上QQ阅读APP看书，第一时间看更新

How to do it...

Let's create a User class for our recipe:

public class User {

    private String name;
    private String email;

    //DO NOT FORGET TO IMPLEMENT THE GETTERS AND SETTERS

}

And then our servlet:

@WebServlet(name = "UserServlet", urlPatterns = {"/UserServlet"})
public class UserServlet extends HttpServlet {
    
    private User user;
    
    @PostConstruct
    public void instantiateUser(){
        user = new User("Elder Moraes", "elder@eldermoraes.com");
    }

   ...

We use the @PostConstruct annotation over the instantiateUser() method. It says to the server that whenever this servlet is constructed (a new instance is up), it can run this method.

We also implement the init() and destroy() super methods:

    @Override
    public void init() throws ServletException {
        System.out.println("Servlet " + this.getServletName() + 
                           " has started");
    }

    @Override
    public void destroy() {
        System.out.println("Servlet " + this.getServletName() + 
                           " has destroyed");
    }

And we also implemented doGet() and doPost():

    @Override
    protected void doGet(HttpServletRequest request, 
    HttpServletResponse response)
            throws ServletException, IOException {
        doRequest(request, response);
    }

    @Override
    protected void doPost(HttpServletRequest request, 
    HttpServletResponse response)
            throws ServletException, IOException {
        doRequest(request, response);
    }

Both doGet() and doPost() will call our custom method doRequest():

    protected void doRequest(HttpServletRequest request, 
    HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        try (PrintWriter out = response.getWriter()) {
            out.println("<html>");
            out.println("<head>");
            out.println("<title>Servlet UserServlet</title>");
            out.println("</head>");
            out.println("<body>");
            out.println("<h2>Servlet UserServlet at " + 
                         request.getContextPath() + "</h2>");
            out.println("<h2>Now: " + new Date() + "</h2>");
            out.println("<h2>User: " + user.getName() + "/" + 
                        user.getEmail() + "</h2>");
            out.println("</body>");
            out.println("</html>");
        }
    }

And we finally have a web page to call our servlet:

    <body>
        <a href="<%=request.getContextPath()%>/UserServlet">
        <%=request.getContextPath() %>/UserServlet</a>
    </body>