Struts自定义标签的过程

近日体验了一下Eclipse

打开某个jsp页面页面上的select下拉列表框用Struts自定义标签来完成

新建页面Testjsp

在Web应用的WEBINF目录下自定义标签TLD文件TestTagtld

<?xml version= encoding=UTF?>

<!DOCTYPE taglib PUBLIC //Sun Microsystems Inc//DTD JSP Tag Library //EN jsptaglibrary__dtd>

<taglib>

<tlibversion></tlibversion>

<jspversion></jspversion>

<shortname>dtree</shortname>

<uri>bean</uri>

<tag>

<name>selectResnodes</name>

<tagclass>myWebtaglibSelectTag</tagclass>

<bodycontent>empty</bodycontent>

<attribute>

<name>id</name>

<required>true</required>

<rtexprvalue>false</rtexprvalue>

</attribute>

<attribute>

<name>nodeslist</name>

<required>true</required>

<rtexprvalue>false</rtexprvalue>

</attribute>

<attribute>

<name>scope</name>

<required>false</required>

<rtexprvalue>false</rtexprvalue>

</attribute>

</tag>

</taglib>

在myWebAction包下定义AbstractResActionjava文件和TestActionjava文件（利用了java的反射机制）

AbstractResActionjava文件

package myWebAction;

import javalangreflectMethod;

import javaxservlethttpHttpServletRequest;

import javaxservlethttpHttpServletResponse;

import orgapachestrutsactionAction;

import orgapachestrutsactionActionForm;

import orgapachestrutsactionActionForward;

import orgapachestrutsactionActionMapping;

public abstract class AbstractResAction extends Action {

public final ActionForward execute(ActionMapping actionMapping

ActionForm actionForm HttpServletRequest httpServletRequest

HttpServletResponse httpServletResponse) {

String cmd = (actionType); // 获取参数其实为函数名

Systemoutprintln(actionType = + cmd);

if (cmd == null || cmdequals())

return actionMappingfindForward(default);

try {

Method method = thisgetClass()

getMethod(

cmdnew Class[] { ActionMappingclass

ActionFormclass HttpServletRequestclass

HttpServletResponseclass });

// 利用反射机制调用method方法而这个method方法是由页面指定的actionType定义的

return (ActionForward) methodinvoke(this new Object[] {

actionMapping actionForm httpServletRequest

httpServletResponse });

} catch (Exception e) {

eprintStackTrace();

return actionMappingfindForward(default);

}

}

}

TestActionjava文件

package myWebAction;

import javautilArrayList;

import javaxservlethttpHttpServletRequest;

import javaxservlethttpHttpServletResponse;

import orgapachestrutsactionActionForm;

import orgapachestrutsactionActionForward;

import orgapachestrutsactionActionMapping;

import comasiainfoainxadvancedresboResnodesBO;

public class QueryNodesAction extends AbstractResAction {

public ActionForward showNodesList(ActionMapping mapping ActionForm form

HttpServletRequest request HttpServletResponse response) {

ResnodesBO bo = new ResnodesBO();

ArrayList alNodes = boselectData(); //我的应用中定义了BO和DAO类来封装对数据库的读写此处为从数据库中取出的数据结果集

requestsetAttribute(resnodesListalNodes); //页面中的用到该自定义标签时要用到resnodesList这个属性

return mappingfindForward(showResnode);

}

}

在myWebtaglib包下定义SelectTagjava文件

package myWebtaglib;

import javaioIOException;

import javautilArrayList;

import javaxservletjspJspException;

import javaxservletjspJspWriter;

import javaxservletjsptagextTagSupport;

import orgapachestrutsutilRequestUtils;

import myWebvoResnodesVO;

public class SelectTag extends TagSupport {

//这里的三个属性对应TestTagtld文件中对selectResnodes定义的三个属性

private String id;

private String scope;

private String nodeslist;

/**

* @throws IOException

*/

public int doStartTag() {

ArrayList list = null;

try {

list = (ArrayList) RequestUtilslookup(pageContext nodeslist

scope);

} catch (JspException e) {

eprintStackTrace();

}

if (list == null || listsize() == )

return SKIP_BODY;

JspWriter out = pageContextgetOut();

try {

if (list != null) {

outprintln(<select name=\Sel_Nodes\ style=\width:%\>);

for (int i = ; i < listsize(); i++) {

ResnodesVO nodevo = (ResnodesVO) listget(i);

outprintln(<option value=\ + nodevogetId() + \>

+ nodevogetSName() + </option>);

//Systemoutprintln(nodevogetSName());

}

outprintln(</select>);

outflush();

}

} catch (IOException e) {

eprintStackTrace();

}

return EVAL_BODY_INCLUDE;

}

public String getId() {

return id;

}

public void setId(String id) {

thisid = id;

}

public String getNodeslist() {

return nodeslist;

}

public void setNodeslist(String nodeslist) {

thisnodeslist = nodeslist;

}

public String getScope() {

return scope;

}

public void setScope(String scope) {

thisscope = scope;

}

}

修改strutsconfigxml文件

……

<actionmappings>

……

<action type=myWebActionTestAction scope=request path=/queryResnodes> <! 在地址栏或链接中请求时用该路径queryResnodes>

<forward name=showResnode path=/Testjsp /> <! 在TestActionjava中执行查询数据的函数后跳转至该showResnode定义的页面即Testjsp>

</action>

……

</actionmappings>

……

保证Testjsp中包含如下的代码

<%@ taglib uri=/WEBINF/TestTagtld prefix=slotnode%>

<body>

……

<slotnode:selectResnodes id=nodelist nodeslist=resnodesList scope=request />

……

</body>

其中prefix的名字是随便起的只要有意义就可以

但是在后面用的时候就要用这个名字本例中是slotnode

<slotnode:selectResnodes …… 中的selectResnodes和TestTagtld中定义的<tag><name>selectResnodes</name>……必须是相同的的

另外nodeslist=resnodesList中resnodesList即TestActionjava中定义的

requestsetAttribute(resnodesListalNodes); 中写入的属性resnodesList两个名字必须是相同的

比如我的Web应用发布的名字为LearnTag发布在本地的Tomcat中默认端口则在地址栏输入？actionType=showNodesList

OK出来结果了吧

整理的有点乱再总结一下

从页面发起do请求请求转至action在action文件中执行数据库查询取得需要的数据

将查询得到的数据列表用setAttribute加入request

自定义标签中取request中的加入的数据列表

由自定义标签中的标签java文件完成将数据打印出来的功能（用JspWriter类）

在页面显示出来查看jsp文件的源代码可以看到自定义的标签和数据都转换为html的代码了