Here is a simplified (NOT real world) example. Suppose there is a domain model - a class Movie, which has a List of actors. A class Actor has three fields (name, birthDate, rolesNumber). The following code is an illustration of this scenario:
Movie.java
public class Movie {
// some fields
private List<Actor> actors;
// getters and setters
}
Actor.java
public class Actor {
private String name;
private Date birthDate;
private int rolesNumber;
// getters and setters
}
There is also a JSP page where we output in a loop the information about every actor that plays in a concrete movie and the user can update the corresponding text field values and submit changes to a servlet:
actorsUpdate.jsp
...
<c:forEach items="${movie.actors}" var="actor">
<table>
<tr>
<th>Name</th>
<td><input type="text" value="${actor.name}" /></td>
</tr>
<tr>
<th>Birth Date</th>
<td><input type="text" value="${actor.birthDate}" /></td>
</tr>
<tr>
<th>Number of Previous Roles</th>
<td><input type="text" value="${actor.rolesNumber}" /></td>
</tr>
</table>
<hr />
</c:forEach>
...
It is known that in order to retrieve text fields in a servlet, one can use ServletRequest's methods like getParameter()
or getParameterValues()
etc. But how to retrieve the updated input fields as a List of objects (so that every three related values were grouped)?
If it were Spring project we could use Spring's <form:form modelAttribute="modelName">
tag and have a backing object defined in the modelAttribute. But how about pure JSP/Servlet project?
Possible solution
One of the possible solutions is to assign names in the "name" attribute of the text inputs and append varStatus.index, like this:
<c:forEach items="${movie.actors}" var="actor" varStatus="counter">
<table>
<tr>
<th>Name</th>
<td><input type="text" name="name${counter.index}" value="${actor.name}" /></td>
</tr>
...
</table>
<hr />
</c:forEach>
So this index would allow us to identify values related to ONE object. And we could also generate some hidden input field where we could store a loop count (a number of actors), and then in a servlet we could retrieve the values related to one object like this:
List<Actor> actors= new ArrayList<Actor>();
DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
for (int i = 0; i < count; i++) {
String name= request.getParamater("name" + i);
Date birthDate = dateFormat.parse(request.getParamater("birthDate" + i));
int rolesNumber = Integer.parseInt(request.getParamater("rolesNumber" + i));
Actor actor = new Actor(name, birthDate, rolesNumber);
actors.add(actor);
}
My questions are:
Is there another, more elegant and effective way of passing the updated text field values to a servlet as a List of objects?
Is there any solution similar or equivalent to that of the Spring's
<form:form>
tag in a world of pure JSP/JSTL/EL/Servlets?
UPDATE
Looks like nobody knows the answer to the above questions. The accepted answer is not exactly what I asked for (see my comments to it).
There seems to be no equivalent of Spring's <form:form modelAttribute>
tag or something similar in the world of pure Servlets/JSP.
Well, full Java EE, or Spring Framework, Apache Struts or another powerful web application framework to the rescue!