Jsoup

简介

　　jsoup 是一款Java 的HTML解析器，可直接解析某个URL地址、HTML文本内容。

添加依赖

<dependency>
    <groupId>org.jsoup</groupId>
    <artifactId>jsoup</artifactId>
    <version>1.10.2</version>
</dependency>

查找DOM元素

　　使用Jsoup提供的API，可以通过标签名，Id，Class样式等来搜索DOM

　　常用API

getElementById(String id)  // 根据id来查询DOM

getElementsByTag(String tagName)  // 根据tag名称来查询DOM

getElementsByClass(String className)  // 根据样式名称来查询DOM

getElementsByAttribute(String key)  // 根据属性名来查询DOM

getElementsByAttributeValue(String key,String value)  // 根据属性名和属性值来查询DOM

　　实例代码

package cn.cslg.Jsoup;

import org.apache.http.HttpEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;
import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;
import org.jsoup.select.Elements;

public class JsoupDemo {

    public static void main(String[] args)throws Exception {
        CloseableHttpClient httpclient = HttpClients.createDefault(); // 创建httpclient实例
        HttpGet httpget = new HttpGet("http://www.cnblogs.com/"); // 创建httpget实例

        CloseableHttpResponse response = httpclient.execute(httpget); // 执行get请求
        HttpEntity entity=response.getEntity(); // 获取返回实体
        String content=EntityUtils.toString(entity, "utf-8");
        response.close(); // 关闭流和释放系统资源

        Document doc=Jsoup.parse(content);// 解析网页 得到文档对象

        Element navTopElement=doc.getElementById("site_nav_top"); // 根据id来查询DOM
        String navTop=navTopElement.text(); // 返回元素的文本
        System.out.println("口号："+navTop);

        Elements titleElements=doc.getElementsByTag("title"); // 根据tag名称来查询DOM
        Element titleElement=titleElements.get(0); // 获取第1个元素
        String title=titleElement.text(); // 返回元素的文本
        System.out.println("网页标题是："+title);

        Elements postItemElements=doc.getElementsByClass("post_item "); // 根据样式名称来查询DOM
        for(Element e:postItemElements){
            System.out.println(e.html());
            System.out.println("================");
        }

        Elements widthElements=doc.getElementsByAttribute("width"); // 根据属性名来查询DOM
        for(Element e:widthElements){
            System.out.println(e.toString());
            System.out.println("================");
        }

        System.out.println("target-_blank");
        Elements targetElements=doc.getElementsByAttributeValue("target", "_blank");  // 根据属性名和属性值来查询DOM
        for(Element e:targetElements){
            System.out.println(e.toString());
            System.out.println("================");
        }

    }

}

使用选择器查找DOM元素

　　对于很多个有规律的标签层次，可以使用Jsoup使用选择器语法查找DOM元素

　　在选择器语法中一般为 "#id名 .class名 .class名 标签 标签"

　　实例代码

package cn.cslg.Jsoup;

import org.apache.http.HttpEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;
import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;
import org.jsoup.select.Elements;

public class JsoupDemo {

    public static void main(String[] args)throws Exception {
        CloseableHttpClient httpclient = HttpClients.createDefault(); // 创建httpclient实例
        HttpGet httpget = new HttpGet("http://www.cnblogs.com/"); // 创建httpget实例

        CloseableHttpResponse response = httpclient.execute(httpget); // 执行get请求
        HttpEntity entity=response.getEntity(); // 获取返回实体
        String content=EntityUtils.toString(entity, "utf-8");
        response.close(); // 关闭流和释放系统资源

        Document doc=Jsoup.parse(content); // 解析网页 得到文档对象

        Elements linkElements=doc.select("#post_list .post_item .post_item_body h3 a"); //通过选择器查找所有博客链接DOM
        for(Element e:linkElements){
            System.out.println("博客标题："+e.text());
        }

        System.out.println("===============");
        Elements hrefElements=doc.select("a[href]"); // 带有href属性的a元素
        for(Element e:hrefElements){
            System.out.println(e.toString());
        }

        System.out.println("===============");
        Elements imgElements=doc.select("img[src$=.png]"); // 查找扩展名为.png的图片DOM节点
        for(Element e:imgElements){
            System.out.println(e.toString());
        }

        Element element=doc.getElementsByTag("title").first(); // 获取tag是title的第一个DOM元素
        String title=element.text(); // 返回元素的文本
        System.out.println("网页标题是："+title);

    }
}

获取DOM属性值

　　例如获取href的属性值

package cn.cslg.Jsoup;

import org.apache.http.HttpEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;
import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;
import org.jsoup.select.Elements;

public class JsoupDemo {

    public static void main(String[] args)throws Exception {
        CloseableHttpClient httpclient = HttpClients.createDefault(); // 创建httpclient实例
        HttpGet httpget = new HttpGet("http://www.cnblogs.com/"); // 创建httpget实例

        CloseableHttpResponse response = httpclient.execute(httpget); // 执行get请求
        HttpEntity entity=response.getEntity(); // 获取返回实体
        String content=EntityUtils.toString(entity, "utf-8");
        response.close(); // 关闭流和释放系统资源

        Document doc=Jsoup.parse(content); // 解析网页 得到文档对象

        Elements linkElements=doc.select("#post_list .post_item .post_item_body h3 a"); //通过选择器查找所有博客链接DOM
        for(Element e:linkElements){
            System.out.println("博客标题："+e.text());
            System.out.println("博客地址："+e.attr("href"));
            System.out.println("target:"+e.attr("target"));
        }

        Element linkElement=doc.select("#friend_link").first();
        System.out.println("纯文本："+linkElement.text()); // 获取纯文本
        System.out.println("html："+linkElement.html()); // 获取整个html

    }
}