) {
        System.out.println(matcher2.group("imgsrc"));
    }
}

XPath解析RSS

public class RssItem {
    String title;
    String link;
    Date publishDate;
    String author;
    String description;
    String blogImage;
    //....get/set
｝

public static List<RssItem> getRssItem(String url, int maxLimit){
    List<RssItem> rssItems = new ArrayList<RssItem>();
    try {
        long startTime = System.currentTimeMillis();
        //<?xml version="1.0" encoding="UTF-8"?><rss version="2.0">
        //<root>
        //    <blog>
        //          <title>xxxxxxxx</title>
        //          <link>xxxxxxxx</link>
        //          <pubDate>xxxxxxxx</pubDate>
        //          <description><![CDATA[<img src="xxxxxxxx" class="dddd" /><p>sdf eere. dfdeer, 8989.</p>
        //                       <p>Our content and resources are freely<a rel=\"nofollow\" href=\"https://blogs.baidu.com/code\">and             //                         much more.</a>.</p>
        //           </description>
        //    </blog>
        //    ....
        //    <blog>...</blog>
        //<root>
        //</rss>
        com.liferay.portal.kernel.xml.Document doc = SAXReaderUtil.readURL(url);
        String xpath = "//root/blog";
        // 如果maxLimit大于0，则获取前maxLimit个blog对象
        if(maxLimit > 0) xpath += "[position()<=" + maxLimit + "]";
        List<com.liferay.portal.kernel.xml.Node> items = doc.selectNodes(xpath);
        for(com.liferay.portal.kernel.xml.Node item : items) {
            RssItem rssItem = new RssItem();
            rssItem.setTitle(item.selectSingleNode("title").getText());
            rssItem.setLink(item.selectSingleNode("link").getText());
            rssItem.setPublishDate(dateFormat.parse(item.selectSingleNode("pubDate").getText()));
            String description = item.selectSingleNode("description").getText();
            Pattern p =Pattern.compile("<p>(?<description>.+?)</p>");
            Matcher matcher = p.matcher(description);
            if(matcher.find()) {
                rssItem.setDescription(matcher.group("description"));
            } else {
                rssItem.setDescription(description);
            }
            _log.info("******************description: " + rssItem.getDescription());
            Pattern p2 =Pattern.compile("<img\\s+src=\"(?<blogImage>.+\\.\\w+)\"\\s+");
            Matcher matcher2 = p2.matcher(description);
            if (matcher2.find()) {
                rssItem.setBlogImage(matcher2.group("blogImage"));
            }
            _log.info("******************thumbnailImage: " + rssItem.getBlogImage());
            rssItems.add(rssItem);
        }
        long elapsedTime = System.currentTimeMillis() - startTime;
        _log.info(String.format("Loaded RSS feeds %s, elapsed time: %s ms", url, elapsedTime));
    } catch (Exception e) {
        _log.error("Loaded RSS failed from " + url);
        e.printStackTrace();
    }
    return rssItems;
}

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