CODEWITHSUNDEEP
struts2
user1254422
user1254422

Reputation: 193

How to return a ArrayList incase of Struts2 Action class execute method?

I have a question with respect to returning data inside Struts2 . Inside my Action class as shown below , i am getting the Records and setting them inside ArrayList .

But could anybody please tell me , how can i return the Obtained ArrayList to the JSP Page ? because with the syntax of the Action class execute method , it allows us to return only a String ?

public class DBDisplay extends ActionSupport{
private String name ;
List list = null;

public String execute() throws Exception
{
list = DBClass.getInstance().list();
Iterator it = list.iterator();
while(it.hasNext())
{
name = (String) it.next();
}
setName(name);
}
public String getname()
{
return name;
}
public void setName(String name)
{
this.name = name;
}

}

Upvotes: 1

Views: 3026

Answers (2)

Dave Newton
Dave Newton

Reputation: 160191

Action classes return a string to name the result, not to return data. Data is exposed via either action properties (like the name you already expose) or a model instance (if implementing ModelDriven).

Access to the list is the same as name–by providing a public accessor to the list:

public class DBDisplay extends ActionSupport {
    private List list;
    public List getList() { return list; }
    // Rest of class elided.
}

Then from the JSP, for example:

<s:iterator value="list">
    <s:property /><br/>
</s:iterator>

The iterator tag "value" attribute refers to the list action property, and will call getList() on the action. The property tag will access the value on the top of the stack if given no "value" attribute.

You may wish to spend some time looking over the Struts 2 "nutshell" documentation.

Upvotes: 2

MohanaRao SV
MohanaRao SV

Reputation: 1125

One of the fundamental design goals of Struts 2 framework is to bring MVC (Model-View-Controller) design pattern into the Web application development. MVC pattern enables separation of concerns and allows for the clean and loosely coupled code which is easy to maintain. MVC pattern consists of 3 distinct pieces. Model, View and Controller. Let us see how these three elements are implemented in Struts 2. Controller (StrutsPrepareAndExecuteFilter) – Controller is the component which handles co-ordination of various requests. In a Web application, different user requests needs to be served by different application components and this decision is taken by the Controller component. In Struts 2, every request to the Web application first reaches the front controller class – StrutsPrepareAndExecuteFilter. This inspects the incoming requests and then routes the request to the appropriate class (known as Action class in Struts) configured to handle the request.

Model (Action) – Model is the component which is responsible for executing application’s business functionality. It is the core of the application. It represents the state of the application and includes business logic and business data. In Struts 2, action classes act as the gateway to an application’s model. These classes are responsible for handling every user request and then delegates business logic to other classes written by the application developer. Having different action classes for different user requests ensures that we have clean code which can be easily maintained. But what about functionality that is required across different user requests(such as application logging)?. For such cross cutting concerns, Struts 2 has a different component called interceptors.

View (Result) – View in an MVC architecture is the component responsible for the presentation(user interface). View component makes use of the Model component to get data and then display it. Struts 2 supports multiple technologies such as JSP, Velocity templates, FreeMarker, XSLT for View component. In Struts 2 terminology, View is know as the Result. The action class (Model) determines what Result (View) should be presented to the user.

User accesses a Struts 2 application functionality by accessing the application URL in a browser. The request always comes to the StrutsPrepareAndExecuteFilter controller(Since it is configured in the web.xml of all Struts 2 applications). StrutsPrepareAndExecuteFilter looks for the Action class to call in the struts.xml file. Alternatively it can guess it using conventions. Action class execute() method is then invoked which in turn calls the business logic classes. Action classes can specify the view to display using annotations or it can be specified in the struts.xml file. Either way Struts 2 knows which View (Result) is to be invoked for displaying the data back to the user. Another important thing to note here is that the objects in the Action class is available to the View component. Hence Actions not only determine which View(Result) to display but also provides data required by the View.

The valueStack(it's combination of objectStack and contextMap) OGNL is used to store the action and other objects. You can use OGNL to access the objects stack and Context Map.

OGNL

Bind the elements to modal objects and converts values from one type to another Bind generic tags with modal objects. Create lists and maps on the fly, to be used with GUI methods Invoke methods. you can invoke any method, not only getters and setters.

Upvotes: -1

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