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EL Model

The JSP can display data that has been added to its model.

model

Think of this as a container of data the JSP can access.

Data is often added by a servlet before forwarding to a JSP.

(This is not the "model" in MVC.)

Data is stored in the model as a set of key-value pairs. * The JSP can use EL to refer to data by its key.

Below, a Stock object has been added to the model with the key "stock", so the JSP accesses the data using EL's ${ } syntax: ${stock} (no quotes).

EL model and keys

Adding Data to the Model

Servlets add data to the model using HttpServletRequest.setAttribute(String key, Object value)

@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

  // ...

  Stock s = findStockBySymbol(stocks, symbol);
  req.setAttribute("stock", s);

  // ...
  req.getRequestDispatcher("/WEB-INF/select.jsp").forward(req, resp);
}

Practice Exercise

Make sure the call to forward is the last operation in the method, after you have set all attributes in the request. * Note that forward is not a Java return. You could still execute code after forwarding. * Executing code after forward could cause your servlet to break.


Drill

ExpressionLanguage/com.example.el.drills.servlets.StockServletJSP

  • Store this Stock object in the request with the key "stock".

ExpressionLanguage/src/main/webapp/WEB-INF/select.jsp

  • Output the stock using EL.

(Solution: /WEB-INF/solutions/selectStock.jsp, com.example.el.solutions.servlets.StockServletJSP)

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