下拉列表的超链接

Question

In a spring mvc application JSP page, I am trying to simplify the layout by giving the user a drop down list from which to select a desired action. The items in the drop down list would each correspond with a different url for other JSPs to which the user would be directed. This would make the user interface a lot cleaner than having a separate button for each possible URL. How do I set this up in code?

Here is the jsp code in Spring Expression Language for creating the drop down list that I have so far:

<form:select path="AddLink" cssClass="textArea">
    <option value="Select" label=" - Select - " ></option>
    <form:options items="${AddLinks}"/>
</form:select>

Here are the methods in the controller for populating the drop down list and then for handling its selection that I have so far:

@RequestMapping(value = "/encounters", method = RequestMethod.GET)
public String processFindForm(@RequestParam("encounterID") String encounterId, Encounter encounter, BindingResult result, Map<String, Object> model) {
    int encountId = Integer.parseInt(encounterId);
    Encounter sel_encounter = this.clinicService.findEncounterById(encountId);//I added this
    HashMap<String,String> AddLinks = new HashMap<String,String>();
    AddLinks.put("New this","/thislink");
    AddLinks.put("New that","/thatlink");
    AddLinks.put("New other thing","/otherlink");
    model.put("sel_encounter",sel_encounter);
    ((Model) model).addAttribute("AddLinks", AddLinks);
    return "encounters/encountersList";
}

@RequestMapping(value = "/encounters", method = RequestMethod.POST)
public String processFindForm(@ModelAttribute("encounter") Encounter encounter, @ModelAttribute("AddLink") String addLink, BindingResult result, SessionStatus status) {
    int encountId = encounter.getId();
    System.out.println("............ addLink is:  "+addLink);
    return "/"+addLink;
}

This is causing the following stack trace:

org.apache.jasper.JasperException: An exception occurred processing JSP page /WEB-INF/jsp/encounters/encountersList.jsp at line 116

113:                 <spring:url value="" var="medications_newUrl"></spring:url>
114:                 <a href="${fn:escapeXml(medications_newUrl)}" class="btn btn-info" >Add New Medication</a>
115:
116: <form:select path="AddLink" cssClass="textArea">
117:     <option value="Select" label=" - Select - " ></option>
118:     <form:options items="${AddLinks}"/>
119: </form:select>

Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:568)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:465)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
org.springframework.web.servlet.view.InternalResourceView.renderMergedOutputModel(InternalResourceView.java:238)
org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:263)
org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1208)
org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:992)
org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:939)
org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:856)
org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:936)
org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:827)
javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:812)
javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77)
org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
com.github.dandelion.datatables.core.web.filter.DatatablesFilter.doFilter(DatatablesFilter.java:73)
com.github.dandelion.datatables.extras.servlet2.filter.DatatablesFilter.doFilter(DatatablesFilter.java:71)
org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)

root cause 
java.lang.IllegalStateException: Neither BindingResult nor plain target object for bean name 'AddLink' available as request attribute
org.springframework.web.servlet.support.BindStatus.<init>(BindStatus.java:141)
org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.getBindStatus(AbstractDataBoundFormElementTag.java:179)
org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.getPropertyPath(AbstractDataBoundFormElementTag.java:199)
org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.getName(AbstractDataBoundFormElementTag.java:165)
org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.autogenerateId(AbstractDataBoundFormElementTag.java:152)
org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.resolveId(AbstractDataBoundFormElementTag.java:143)
org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.writeDefaultAttributes(AbstractDataBoundFormElementTag.java:127)
org.springframework.web.servlet.tags.form.AbstractHtmlElementTag.writeDefaultAttributes(AbstractHtmlElementTag.java:421)
org.springframework.web.servlet.tags.form.SelectTag.writeTagContent(SelectTag.java:200)
org.springframework.web.servlet.tags.form.AbstractFormTag.doStartTagInternal(AbstractFormTag.java:103)
org.springframework.web.servlet.tags.RequestContextAwareTag.doStartTag(RequestContextAwareTag.java:80)
org.apache.jsp.WEB_002dINF.jsp.encounters.encountersList_jsp._jspx_meth_form_005fselect_005f0(encountersList_jsp.java:1396)
org.apache.jsp.WEB_002dINF.jsp.encounters.encountersList_jsp._jspService(encountersList_jsp.java:405)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
org.springframework.web.servlet.view.InternalResourceView.renderMergedOutputModel(InternalResourceView.java:238)
org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:263)
org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1208)
org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:992)
org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:939)
org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:856)
org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:936)
org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:827)
javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:812)
javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77)
org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
com.github.dandelion.datatables.core.web.filter.DatatablesFilter.doFilter(DatatablesFilter.java:73)
com.github.dandelion.datatables.extras.servlet2.filter.DatatablesFilter.doFilter(DatatablesFilter.java:71)
org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)

For reference, here are the taglibs included at the top of the JSP:

<%@ taglib prefix="spring" uri="http://www.springframework.org/tags" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ taglib prefix="datatables" uri="http://github.com/dandelion/datatables" %>
<%@ taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions" %>
<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form" %>
<%@ taglib prefix="petclinic" tagdir="/WEB-INF/tags" %>
<%@ taglib prefix="joda" uri="http://www.joda.org/joda/time/tags" %>

NOTE: I think the problem is from using atModelAttribute to pass a string into the controller method. I think the error means that spring is looking for an object AddLink when I just want to pass a string. Does this help you see the solution?

---

EDIT:

By changing all the AddLink references to AddLinks , I got the JSP to compile with a drop down list of the link choices, but selecting any of the choices has NO EFFECT. The JSP does not redirect, and the System.out.println() in the POST controller method does not print anything out, indicating that the POST controller method has not been called.

Here is the only code that I changed:

// in the JSP
<form:select path="AddLinks" cssClass="textArea">
    <option value="Select" label=" - Select - " ></option>
    <form:options items="${AddLinks}"/>
</form:select>  

// in the controller
@RequestMapping(value = "/encounters", method = RequestMethod.POST)
public String processFindForm(@ModelAttribute("encounter") Encounter encounter, @ModelAttribute("AddLink") String AddLinks, BindingResult result, SessionStatus status) {
    int encountId = encounter.getId();
    System.out.println("............ addLink is:  "+AddLinks);
    return "/"+AddLinks;
}

The complete JSP can be found on a file sharing site at this link .

Answer 1

Similar like @looser I would also argue you'd better off coding this on client side using javascript, but anyway here's the server side answer:

Firstly I think you forgot to model.addAttribute("AddLinks", AddLinks) . I can see you're creating a HashMap which never gets added to the model.

Secondly in processFindForm you can return the string "redirect:/blah" to give a HTTP 3xx redirect into /blah URI. The redirection URL is relative to your context path.

Read more about spring view redirection here .

Answer 2

try this,

Modify your Encounter class to hold a value of selectedLink like:

public class Encounter {

    private String selectedLink;

    //getters and setters

} 

then, in controller to add a AddLinks options as a modelAttribute do like this:

    public String getFindForm(Model model){
        model.addAttribute("enctr",new Encounter());
        return "AddLink";
    }

    @RequestMapping(method=RequestMethod.POST)
    public String processFindForm(@ModelAttribute("enctr")Encounter encounter){
        System.out.println(encounter.getSelectedLink());    

        return "AddLink";//"redirect:"+encounter.getSelectedLink();
    }

    @ModelAttribute("addLinkOptions")
    public Map loadLinkOptions(){
        LinkedHashMap<String, String> addLinks = new LinkedHashMap<String,String>();
        addLinks.put("/thislink","New this");
        addLinks.put("/thatlink","New that");
        addLinks.put("/otherlink","New other thing");
        return addLinks;
    }

and in your jsp add a spring form:form tag to perform action.

    <form:form method="post" modelAttribute="enctr">
        SelectLink:
        <form:select path="selectedLink">
            <form:option value="NONE">--select--</form:option>
            <form:options items="${addLinkOptions}"/>
        </form:select>

        <input type="submit"/>
    </form:form>

Answer 3

Okay i am not familiar with Spring MVC but in your requirement

 onChange or onSelect event is enough

<form:select path="AddLink" cssClass="textArea" onChange='setAction()' >
<option value="Select" label=" - Select - " ></option>
<form:options items="${AddLinks}"/>
</form:select>

In javaScript

  <script type="text/javascript">

        function setAction()
        {
           var temp = document.getElementById("selectTagID"); 
           var action = temp.options[temp.selectedIndex].value;//get Selected option key value
            document.form_name.action =action;//Send the action
             document.form_name.submit();//Submit the form

        }
  </script>   

Where in your Otions list make those actions are available .. as keys for that selected options