BAEL-325 - adding optional construct

patterns/intercepting-filter/src/main/java/com/baeldung/patterns/intercepting/filter/commands/LoginCommand.java

@@ -3,6 +3,7 @@ package com.baeldung.patterns.intercepting.filter.commands;
 import javax.servlet.ServletException;
 import javax.servlet.http.HttpSession;
 import java.io.IOException;
+import java.util.Optional;
 
 public class LoginCommand extends FrontCommand {
     @Override
@@ -12,10 +13,8 @@ public class LoginCommand extends FrontCommand {
             session.setAttribute("username", request.getParameter("username"));
             response.sendRedirect(request.getParameter("redirect"));
         } else {
-            String queryString = request.getQueryString();
+            String queryString = Optional.ofNullable(request.getQueryString())
-            if (queryString == null) {
+              .orElse("command=Home");
-                queryString = "command=Home";
-            }
             request.setAttribute("redirect", request.getRequestURL()
               .append("?").append(queryString).toString());
             forward("login");

patterns/intercepting-filter/src/main/java/com/baeldung/patterns/intercepting/filter/commands/LogoutCommand.java

@@ -3,14 +3,17 @@ package com.baeldung.patterns.intercepting.filter.commands;
 import javax.servlet.ServletException;
 import javax.servlet.http.HttpSession;
 import java.io.IOException;
+import java.util.Optional;
 
 public class LogoutCommand extends FrontCommand {
     @Override
     public void process() throws ServletException, IOException {
         super.process();
-        HttpSession session = request.getSession(false);
+        Optional.ofNullable(request.getSession(false))
+          .ifPresent(session -> {
               session.removeAttribute("username");
               session.removeAttribute("order");
+          });
         response.sendRedirect("/?command=Home");
     }
 }

patterns/intercepting-filter/src/main/java/com/baeldung/patterns/intercepting/filter/commands/OrderCommand.java

@@ -8,6 +8,7 @@ import com.baeldung.patterns.intercepting.filter.data.OrderImpl;
 import javax.servlet.ServletException;
 import javax.servlet.http.HttpSession;
 import java.io.IOException;
+import java.util.Optional;
 
 public class OrderCommand extends FrontCommand {
     @Override
@@ -15,11 +16,10 @@ public class OrderCommand extends FrontCommand {
         super.process();
         if (request.getMethod().equals("POST")) {
             HttpSession session = request.getSession(false);
-            Order order = (Order) session.getAttribute("order");
+            Order order = Optional
-            if (order == null) {
+              .ofNullable(session.getAttribute("order"))
-                String username = (String) session.getAttribute("username");
+              .map(Order.class::cast)
-                order = new OrderImpl(username);
+              .orElseGet(() -> new OrderImpl((String) session.getAttribute("username")));
-            }
             Bookshelf bookshelf = (Bookshelf) request.getServletContext()
               .getAttribute("bookshelf");
             String isbn = request.getParameter("isbn");

patterns/intercepting-filter/src/main/java/com/baeldung/patterns/intercepting/filter/filters/EncodingFilter.java

@@ -4,6 +4,7 @@ import javax.servlet.*;
 import javax.servlet.annotation.WebFilter;
 import javax.servlet.annotation.WebInitParam;
 import java.io.IOException;
+import java.util.Optional;
 
 @WebFilter(
   servletNames = {"intercepting-filter"},
@@ -24,10 +25,9 @@ public class EncodingFilter extends BaseFilter {
       ServletResponse response,
       FilterChain chain
     ) throws IOException, ServletException {
-        String encoding = request.getParameter("encoding");
+        String encoding = Optional
-        if (encoding == null) {
+          .ofNullable(request.getParameter("encoding"))
-            encoding = this.encoding;
+          .orElse(this.encoding);
-        }
         response.setCharacterEncoding(encoding);
         chain.doFilter(request, response);
     }

patterns/intercepting-filter/src/main/java/com/baeldung/patterns/intercepting/filter/filters/LoggingFilter.java

@@ -10,6 +10,7 @@ import javax.servlet.ServletResponse;
 import javax.servlet.annotation.WebFilter;
 import javax.servlet.http.HttpServletRequest;
 import java.io.IOException;
+import java.util.Optional;
 
 @WebFilter(servletNames = "intercepting-filter")
 public class LoggingFilter extends BaseFilter {
@@ -23,10 +24,10 @@ public class LoggingFilter extends BaseFilter {
     ) throws IOException, ServletException {
         chain.doFilter(request, response);
         HttpServletRequest httpServletRequest = (HttpServletRequest) request;
-        String username = (String) httpServletRequest.getAttribute("username");
+        String username = Optional
-        if (username == null) {
+          .ofNullable(httpServletRequest.getAttribute("username"))
-            username = "guest";
+          .map(Object::toString)
-        }
+          .orElse("guest");
         log.info("Request from '{}@{}': {}?{}", username, request.getRemoteAddr(),
           httpServletRequest.getRequestURI(), request.getParameterMap());
     }

patterns/intercepting-filter/src/main/java/com/baeldung/patterns/intercepting/filter/filters/VisitorCounterFilter.java

@@ -5,6 +5,7 @@ import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpSession;
 import java.io.IOException;
 import java.util.HashSet;
+import java.util.Optional;
 import java.util.Set;
 
 public class VisitorCounterFilter implements Filter {
@@ -21,8 +22,9 @@ public class VisitorCounterFilter implements Filter {
       FilterChain chain
     ) throws IOException, ServletException {
         HttpSession session = ((HttpServletRequest) request).getSession(false);
-        String username = (String) session.getAttribute("username");
+        Optional.ofNullable(session.getAttribute("username"))
-        users.add(username);
+          .map(Object::toString)
+          .ifPresent(users::add);
         request.setAttribute("counter", users.size());
         chain.doFilter(request, response);
     }