Ajax与Struts 联动的下拉框

最新推荐文章于 2017-02-22 13:12:24 发布

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#struts #ajax #xmlhttprequest #string #html #action

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本文介绍了一个使用Ajax与Struts实现联动下拉框的选择功能示例。当用户选择一个电视节目后，会通过Ajax请求从服务器获取与该节目相关的角色列表，并动态更新到另一个下拉框中。示例包括客户端脚本代码、HTML界面代码及服务器端Struts Action处理代码。

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Ajax与Struts 联动的下拉框
1，处理的脚本语言代码：
<script>

var req;
var which;

function processStateChange() {
    if (req.readyState == 4) { // Complete
      if (req.status == 200) { // OK response
        document.getElementById("characters").innerHTML = req.responseText;
      } else {
        alert("Problem: " + req.statusText);
      }
    }
}

</script>

2.客户端界面代码：
<form name="dynamicSelect">
TV Show: <select name="TVShowSelect" onChange="retrieveURL('example3GetCharacters.do?tvShow=' + this.value);">
    <option value=""></option>
    <option value="Babylon5">Babylon 5</option>
    <option value="StargateSG1">Stargate SG-1</option>
    <option value="StarTrekTNG">Star Trek: The Next Generation</option>
</select>
<br>
Characters: <span id="characters"></span>
</form>

3.服务器端相应处理的Action代码（use Struts）

import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Iterator;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import org.apache.struts.action.Action;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;

public class GetCharactersAction extends Action {

public ActionForward execute(ActionMapping mapping, ActionForm inForm, HttpServletRequest request, HttpServletResponse response) throws Exception {

    // Get a list of characters associated with the select TV show
    String tvShow = (String)request.getParameter("tvShow");
    if (tvShow == null) {
      tvShow = "";
    }
    ArrayList characters = getCharacters(tvShow);

    // And yes, I know creating HTML in an Action is generally very bad form,
    // but I wanted to keep this exampel simple.
    String html = "<select name=/"CharactersSelect/">";
    int i = 0;
    for (Iterator it = characters.iterator(); it.hasNext();) {
      String name = (String)it.next();
      i++;
      html += "<option value=/"" + i + "/">" + name + "</option>";
    }
    html += "</select>";

    // Write the HTML to response
    response.setContentType("text/html");
    PrintWriter out = response.getWriter();
    out.println(html);
    out.flush();

return null; // Not forwarding to anywhere, response is fully-cooked

} // End execute()

// This method returns a list of characters for a given TV show. If no TV
// show is selected, i.e., initial page view, am empty ArrayList is returned.
private ArrayList getCharacters(String tvShow) {//实际应用中应该是从数据库中取数据

ArrayList al = new ArrayList();

    if (tvShow.equalsIgnoreCase("StarTrekTNG")) {
      al.add("Jean Luc Picard");
      al.add("William T. Riker");
      al.add("Data");
      al.add("Deanna Troi");
      al.add("Geordi LaForge");
    }

    if (tvShow.equalsIgnoreCase("Babylon5")) {
      al.add("John Sheridan");
      al.add("Delenn");
      al.add("Londo Mollari");
      al.add("Stephen Franklin");
      al.add("Vir Cotto");
    }

    if (tvShow.equalsIgnoreCase("StargateSG1")) {
      al.add("Samantha Carter");
      al.add("Jack O'Neil");
      al.add("Teal'c");
      al.add("Daniel Jackson");
      al.add("Baal");
    }

return al;

} // End getCharacters()

} // End class
4.个人总结：
上面显示代码不过是起到一个抛砖引玉的作用，如果下拉框的内容多些，改用XML
进行传输较好，在页面上再进行解析，再组装成HTML代码，进行赋值(此处指的对span)

效果图：