如何提取meta name = generator标签的content属性? [英] How to extract the content attribute of the meta name=generator tag?

问题描述

我正在使用以下代码使用Jsoup从网页中提取元生成器"标签内容:

I am using the below code to extract meta 'generator' tag content from a web page using Jsoup:

Elements metalinks = doc.select("meta[name=generator]");
boolean metafound=false;

if(metalinks.isEmpty()==false)
{ 
    metatagcontent = metalinks.first().select("content").toString();
    metarequired=metatagcontent;
    metafound=true;
}
else 
{
    metarequired="NOT_FOUND";
    metafound=false;
}

问题在于，对于包含meta生成器标签的页面，没有显示任何值(当我输出变量'metarequired'的值时.对于没有meta生成器标签的页面，则值为'NOT_FOUND'正确显示了.我在这里做什么错了?

The problem is that for a page that does contain the meta generator tag, no value is shown (when I output the value of variable 'metarequired'. For a page that does not have meta generator tag, the value 'NOT_FOUND' is shown correctly. What am I doing wrong here?

推荐答案

从您的代码中

metalinks.first().select("content").toString();

这是不正确的.这只是选择

This is not correct. This is merely selecting

<meta ...>
    <content ... /> <!-- This one, which of course doesn't exist. -->
</meta>

实际上 要获取属性

<meta ... content="..." />

您需要使用 attr("content") 代替 select("content") .

You need to use attr("content") instead of select("content").

metatagcontent = metalinks.first().attr("content");

另请参见:

• Jsoup食谱-选择器语法
• Jsoup Selector API文档
• W3 CSS3选择器规范

See also:

• Jsoup cookbook - Selector syntax
• Jsoup Selector API documentation
• W3 CSS3 selector specification

无关与具体问题无关，您无需针对if块内的boolean进行测试. isEmpty() 已经已返回boolean:

Unrelated to the concrete problem, you don't need to test against a boolean inside an if block. The isEmpty() already returns a boolean:

if (!metalinks.isEmpty())

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