bind a dynamic drop-down list

[zliu]

I have an HTML form which has a drop-down list (indexed properties). The values of the list are retrieved from the database. How do I bind the list? Is there an example? Thanks.

[fanfaron]

You should check the petclinic example that comes with the spring distribution.

the form to add or edit a pet have a drop down list.
that drop down list created with values from the TYPES table. the jsp is
petForm.jsp

is not complicated, to bind a select list is like to bind a input text.

use the tag <spring:bind>

examples :

<spring:bind path="command.type">
<FONT color="red">
<B><c:out value="${status.errorMessage}"/></B>
</FONT>
<BR>
<SELECT name="typeId">
<c:forEach var="type" items="${types}">
<c:if test="${command.type.id == type.id}">
<OPTION selected="<c:out value="${command.type.id}"/>" value="<c:out value="${type.id}"/>"><c:out value="${type.name}"/></OPTION>
</c:if>
<c:if test="${command.type.id != type.id}">
<OPTION value="<c:out value="${type.id}"/>"><c:out value="${type.name}"/></OPTION>
</c:if>
</c:forEach>
</SELECT>
</spring:bind>

[zliu]

Thank you very much for pointing me to the example.

In EditPetForm.jave, there is refereceData() method as
protected Map referenceData(HttpServletRequest request) throws ServletException {
Map refData = new HashMap();
refData.put("types", getClinic().getPetTypes());
return refData;
}

Then petForm.jsp uses the following code to get the list of types.
<c:forEach var="type" items="${types}">

I assume that this is how the "types" are set and retrieved. So I was trying the same way for a list of products (just product descriptions). I simply use
refData.put("products", productManager.getProducts());
in form controller and
<c:forEach var="item" items="${products}">
in JSP.

However, I got the error message below:
An error occurred while evaluating custom action attribute "items" with value "${order.products}": Unable to find a value for "products" in object of class "bus.Order" using operator "." (null)

I ran debug and found the list of products were retrieved correctly in referenceData(). However, it was not bound to the JSP somehow.

Thanks in advance.

[fanfaron]

I don't understand where did the JVM find the order variable?

you have to show me more codes.

[Mark Fisher]

Is your controller a subclass of AbstractFormController (or one of its subclasses: SimpleFormController or AbstractWizardFormController)?

[jettro]

You should have a look at your jsp page, what are the spring:bind tags around your <c:foreach ... /> tag?

[fanfaron]

My form is a subclass of SimpleFormController

[Mark Fisher]

zliu,

Can you post your referenceData method and the handling method (or at least an excerpt of code from the controller where you return the ModelAndView object)?

[zliu]

Thank you for your help. Here is the code. By the way, I wonder if I missed something special for AbstractWizardFormController. Similar code works fine for SimpleFormController.

public class OrderFormController extends AbstractWizardFormController {
...

public OrderFormController() {
setPages(new String[] { "order", "order-confirm" });
setCommandName("order");
}

protected Map referenceData(HttpServletRequest request, int page) {
Map refData = new HashMap();
refData.put("products", productManager.getProducts());
// getProducts() returns a "List" of "Product"s.
return refData;
}

...
}

public class Order {
private String product; // the type is "String", not "Product"
private int amount;
// getters and setters
}

public class Product {
private int id;
private String description;
private double price;
// getters and setters
}

// order.jsp
<spring:bind path="order.product">
<select name="product">
<c:forEach var="entry" items="${products}">
<option value="<c:out value="${entry.description}"/>"
<c:if test="${entry.description == order.product}">selected="selected"</c:if>
>
<c:out value="${entry.description}"/>
</option>
</c:forEach>
</select>
</spring:bind>

[jettro]

I am not really sure if this helps, but this is one of the select boxes I have created within a wizard form. All the other parts seem oke, just the jsp has some difference. I just cannot point you what is wrong. Probably is something small :-)

<spring:nestedPath path="order.paymentMethod">
	<spring:bind path="id">
	        <select name="${status.expression}">
	        	<option value=""></option>
	        	<c:forEach items="${paymentMethods}"  var="payMethod">
				<option value="${payMethod.id}"
					<c:if test="${status.value == payMethod.id}">selected="selected"</c:if>
				>${payMethod.name}</option>
	        	</c:forEach>
	        </select>
	        <span class="fieldError">${status.errorMessage}</span>
	</spring:bind>
</spring:nestedPath>

Hope this helps.