Binding parameters to a collection in Struts 2 without the need for indexes

Question

Binding parameters to a collection in Struts 2 without the need for indexes

Struts Version: 2.3.16.3

Is there a way to populate a list of objects without specifying the index? Currently, I am required to reference the collection in this manner:

<input name="myCollection[0].myProperty" value="some value" />

I wish to be able to achieve something like the following:

<input name="myCollection[].myProperty" value="some value" />

As I am dynamically adding and removing elements on the page using JavaScript, it has been challenging to correctly manage the indexing. It would be more convenient if the backend could simply add new elements to the end of the collection as they come across from the form, similar to how PHP handles it.

The documentation for the parameters interceptor suggests that the input name is binding to an OGNL expression. Upon checking the OGNL docs, I found that arrays can be referenced in this way:

array["length"]

This would indicate the next element in the array. However, when attempting this approach, the parameter interceptor indicates rejection of this parameter name. I am eager to discover a solution for this issue, even if it involves extending the parameters interceptor.

javascript java jsp struts2 ognl

Answer 1

Answer №1

When you find yourself manipulating the page using Javascript and encountering difficulty in detecting or updating the index of elements when adding or removing them, a straightforward solution is to:

Utilize the preferred syntax for manipulation, such as myCollection[].myProperty.
Transform them into the desired format for Struts during a pre-submit action.

This approach eliminates the need to manage indexes while manipulating elements. Instead, you can loop through them by name at the end and adjust their names with JavaScript by assigning the correct index.

Here's a quick example using jQuery:

$(function() {
  $('#myform').submit(function() {
    $('[name^="myCollection[]"]').each(function(index) {
      var oldV = this.name;
      var newV = oldV.replace("myCollection[]", "myCollection[" + index + "]");
      console.log("was: " + oldV + " - now is: " + newV);
      this.name = newV;
    });
    return false;
  });
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<form id="myform">
  Open Javascript Console, then press submit, then inspect input elements
  <br>
  <input name="myCollection[].myProperty" />
  <br>
  <input name="myCollection[].myProperty" />
  <br>
  <input name="myCollection[].myProperty" />
  <br>
  <input name="myCollection[].myProperty" />
  <br>
  <input name="myCollection[].myProperty" />
  <br>
  <button>submit</button>
</form>

Answer 2

When you find yourself manipulating the page using Javascript and encountering difficulty in detecting or updating the index of elements when adding or removing them, a straightforward solution is to:

Utilize the preferred syntax for manipulation, such as myCollection[].myProperty.
Transform them into the desired format for Struts during a pre-submit action.

This approach eliminates the need to manage indexes while manipulating elements. Instead, you can loop through them by name at the end and adjust their names with JavaScript by assigning the correct index.

Here's a quick example using jQuery:

$(function() {
  $('#myform').submit(function() {
    $('[name^="myCollection[]"]').each(function(index) {
      var oldV = this.name;
      var newV = oldV.replace("myCollection[]", "myCollection[" + index + "]");
      console.log("was: " + oldV + " - now is: " + newV);
      this.name = newV;
    });
    return false;
  });
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<form id="myform">
  Open Javascript Console, then press submit, then inspect input elements
  <br>
  <input name="myCollection[].myProperty" />
  <br>
  <input name="myCollection[].myProperty" />
  <br>
  <input name="myCollection[].myProperty" />
  <br>
  <input name="myCollection[].myProperty" />
  <br>
  <input name="myCollection[].myProperty" />
  <br>
  <button>submit</button>
</form>

Answer 3

Answer №2

It is important to be able to identify which object a particular property belongs to, and indexes are commonly used for that purpose. It's not advisable to simply remove them without considering other methods.

There are multiple approaches you can take to achieve your desired outcome. Take a look at Andrea's answer for a potential solution using JavaScript.

Another option is to extract object properties into simple lists and then assign them back to the object.

For example:

private List<String> myProperty;

You can reference this in JSP without needing indexes:

<input name="myProperty" value="first value" />
<input name="myProperty" value="second value" />

However, if you have multiple properties, you will need to ensure they are synchronized in JSP so that the order and size of properties in the list remains consistent for each property.

Answer 4

It is important to be able to identify which object a particular property belongs to, and indexes are commonly used for that purpose. It's not advisable to simply remove them without considering other methods.

There are multiple approaches you can take to achieve your desired outcome. Take a look at Andrea's answer for a potential solution using JavaScript.

Another option is to extract object properties into simple lists and then assign them back to the object.

For example:

private List<String> myProperty;

You can reference this in JSP without needing indexes:

<input name="myProperty" value="first value" />
<input name="myProperty" value="second value" />

However, if you have multiple properties, you will need to ensure they are synchronized in JSP so that the order and size of properties in the list remains consistent for each property.

Binding parameters to a collection in Struts 2 without the need for indexes

Answer №1

Answer №2

Similar questions

Attempting to maintain the main navigation highlighted while browsing through the secondary navigation

Is the memory consumption higher for a subclass compared to a superclass?

Checking for file existence using the HEAD command can be done by specifying the file path as

How to take advantage of the onOk method in Vue Ant Design's Modal component

Switching styles in AngularJS without using ng-class

How should FormData be structured?

When the email field is changed, the string is not being set to the state if it is

What is the best way to apply lodash's max function to a jQuery array?

Loading JavaScript on a different page using AJAX is not possible

Transferring Information from a JavaScript Page to an HTML Page without the Use of a Form or URL

Troubleshooting: How to resolve the issue of "Error [ERR_HTTP_HEADERS_SENT]: Unable to set headers after they have been sent to the client"

Activate the ng-change event when the selection option tag is fired

Is there a way to adjust the width of the datepicker on my device?

Tips on how to lock a dropdown field to prevent editing while retaining the current value

Retrieving a specific attribute pair from a JSON object

Pagination with composite queries in Firestore allows for efficient retrieval of

Switching Iframe Source with Javascript Button State

Is it possible for me to interact with different elements upon hovering?

Retrieve a Google map using Ajax in a PHP script

Locating an element using XPath in Java with Selenium