首先，当然是需要你先对struts有一定的了解：）

1. 定义相应页面(client.jsp)的form bean，这里假设为ClientForm；注意在struts_config.xml中定义映射关系；client.jsp中包含了你需要的html form内容，比如一个select下拉框；

这里是form bean的代码（其实就是一个java bean，继承了ActionForm，然后需要重载reset和validate方法）：
-----------------------------------------------
package com.egi.core.ioblock.form;

import javax.servlet.http.HttpServletRequest;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionMapping;
import org.apache.struts.action.ActionError;
import org.apache.struts.action.ActionErrors;

/**
* Copyright: Copyright (c) 2002</p> <p>
*@author sjoy
*@created 2003年6月4日
*@version 1.0
*/

public class LoginForm extends ActionForm {

//-----------------------------Instance Variable
private String appName = null;
private String type = null;

public String getAppName() {
return appName;
}

public void setAppName(String appName) {
this.appName = appName;
}

public String getType() {
return type;
}

public void setType(String type) {
this.type = type;
}

public void reset(ActionMapping mapping, HttpServletRequest request) {
appName = null;
type = null;
}

public ActionErrors validate(ActionMapping mapping, HttpServletRequest request) {

ActionErrors errors = new ActionErrors();
if (appName == null || appName.length() < 1) {
errors.add("application name", new ActionError("error.appname.required"));
}
return errors;
}
}
-----------------------------------------------


这里是ActionServlet代码，继承Action：
-----------------------------------------------
package com.egi.core.ioblock.action;

import java.io.IOException;
import java.sql.SQLException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.struts.action.Action;
import org.apache.struts.action.ActionError;
import org.apache.struts.action.ActionErrors;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionMapping;
import org.apache.struts.action.ActionForward;
import com.egi.core.ioblock.form.LoginForm;
import com.mainet.core.spreadsheet.db.MenusTreeTable;
import com.mainet.core.spreadsheet.ProjectFactory;

/**
* Copyright: Copyright (c) 2002</p> <p>
*@author sjoy
*@created 2003年6月4日
*@version 1.0
*/

public class LoginAction extends Action {

public ActionForward perform(ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response)
throws IOException, ServletException {

ActionErrors errors = new ActionErrors();
String appName = ((LoginForm) form).getAppName();

//下面是你所需要的一些逻辑
...
HttpSession session = request.getSession();
...

return mapping.findForward("success");
}
}

-----------------------------------------------


2. 写一个bean，专门用来保存select的option集合。代码如下：
-----------------------------------------------
package com.egi.core.ioblock.util;

import java.io.Serializable;

/**
* Description: This class is a bean, used to represent one option in an HTML
* drop-down \'select\' list. It contains two properties - see {@link
* getDisplayName()} and {@link getInternalId()} for a description. Useful in a
* struts Form class for constructing a select list to pass to the jsp with the
* <tt><html:select></tt> and <tt><html:option></tt> tags.</p> <p>
*@author sjoy
*@created 2003年6月4日
*@version 1.0
*/

public class HtmlSelectOption implements Serializable {
private String id;
private String displayName;

/**
* Constructor for the HtmlSelectOption object
*/
public HtmlSelectOption() { }

/**
* Constructor for the HtmlSelectOption object
*
*@param id Description of the Parameter
*@param displayName Description of the Parameter
*/
public HtmlSelectOption(String id, String displayName) {
this.id = id;
this.displayName = displayName;
}

public String getDisplayName() {
return displayName;
}

public void setDisplayName(String displayName) {
this.displayName = displayName;
}

public String getId() {
return id;
}

public void setId(String id) {
this.id = id;
}
}
-----------------------------------------------

3. ok，接下来从db或者其它地方去取下拉列表中的具体内容；
java.util.Iterator iter = ....;//这里假设从数据库中取得数据
java.util.ArrayList list = new java.util.ArrayList();
String obj;
while(iter.hasNext()){
obj = (String)iter.next();
list.add(new com.egi.core.ioblock.util.HtmlSelectOption(obj,obj));
}
pageContext.setAttribute("appNames", list);

注意：这段逻辑也可以写在ClienetForm中通过javabean的方式在页面上获得这个集合。

4. 然后就是页面上使用啦:)
<html:select property="type">
<html:options collection="appNames" property="id"
labelProperty="displayName"/>
</html:select>