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The Collection Utility Tag
There is only one tag in this category, iterate. This tag is used to iterate a collection. For each iteration, the iterate tag creates a scoped variable that references the element being iterated. Table 9.5 lists the attributes of this tag.
| Attribute | Description |
|---|---|
| id | A required attribute that specifies the name of the page-scoped variable that is created in each iteration to reference the element being iterated. |
| collection | Specifies the scoped variable that references the collection to be iterated over. |
| name | Specifies the scoped variable that references a collection or an object that contains a collection. If the latter is the case, the property attribute must be present. |
| property | Specifies the property of the scoped object specified by the name attribute. The property must return a collection. |
| scope | The scope within which the scoped object named by the name property will be searched for. The possible values are page, request, session, application, or any scope (default). |
| length | The maximum number of elements to be iterated through. If the length attribute is not present, the iterate tag iterates through all the elements. |
| offset | The zero-based index that specifies the number of first elements to be skipped. If the value of this attribute is 3, for example, the first four elements will not be iterated. |
| type | The type of the element to be iterated. If not present, no type conversion is performed. |
Table 9.5: The iterate tag’s attributes.
As an example, consider the execute method of the TestLogicAction class in the app09a application, which is given in Listing 9.1.
Listing 9.1: The execute method of the TestLogicAction class
public ActionForward execute(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response)
throws Exception {
request.setAttribute("position", "StrutsProgrammer");
ArrayList addresses = new ArrayList();
AddressTO address1 = new AddressTO();
address1.setStreetAddress("315 Avoca Street");
address1.setCity("Albany");
address1.setState("NY");
address1.setZipCode("12110");
ArrayList phones = new ArrayList(2);
phones.add("432 89894949");
phones.add("432 84839283");
address1.setPhones(phones);
addresses.add(address1);
AddressTO address2 = new AddressTO();
address2.setStreetAddress("144 Tiara Road");
address2.setCity("Sydney");
address2.setState("NSW");
address2.setZipCode("2000");
phones = new ArrayList(2);
phones.add("02 89898999");
phones.add("02 87282911");
address2.setPhones(phones);
addresses.add(address2);
request.setAttribute("addressList", addresses);
return mapping.findForward("success");
}
The execute method creates a scoped variable addressList that references the ArrayList addresses. You can iterate the content of the collection by using the following iterate tag.
<logic:iterate id="address" name="addressList">
Street Address:<bean:write name="address"
property="streetAddress"/><br/>
City:<bean:write name="address" property="city"/><br/>
State:<bean:write name="address" property="state"/><br/>
Zip Code:<bean:write name="address" property="zipCode"/><br/>
<logic:iterate id="phone" name="address" property="phones">
Phone:<bean:write name="phone"/><br/>
</logic:iterate>
<hr/>
</logic:iterate>
Note, you can even iterate an element of iteration by using an iterate tag inside the main iterate tag.