HtmlParser用法
htmlparser中有两种访问节点的方式
1、filter。通过filter，能够过滤出我们关心的节点。从而对节点进行进一步的访问。
2、vistor。vistor和filter不同。vistor是遍历内容树的每一个节点，对于符合条件的节点做相应的处理。
先看一下下面的html代码：
<ul class="ztree" id="treeDemo">
<li treenode="" hidefocus="true" tabindex="0" class="level0" id="treeDemo_1">
<span treenode_switch="" class="button level0 switch root_open" title=""
id="treeDemo_1_switch">
</span>
<a title="父节点 1" style="" target="_blank" onclick="editShow(this)" treenode_a=""
class="level0" id="treeDemo_1_a" showlistplaytimes="1">
<span style="" class="button ico_open" treenode_ico="" title="" id="treeDemo_1_ico">
</span>
<span id="treeDemo_1_span">
父节点 1
</span>
</a>
<ul style="" class="level0 " id="treeDemo_1_ul">
<li treenode="" hidefocus="true" tabindex="0" class="level1" id="treeDemo_2">
<span treenode_switch="" class="button level1 switch center_docu" title=""
id="treeDemo_2_switch" disabled="disabled">
</span>
<a title="新节点1" style="" target="_blank" onclick="" treenode_a="" class="level1"
id="treeDemo_2_a" showname="a" showtimeinterval="3" showplaytimes="2" showurl="asdf">
<span class="button ico_docu" treenode_ico="" title="" id="treeDemo_2_ico"
style="">
</span>
<span id="treeDemo_2_span">
新节点1
</span>
</a>
</li>
<li treenode="" hidefocus="true" tabindex="0" class="level1" id="treeDemo_3">
<span treenode_switch="" class="button level1 switch center_open" title=""
id="treeDemo_3_switch">
</span>
<a title="新节点2" style="" target="_blank" onclick="" treenode_a="" class="level1"
id="treeDemo_3_a" showlistplaytimes="2">
<span class="button ico_open" treenode_ico="" title="" id="treeDemo_3_ico"
style="">
</span>
<span id="treeDemo_3_span">
新节点2
</span>
</a>
<ul style="" class="level1 line" id="treeDemo_3_ul">
<li treenode="" hidefocus="true" tabindex="0" class="level2" id="treeDemo_7">
<span treenode_switch="" class="button level2 switch center_docu" title=""
id="treeDemo_7_switch" disabled="disabled">
</span>
<a title="新节点6" style="" target="_blank" onclick="" treenode_a="" class="level2"
id="treeDemo_7_a" showname="b" showtimeinterval="3" showplaytimes="3" showurl="adsf">
<span class="button ico_docu" treenode_ico="" title="" id="treeDemo_7_ico"
style="">
</span>
<span id="treeDemo_7_span">
新节点6
</span>
</a>
</li>
<li treenode="" hidefocus="true" tabindex="0" class="level2" id="treeDemo_8">
<span treenode_switch="" class="button level2 switch bottom_docu" title=""
id="treeDemo_8_switch">
</span>
<a title="新节点7" style="" target="_blank" onclick="" treenode_a="" class="level2"
id="treeDemo_8_a" showname="c" showtimeinterval="5" showplaytimes="5" showurl="rsdaf">
<span style="" class="button ico_docu" treenode_ico="" title="" id="treeDemo_8_ico">
</span>
<span id="treeDemo_8_span">
新节点7
</span>
</a>
</li>
</ul>
</li>
<li treenode="" hidefocus="true" tabindex="0" class="level1" id="treeDemo_4">
<span treenode_switch="" class="button level1 switch center_docu" title=""
id="treeDemo_4_switch" disabled="disabled">
</span>
<a title="新节点3" style="" target="_blank" onclick="" treenode_a="" class="level1"
id="treeDemo_4_a" showname="d" showtimeinterval="2" showplaytimes="5" showurl="wrgwrg">
<span class="button ico_docu" treenode_ico="" title="" id="treeDemo_4_ico"
style="">
</span>
<span id="treeDemo_4_span">
新节点3
</span>
</a>
</li>
<li treenode="" hidefocus="true" tabindex="0" class="level1" id="treeDemo_5">
<span treenode_switch="" class="button level1 switch bottom_docu" title=""
id="treeDemo_5_switch">
</span>
<a title="新节点4" style="" target="_blank" onclick="" treenode_a="" class="level1 curSelectedNode"
id="treeDemo_5_a" showname="e" showtimeinterval="7" showplaytimes="4" showurl="asdf">
<span style="" class="button ico_docu" treenode_ico="" title="" id="treeDemo_5_ico">
</span>
<span id="treeDemo_5_span">
新节点4
</span>
<span onfocus="this.blur();" title="add node" id="addBtn_105" class="button add">
</span>
<span style="" treenode_remove="" title="remove" id="treeDemo_5_remove"
class="button remove">
</span>
</a>
</li>
</ul>
</li>
</ul>
这段代码描述了一些ul和li。
Visitor的访问顺序如下：
class org.htmlparser.tags.Bullet
class org.htmlparser.tags.Span
class org.htmlparser.tags.LinkTag
class org.htmlparser.tags.BulletList
class org.htmlparser.tags.Span
class org.htmlparser.tags.Span
class org.htmlparser.tags.Bullet
class org.htmlparser.tags.Bullet
class org.htmlparser.tags.Bullet
class org.htmlparser.tags.Bullet
class org.htmlparser.tags.Span
class org.htmlparser.tags.LinkTag
class org.htmlparser.tags.Span
class org.htmlparser.tags.Span
class org.htmlparser.tags.Span
class org.htmlparser.tags.LinkTag
class org.htmlparser.tags.BulletList
class org.htmlparser.tags.Span
class org.htmlparser.tags.Span
class org.htmlparser.tags.Bullet
class org.htmlparser.tags.Bullet
class org.htmlparser.tags.Span
class org.htmlparser.tags.LinkTag
class org.htmlparser.tags.Span
class org.htmlparser.tags.Span
class org.htmlparser.tags.Span
class org.htmlparser.tags.LinkTag
class org.htmlparser.tags.Span
class org.htmlparser.tags.Span
class org.htmlparser.tags.Span
class org.htmlparser.tags.LinkTag
class org.htmlparser.tags.Span
class org.htmlparser.tags.Span
class org.htmlparser.tags.Span
class org.htmlparser.tags.LinkTag
class org.htmlparser.tags.Span
class org.htmlparser.tags.Span
class org.htmlparser.tags.Span
class org.htmlparser.tags.Span
从上可以看出，visitor的访问是层次遍历的。
在访问完毕一层之后，才顺序访问上一层中的每个节点的下一层节点。
从上面可以看出，Bullet节点是li节点。BulletList节点是ul节点。
html也可以看做是树形来组织的。visitor的访问方式是后根遍历的方式。