dom4j学习小结 (转)

dom4j学习总结 (转)

dom4j学习总结 ??

（一）移除节点及属性 ??

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??/**?*//**移除节点和属性的操作 ?

??*?@throws?DocumentException ?

*/??

?public?void?RemoveOperator()?throws?DocumentException...{ ??

?//待生成xml的字符串 ??

????????String?str="<root><book?type='science'><Name>Java</Name><price>100</price></book>"??????????????+"<book?type='society'><Name>Society?security</Name><price>130</price></book>"??????????????+"<author><name>chb</name><sex>boy</sex></author></root>"; ??????????//生成一个Document ??????????Document?document?=?DocumentHelper.parseText(str); ?????????? ??????????Element?root=document.getRootElement(); ??????????//删除类型为society的book节点 ??????????Element?book_society=(Element)document.selectSingleNode("//book[@type='society']"); ??????????root.remove(book_society); ??????????System.out.println("1。正确的删除了类型为society的book节点"); ??????????System.out.println(document.asXML()); ?????????? ??????????//删除sex节点 ??????????Element?sex=(Element)root.selectSingleNode("//sex"); ?????????? ??????????//从root节点删除 ??????????root.remove(sex); ??????????System.out.println("2。这样是不能删除sex节点的"); ??????????System.out.println(document.asXML()); ?????????? ??????????//从author节点删除 ??????????root.element("author").remove(sex); ??????????System.out.println("3。这样就可以正确删除sex节点"); ??????????System.out.println(document.asXML()); ?????????? ??????????//删除属性 ??????????Attribute?type=root.element("book").attribute("type"); ??????????root.element("book").remove(type); ??????????System.out.println("4。正确删除book节点的type属性"); ??????????System.out.println(document.asXML()); ??????} ??输出结果为： ????1。正确的删除了类型为society的book节点 ??<?xml?version="1.0"?encoding="UTF-8"?> ??<root><book?type="science"><Name>Java</Name><price>100</price></book><author><name>chb</name><sex>boy</sex></author></root> ??2。这样是不能删除sex节点的 ??<?xml?version="1.0"?encoding="UTF-8"?> ??<root><book?type="science"><Name>Java</Name><price>100</price></book><author><name>chb</name><sex>boy</sex></author></root> ??3。这样就可以正确删除sex节点 ??<?xml?version="1.0"?encoding="UTF-8"?> ??<root><book?type="science"><Name>Java</Name><price>100</price></book><author><name>chb</name></author></root> ??4。正确删除book节点的type属性 ??<?xml?version="1.0"?encoding="UTF-8"?> ??<root><book><Name>Java</Name><price>100</price></book><author><name>chb</name></author></root> ??????分析： ????第二个输出结果不能删除sex节点，我们需要看dom4j的API ????remove ??public?boolean?remove(Element?element)Removes?the?given?Element?if?the?node?is?an?immediate?child?of?this?branch.?If?the?given?node?is?not?an?immediate?child?of?this?branch?then?the?Node.detach()method?should?be?used?instead.? ??? ????Parameters:? ??element?-?is?the?element?to?be?removed? ??Returns:? ??true?if?the?element?was?removed ??从中我们可以看出，remove只能用在它自己的直接孩子节点上，不能用在孙子节点上，因为sex节点不是root节点的直接孩子节点，所以不能删除；而sex节点却是author节点的直接孩子节点，所以第三个输出可以删除。 ????（二）将两个Document合并为一个Document ????先看一个错误的情况 ????（1）使用add()方法添加 ????public?void?CombineDocument()?throws?DocumentException...{ ??????????//待生成两个Document的字符串 ??????????String?str_book="<root><book?type='science'><Name>Java</Name><price>100</price></book>"??????????????+"<book?type='society'><Name>Society?security</Name><price>130</price></book>"??????????????+"</root>"; ??????????String?str_author="<root><author><name>chb</name><sex>boy</sex></author></root>"; ?????????? ??????????//生成两个Document ??????????Document?doc_book=DocumentHelper.parseText(str_book); ??????????Document?doc_author=DocumentHelper.parseText(str_author); ?????????? ??????????//取出doc_author的author节点，添加到doc_book的根结点 ??????????Element?author=(Element)doc_author.selectSingleNode("//author"); ??????????doc_book.getRootElement().add(author); ??????????System.out.println(doc_book.asXML()); ??????} ??调用CombineDocument函数，会出现以下错误： ????org.dom4j.IllegalAddException:?The?node?"org.dom4j.tree.DefaultElement@17bd6a1?[Element:?<author?attributes:?[]/>]"?could?not?be?added?to?the?element?"root"?because:?The?Node?already?has?an?existing?parent?of?"root"???at?org.dom4j.tree.AbstractElement.addNode(AbstractElement.java:1521) ???at?org.dom4j.tree.AbstractElement.add(AbstractElement.java:1002) ???at?xml_chb.dom4j_chb.CombineDocument(dom4j_chb.java:189) ???at?xml_chb.dom4j_chb.main(dom4j_chb.java:199) ??Exception?in?thread?"main"? ????即提示author节点已经有一个root节点了，不能再添加到另一个节点上去。 ????（2）使用appendContent()方法 ????即将doc_book.getRootElement().add(author); ????改为：doc_book.getRootElement().appendContent(author); ????输出结果为： ????<?xml?version="1.0"?encoding="UTF-8"?> ??<root> ??<book?type="science"><Name>Java</Name><price>100</price></book> ??<book?type="society"><Name>Society?security</Name><price>130</price></book> ??<name>chb</name><sex>boy</sex> ??</root> ????可以看出，缺少了author节点，只是把author节点的子节点添加上去了，但是由此可见，appendContent方法是有希望的。 ????我们看一下dom4j的API: ????appendContent ??public?void?appendContent(Branch?branch)Appends?the?content?of?the?given?branch?to?this?branch?instance.?This?method?behaves?like?the?Collection.addAll(java.util.Collection)?method.? ??? ????Parameters:? ??branch?-?is?the?branch?whose?content?will?be?added?to?me. ????-------------------------------------------- ????（3）使用正确的appendContent方法 ????将：Element?author=(Element)doc_author.selectSingleNode("//author"); ????doc_book.getRootElement().appendContent(author); ????改为：doc_book.getRootElement().appendContent(doc_author.getRootElement()); ????输出： ????<?xml?version="1.0"?encoding="UTF-8"?> ??<root> ??<book?type="science"><Name>Java</Name><price>100</price></book> ??<book?type="society"><Name>Society?security</Name><price>130</price></book> ??<author><name>chb</name><sex>boy</sex></author> ??</root> ????是正确结果 ????（4）另一种可行的方法 ????public?void?CombineDocument()?throws?DocumentException...{ ??????????//待生成两个Document的字符串 ??????????String?str_book="<root><book?type='science'><Name>Java</Name><price>100</price></book>"??????????????+"<book?type='society'><Name>Society?security</Name><price>130</price></book>"??????????????+"</root>"; ??????????String?str_author="<root><author><name>chb</name><sex>boy</sex></author></root>"; ?????????? ??????????//生成两个Document ??????????Document?doc_book=DocumentHelper.parseText(str_book); ??????????Document?doc_author=DocumentHelper.parseText(str_author); ?????????? ??????????//新生成一个Document ??????????Element?author=DocumentHelper.createElement("author"); ??????????author.appendContent((Element)doc_author.selectSingleNode("//author")); ??????????//当前author尚无父节点，所以可以使用add方法添加 ??????????doc_book.getRootElement().add(author); ????????????System.out.println(doc_book.asXML()); ??????}??

http://kuangbaoxu.iteye.com/blog/196151（转）