I have stored a list in ehCache from my J2EE Model. In one of my view(.jsp page), I want to access the stored list directly from ehCache. Is it possible?
Some code of yours needs to put that value on the context of the page, Ehcache does not have any magic in it to make that happen.
Related
I am experiencing a weird issue using spring mvc and session items.
We have a controller class annotated as follows:
#SessionAttributes({"customerPosition"})
according to the Spring doc, if I put into the model an object with the key customerPosition it gets automatically put into the session.
When I "manually" set the item with session.setAttribute("customerPosition",customerPosition) I exepect the item to be saved in session. if I get this item from the session by means of session.getAttribute("customerPosition") I get a different Item, not the one I expect. Actually what I get is data from previous iterations of the software flow.
It looks like that session.setAttribute("customerPosition",customerPosition) is not overwriting the object in session.
Does using #SessionAttributes prevents the possibility to manually control the session by means of session.setAttribute("customerPosition", customerPosition)
I have a single JSP that serves multiple methods in a Controller -- it is the result of Add, Edit, Delete, etc. It may even serve multiple Controllers, so it's used in a lot of places.
This JSP always has a List Box displaying a set of records. So I need to re-fetch the list on every request every time this JSP is displayed.
On the one hand, I can do request.setAttribute("contents",
service.getForms()) and then retrieve this Req. Attr., but this has
to be done on every method that uses the JSP. There may be dozens,
and it's redundant.
Can't use a Session object, the list may change depending some
Add/Delete operations, so it needs to be re-fetched.
I was thinking of scriptlets: in this case, although generally
ill-advised, there's a single JSP, so the List Box can be populated
on the JSP level, without worrying about controllers. But
unfortunately I can't do this:
<% service.getForms(); %>
My service is auto-wired. According to this thread, I can't expose autowired objects to JSPs:
What is the cleanest way to autowire Spring Beans in a JSP?
#Autowired
#Qualifier("Myervice")
private MyService service;
What's the best way to go about it?
We Developed Header & Footer for our site. we created a content hierarchy and from a java service class we accessed content hierarchy and for each level there is a java bean to hold the values
For ex
LevelOneBean.java
{
string linkName; String linkUrl, List<LevelTwoBean> LeveltwoBeanList;
}
LevelTwoBean.java
{
string linkName; String linkUrl, List<LevelTwoBean> LevelthreeBeanList;
}
LevelThreeBean.java
{
string linkName; String linkUrl,
}
After that i am rendering bean in my component jsp.
when we deployed on web server, found that these two component using 70% of cpu and hence it is slow. we do have dispatcher and page should get cached in dispatcher.
My senior said since you have created java bean and java bean not get cached. and he asked to create JSON for header and footer. Json will get chached at dispatcher level.Java bean not.
My Q - I want to validate my above statement statement. Ideally page get should cached regardless of rendering design.
Please help to understand this.
Calling a bean is irrelevant here. Beans are generally called during transformation of the JCR section to HTML/CSS/JS.
If you are calling the bean during the JSP transformation phase, and then serving HTML based upon the bean results, the response should be cached.
If the browser has been served with the page, and you are making an AJAX call, a JSON or XML request is made, which can be set to cache. By default, JSON and XML are not configured to cache in a dispatcher.
The JSON call back from the dispatcher would hit the publisher, and then the JSP would call your bean to render the response. Again, it should not have anything to do with your bean.
The only thing to be careful of when you're caching, is what actions trigger to flush or clear your cache. If you are updating content, the stats file flush approach of the dispatcher works well. The danger with JSON and XML, is that you are likely to be synthesizing the response from several different source points in the tree, which if they do not match between the content and the json path, the cache is likely to not be flushed unless if you are using Dispatcher Flush for ACS commons.
https://adobe-consulting-services.github.io/acs-aem-commons/features/dispatcher-flush-rules.html
From what you have described, your bolded statement does not make sense. I would check to see what you are producing as a rendered artefact, and whether those artefacts are being cached/flushed.
I have a page with a dataTable, which is populated based on the query parameters (e.g., username and pagenum). Each entry in the table has a delete commandButton
When the pagenum != 0 and we click delete, the list of records to display is generated during the "apply" phase. During this phase the view parameters have not been set, so the list of records is empty so nothing get's deleted (our delete method doesn't get called)
To work around this I've added a #PostConstruct method that retrieves the query parameters from the Servlet request and sets the values in the bean, so they are available when we get the list of away records, which allows my delete method to be called.
I'm certain that JSF has a better way of handling this scenario and the #PostConstruct work around is a hack.
What is the correct way to implement this scenario, without resorting to a View or Session scoped bean?
Surely there must be a way to just POST the form and delete the appropriate record without having to waste time regenerating the list of records.
What is the correct way to implement this scenario, without resorting to a View or Session scoped bean? Surely there must be a way to just POST the form and delete the appropriate record without having to waste time regenerating the list of records
Sorry, there's no way. At least not when using a standard <h:commandButton> inside a standard <h:dataTable>. This is the consequence of the stateful nature of JSF. JSF just wants to ensure that the view is exactly the same during processing the postback as it was during generating the HTML output.
This is part of JSF's safeguard against tampered requests wherein the enduser/hacker can manipulate the request parameters in such way that it could do hazardful things, e.g. changing the ID of entry to delete, or bypassing the check on rendered attribute, etc. All those things on which you would/should do additional pre-validation anyway if JSF didn't do that for you and are easily overlooked by starters (they would then blame JSF for being insecure instead of themselves). See also Why JSF saves the state of UI components on server? and commandButton/commandLink/ajax action/listener method not invoked or input value not updated.
In case of <h:commandButton> inside <h:dataTable>, JSF simply needs to have the data model available during the apply request values phase, so that it can iterate over the <h:dataTable> in the component tree in order to find the pressed button and queue the action event. If there's no datamodel, then it can't find the pressed button and the action event won't be queued. Normally, this is to be solved by placing the managed bean in the JSF view scope. See also How to choose the right bean scope?
In case of request scoped beans, the <f:viewParam> is indeed not the right tool for the job of preserving the data model before apply request values phase takes place. You need to do the job in a #PostConstruct annotated method instead. The request parameters can in case of JSF managed beans be injected via #ManagedProperty. See also ViewParam vs #ManagedProperty(value = "#{param.id}"). In case of CDI or Spring managed beans, there's no standard annotation available to inject a HTTP request parameter as a bean property. For CDI, the JSF utility library OmniFaces has a #Param for the very purpose. See also OmniFaces #Param showcase. For Spring, you'd need to homegrow it yourself. I, as non-Spring-user have however no idea how to do that. Google also doesn't seem to reveal much.
Alternatively, you can also just put the bean in the view scope by #ViewScoped. It'll then live as long as you postback to the same view. JSF 2.2 has a CDI compatible annotation for that in javax.faces.view package. The one in javax.faces.bean package is the old JSF 2.0/2.1 annotation for #ManagedBean. Spring has no annotation out the box for this as that would otherwise put a dependency on JSF API. You'd need to homegrow it yourself. Google shows several examples.
What is the correct way to implement this scenario
Before executing the any logic on the backing bean, JSF always have to rebuild the view in order to get information about what to execute. For displaying and updating purpose, the best (and correct) solution is certainly the #ViewScoped.
without resorting to a View or Session scoped bean?
If you insist on using #RequestScoped, I'd say there're no correct ways but work-arounds or hacks. One way is to initialise the list in a #PostConstruct method like you've mentioned. Another way may be to use a JavaScript function for the onclick attribute of your delete button. The JS function, for example, will make a call to the server using a URL to request a delete. Or else, you can also use PrimeFace's RemoteCommand for the JS function.
I am working on a java MVC project. Currently i've a login.jsp, profile.jsp, ``CheckLogin servlet, User.java bean class and UserDAO dao class (the beans and jsp's and all other things are to be added also).
What i am currently doing here whenever the user gets logged in successfully it is redirected to the profile page which shows all the details of user.
My question here is:
Is it better to set a User type object for particular userID in the session object that prevails in whole session and retrieve all values directly as ${sessionScope.user.property} everywhere?
or
Is it better to set just a userID in the session object that prevails in whole session and retrieve the values in all pages using these lines of code :
<jsp:useBean id="userDAO" scope="page" type="com.project.dao.UserDAO" />
<c:set var="user" value="<%= userDAO.getUser(%>${sessionScope.userID}<%) %>" />
${user.property}
I hope i am clear to you in my question.
Please suggest me.
First rule: avoid scriptlets. The fact that you have no other solution than scriptlets shows a design problem. The controller should prepare the model for the view. The view should not call DAOs directly. That's the responsibility of the controller.
Now, storing the user in the session or loading it at each request (from the controller) is a matter of performance and stale data.
If the user only contains data that won't change through the whole session (or that could change, but only from this session, allowing to refresh the data when needed), then store it in the session. That's its goal: store data that have a session scope.
If there might be some external session or process modifying the data of the user, and you want to make sure you always display the freshest data, then reload it at every request.