JavaServer Faces (JSF) is a user interface (UI) framework for Java web applications. It is designed to significantly ease the burden of writing and maintaining applications that run on a Java application server and render their UIs back to a target client. JSF provides ease-of-use in the following ways:
Makes it easy to construct a UI from a set of reusable UI components
Simplifies migration of application data to and from the UI
Helps manage UI state across server requests
Provides a simple model for wiring client-generated events to server-side application code
Allows custom UI components to be easily built and re-used
Most importantly, JSF establishes standards which are designed to be leveraged by tools to provide a developer experience which is accessible to a wide variety of developer types, ranging from corporate developers to systems programmers. A "corporate developer" is characterized as an individual who is proficient in writing procedural code and business logic, but is not necessarily skilled in object-oriented programming. A "systems programmer" understands object-oriented fundamentals, including abstraction and designing for re-use. A corporate developer typically relies on tools for development, while a system programmer may define his or her tool as a text editor for writing code. Therefore, JSF is designed to be tooled, but also exposes the framework and programming model as APIs so that it can be used outside of tools, as is sometimes required by systems programmers.
2)How to pass a parameter to the JSF application using the URL string?
if you have the following URL: http://your_server/your_app/product.jsf?id=777, you access the passing parameter id with the following lines of java code:
FacesContext fc = FacesContext.getCurrentInstance();
String id = (String) fc.getExternalContext().getRequestParameterMap().get("id");
From the page, you can access the same parameter using the predefined variable with name param. For example,
Note: You have to call the jsf page directly and using the servlet mapping.
3)How to add context path to URL for outputLink?
Current JSF implementation does not add the context path for outputLink if the defined path starts with '/'. To correct this problem use #{facesContext.externalContext.requestContextPath} prefix at the beginning of the outputLink value attribute. For example:
4)How to get current page URL from backing bean?
You can get a reference to the HTTP request object via FacesContext like this:
FacesContext fc = FacesContext.getCurrentInstance();
HttpServletRequest request = (HttpServletRequest) fc.getExternalContext().getRequest(); and then use the normal request methods to obtain path information. Alternatively,
context.getViewRoot().getViewId();
will return you the name of the current JSP (JSF view IDs are basically just JSP path names).
5)How to access web.xml init parameters from java code?
You can get it using externalContext getInitParameter method. For example, if you have:
You can access this connection string with:
FacesContext fc = FacesContext.getCurrentInstance();
String connection = fc.getExternalContext().getInitParameter("connectionString");
6)How to access web.xml init parameters from jsp page?
You can get it using initParam pre-defined JSF EL valiable.
For example, if you have:
You can access this parameter with #{initParam['productId']} . For example:
Product Id:
7)How to terminate the session?
In order to terminate the session you can use session invalidate method.
This is an example how to terminate the session from the action method of a backing bean:
Public String logout() {
FacesContext fc = FacesContext.getCurrentInstance();
HttpSession session = (HttpSession) fc.getExternalContext().getSession(false);
session.invalidate();
return "login_page";
}
The following code snippet allows to terminate the session from the jsp page:
<% session.invalidate(); %>
8)How to implement "Please, Wait..." page?
The client-side solution might be very simple. You can wrap the jsp page (or part of it you want to hide) into the DIV, then you can add one more DIV that appears when user clicks the submit button. This DIV can contain the animated gif you speak about or any other content.
Scenario: when user clicks the button, the JavaScript function is called. This function hides the page and shows the "Wait" DIV. You can customize the look-n-fill with CSS if you like.
10)How to download PDF file with JSF?
This is an code example how it can be done with action listener of the backing bean.
Add the following method to the backing bean:
public void viewPdf(ActionEvent event) {
String filename = "filename.pdf";
// use your own method that reads file to the byte array
byte[] pdf = getTheContentOfTheFile(filename);
FacesContext faces = FacesContext.getCurrentInstance();
HttpServletResponse response = (HttpServletResponse) faces.getExternalContext().getResponse();
response.setContentType("application/pdf");
response.setContentLength(pdf.length);
response.setHeader( "Content-disposition", "inline; filename=\""+fileName+"\"");
try {
ServletOutputStream out;
out = response.getOutputStream();
out.write(pdf);
} catch (IOException e) {
e.printStackTrace();
}
faces.responseComplete();
}
This is a jsp file snippet:
