BAEL-2080 - Check if a user is logged-in with Servlets and JSP

* new module: javax-servlets-2

javax-servlets-2/README.md

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+## Servlets
+
+This module contains articles about Servlets.
+
+### Relevant Articles:

javax-servlets-2/pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <groupId>com.baeldung.javax-servlets</groupId>
+    <artifactId>javax-servlets-2</artifactId>
+    <version>1.0-SNAPSHOT</version>
+    <name>javax-servlets-2</name>
+    <packaging>war</packaging>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <!-- File Uploading -->
+        <dependency>
+            <groupId>commons-fileupload</groupId>
+            <artifactId>commons-fileupload</artifactId>
+            <version>${commons-fileupload.version}</version>
+        </dependency>
+        <!-- Servlet -->
+        <dependency>
+            <groupId>javax.servlet</groupId>
+            <artifactId>javax.servlet-api</artifactId>
+            <version>${javax.servlet-api.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>javax.servlet.jsp</groupId>
+            <artifactId>javax.servlet.jsp-api</artifactId>
+            <version>${javax.servlet.jsp-api.version}</version>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>javax.servlet</groupId>
+            <artifactId>jstl</artifactId>
+            <version>${jstl.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.httpcomponents</groupId>
+            <artifactId>httpclient</artifactId>
+            <version>${org.apache.httpcomponents.version}</version>
+            <scope>test</scope>
+            <exclusions>
+                <exclusion>
+                    <artifactId>commons-logging</artifactId>
+                    <groupId>commons-logging</groupId>
+                </exclusion>
+            </exclusions>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <org.apache.httpcomponents.version>4.5.13</org.apache.httpcomponents.version>
+        <javax.servlet-api.version>4.0.1</javax.servlet-api.version>
+    </properties>
+</project>

javax-servlets-2/src/main/java/com/baeldung/user/check/User.java

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+package com.baeldung.user.check;
+
+import java.io.Serializable;
+import java.util.ArrayList;
+import java.util.Date;
+import java.util.HashMap;
+import java.util.List;
+
+/**
+ * @since 6 de fev de 2022
+ * @author ulisses
+ */
+public class User implements Serializable {
+    private static final long serialVersionUID = 1L;
+
+    protected static final HashMap<String, User> DB = new HashMap<>();
+    static {
+        DB.put("admin", new User("admin", "password"));
+        DB.put("user", new User("user", "pass"));
+    }
+
+    private String name;
+    private String password;
+
+    private List<Date> logins = new ArrayList<Date>();
+
+    public User(String name, String password) {
+        this.name = name;
+        this.password = password;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public List<Date> getLogins() {
+        return logins;
+    }
+
+    public void setLogins(List<Date> logins) {
+        this.logins = logins;
+    }
+
+    public String getPassword() {
+        return password;
+    }
+
+    public void setPassword(String password) {
+        this.password = password;
+    }
+
+    @Override
+    public int hashCode() {
+        final int prime = 31;
+        int result = 1;
+        result = prime * result + ((name == null) ? 0 : name.hashCode());
+        return result;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj)
+            return true;
+        if (obj == null)
+            return false;
+        if (getClass() != obj.getClass())
+            return false;
+        User other = (User) obj;
+        if (name == null) {
+            if (other.name != null)
+                return false;
+        } else if (!name.equals(other.name))
+            return false;
+        return true;
+    }
+}

javax-servlets-2/src/main/java/com/baeldung/user/check/UserCheckFilter.java

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+package com.baeldung.user.check;
+
+import java.io.IOException;
+
+import javax.servlet.Filter;
+import javax.servlet.FilterChain;
+import javax.servlet.ServletException;
+import javax.servlet.ServletRequest;
+import javax.servlet.ServletResponse;
+import javax.servlet.annotation.WebFilter;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
+@WebFilter("/user-check/*")
+public class UserCheckFilter implements Filter {
+    public static void forward(HttpServletRequest request, HttpServletResponse response, String page) throws ServletException, IOException {
+        request.getRequestDispatcher("/WEB-INF/user.check" + page)
+            .forward(request, response);
+    }
+
+    @Override
+    public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
+        if (!(req instanceof HttpServletRequest)) {
+            throw new ServletException("Can only process HttpServletRequest");
+        }
+
+        if (!(res instanceof HttpServletResponse)) {
+            throw new ServletException("Can only process HttpServletResponse");
+        }
+
+        HttpServletRequest request = (HttpServletRequest) req;
+        HttpServletResponse response = (HttpServletResponse) res;
+
+        request.setAttribute("origin", request.getRequestURI());
+
+        if (!request.getRequestURI()
+            .contains("login") && request.getSession(false) == null) {
+            response.setStatus(HttpServletResponse.SC_UNAUTHORIZED);
+            forward(request, response, "/login.jsp");
+            // we return here so the original servlet is not processed
+            return;
+        }
+
+        chain.doFilter(request, response);
+    }
+}

javax-servlets-2/src/main/java/com/baeldung/user/check/UserCheckLoginServlet.java

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+package com.baeldung.user.check;
+
+import java.io.IOException;
+import java.util.Date;
+
+import javax.servlet.ServletException;
+import javax.servlet.annotation.WebServlet;
+import javax.servlet.http.HttpServlet;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import javax.servlet.http.HttpSession;
+
+@WebServlet("/user-check/login")
+public class UserCheckLoginServlet extends HttpServlet {
+    private static final long serialVersionUID = 1L;
+
+    @Override
+    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
+        if (request.getSession(false) != null) {
+            response.sendRedirect(request.getContextPath() + "/user-check/home");
+            return;
+        }
+
+        String referer = (String) request.getAttribute("origin");
+        request.setAttribute("origin", referer);
+        UserCheckFilter.forward(request, response, "/login.jsp");
+    }
+
+    @Override
+    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
+        String key = request.getParameter("name");
+        String pass = request.getParameter("password");
+
+        User user = User.DB.get(key);
+        if (user == null || !user.getPassword()
+            .equals(pass)) {
+            response.setStatus(HttpServletResponse.SC_UNAUTHORIZED);
+            request.setAttribute("origin", request.getParameter("origin"));
+            request.setAttribute("error", "invalid login");
+            UserCheckFilter.forward(request, response, "/login.jsp");
+            return;
+        }
+
+        user.getLogins()
+            .add(new Date());
+
+        HttpSession session = request.getSession();
+        session.setAttribute("user", user);
+
+        String origin = request.getParameter("origin");
+        if (origin == null || origin.contains("login"))
+            origin = "./";
+
+        response.sendRedirect(origin);
+    }
+}

javax-servlets-2/src/main/java/com/baeldung/user/check/UserCheckLogoutServlet.java

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+package com.baeldung.user.check;
+
+import java.io.IOException;
+
+import javax.servlet.ServletException;
+import javax.servlet.annotation.WebServlet;
+import javax.servlet.http.HttpServlet;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import javax.servlet.http.HttpSession;
+
+@WebServlet("/user-check/logout")
+public class UserCheckLogoutServlet extends HttpServlet {
+    private static final long serialVersionUID = 1L;
+
+    @Override
+    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
+        HttpSession session = request.getSession(false);
+        if (session != null) {
+            session.invalidate();
+        }
+
+        request.setAttribute("loggedOut", true);
+        response.sendRedirect("./");
+    }
+}

javax-servlets-2/src/main/java/com/baeldung/user/check/UserCheckServlet.java

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+package com.baeldung.user.check;
+
+import java.io.IOException;
+
+import javax.servlet.ServletException;
+import javax.servlet.annotation.WebServlet;
+import javax.servlet.http.HttpServlet;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import javax.servlet.http.HttpSession;
+
+@WebServlet(name = "home", urlPatterns = { "/user-check/", "/user-check", "/user-check/home" })
+public class UserCheckServlet extends HttpServlet {
+    private static final long serialVersionUID = 1L;
+
+    @Override
+    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
+        HttpSession session = request.getSession(false);
+        if (session == null || session.getAttribute("user") == null) {
+            throw new IllegalStateException("user not logged in");
+        }
+
+        User user = (User) session.getAttribute("user");
+        request.setAttribute("user", user);
+
+        UserCheckFilter.forward(request, response, "/home.jsp");
+    }
+}

javax-servlets-2/src/main/resources/logback.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<configuration>
+    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
+        <encoder>
+            <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n
+            </pattern>
+        </encoder>
+    </appender>
+
+    <root level="INFO">
+        <appender-ref ref="STDOUT" />
+    </root>
+</configuration>

javax-servlets-2/src/main/webapp/WEB-INF/user.check/home.jsp

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+<%@ page contentType="text/html;charset=UTF-8" session="false"%>
+<%@ taglib uri="http://java.sun.com/jstl/core_rt" prefix="c"%>
+
+<html>
+    <head>
+        <title>login success - current session info</title>
+    </head>
+    <body>
+        <section>
+            <h2>user info</h2>
+            <div>
+                <span>name: ${user.name}</span>
+            </div>
+    
+            <div>
+                <span>logins:</span>
+                <ul>
+                    <c:forEach var="login" items="${user.logins}">
+                        <li>${login}</li>
+                    </c:forEach>
+                </ul>
+            </div>
+    
+            <div>
+                <a href="${pageContext.request.contextPath}/user-check/logout">
+                    logout
+                </a>
+            </div>
+        </section>
+    </body>
+</html>

javax-servlets-2/src/main/webapp/WEB-INF/user.check/login.jsp

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+<%@ page contentType="text/html;charset=UTF-8" session="false"%>
+<%@ taglib uri="http://java.sun.com/jstl/core_rt" prefix="c"%>
+
+<html>
+    <head>
+        <title>login</title>
+    </head>
+    <body>
+        <form action="${pageContext.request.contextPath}/user-check/login"
+          method="POST">
+            <input type="hidden" name="origin" value="${origin}">
+            <c:if test="${not empty origin}">
+                <div>* redirected to login from: ${origin}</div>
+            </c:if>
+    
+            <c:if test="${not empty error}">
+                <div>* error: ${error}</div>
+            </c:if>
+    
+            <fieldset>
+                <legend>credentials</legend>
+                
+                <label for="name">name</label> 
+                <input type="text" name="name">
+    
+                <label for="password">password</label> 
+                <input type="password" name="password"> 
+                
+                <input type="submit">
+            </fieldset>
+        </form>
+    </body>
+</html>

javax-servlets-2/src/test/java/com/baeldung/user/check/UserCheckServletLiveTest.java

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+package com.baeldung.user.check;
+
+import static org.junit.Assert.assertTrue;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
+import org.apache.http.client.entity.UrlEncodedFormEntity;
+import org.apache.http.client.methods.CloseableHttpResponse;
+import org.apache.http.client.methods.HttpGet;
+import org.apache.http.client.methods.HttpPost;
+import org.apache.http.impl.client.CloseableHttpClient;
+import org.apache.http.impl.client.HttpClientBuilder;
+import org.apache.http.impl.client.LaxRedirectStrategy;
+import org.apache.http.message.BasicNameValuePair;
+import org.apache.http.util.EntityUtils;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.junit.MockitoJUnitRunner;
+
+@RunWith(MockitoJUnitRunner.class)
+public class UserCheckServletLiveTest {
+    private static final String BASE_URL = "http://localhost:8080/javax-servlets-2/user-check";
+
+    @Mock
+    HttpServletRequest request;
+
+    @Mock
+    HttpServletResponse response;
+
+    private CloseableHttpClient buildClient() {
+        return HttpClientBuilder.create()
+            .setRedirectStrategy(new LaxRedirectStrategy())
+            .build();
+    }
+
+    @Test
+    public void whenCorrectCredentials_thenLoginSucceeds() throws Exception {
+        try (CloseableHttpClient client = buildClient()) {
+            HttpPost post = new HttpPost(BASE_URL + "/login");
+
+            List<BasicNameValuePair> form = new ArrayList<>();
+            form.add(new BasicNameValuePair("name", "admin"));
+            form.add(new BasicNameValuePair("password", "password"));
+
+            post.setEntity(new UrlEncodedFormEntity(form));
+            try (CloseableHttpResponse response = client.execute(post)) {
+                String body = EntityUtils.toString(response.getEntity());
+
+                assertTrue(response.getStatusLine()
+                    .getStatusCode() == 200);
+
+                assertTrue(body.contains("login success"));
+            }
+        }
+    }
+
+    @Test
+    public void whenIncorrectCredentials_thenLoginFails() throws Exception {
+        try (CloseableHttpClient client = buildClient()) {
+            HttpPost post = new HttpPost(BASE_URL + "/login");
+
+            List<BasicNameValuePair> form = new ArrayList<>();
+            form.add(new BasicNameValuePair("name", "admin"));
+            form.add(new BasicNameValuePair("password", "invalid"));
+
+            post.setEntity(new UrlEncodedFormEntity(form));
+            try (CloseableHttpResponse response = client.execute(post)) {
+                String body = EntityUtils.toString(response.getEntity());
+
+                assertTrue(response.getStatusLine()
+                    .getStatusCode() == 401);
+
+                assertTrue(body.contains("invalid login"));
+            }
+        }
+    }
+
+    @Test
+    public void whenNotLoggedIn_thenRedirectedToLoginPage() throws Exception {
+        try (CloseableHttpClient client = buildClient()) {
+            HttpGet get = new HttpGet(BASE_URL + "/home");
+
+            try (CloseableHttpResponse response = client.execute(get)) {
+                String body = EntityUtils.toString(response.getEntity());
+
+                assertTrue(response.getStatusLine()
+                    .getStatusCode() == 401);
+
+                assertTrue(body.contains("redirected to login"));
+            }
+        }
+    }
+}